403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.mongoliajol.info port 443 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.mongoliajol.info port 443 some properties of testicular hyaluronidases enkhmaa ts., purev d., bayarmaa j 1 1 num, school of biology and biotechnology e-mail: enhma_87@yahoo.com abstract: the properties (phopt, topt, km, temperature, acid and base stability of the enzyme activity) of hyaluronidase prepared from testes of bovine, horse, pig and antelope were determined. keywords: hyaluronidases, hyaluronic acid, glycosaminoglycan introduction he hyaluronidases (ec 3.2.1.35) have been detected in many mammalian tissues and organs. some bacteria such as streptococcus pyogenes and clostridium perfringens produce hyaluronidase (ohya t., 1970). hyaluronidase resists spreading of venoms and virulence of bacteria and may play a role in cancer metastasis and angiogenesis (beckenlehner k., 1992). therefore it is used in medicine (schomberg d., 1991). there are many beneficial effects of hyaluronidase in the biological function. mammalian oocytes are surrounded by several layers of cells embedded in extracellular matrix which contains protein and hyaluronic acid. that is why hyaluronidase degrades these layers. this process helps to spermatozoon fertelizing egg (dandekar p., 1992). the substrate of hyaluronidase is hyaluronic acid (ha). it is a glycosaminoglycan with high molecular weight linear polymer built of large numbers of repeating units consisting of [-dglucuronic acid-β1,3-n-acetyl-dglucosamineβ1,4-]n (laurent t.c., 1992). experimental materials and chemicals: the testes of bovine, pig and horse were purchased from “мах impex” company and testes of antelope were taken from bayandun sum of dornod aimag. determination of enzyme activity: the enzyme activity was determined by classic turbidimetric assay (yang c., 1975). this method is based on the estimation due to an interaction between albumin and ha. mixture of 0.5 ml of hyaluronate solution (0.04-0.32 mg/ml of ha (wortington) in 0.2-1.0 ml of 0.1 m sodium phosphate buffer with ph 5.3 which contains 0.15 m nacl) and 0.5 ml of testicular extract was incubated at 37°c for 25 minutes. then 9 ml of albumin was added to the solution and was being stayed for 10 minutes at room temperature. the color development was measured at 540 nm against control solution by the spectrophotometer. the results were compared with the standard curve. plotting the standard curve: the solution of ha was heated for 5 minutes in a boiling water bath and 9 ml of albumin was added to test tubes and was measured at 540 nm against control solution. t 38 p 38-41 determination of the protein concentration: protein concentration in solutions was determined by the biuret reaction(tsevegsuren n., 2001), phopt was determined along with the enzyme activity in buffer indicating various ph (2-11), topt by the enzyme activity at 20-60 o c, km by lineweaver-burk plot, temperaturedependence by denaturation time of enzyme activity at various temperatures, acid influence on enzyme activity was determined by enzyme activity at ph 1, while base influence on enzyme activity was determined at ph 10 (purev d., 2003). results and discussion the testes of bovine, pig, antelope and horse were cleaned from lipid mass and connective tissue following with cut and mash. hyaluronidase activity and protein concentrations were estimated in all samples. results are shown in the table 1. table 1. protein concentration and hyaluronidase activity in all samples № sample protein concentration, % enzyme activity, units* 1 bovine 4.57±0.74 13.76±1.59 2 horse 4.00±0.82 14.28±1.86 3 antelope 3.45±0.45 20.78±6.41 4 pig 4.80±0.49 11.29±1.13 note: *300 units for sigma pure hyaluronidase results indicated that pig testicular samples contained much protein, while the testicular protein of the antelope was lower than other samples by 0.55-1.35% . however the enzyme activity of the antelope was the highest than others (1.46-1.84 times more active in comparison with other samples). the temperature influence on testicular hyaluronidase activity was assayed at t=20°c-60°c. the topt was determined at 25-30°c for all samples, except pig's hyaluronidase, which was completely denaturated.the optimal ph of hyaluronidase of all samples were determined at ph4 and ph8-9 (table 2, fig 1 and table 3, fig 2 ). table 2. temperature influence on enzyme activity т, 0 с relative activity, % bovine antelope horse 20 84.5 84.6 91.8 25 100 100 100 30 100 100 100 35 89.7 96.3 94.1 40 72.5 83.2 80.1 45 64.5 71.9 73.5 50 58.4 70.0 62.3 55 56.7 62.1 52.9 60 56.0 58.3 43.7 figure1. temperature influence on enzyme activity table 3. ph influence on enzyme activity рн relative activity, % bovine (6) antelope (3) horse (5) pig (5) 2 78.0± 93.4± 52.2± 82.9± 3 92.0± 97.9± 65.2± 86.6± 4 100± 100± 100± 100± 5 56.8± 76.6± 73.2± 78.3± 6 44.8± 72.5± 61.8± 65.2± 7 57.1± 77.3± 71.7± 65.5± 8 58.2± 78.6± 77.6± 66.4± 9 53.0± 77.4± 89.5± 59.7± 10 43.4± 72.8± 87.7± 45.3± 11 37.5± 70.6± 75.7± 37.7± note: figures in bracket are the number of repeated experiments figure 2. ph influence the enzyme activity. two meanings of phopt for testicular hyaluronidase were detected. those results were same as researchers’ findings who found the enzyme polymorphism (cevallos m.a. et all, 1992). the phopt range for antelope hyaluronidase was wide, while for horse enzyme it was narrower than other samples. 0 20 40 60 80 100 120 0 50 100 r e la ti v e a c ti v it y , % temperature, °c bovine antelope horse 0 20 40 60 80 100 120 0 5 10 15 r e la ti v e a c ti v it y , % ph bov ine 39 for bovine and pig hyaluronidase the same values of phopt were determined. base influence on the enzyme activity was at first estimated at рн=9 after incubation for 120 minutes. here no changes were observed. then at рн=10 after incubating for 60 minutes enzyme activity was decreased. (table 4). table 4. base influence on the enzyme activity, рн=10 inactivation time,minutes relative activity, % bovine antelope horse 0 100 100 100 60 100 95.3 99.5 120 97.7 88.2 97.2 180 89.4 81.2 94.4 240 84.7 76.5 86.2 figure 3. base influence on enzyme activity the base influence on the enzyme activity was estimated after incubation for 240 minutes. while three samples (bovine, horse, antelope) on ph=10 were being observed and measured within each 60 minutes at 25 o c. in the result enzyme activity decreased until 84.7%, 76.5%, 86.2 % (figure 3). figure 4. hyaluronidases base inactivation reaction order base inactivation reaction order for bovine, horse and antelope hyaluronidases were calculated as n-th order reaction (figure 4). table 5. acid influence on the enzyme activity, рн=1.0 the acid influence of enzyme activity was determined on three samples(bovine, horse, antelope) by incubated for 90 minutes within each 30 minutes at ph=1. in the result bovine enzyme completely denaturated after 90 minutes, while horse enzyme after 60 minutes and antelope hyaluronidase after 30 minutes of incubation. thus hyaluronidase is not stable at acid environment (figure 5). figure 5. acid influence on the enzyme activity we have determined the km meanings for bovine, horse and antelope hyaluronidase by lineweaver-burk plot. which was calculated as 0.23 mg/ml for bovine enzyme, 0.48 mg/ml for antelope and 0.83 mg/ml for horse testicular hyaluronidase, respectively. conclusions 1. results indicated that pig testicular samples contained much protein, while the testicular protein of the antelope was lower than other samples by 0.55-1.35%. however the enzyme activity of the antelope was the highest than others. 2. topt of hyaluronidase was in 25-30 o c except pig's and phopt at 4.0 for all four samples. 0 20 40 60 80 100 120 0 60 120 180 240 r e la ti v e a c ti v it y , % inactivation time, min bovine antelo pe 1.85 1.9 1.95 2 2.05 0 200 400 l o g [ a c ti v it y ] inactivation time, min bovine antelope horse 0 20 40 60 80 100 120 0 50 100 150 r e la ti v e a c ti v it y , % inactivation time, min bovine antelope horse 40 3. the optimal ph of hyaluronidase of all samples were determined at ph4 and ph8-9. 4. km meanings for bovine, horse and antelope hyaluronidase by lineweaverburk plot. which was calculated as 0.23 mg/ml for bovine enzyme, 0.48 mg/ml for antelope and 0.83 mg/ml for horse testicular hyaluronidase, respectively. references 1. beckenlehner k., banoke s., bernhardt g. and schiess w (1992). hyaluronidase enhances the activity of adriamycin in breast cancer models in vitro and in vivo. j. cancer res. clin. oncol. 188: 591. 2. cevallos m.a., navarro-duque c.,. varela-julia m, and alagon a.c (1992). molecular mass determination and assay of venom hyaluronidases by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. toxicon. 30: 925. 3. dandekar p., aggeler j., and talbot p (1992). structure, distribution and composition of the extracellular matrix of human oocytes and cumulus masses. hum. reprod. 7: 391. 4. laurent t.c. and fraser j.r.e. (1992) hyaluronan, faseb j. 6: 2397. 5. ohya t. and kanako y. (1970) novel hyaluronidase from streptomyces. biochem. biophys. acta 198: 607. 6. purev d, bayarmaa j. enzymology (2003) ulaanbaatar, pp 247-248, 291292 7. schomberg d. and salzmann m., eds. (1991) enzyme handbook. springer verlag, berlin. 8. tsevegsuren n., purev d. (2001) bioorganic chemistry practices. ulaanbaatar. p.76-81 9. yang c. and srivastava p.n. (1975) purfication and properties of hyaluronidase from bull sperm. j. biol. chem. 250: 79. 41 403 forbidden forbidden you don't have permission to access this resource. apache/2.4.54 (ubuntu) server at www.mongoliajol.info port 443 the precious metals (au, ag, pt, pd, rh) adsorption on the silicon – organic sorbents g. burmaa 1 , s. alen 1 , yu. ganchimeg 2 , i. sukhbaatar 2 1 institute of chemistry and chemical technology, mas 2 mongolian university of science and technology, school of materials technology abstract: sorption activity of two types of silicon-organic sorbents for the previous metals has been studied. a polymer – poly (3silsesquioxanilpropylthiocarbamate) 3silsesquioxanilpropylammonium which was obtained by the hydrolytic poly-condensation reaction and has been determined its physical, chemical characteristics and its sorption activity for the ag(i), au(iii), pt(iv), pd(ii), rh(iii). it has been found out that the sorbent shows high static sorption of gold (iii), mercury (ii) at acidic condition. the second a net structured silicon-organic copolymer {sio2*2[o1.5si(ch2)3nhc5h4n}n was synthesized by hydrolytic co-poly-condensation reaction. it likely to react as an anionit that adsorbs chloro-complex anion of the au (iii), pt(iv), pd(ii), rh(iii). keyword: dithiocarbamate, 2-aminopyridine, sorption capacity, ion-coordination. introduction nitial systemic research about the complexity and silicon-organic ionite which contain complex forming or ion exchange groups started since 1977, when discovered the polymercaptomethylsilsesquioxane’s xerogel [1,2]. it was taken from hydrolytic polycondensation of the mercaptomethyltrialcosisilan hsch2si(ro)3 (r =ch3, c2h5). poly-mercaptomethylsilsesquioxane’s xerogel is an adsorbent that has ability to adsorb mercury (ii) from the extremely diluted solution (0.012mg/l hg) in the high diapason of the ph, fully [3]. this adsorbent showed high selective adsorption of mercury(ii) from solution which contains over concentrated ions of the zn(ii), fe(ii), co(ii), ni(ii) at ph 0.3-3. now days this adsorbent is using for removal of mercury from waste water of chlorine industry [3]. also this sorbent has shown high activity (1.1mg-equa/g) in case of ag(i) [4]. then, adsorbed silver was fully desorbed by 0.25m ammonium hydroxide. when solution ph > 3, this sorbent has full sorption capacity for pb(ii) and sn(ii) and developed a spectrometer speedy method that used to determine these elements in spa water [4]. therefore, silicon-organic sorbent (ptca-3a) with dithiocarbamate group has been synthesized [5-7]. we are performing research evaluating of adsorption capacity of hg(ii), au(iii), ag(i), pt(iv), rh(iii) from aqueous solution . organic derivatives of the dithiocarbamate have been used widely in practice. most of them have an unique biological activity and therefore, it is become raw material of the pharmacy [8]. there is a special trend of the practical usage of organic compounds with dithiocarbamate group for determination of heavy metals in the i 29 p 29-34 industrial waste water and its purification [9.10]. also, there are different types of adsorbent materials which contain dithiocarbamate group and parts [11.12]. silicon-organic complexities and ionits [13.14] have stability to high temperature (till 250 0 c). but study of their ion exchange property is scarce and never been studied its practical usage. silicon-organic compounds with hetero-cycle ion has unique biological activeness. but poly-orginalsilsesquioxanes containing hetero-cycle in their organic radical are effective adsorbents which could form complex [7.17]. therefore, we did research for eluvidation of precious metals (au, ag, pt, pd, rh) adsorption ability of the silicon-organic copolymer (paps-2) or {sio2*2[o1.5si(ch2)3nhc5h4n}n that contains 2-aminopyridin which was synthesized by the co-poly-condensation reaction [18]. experimental materials. poly(3-silsesquioxanil propylthiocarbamate) 3-silsesquioxanilpropyl ammonia (ptca-3a) is a net constructed polymer with yellow color, finely dispersed powder. siliconorganic copolymer paps-2 is brown colored and coarse sized powder. table 1 shows physical and ir spectrum data of used polymers. table 1. polymer (ptca-3а) and paps-2 f o rm u la physical data т 0 с ir spectrum (, cm -1 ) р б ( g /c m 3 ) р п ( g /c m 3 ) р т ( g /c m 3 ) р а ( % ) v (c m 3 /g ) s ( m 2 /g ) s i 2 c 7 h 1 6 n 2 s 2 o 3 ( p c k a 3 а ) 1 .2 4 0 .5 8 0 .5 5 5 6 .0 1 .0 1 2 2 0 3400, 2930, 1540,1020 (nh), 2570(s-h), 1340 (c=s), 1100(si-osi) c 1 6 h 2 2 n 4 o 5 s i 3 (p a p s -2 ) 1 .3 9 5 1 5 2 8 0 3400, 3300 (nh), 1615, 1595, 1480, 1440 ( circle of the pyridine c=c, c=n), 11201000(si-o-si), 1560 [(nh)] рб – density, рп – pour density, рт – apparent density, ра – porosity , v – total pore volume, s – surface area ir spectrum of polymers before and after sorption of the precious and rare metal ions were obtained by using high purity kbr with specord ir 75 and specord m 80. physical data were determined according to previous method [19]. colour of polymer (ptca-3a) is changing to yellow after adsorption of hg(ii) while with au(iii) – orange, pt(iv) – yellowish, pd(ii) – brown, rh(iii) – pink, ag(i) – amber. sorption method of the precious metals sorption of hg(ii), au(iii), pt(iv), pd(ii), rh(iii) was studied in hydrochloric acid with concentration of 0.1-5.0 mol/l while ag(i) sorption was studied in nitric acid with same concentration. polymers (ptca-3a, paps-2) were taken 0.05g of and mixed and shaked with solution of precious metal’s chloro-complex in 0.15.0mol/l concentrated hydrochloric and nitric acids by shaker hy-4. content of the metals in the solution was 0.05-0.8mg/ml. after a certain time polymer was separated from solution and washed thoroughly and concentration of metal ions left in the solution was determined by spectrophotometer method (hitachi u-1000 and kfk-2) with tin chloride [20,21]. precious metals absorption capacity of the of polymers was calculated by maximum content of the metal per gram of polymers at the equilibrium condition. . standard solutions of precious metals were prepared by dissolving of agno3; h[aucl]4h2o; h2[ptcl6]6h2o; pdcl2 and rhcl34h2o in distilled water. result and d iscussion sorption study of ptca-3a polymer adsorption ag(i) and pd(ii) is correlated with acid concentration, while other ions have no direct correlation. however, ag(i) and pd(ii) correlation shows reverse behaviour (figs 1 and 2). figures 1 and 2 indicate when ag(i) is adsorbed from nitric acid, proton concentration is increased because of h + is interacting with sulfur atom of the thiolyate that caused decreasing ag(i) adsorption. sorption of [pdcl4] 2 and [rhcl6] improved in 30 result of increasing of chloride ions concentration in solution. influence hydrochloric acid concentration on the au(iii) and hg(ii) sorption was much weaker than other ions. it can be suggested that in acid solution thiocarbamate group of polymer (ptca-3a) is interacting with acid molecule (ha) and reaching to equilibrium condition (equation 1.1). ir spectroscopy result indicated (not shown) peak at 1500cm -1 is related in asymmetric fluctuation of nh3 + group of the polymer (ptca-3a) which showed in the equation 1.1. after sorption in nitric acid there appeared a new peak at 1380cm -1 . it proves that nitrate ion was entered into structure of the polymer. figure 1. influence of the acid concentration on sorption of au(iii), pt(iv) and rh(iii) figure 2. influence of the acid concentration on sorption ag(i), hg(ii) a solution ph increased a little due to protonation of functional group of polymer (ptca-3a). this behaviour of the polymer (ptca-3a) in acid solution shows its functional group has ion-coordination property. also determines influence of acid concentration on metal ions sorption (figure1and 2). in the matter sorption of the hg(ii) and ag(i) ions occurred by ion coordination mechanism and possibly was interacted with both 2 atoms of the sulfur (equation 1.2): in the ir spectra of polymer (ptca -3a) saturated by hg(ii) and ag(i) ions, disappeared peaks at 1340 (c=s) and 2570 (s-h) cm -1 an indication of mechanism shown in equation 1.2 takes place. there weren't shown any changes in amine (1540cm -1 ) and amino (1500cm -1 ) groups fluctation. desorption of the hg 2+ and ag 1+ cations by 6m solution of nitric acid indicates that they were adsorbed by ion exchange mechanism. functional groups of the polymers could be interacted with aucl4 , ptcl6 2, pdcl4 2 and rhcl6 2 via atoms of the nitrogen and sulfur. in the ir spectra of polymers saturated with these ions disappeared peak at 1500cm -1 (nh3 2+ ). also there were not appeared any peaks associated with the other forms of precious metals in the polymer matrix. elemental analysis indicated that polymer (ptca-3a) in acid solution contains au and pd as aucl and pdcl0.5. this shows these element atoms are connected with no less than 3 atoms of functional groups (coordination number 4). in the spectrum of polymer saturated with ions au(iii), pt(iv), pd(ii) and rh(iii) disappeared peak at 1340cm -1 (c=s) and peaks of the amine group at 3400 and 1540cm -1 were shifted to high wave numbers region. these results and low desorption values (not more than 5-10%) of gold, platinum, palladium, rhodium by hydrochloric and nitric acid solutions (6-9 0 10 20 30 40 50 60 70 80 90 0 2 4 6 с (mol/l) r (%) au (iii) pd (ii) pt (iv) rh (iii) 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 с (mol/l) r (%) hg (ii) ag (i) 31 mol/l) showed that acido-complexes of these metals interacting via ion-coordination mechanism with sulfur atom of thion group and nitrogen atoms of ammonium and amine group. there is chance of ammonium group participation decrease in adsorption of precious metals with increase of hydrochloric acid concentration. gold and palladium in hydrochloric acid with concentration of 5 mol/l exist as aucl2 and pdcl2. static sorption capacity (ssc) was determined in 3 mol/l acid solution. connection degree of active group of the polymer (ptca-3a) was determined by comparison of static sorption capacity value with theoretical sorption capacity value (ssc∙100/tsc) and showed in table 2. table 2. ssc, tsc and ratio to connect with chemical active group of ptca-3a sorbent volume rh(i ii) pt(iv) pd(ii) au(iii) ag(i) hg(ii) ssc, mg/g 26 86 122 300 160 400 tsc, mg/g 340 660 350 650 370 658 ssc·100/tsc (%) 9.0 14.0 33.0 45.0 46.0 59.0 connection degree of active group of polymer was increased as: rh(iii)<pt(iv)<pd(ii)<au(iii)<ag(i)<hg(ii). this result is in agreement with the previous published reference [22]. it also shows direct dependence with the metal sulfides solubility. adsorption equilibrium time in hydrochloric and nitric acids with 3 mol/l were for pd(ii)1.5h, au(iii)-2h, hg(ii)-2h, ag(i)3h, pt(iv)3h and rh(iii)-3h, respectively. poly (3silsesquioxanilpropylthiocarbamate)3silsesquioxanilpropylammonium has high adsorption capacity to gold and mercury from acid solution and its static sorption capacity ssc is not less than silicon-organic and organic sorbents which studied previously [57,22]. sorption study of copolymer(paps-2) this silicon-organic copolymer’s au(iii), pt(iv), pd(ii), rh(iii) sorption activity was determined in the hydrochloric acid solution with concentration of 0.1-0.5 mol/l. their sorption activity was the highest in hydrochloric acid solution with concentration of less than 1mol/l. when acid concentration is more than 1mol/l, the precious metals sorption (r%) was decreased considerably (figure 3a,b). when temperature of solution increased from 20 o c to 40 o c there wasn’t any change in sorption behaviour of metals (figure 3a,b) as well as in equilibrium time. equilibrium time in 0.5m hc at 20 o c and 40 o c was similar i.e 20-40 min. static sorption capacity and coefficient of interphase distribution (d, cm 3 /g) were calculated based on isotherm curves of sorption and showed in table 3. figure 3. influence of the hydrochloric acid concentration on metal sorption. figure 4. influence of equilibrium time on the metals sorption. table 3. static sorption capacity (ssc, mg/g) and coefficient of interphase distribution (d,cm 3 /g) of the copolymer (paps-2) data au(iii) pt(iv) pd(ii) rh(iii) ssc, mg/g 134.0 141.0 124.0 110.0 d·10 3 cm 3 /g 4.3 5.4 2.8 1.3 the result shown in table 3 indicated that it’s possible to separate precious metals with a micro content in solution by polymer (paps32 2). metals adsorbed on the polymer (paps-2) can be desorbed by 6 mol/l hydrochloric acid solution. when desorption is done at room temperature, 1ml desorbent was capable to desorb 120 ppm au, 190 ppm pt, 90 ppm pd and 35 ppm rh, respectively. sorption mechanism precious metals are adsorbed on the polymer (paps-2) according to the anion exchange mechanism. elemental analysis of the polymer saturated with the precious metals showed adsorption occurs in form of [mcln] nk where m-metal, n-4,6, koxidation degree of metal. adsorption occurred according to ion exchange mechanism and it has been supported by decrease of adsorption activity with increasing of acid concentration. this polymer didn’t show any capacity to adsorb silver and copper in acid solution. in acid solution ag(i) and cu(ii) are presented in cation type and it’s one more evidence that paps-2 acts as an anionit in acid solution. sorption activity of the paps-2 is similar with pyridine based organic sorbents [23]. in order to find out either nitrogen atom of pyridine circle or amine group is participating in anion exchange process were taken comparative ir spectrums of the pure and saturated with precious metals polymer. in the pure polymer (paps-2) ir spectrum were found peaks at 1615, 1600, 1485, 1440 cm -1 due to –c=cand –c=ngroups of pyridine and also peak at 1560cm -1 due to deformation fluctuation of the nh group. in the spectrum of polymer (paps-2) saturated with metal ions was disappeared nh group peak and a clear change in –c=cand –c=ngroups (peaks at 1600 and 1495cm -1 were widened). such clear changes in ir spectrum indicated in anion exchange were participated both nitrogen atom of pyridine and amine group and it can be showed according to equation 1.3. simultaneously with anion exchange occurred substitution of 2 chlorine atoms with the polymer functional group and formation of the coordination bond with nitrogen atoms (example: palladium acido-complex [pdcl4] 2). conclusions the application of ptca-3a and paps-2 polymers for sorption of precious metals was studied. based on the experimental results following conclusion can be drawn: * sorption of au(iii), ag(i), pt(iv), pd(ii) and rh(iii) by silicon-organic polymers depend on the concentration of acids. the best result was obtained for concentration of 0.1 and 1 mol/l. sorption efficiency decreases with the increase of acid 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server at www.mongoliajol.info port 443 study on arsenic removal process from water b.bayarmaa 1 , e.selenge 1 , yang min 2 1 health science university of mongolia. 2 research center for eco-environmental sciences, cas. chuluun73@yahoo.com abstract: in this study a novel adsorbent, iron oxide, is used for as (v) or as (iii) removal. some ferric oxides have been reported to be effective for arsenic removal. ferric oxides powder is a good adsorbent material since it’s has magnetic properties and a good adsorption capacity. the main purpose of this study has been focused on to study the relationship between adsorption capacity (ability, performance) and the surface characteristics of the ferric oxide. prepared sample’s capacity was evaluated. the value was 26.1-67.4 mg/g for as (v) and 20.5-47.8 mg/g for as (iii). ph dependence was evaluated and when ph increasing, adsorption capacity was decreased. the kinetic was evaluated and about 12 hours reached equilibrium and a capacity of 49 mg/g for as (v) and 42 mg/g for as(iii) was gained. the kinetic constants for arsenic adsorption on the ferrihydrite adsorbent’s were fitted. keywords. ferrihydrite, adsorption, arsenic removal introduction errihydrite is an iron oxy-hydroxide known to play an important role in the natural environment and fresher it is, higher the adsorption capacity it has. its large surface area, strong adsorptive properties, and low cost make it an attractive material for removal of both cationic and anionic impurities from wastewater and drinking water. the use of ferrihydrite to remove arsenic from hydrometallurgical process solutions and wastewaters has received a great deal of attention over a number of years. ferrihydrite readily adsorbs arsenic (v) in the form of arsenate anion (aso4 3), but probably the most effective method of removal of arsenic from aqueous solutions is through coprecipitation of arsenic with ferrihydrite.(1) the main arsenic removal techniques from drinking water are: oxidation, precipitation/co precipitation, coagulation, sorption, ionexchange and reverse osmosis. although these methods have been widely employed, they have several drawbacks: high operating and waste treatment costs, high consumption of reagents and large volume of sludge formation. in contrast, adsorption methods are considered to be very important because of their treatment stability, easy operation and compact facility. when the loaded adsorbent can be regenerated properly, the process can be sludge free. conventional adsorbents used in arsenic removal are activated carbons and alumina, soils and resins which can be coated with different materials like iron or alumina. (the major disadvantages of these techniques are difficult separation (centrifugation or filtering), waste formation (both liquid and sludge) and in many cases poor adsorption capacity.) so in this study i use ferric oxides. f 53 p 53-55 otgonsuren.d highlight otgonsuren.d highlight experimental. materials. all the chemicals used were of analytical reagent grade. a 100 mg /l as (v) and as (iii) stock solutions were prepared by dissolving na3aso4·12h2o or as2o3 in 1 liter of distilled water. as(v) or as(iii) bearing water were prepared by diluting as(v) or as(iii) stock solutions to given as concentrations. preparation. the iron based adsorbent was prepared by mixing fe(no3)3•9h2o and koh for 20 minutes at ph 9.5. in all the process, the mixed solution needs to be intensely stirred. then the pulp was settled, and supernatant was discarded. and the paste was washed with distilled water for many times until the conductivity lower than 500 μs/cm 2 . then the paste was oven drying at 45 o c to make it dry about 48-72 hours. also the drying process can be substituted or refrigerated centrifugation. after that prepared samples were powdered by agate mortar. isotherm experiments were carried out in 250 ml conical flasks, with a reaction volume of 100 ml, and the initial as(v)/as(iii) concentration: 8，10，12，18，24，26，30，34，38 mg/l. the adsorbent was fixed at a dose of 300 mg/l. the ph of the suspension was adjusted and kept at ph 5.0 ± 0.1 during the experiment period. these flasks were shaken at 160 rpm and maintained at 25 ± 1 °c for 24 hours. and the solutions were filtered with a 0.45 μm cellulose acetate membrane, then the concentrations of the residual as was analyzed in using hg-afs. to investigate the influence of ph on the as adsorption, experiments were carried out in 250 ml vessels, containing 25 mg/l as(v), respectively, with 300 mg/l adsorbent and a total suspension volume of 100 ml. and the equilibrium ph was adjusted in the range of 3 to 10 at an experiment period of 24 hours. during the experiment, samples were shaken at 160 rpm, and the temperature was controlled at 25 ± 1 °c. after reaction, the final ph values were recorded, and the solutions were filtered with a 0.45 μm cellulose acetate membrane, and the concentrations of the residual as were analyzed. in order to evaluate the adsorption rate, the kinetics experiments were performed at room temperature (21-25 o c). some amounts stock solution was added in 2000 ml to make a total volume of 1500 ml, with initial as concentrations of 25 mg/l. then, 0.45 g of ferrichydrite was added to obtain a 300 mg/l suspension. further the ph of the mixed suspended solution was adjusted and maintained at 5.0 ± 0.1 throughout the experiment by addition 0.05 m hcl or naoh. the suspension was mixed with a magnetic stirrer at an agitation speed of about 160 rpm. approximately 5 ml aliquots were taken from the suspension at 0, 30 min, 1 h, 4 h, 8 h, 12 h, 24 h, 30 hours. the samples were immediately filtered through a 0.45 μm cellulose acetate membrane. the concentrations of residual as were analyzed by hg-afs. results and discussion prepared ferrihydrite’s sample. prepared adsorbent’s adsorption capacity was presented figure 1. a b figure 1. adsorption isotherm. a. as(iii); b. as(v). the value was 26.1-67.4 mg/g for as(v)and 20.5-47.8mg/g for as(iii). figure 2. effect of ph. 54 ph dependence was presented figure 2 and when ph increasing adsorption capacity was decreasing. a b figure 3. adsorption kinetics. a. as(v); b. as(iii). the kinetic results are presented figure 3 and about 12 hours reached equilibrium and a capacity of 49 mg/g for as(v) and 42 mg/g for as(iii) was gained. the kinetic constants for arsenic adsorption on the ferrihydrite adsorbant’s were fitted and showed following table 1. initial concent rations, 25 mg/l pseudo-first-order model pseudo-second-order model k1, 1/min qe, mg/g r 2 k2, 1/min qe, mg/g r 2 as(v) 0.039 21.58 0.803 0.0041 43.48 0.995 as(iii) -0.00047 25 0.933 table 1. kinetic constants for arsenic adsorption on the ferrihydrite adsorbent.as shown in the table, the result of the study is approved accurately. conclusion an iron based inorganic adsorbent was used for both as(v) and as(iii) removal. in terms of adsorption ph range and adsorption capacity, the new adsorbent demonstrated the probable result. the adsorption mechanism, however, requires further studies. acknowledgement we would like to express our sincere gratitude to professor min yang, and for his important support throughout this work. references. 1. william r. richmond, mitch loan, jonathan morton and gordon m. parkinson. (2004) environ.sci.techno. 38, 2368-2372 2. yu zhang, min yang, xia huang. (2003) chemosphere. 51, 945-952. 3. v.j. inglezakis, helen grigoropoulou.(2004) journal of hazardous materials b112 37–43. effects of operating conditions on the removal of heavy metals by zeolite in fixed bed reactors 4. h. takase, n. katoh. (1995), j. chem. eng. jpn.28 165–170. recovery of heavy metal ion from slurry adsorbent by packed column of ion exchange. 5. do, d. d. (1998). london:imperial college press. adsorption analysis: equilibria and kinetics. 55 discussion organic chemistry is the chemistry of thermodynamic (td) functions, gibbs free energy and the action of entropy, from which all processes are derived. any stress observed within the molecules of organic compounds arise from mutual interatomic actions, gibbs energy and action entropy, bond polarization, charge density, dissipation, scattering, baier stress, van der waals forces, electron donor and acceptor groups, mesomerism, tautomerism, configuration, conformation etc. the td properties are state functions that involves enthalpy, internal energy, entropy etc. gibbs energy is the internal energy of the compound and is one of the forms of the thermodynamic potential. the higher the internal stress of molecules, the higher is the gibbs energy. in the case of van der waals impulse the td stability of the compound will be lost and the standard entropy will be an equilibrium indicator: the organic reaction rate and the yield of the product depend on the action of the td functions. in this context the organic reaction is different from the ionic reaction. the organic reaction does not occur directly but proceeds through intermediate states (im) because the covalent bond has definite energy: the im has a large chemical potential because they exist mostly as free radicals such as sr-reactions, carbocations or ae, se, sn, e1 reactions. the faster the im formation rate, the faster the reaction rate, (if the rate of decomposition of the im is faster than their formation). however, the reaction rate and im formation rate depend on the following factors: • td stability of the im • td stability of the im free energy decrease and entropy increase • the free energy decrease of the free radical, the charge dispersibility for the carbocation (cc) and the decrease in the charge force • the charge force decrease of the free radical, cc alkylation, phenylation, vinylation and mesomerism. the formation rate sequence and the td stability of the im (free radical, cc): since it is an electronic donor, the alkali group will have an effect. thus, tertiary butyl bromide (1,1 dimethylbromoethane) will enter into an sn1 reaction 1×106 times faster than bromoethane. here especially, the phenyl, vinyl group will exert a stronger influence on the dt stability and formation rate of the im because their structures are mesomeric. a strong dissipation or scattering of internal action and charge of the im is also affected by a mesomeric structure. the reaction rates of the following compounds for s r reaction by bromide are: jambal d, mong. j. chem., 23(49), 2022, 63-64 relationship between thermodynamics and the rate of organic reaction (open discussion) jambal damdinchogsom1 1department of chemistry, school of arts and sciences, national university of mongolia, ulaanbaatar 14201, mongolia * corresponding author: irekhbayar@num.edu.mn; received: 2 november 2021; revised: 29 november; accepted: 8 december 2022 mongolian journal of chemistry www.mongoliajol.info/index.php/mjc © the author(s). 2022 open access. this article is distributed under the terms of the creative commons attribution 4.0 international license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the creative commons license, and indicate if changes were made. 63 ch3(ch2)6ch3 ch3ch2chch2ch3 ch3 ch3c ch3 ch3 cch3 ch3 ch3 (111) 109.5 94 a + b im c h2c ch ch2 ph-ch2 r cr r ; > chr r ch2 r > > ch3> h3c ch3 ch3 br naoh -nabr h3c c ch3 ch3 oh -nabr h3c ch3 ch3 oh h3c h h3c h2 c h h h c ch3 ch3 ph ch2 h h h c ph ph (0.0007) (1.0) (220.0) (64000.0) (1.1*106) jambal d, mong. j. chem., 23(49), 2022, 63-65 influence may be exerted upon the im reaction rate by the implantation of an electron donor and acceptor group in the phenyl cycle i.e., addition of a catalyst. the free radical (im) formed as a result of an s r reaction will be stabilized by a π-p bond with a π-link and a p-σ bond with a c-h link (hyperconjugation) respectively, because in these cases the octet is more likely to be filled: so on stabilization, the propylene and toluene products will be formed 100 million times faster in the sr-reaction. the im formed from the chlorite allyl and benzyl will be transferred into the mesomer form and also stabilized. the π-link will be dispersed into the vacant space and attracted by the very powerful cc electron acceptor. moreover, the im (cc) formed from the chloride allyl and benzoyl will be transferred into the mesomer and spontaneously stabilized: the shared pair of free electrons will also exert a strong influence on the reaction rate of nucleophile displacement. for example: here, the “a”-reaction progresses 1×109 times faster than the “b”-reaction and the resulting im is 1×109 times as stable than b-reaction. as far as the “b”-case is concerned, the methyl group exerts an influence upon the im-cc stabilization. in regard to its donor nature, the stereochemistry factor exerts a negative influence. the stabilized one as far as td will be forced forcibly, above all else from the reaction. the reaction yield depends on the td stabilization of the forming compounds (a, b, c-reactions): the trimethylethylene (2-methylbut-2-ene) has a lower activation energy and stability in regard to the td and therefore it will be formed faster because the π-link entered into the hyperconjugation of whole c-h bonds of methyl groups. the mesomeric structure will be formed 100 percent because it has low gibbs’s energy and stability as far as the td is concerned. c. dehydration of 1,2-dimethyl-3-methylcyclopenthanol: the reaction rate will be higher because both the it and the final product have stability in regard to the td in the a-compound reaction, low gibbs energy and high entropy. the formation of b, ccompounds will be closed in regard to the td. a spirit’s dehydration: the formation rate of the oxonium ion → cc → final product depends on the alkylation of carbonyl group. activation energy will be decreased and reaction will be easier: from the previous analysis, the following is a new open discussion point which is being presented: “when the im and final product of reaction in regard to td is stable, the gibbs free energy is low and entropy is higher, then the reaction rate will be higher and the activation energy will be lower.” presently, the rate of organic reaction has been explained as a concentration change. even if it is considered as a classic explanation, it is insufficient to be explained as “origin compound is active”. the reason in this case remains unclear, not withstanding a basic explanation of reaction rate of organic compound, which is completely different from the ionic compound. 64 h c h h h h h2c ch ch2 h2c c ch2 h2c ch ch2 h2c c ch2 h3c o h c r cl r-coona sn1 h3c o h c r h3c o ch2 r r -c o o h3c o c or o h3c c oh ch3 ch3 h3c c oh ch3 ch3 h3c h c h c ch3 ch3 oh h+ h3c h c h c ch3 ch3 h3c c ch ch3 ch3 h3c h c c h ch2 ch3 h2 c h c ch3 oh c h c h ch3 h2 c c h ch2 c h c h ch3 ch2oh ch3 oh h3c ch2oh ch3 ch3 ch2oh ch3 ch3 ch2 ch3 h3c oh (a=100%) (b) (c) h3c h2 c oh h2so4 (95%) 170oc h3c h2 c h c ch3 oh h2so4 (95%) 100oc h2so4 (95%) 85-90oc h3c c ch3 oh ch3 jambal d, mong. j. chem., 23(49), 2022, 63-65 the explanation of reaction rate is necessarily connected to the tdfunction, because chemical activation of any compound depends on internal potential energy. from the point of the td a chemical reaction is a result of energy exchange of particles in reaction. to the best of author’s knowledge, there are no references on the organic reaction rate with the thermodynamic stability of the im and final products, except a few chemical study books which mentioned about such possibility [1, 2]. therefore, the discussion point is considering by myself as a new finding. references 1. morrison r., moid r. (1974) organic chemistry. publishing house, mir, moscow, 124-125; 157, 163, 165, 179, 188, 202, 203. (in russian) 2. reid k. (1972) course of physical organic chemistry. publishing house, mir, 185. (in russian) 65 recent and future of cement and concrete industriesa root of our development ts.erdenebat 1 , j.otgonlham 1 , e.oyunzul 1 , r.sanjaasuren 1 1 centre for chemistry and technology of new materials, school of chemistry and chemical engineering, national university of mongolia abstract: this paper considers that cement and concrete industry is contributing to our country development positively, and cement and concrete industry also can be reduced environmental pressure by;continuously reducing the co2 emission from cement production by increased use of biofuels and alternative raw materials as well as introducing modified low energy clinker types and cement with reduced clinker content or geopolymer cement and a new type concrete. exploiting the potential of waste bricks, cement and concrete recycling to decrease the emission of co2 . exploiting the thermal mass of concrete to create energy optimized solutions for heating and cooling residential and office buildings. keywords: climate change, co2 emission, brick, block, cementitious materials, cement and concrete, building and policymakers introduction eading branches of industry at present in mongolia are: coal mining for electric power station, ore dressing plant (copper, molybdenum, fluorspar, gold etc.), manufacture of building materials (cement, concrete, brick, lime etc.), manufacture of food products manufacture of light industry (clothing, cashmere, wool, leather and other products). cement is an essential material in today’s society because, it major constituent of concrete which act, as a fundamental element of any housing, commercial or infrastructure development. but the cost to manufacture cement is expected to increase from year to year, because of increasing energy prize. therefore scientists are attempting to prepare opc and other binding materials at lower cost by using agricultural and industrial wastes during clinkerization and by making blended cements. the measures are changed to decrease the cost of production, conserve mineral resources and protect the environment by beneficial disposal of wastes. so blended cements are usually blends of portland cement clinker with other finely ground materials (known as mineral admixtures) that take part in the hydration reactions and thereby make a substantial contribution to the hydration products. in last 10 years at the centre for chemistry and technology of new materials, national university of mongolia, our researchers have l 123 p 123-125 focused on obtaining of a new crystallizing component such as mineral admixtures, from natural aluminosilicate as kaoline, basalts and zeolites for blended cement additive materials. it was established that cement compressive strength increased by 100-250 kg/cm 2 when doped 5-10% of crystallizing component to the cement weight [3-6]. nowadays large numbers of blended cements are studied by re-using a variety of waste materials because of construction material demand due to increased infrastructure development in ulaanbaatar city and other places. in recent 2 years research capacity of the centre for chemistry and technology of new materials, national university of mongolia is focused to substitute some part of cement powder with waste alumosilicate material as crystallizing component that has also started in high developed countries since 2000. experimental recent and future tendency of cement and concrete industries in the world. batelle offered the following vision[?]: by 2020 cement companies will integrated in sustainable development of their global operations. they will known as innovators in industrial ecology and carbon dioxide management, are regarded as attractive employers, and have established relationships of trust with the communities in which they operate. the actions leading to this integrated sustainable development were suggested to be: 1) resource productivity the industry makes productive use of specific materials that otherwise would be discarded as waste, and applies state-of-the-art technologies and operating practices to cost-effectively improve its efficiency in energy and material consumption. 2) climate protection . the industry has implemented practical, technological, operational, and market-based strategies to significantly reduce emissions of co2 and is technologically positioned for even greater reductions in the future. 3) emission reduction . the industry has continuously improved its environmental practices and controls to achieve a minimal release of wastes or emissions that could adversely affect human health, ecosystems, and aesthetics. 4) ecological stewardship . the industry develops, operates, and retires its plants and quarries in a manner that minimises adverse impacts on the environment, including biodiversity and aesthetics, and protects and restores potentially impacted ecosystems. in doing so, it has earned support and recognition in the eyes of the community and regulators. 5) employee well-being . the industry builds and operates its facilities in a way that fosters employee satisfaction and productivity, provides fair wages and benefits, and is a safe, clean, healthy and desirable place to work. 6) community well-being . the industry is well understood and respected by the communities in which it operates because companies and plants make efforts to understand community needs and to help find ways to meet those needs. the industry has implemented measures to address nuisance disturbances associated with quarrying, transportation, and plant operations. 7) regional development . the industry and its associated value chain are viewed as positive contributors to local and regional economies and countries welcome the growth and prosperity of the industry because it is considered a critical component of infrastructure development and maintenance. 8) shareholder value creation. the industry provides competitive returns to investors and is able to readily secure capital resources. cement companies that have adopted sd practices are desirable investments for sustainable development index funds, and have increased their profitability and market share. the batelle report went further to recommend sustainable development goals and key performance indicators for cement manufacturers using the same list of actions given above. 124 conclusions recommended sustainable development goalsand key performance indicators /kpi/: issues goal kpi resource productivity conserve resources by using less energy and recycling wastes energy efficiency: tonnes of cement per megajoule (quarry and plant)  fuel material substitution rate (%)  raw material substitution rate (%) climate protection reduce greenhouse gas emissions net co2 (kg) emissions per tonne of cement emission reduction reduce environme ntal waste streams waste (non-product output) produced (kg) per tonne of cement (can include airborne emissions waterborne effluents, fugitive dust, and solid wastes) ecological stewardship reduce adverse impacts of quarrying potential kpis: investments in quarry restoration, overburden waste reduction, water use efficiency, biodiversity action plans etc employee wellbeing assure worker health and safety incident rate (injury, workrelated illness) per 200,000 hours (can include both employees and contractors) community wellbeing respect the needs of local communiti es potential kpis: frequency of community meetings, hours of volunteer community service, public health initiatives, community opinion surveys, etc regional development support host region economies potential kpis; job creation, local investment, technology transfer, contribution to gdp, etc shareholder value creation create superior value for shareholder s potential kpis: return on investment (roi), return on assets (roa), return on net assets (rona), return on capital employed (roce), economic value added (eva), etc. action plan worldwide agreed by association of cementitious material producers (wacmp): wacmp members have committed to reducing co2 emissions per ton of cementitious material and will correct subsequent analysis for trending action as substituting local waste material for blended cement and for concrete. building and our policymakers have to undertake health management programs with particular attention to clean air especially from the dust given to our domestic and citizens’ health. references: 1. world business council for sustainable development, towards a sustainable cement industry, geneva: wbcsd, 2002. 2. world business council for sustainable development, towards a sustainable cement industry summary report, geneva: wbcsd, 2002 3. world business council for sustainable development, the cement sustainability initiative: our agenda for action, geneva: wbcsd, 2002. 4. j.lukasik, j.s.damtoft, d.herfort, d.sorrentino, e.m.gartner, sustainable development and climate change initatives, proceeding of xiith iccc, montreal, canada, 2007, vol 1. p23-32 5. k.humphreys, m.mahasenan, toward a sustainable cement industry. climate change. an independent study commissioned to batelle by world business council for sustainable development, 2002 6. impact of europe’s changing climate, european environment agency report no2/2004 125 biochemical study on the meat and oil of mongolian fishes b.chantsalnyam 1 , ch.otgonbayar 1 , p.odonmajig 1 , n.tsevegsuren 2 1 institute of chemistry and chemical technology, mas 2 school of chemistry and chemical engineering, num e-mail:chantsaa_001@yahoo.com abstract: the objective of this study was to determine the meat quality and fish oil’s physical and chemical characteristics of the mongolian fishes: syrok (coregonus peled), and lenok (brachymystax lenok). lipid content was 3.1 to 14.15%, moisture was 72.14 to 80.5%, protein content was 8.54 to 9.8% and total mineral element was 0.5 to 3.1%. the caloric value lenok (brachymystax lenok) was 68.7 and syrok (coregonus peled) 142.8 kj/100g, respectively. minerals included potassium (46.32 to 52.22%), phosphorous (39.06 to 41.3%), calcium (3.26 to 5.87%), magnesium (2.08 to 3.97%) and silicon (1.14 to 2.24%), while zinc, iron and copper were present intrace amounts. eight non essential amino acids with total amount of 58.61 to 59.64% were identified, and histidine detected as in highest value in all the species, followed by arginine. the data showed that the mongolian fishes are of high nutritional value and good source of proteins, minerals as well as non essential amino acids. the physical and chemical characteristics of syrok (coregonus peled), and lenok (brachymystax lenok) fish oil were analyzed. these parameters are: iodine value (iv), peroxide value (pv), acid value (av), saponification value (sv), percentage of free fatty acid (%ffa), refractive index (ri) and colour. the extracted lipid content obtained from muscles of syrok and lenok was about 14.15% and 3.1%. the percentages of unsaturated fatty acids were higher than saturated fatty acids accounting for 74.37% and 25.6%, 83.83% and 16.46% respectively. keywords: syrok (coregonus peled), lenok (brachymystax lenok), protein, fish oil, macroand micro-elements, amino acid, infrared spectrophotometer introduction ish and other sea foods remain an important source of white meat for the human diet to its beneficial effect in reducing coronary heart diseases. this effects especially, due to the fat for the fish. fishes living in fresh water and ocean are contained oils which used as food and in medicine. fresh water’s and ocean’s fish oil are contained 14-35 highly unsaturated fatty acids. the fatty acid pattern of triacylglycerol and phospholipids of various fish oils were also assessed [1]. epidemiological studies on the last assure that omega-3 fatty acids are derived from fish and fish oil to decrease the risk of coronary heart disease, hypertension and stroke, and their complications [2]. the liver obtained from fish has high pharmacological activity (serve as hypolipidemic agent an antiarthristic agent) [1]. it is known to be that mongolia is rich in fishes. from ancient times mongolian people have been used fish oil as food and remedy in traditional and physical treatment of some illnesses. therefore, we have used fish syrok (coregonus peled) and lenok (brachymystax lenok) which are widely distributed in mongolia. the purpose of our study was biochemical study of meat obtained from two species of syrok (coregonus peled) and lenok (brachymystax lenok) experimental methods. moisture content was determined by gravimetric method. the ash content was determined by incinerating in a muffle furnance at 550 0 c. composition of the ash was measured f 12 mongolian journal of chemistry 13 (2012) 12-15 by the using an x-ray fluorescence. the total protein and protein nitrogen amount were determined by the kjeldahl method [1]. amino acids were determined by paper chromatography method using standard amino acid as a standards [3]. the total lipid was determined by the folch extract method [4]. results and discussion biochemical characteristics of fish’s meat is shown in table 1. table 1. biochemical characteristics of syrok’s and lenok’s meat c h a ra c te ri s ti c s syrok (coregonus peled) lenok (brachymystax lenok) our research kleimonov et al our research kleimonov et al content [5] content [5] moisture (%) 72.14 70-78% 80.5 mineral element (%) 2.95 1,3-1,5 3.07 1.1 protein (%) 8.54 18-19.2 9.8 18.2 fat (%) 14.15 3,1-11 3.1 3.8-7.7 calories (ccal) 142.8 141.8 68.7 146 a study result has been shown that the component of the minerals were 2.95%, 3.07%; protein 8.54%, 9.8%; and fat 14.15%, 3.1%, respectively compared to result of study of kleimonov. however, the lipid content in the meat of syrok was relatively high (14.15%). this is very valuable data and it is possible to be used as fat source. the concentration of mineral element was determined by using horiba x-ray fluorescence analyzer mesa500w (at the laboratory of chemical analysis, school of material and technology, must). the results of investigation were shown at table 2 and fig 1a, b. table 2. mineral content in meat of syrok and lenok ash content was emergenced by total 12 mineral elements in meat of syrok and lenok. the content of potassium was (39.06%, 52.22%) and phosphorium (41.30%, 46.32%), respectively. in all species the highest content calcium, magnium and siliconium were observed; the medium concentration zinc, iron and copper intrace amount. the composition of mineral elements of coregonus peled and brachymystax lenok were similar to the mineral composition of oreochromis niloticus. figure 1. x-ray fluorescence spectrum in meat of syrok (a), lenok (b) the contents of free and protein amino acids were determined by paper chromatographic method, results of study was shown in table 3. from results of this study we detected totally 14 amino acids in protein of two fish’s meat. there are 6 essential amino acids and 8 non essential amino acids. 13 mongolian journal of chemistry 13 (2012) table 3. the content of amino acids of syrok’s and lenok’s meat figure 2. chromatogram of amino acids the protein are contained the highest value of glutamic (10.66%, 11.3%), phenylalanine (8.45%, 7.34%), arginine (9.6%, 8.47%) and histidine (8.17%, 13.08%); the total non essential amino acid ranged 58.61-59.64%. in generally, the quality of oil was determined by its chemical characteristics. chemical characteristics in oil of twospecies of fishes are shown in table 4. the results showed that the iodine value of syrok’s oil (137.3 j2%) is relatively lower than lenok’s oil (207.6 j2%). this iodine value is depended on content of unsaturated fatty acids. on the other hand, unsaturated content of syrok’ oil was lower than lenok’s oil. table 4. chemical characteristics of fish oil infrared spectra of the fish’s oil were obtained on ft-ir spectrophotometer (at the associate laboratory of nature science, mas) for samples dispersed in kbr discs. figure 4 shows the infrared spectrum of the fish’s oil (syrok and lenok). among the absorption bands are observed common bands at 2950-3000 cm -1 c-c-h (sp 3 ) (stretching vibration) and 1730-1750 cm -1 c=o (streching vibration of ester group), 1465 cm -1 -ch2 (σ) (stretching vibration) as well as at 665-730 см -1 rch=chr 1 (cis-orientation of double bond).this explanation of spectrogram shows the all unsaturated fatty acids presented in cisstereoisomer form in both oils. table 5. the content of saturated and unsaturated fatty acids of fish’s oil, % the results showed that the content of unsaturated fatty acid’s in syrok’s and lenok’s oil were 74.37%, 83.83%, respectively. conclusions 1. the content of proteins and mineral elements of both fishes were similar. the syrok’s total oil amount was 14.15% and lenok’s was 3.1%. ash content was emergenced by total 12 mineral elements in b.chantsalnyam et al. 14 mongolian journal of chemistry 13 (2012) meat of syrok and lenok. the content of potassium was (39.06%, 52.22%) and phosphorium (41.30%, 46.32%), respectively 2. the syrok’s proten contained non essential amino acid 59.6%, essential amino acid 40.2%.; the lenok’s protein non essential amino acid is 58.6%, essential amino acid is 41.3% , respectively. 3. it is shown to be that lenok’ oil has high iodine value (207.62 j2%) due to high amount of unsaturated fatty acids thereas syrok’ oil has low iodine value (137.28 j2%). 4. the content of saturated and unsaturated fatty acids of the syrok’s and lenok’s oils were 25.6%, 16.5% and were 74.4%, 83.8%, respectively. references 1. saify s.s., akhtar s., khan, k.m., perveen s et al. 2003. a study on the fatty acid composition of fish oil from two marine fish, eusphyra blochii and carcharhinius bleekeri. turk j chem, 27:251-258. 2. simopoulos a.p., 2002. omega-3 fatty acids and cardiovascular disease: the epidemiological evidence. environmental health and preventive medicine, 6:203-209. 3. pleshkov b.p. (1985). practices of phytochemistry. p 90-95, 238-240 4. http://www.cyberlipid.org/extract/extr0005. htm 5. baasanjaw.g., tsend-ayush,ya.,(2001). fish of mongolia. p. 24-27, 35-36 6. elagba mohamed, h.a., (2010). proximate composition, amino acid and mineral contents of five commercial nile fishes in sudan. african journal of food science, 4: 650-654. 15 mongolian journal of chemistry 13 (2012) coumarins of peucedanum baicalense and cytotoxic activity of some isolated coumarins j.ganbaatar 1 , e.e.shults 2 , т.n.petrova 2 , m.м.shakirov 2 , d.оtgonsuren 1 , e.munkhbat 1 , d.badamkhand 1 , g.a.tolstikov 2 , d.batsuren 1 1 institute of chemistry and chemical technology, mas 2 novosibirsk institute of organic chemistry so ran abstract: it was shown that the plant peucedanum baicalense (redow.) koch is the source of valuable coumarins. five linear furocoumarins – isoimperatorin, fellopterin, 8-(1,1-dimethylallyloxy) bergapten, deltoin and marmesin were isolated from the roots of peucedanum baicalense (redow.) koch. the structures of these compounds were elucidated by spectroscopic methods. the cytotoxicity of isoimperatorin, fellopterin, 8-(1,1-dimethylallyloxy)bergapten and deltoin was studied on models of human сem-13, mt-4 and u-937 tumor cells. compound 8-(1,1dimethylallyloxy)bergapten had the greatest cytotoxicity. keywords: peucedanum baicalense, furocoumarins, isoimperatorin, fellopterin, 8-(1,1-dimethylallyloxy)bergapten, deltoin, cytotoxic activity, tumor cells, x-ray analysis introduction lants of the genus peucedanum sp. attract an attention of many researchers as a source of coumarins. previously, we isolated pyranocoumarin (+)-pterixin from peucedanum terebinthaceum fischer et turcz. of the mongolian flora [1]. plants belonging to peucedanum species characterized as the source of angular furocoumarins [2]. coumarins are considered as phytoalexins since plants produce them as defence substances when wounded or attacked by other organisms. coumarins can be suggested to be beneficial for the plants themselves as natural biocontrolling antipathogenic compounds as well as for humans as remedy for hyperproliferative skin deseases and as reference compounds in various bioactive tests. furthermore, coumarin containing plants are valuable as dietary supplements on the basis of their mild antimicrobial and anti-inflammatory effects. coumarins are also active in a plant metabolism, taking part in growth regulation. peucedanum baicalense (redow.) koch is a plant which widely spread throughout the mongolian territory [3]. to our knowledge a systematic phytochemical investigation of this plant has not been properly carried out yet. the aim of this study was to investigate coumarins of peucedanum baicalense (redow.) koch and cytoxic activity some of the pure coumarins. experimental roots of p. baicalense were collected near the place baruun buren, selenge aimag, mongolia in its butonization-flowering period in 2012. . air-dried ground roots of peucedanum baicalense (redow.) koch (400 g) were exhaustively extracted by maceration with 96% etoh (3x500 ml) at room temperature. the etoh extract was evaporated to an aqueous residue, which diluted with distilled water (1:1), and filtered. the filtrate was fractionated by solvents with increasing polarity, i. e., n-hexane, diethyl ether and ethylacetate, respectively. each fraction was condensed by a rotatory evaporator. then, the fractions were separated by column chromatography over silica gel. p 23 mongolian journal of chemistry 13 (2012) 23-27 plant material. extraction and fractionation the nhexane fraction was subjected to a column chromatography (eluent: chloroform, chloroform-ethanol 100:110:1) which afforded successive fractions from which crystallization from et2o isolated diacetylenenic alcohol falcarinol (7) as form of oil (35 mg, 0.008%) [9], coumarins (5 fractions, totally 0.8 g) and sterins. 130 mg isoimperatorin 1, 156 mg fellopterin 2 and 176 mg 8-(1,1dimethylallyloxy)bergapten 3. 1 н nmr spectral data showed that the nhexane fraction contains coumarins (30%) and sterins (12%) as main components. the column chromatography of the diethyl ether fraction afforded successive fractions from which 18 mg of 8-(1,1-dimethylallyloxy) bergapten (4) and 28 mg of deltoin (5) were crystallized from diethyl ether. . the etoac fraction (9.1 g) was dissolved in кон (150 ml, 10%), treated with dioxane (150 ml), heated at 80 o c for 2 h. then the mixture was cooled and neutralized with aqueous н2so4 (10%). coumarins were extracted with dichloromethane, which was removed by evaporating. the solid residue was chromatographed over silica gel to isolate marmesin (66 mg) 6. freshly distilled solvents and pure grade reagents were used. pure compounds were isolated by column chromatography over silica gel (acros, 0.0350.070 mm) with elution by chloroform: ethanol. the purity of the isolated compounds was monitored by tlc on silufol uv-254 plates using chcl3:etoh (10:1) and petroleum ether:et2o (4:1). melting points were determined on stuart smf-38 instrument. the ir spectra were recorded on a vector 22 spectrometer in kbr tablet, uv spectra were measured on a specord uv-vis spectrophotometer in ethanol (с = 10 -4 mol/l). nmr spectra of compounds in cdci3 or cd3od were obtained on bruker av-300 (operating frequency 300.13 mhz for 1 h and 75.47 mhz for 13 c and av-600 (600.13 and 150.96 mhz, respectively) spectrometers. proton-proton and carbon-proton shift correlation spectroscopy cosy, coloc, noesy were used for structure elucidation of substances. the multiplicity of resonances in 13 c nmr spectra was determined by recording spectra in j-mode. a dfs thermoscientific high-resolution mass spectrometer (ionizing electron energy 70 ev, vaporizer temperature 230-280 o c) was used to record mass spectra and determine molecular weights and elemental compositions. specific rotation [α] d was measured on polaar3005 polarimeter. results and discussion the greatest coumarin content was found in the n-hexane and diethyl ether fractions of the ethanolic extract. the substances of the root of peucedanum baicalense (redow.) koch were isolated by column chromatography over silica gel. the structures of the isolated compounds were established using spectral data and comparison to literature data. results of our study showed that peucedanum baicalense might be serve as a source of linear furocoumarins 1,2,3 which were known that for possessing valuable biological properties [4]. thus, fellopterin 2 possesses an antiinflammatory activity on animal inflammatory models [5]. isoimperatorin 1 is proved as an inhibitor of -secretase [6]. deltoin 5 has an anti-tumor activity against erlich cancer’s ascite cells [7]. isoimperatorin (1) (0.032% from sample weight), felloterin (2) (0.038%) and 8(1,1-dimethylallyloxy) bergapten (3) (0.044%) were isolated from n-hexane fraction of the etoh extract. bergapten (4) (0.0045% from weight of the root) and deltoin (5) (0.007% from weight of the roots) were isolated from the diethyl ether fraction. deltoin 5 was detected also in the ethyl acetate fraction. sixty six mg (0.016% from root’s weight) furocoumarin marmesin (6) was isolated after alkaline hydrolysis of the diethyl ether fraction and purified by subsequent column chromatography. we obtained data on the cytotoxic activity of furocoumarins 1-3 and 5 for tumor cells сem13 (т-cellular leucosis), mt-4 (т-cellular leukemia) and u-937 (monocyte leukemia) human tumor cells. cytotoxic activity has been established by means of determination of ccid50 – concentration inhibiting viability of tumor cells by 50%. the standard mtt test according to published recommendations [8] was used to determine ccid50. the selective 24 mongolian journal of chemistry 13 (2012) separation of the n-hexane fraction. separation of the diethyl ether fraction. hydrolysis of the ethyl acetate fraction structure elucidation of compounds. cytotoxicity of linear furocoumarins 1-3 and 5 against u-937 is noteworthy. compound 8-(1,1dimethylallyloxy)bergapten 3 had the greatest cytotoxicity against all tumor cells. compounds 2 had the least cytoxicity against cem-13 cell, whereas compound 5 had the least cytotoxicity against mt-4 cell. we could not find the relationship between structure and activity. it need to provide more detailed investigations of more isolated pure compounds. таble 1. cytotoxic activity of linear furocoumerins 1-3 and 5. characteristics of pure compounds. isoimperatorin {4-(3-methylbut-2-еne-1yl)оxy]-7h-furo[3,2-g]chromen-7-one} (1). m. p. 104-107°с. uv and mass spectra are identical to data in paper [10]. 1 н nmr spectra (сdcl3), δ, ppm, j (hz): 1.67 (3н, s, н-5), 1.77 (3н, s, н-6), 4.88 (2н, d, j = 7.0, н-2), 5.50 (1н, m, н-3), 6.23 (1h, d, j = 9.8, н-6), 6.92 (1н, d, j = 2.5, н-3), 7.11 (1h, s, н-9), 7.56 (1н, d, j = 2.5, н-2), 8.12 (1h, d, j = 9.8, н-5). 13 c nmr spectra, δ, ppm: 18.08 (c-5), 25.66 (c-6), 69.59 (с-2), 94.03 (c-9), 104.91 (c-3), 107.34 (c-4а), 112.38 (c-6), 114.03 (c-3a), 118.96 (c-3), 139.43 (c-5), 139.66 (c-4), 144.74 (c-2), 148.82 (c-4), 152.51 (c-8а), 157.98 (c-9a), 161.14 (c-7). figure 1. the molecular structures of isolated coumarins fellopterin {9-[(3-methylbut-2-ene-1-yl)oxy]4-methoxy-7h-furo[3,2-g]chromen-7-оne} (2). m.p. 101-104°с (from ether). in paper [11] m.p. 103.5-104.5°с. 1 н nmr spectra (сdcl3), δ, ppm, j (hz): 1.68 (3н, s, н-5), 1.72 (3н, s, н-6), 4.15 (3н, s, сн3о), 4.83 (2н, d, j = 7.2, н-2), 5.59 (1н, m, н-3), 6.26 (1h, d, j = 9.7, н-6), 6.97 (1н, d, j = 2.4, н-3), 7.60 (1н, d, j = 2.4, н-2), 8.10 (1h, d, j = 9.7, н-5). 13 c nmr spectra, δ, ppm: 17.97 (c-5), 25.68 (c6), 60.71 (сн3о), 70.27 (с-2), 104.92 (c-3), 107.51 (c-4а), 112.72 (c-6), 114.49 (c-3a), 119.77 (c-3), 126.70 (c-9), 139.22 (c-5), 139.50 (c-4), 144.26 (c-4), 144.28 (c-8a), 144.96 (c-2), 150.70 (c-9a), 160.37 (c-7). mass-spectra, m/z (irel., %): 302 (0.02), 301 (0.11), 264 (0.2), 246 (0.11), 232 (100), 217 (77), 203 (2), 189 (10), 188 (3), 161 (5), 76 (2), 69 (5). found: [m + -68] 232.0364. с17н16o5. calculated: м 300.0992. 8-(1,1-dimethylallyloxy)bergapten {9-[(2methylbutyl-3-ene-2-yl)оxy]-4-methoxy-7hfuro[3,2-g]chromen-7-оne} (3). m.p. 88-90°с (from ether). uv-spectra (ethanol), λmax/nm (lgε): 222 (4.32), 248 (4.17), 265 (4.17), 306 (4.13). 1 н nmr spectra (сdcl3), δ, ppm, j (hz): 1.54 (3н, s, н-5), 1.56 (3н, s, н-6), 4.17 (3н, s, сн3о), 4.99 (1н, dd, j = 10.0, 1.2, н-4а), 5.11 (1н, dd, j = 16.8, 1.2, н-4б), 6.23 (1h, d, j = 9.7, н-6), 6.29 (1н, dd, j = 16.8 and 10.0, н-3), 6.96 (1н, d, j = 2.4, н-3), 7.55 (1н, d, j = 2.4, н-2), 8.08 (1h, d, j = 9.7, н-5). 13 c nmr spectra, δ, ppm: 26.38 (c-5,6), 60.48 (сн3о), 84.12 (с-2), 104.94 (c-3), 107.24 (c4а), 112.72 (c-6), 113.71 (c-4), 113.98 (c-3a), 124.61 (c-9), 139.21 (c-5), 142.70 (c-3), 144.67 (c-4), 144.90 (c-8a), 146.26 (c-2), j. ganbaatar et al. 25 mongolian journal of chemistry 13 (2012) 152.84 (c-9а), 160.45 (c-7). mass-spectra, m/z (irel., %): 302 (0.03), 301 (0.08), 300 (0.02), 243 (4), 233 (13), 232 (100), 231 (4), 218 (9), 217 (72), 189 (10), 188 (3), 175 (2), 161 (5), 133 (2), 104 (1.4), 95 (1.3), 89 (1.1), 69 (3). found: [m + ] 301.1069. с17н16o5. calculated: м 300.0992. bergapten {4 – methoxy – 7 h-furo[3,2-g] chromen-7-оne} (4). m.p. 185-187°с (from ether). 1 н nmr spectra (сdcl3), δ, ppm, j (hz): 4.28 (3н, s, сн3о), 6.28 (1h, d, j = 9.8, н-6), 7.00 (1н, d, j = 2.4, н-3), 7.15 (1н, s, н9), 7.61 (1н, d, j = 2.4, н-2), 8.18 (1h, d, j = 9.8, н-5). 13 c nmr spectra, δ, ppm: 60.00 (сн3о), 94.3 (с-9), 105.04 (c-3), 106.42 (c4а), 112.32 (c-3a), 112.52 (c-6), 139.43 (c-5), 144.56 (c-2), 144.92 (c-4), 148.88 (c-8a), 152.89 (c-9а), 161.35 (c-7). mass-spectra, m/z (irel., %): 216: [m + ] (100), 201 (28), 188 (10), 145 (40), 89 (18), 51 (30). с12н8o4. deltoin (2s)-2-{2-[((z)-2-methylbut-2enoyl)оxy]propan-2-yl}-2,3-dihydro-7hfuro[3,2-g]chromen-7-оne (5). m.p. 105107°с, [α]d = -38.8 (c 0.9, chcl3). in paper [10] m.p. 106-107°с [α]d = -42.3 (c 0.62, chcl3). uv and mass spectra are identical to data in paper [11]. 1 н nmr spectra (сdcl3), δ, ppm, j (hz): 1.66 (3н, s, н-2b), 1.67 (3н, s, н2c), 1.81 (3н, s, н-6), 1.87 (3н, broad d, j = 7.0, н-5), 3.25 (2н, m, н-3), 5.06 (1н, dd, j = 9.0 and 7.8, н-2), 5.71 (1н, m, н-4), 6.18 (1h, d, j = 9.6, н-6), 6.68 (1н, s, н-9), 7.20 (1н, s, н-4), 7.55 (1h, d, j = 9.6, н-5). 13 c nmr spectra, δ, ppm: 15.81 (с-5), 20.78 (с-6), 21.71 (сн3), 22.45 (сн3), 29.86 (c-3), 89.19 (c-2), 82.12 (c-2а), 97.82 (с-9), 112.32 (c-4а), 112.62 (c-6), 123.81 (c-3a), 124.16 (c-4), 127.65 (с-3), 138.71 (с-4), 143.02 (c-5), 155.62 (c-8a), 161.25 (c-7), 163.73 (c-9а), 166.41 (с-2). mass-spectra, m/z (irel, %): 328 [m + ] (2), 229 (26), 228 (41), 213 (100), 214 (17), 185 (19), 176 (15), 159 (21), 115 (15), 103 (24), 102 (17), 83 (65), 55 (49). found: [m + ] 328.1309. с19н20o5. calculated: м 328.1311. marmesin {(2s)-2-(2-hydroxypropan-2-el)2,3-dihydro-7h-furo[3,2-g]chromen-7-one} (6). m.p. 186-189°с, [α]d = +22.5 (c 0.8, chcl3). in paper [11] m.p. 190-191°с [α]d = +25.6 (c 0.51, chcl3). 1 н nmr spectra (сdcl3), δ, ppm, j (hz): 1.23 (3н, s, н-2b), 1.37 (3н, s, н-2c), 1.87 (1н, broad s, oн), 3.25 (2н, m, н-3), 4.76 (1н, dd, j = 9.0 and 7.8, н-2), 6.20 (1h, d, j = 9.6, н-6), 6.71 (1н, s, н-9), 7.20 (1н, s, н-4), 7.60 (1h, d, j = 9.6, н-5). 13 c nmr spectra, δ, ppm: 24.51 (сн3), 26.22 (сн3), 30.54 (c-3), 72.09 (c-2а), 91.12 (c-2), 98.61 (с-9), 113.11 (c-4а), 112.44 (c-6), 125.12 (c-3a), 122.96 (c-4), 143.56 (c-5), 155.81 (c-8a), 161.38 (c-7), 163.35 (c-9а). mass-spectra, m/z (irel, %): 246 [m + ] (12), 231 (8), 230 (22), 229 (16), 213 (11), 201 (15), 199 (10), 189 (61), 187 (100), 175 (12), 160 (25), 131 (20), 77 (18), 59 (38). с14н14o4. falcarinol (panaxinol), [3(r)-(9z)-hepta-1,9diene-4,6-diyn-3-оl, colourless oil, [α]d = -33.7 (c 1.2, chcl3). according to [9] [α]d = -5 (c 0.05, ch2cl2), [12] – [α]d = -34.6 (c 8.09, chcl3). 1 н nmr spectra (сdcl3), δ, ppm, j (hz):0.88 (t, 3н, j = 6.8, н-17), 1.22-1.38 (m, 10н, н-12,13,14,15,16), 1.96-2.18 (2н, m, h11), 3.01 (2h, d, j = 6.9 h-8), 4.89 (1h, broad s, h-8), 5.21 (1h, broad d, j = 4.9, h-3), 5.32 (1h, m, jgem = 10.3, h-1б), 5.39 (1h, m, h-9), 5.46 (1h, m, jgem = 10.3, h-1a), 5.50 (1h, m, h-10), 5.90 (1h, ddd, j = 16.3, 11.2, 5.4, h-2). 13 c nmr spectra, δ, ppm: 136.8 (c-2), 133.0 (c10), 122.2 (c-9), 117.3 (c-1), 80.6 (c-7), 74.9 (c-4), 71.6 (c-5), 64.5 (c-6), 63.2 (c-3), 31.6 (c-15), 28.8 (c-12), 29.0, 29.5 (c-13,14), 27.8 (c-11), 22.4 (c-16), 16.9 (c-8), 14.5 (c-17). conclusions 1. for the first time five linear furocoumarins– isoimperatorin, fellopterin, 8-(1,1dimethylallyloxy)bergapten, deltoin and marmesin were isolated from the roots of peucedanum baicalense (redow.) growing in mongolia. the molecular structures of these compounds were elucidated by spectroscopic methods. 2. the cytotoxicity of some compounds was studied on models of human сem-13, mt-4 and u-937 tumor cells. compound 8-(1,1dimethylallyloxy)bergapten had the greatest cytotoxicity. this work was supported by the russian foundation for basic reasearch (project № 1203-92200). 26 mongolian journal of chemistry 13 (2012) acknowledgements references 1. j. ganbaatar, b. gantumur, s.а. оsadchii, e.e. shults, м.м. shakirov, g.а. тоlstikov, chemistry of natural products, 468 (2008). 2. e.e. shults, j. ganbaatar, т.n. petrova, m.м. shakirov, i.yu. bagryanskaya, v.v. таraskin, l.d. radnaeva, d. оtgonsuren, а.g. pokrovskii, g.а. тоlstikov, chemistry of natural products, 194 (2012). 3. l. p. маrkova, l.м. belenovskaya, т.p. nadejina. wild useful plants of the flora of the mongolian peoples republic. leningrad. 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(1997). j. ganbaatar et al. 27 mongolian journal of chemistry 13 (2012) fourier transform infrared spectroscopy study on cation adsorption on viscose rayon succinate khasbaatar dashkhuu 1 and ung su choi 2 1 institute of chemistry and chemical technology, mongolian academy of sciences, peace avenue 13330, ulaanbaatar 210351, mongolia. 2 energy mechanics research center, korea institute of science and technology, seongbuk gu, hawolgok dong 39-1,seoul, korea. abstract: ion-exchange materials have been considered as suitable material for the recovery of heavy metals in water. a viscose rayon succinate, synthesized from viscose rayon and succinic anhydride in presence of dmso, to remove trace bivalent metal ions such as ag + , cu 2+ , ni 2+ , pb 2+ , zn 2+ and cr 3+ , was studied using ft-ir for the behavior of metal adsorption. both esterification and carboxyl bonding of viscose rayon succinate were assigned essentially at 1729 and 1693cm -1 , respectively. and the essential band of bonding between metal and the material was determined at 1625cm -1 . the available adsorption capacity of this fiber was 6.2mequiv/g. the adsorption of metal ions on the viscose rayon succinate follows the order of cu 2+ >cr 3+ >ni 2+ >pb 2+ >zn 2+ >ag + with maximum adsorptions capacities 4.2, 1.42, 0.91, 0.83, 0.69 and 0.35 mmol/g, respectively. keywords: chelating fiber, cellulose, viscose rayon, metal adsorption, carboxyl group, ft-ir, ph selectivity introduction s the high rate of industrial development in the world, contaminants of heavy metals in wastewater originated from industries are increasing as that influence to the balance of our environment as well as human life. some cancers and serious diseases may be caused from these metals [1-3]. there are lots of methods including chemical precipitation [4], electrolytic methods [5], and adsorption onto activated carbon [6], membrane process [7], and chelating polymer [8] to reduce the heavy metals in wastewater. more recently, researches have been undertaken to extend to the design of polymeric based ion-exchange fibers for the removal of heavy metals. several of designs and applications of chelating fibers have received increased attraction and been investigated [8-10]. in particular, scientists have intensified many efforts to modify fibers in such a way that inherent fiber properties are preserved [11]. whereas, most chelating polymers are composed of petroleum-based synthetic polymers [12-14]. furthermore, the used synthetic chelating polymers often produce on secondary environmental pollution by contaminating the soil or air. in addition, these are usually nonrenewable and nondegradable [14]. viscose rayon is regenerated from cellulose which has renewability [15] and biodegradability [16] and there is more cellulose on earth than any other organic substance [17]. cellulose itself has a very low ion exchange capacity [18, 19]. the ionexchange properties of cellulose are similar to other ion exchange resins, but cellulose ion exchangers are more finely divided than a 136 p 136-141 ordinary ion exchange resins, present a larger surface, because of their porous structure, permit the entrance or attachment of larger molecules which are not readily adsorbed by other resins. the rate of exchange is also very rapid in the case of cellulose ion exchangers [19]. one very attractive feature of cellulose is its chemical composition, with a large amount of relatively easily accessible hydroxyl groups that can be used for attachment of a variety of functional groups. succinic groups can introduce at positions c2, c3, and c6 of each anhydroglucose unit, where available hydroxyl groups exist, in viscose rayon. the vicinal carboxyl groups of succinate are separated by a single bond and are free rotation which allows more flexibility in accommodating the special requirements of larger cations [20]. in this study, carboxylic acid functionalities were introduced to viscose rayon by chemical modification of succinic anhydride in presence of dmso. the modified viscose rayon was then characterized by fourier transform infrared, 13 c nuclear magnetic resonance spectroscopes and sem. adsorption behavior of metal ions such as silver, copper, zinc, nickel, lead and chromium on the synthesized viscose rayon succinate were demonstrated using quantitative analyses and ft-ir under various ph which is one of the fundamental characteristics of aqueous solutions. experimental materials.viscose rayon felt, succinic anhydride and dimethylsulfoxide /dmso/ were used for substrate, reagent and solvent and purchased from /company of viscose rayon/, dea jung chemicals & metals co., ltd., korea, respectively. ag(no3), cu(no3)2∙xh2o, ni(no3)2∙6h2o, zn(no3)2∙6h2o, pb(no3)2 and crcl3∙6h2o (sigma chemical co.) were utilized for testing of being absorbed those metal ions on the ion-exchanger and, 1n naoh and 1n hno3 were supplied from sigma chemical co. synthesis of ion-exchange viscose rayon. an ion-exchange viscose felt was synthesized from viscose rayon felt (ca. 10cm x 10cm, 5g and 2.8mm thick), succinic anhydride (50g), and dmso(500ml) for 5h at 80 0 c with spin. the synthesized viscose rayon succinate washed by cold and hot distilled water and dried in a freeze drier at 50 0 c, 5 torr , for 24 hours. measurements. fourier transform infrared spectra (4000-200cm -1 , kbr disc) were recorded on a gx ftir, perkinelmer spectrometer. 13 c nmr was taken on bruker msl200 spectrometer in the solid state. the polymers were investigated in a scanning electron microscopy (sem). the ph values were measured using a ph 300 (hanna instruments) digital ph meter. the quantitative analysis of adsorbed ions was carried out with atomic adsorption spectrophotometry (aas; spectraaa 800, varian). quantitative analysis of the adsorption of ag + , cu 2+ , ni 2+ , pb 2+ , zn 2+ and cr 3+ 100 ml and ph adjusted solutions including 10mm ag + , cu 2+ , ni 2+ , pb 2+ , zn 2+ and cr 3+ , separately, and 0.1g of the viscose rayon succinate were placed in erlenmeyer flasks and shaken for 24 h at 200rpm. the concentration of ionic metal not removed from the solution was determined by aas. the chelating fibers with metal were dried at 40 0 c in a vacuum oven for 24 hours and characterized by ft-ir spectrometer. in this study, the concentrated hno3 was used to adjust the phs of metal ion aqueous solutions. in order to obtain an adsorption capacity of the chelating fiber, 0.1g of the viscose rayon succinate and 100ml of 0.1n naoh solution in an erlenmeyer flask was shaken for 24 h at 200rpm, then a 30ml of solution sampled from the shaken solution was measured using an auto-titrator (metrohm 728, swiss) utilizing a 0.1n hcl solution as back titration. results and discussion the viscose rayon succinate was successfully synthesized from viscose rayon and succinic anhydride in presence of dmso (scheme 1). the adsorption capacity of the viscose rayon succinate is 6.2meq/g. figure 1 shows 13 c nmr of viscose rayon and the chelating fiber. the application of 13 c nmr is more successful than 1 h nmr for the study of cellulose and cellulose derivatives [21]. the chemical shifts carbons in viscose 137 rayon (a) are obtained as typical chemical shifts of cellulose. resonances for the internal (b) and (d) carbons in viscose rayon and viscose rayon succinate are observed at 105 and 87.3ppm, and 105 and 88ppm, respectively. obviously, it is seen that no degradation is occurred in terms of the synthesizing according to that almost no chemical shifts of (b) and (d) carbons of the viscose rayon succinate are significantly observed. in 13 c nmr spectra of (b), four chemical shifts (g), (h), (i), (j) of carbons are assigned at 173.8, 176, 39.8, and 29.9ppm, respectively. those signals can demonstrate succinic groups successfully introduced on viscose rayon, in particularly resonance line for the (g) of the viscose rayon succinate at 173.8ppm [29]. the signals are shown in table 1. fig. 1, 13 c nmr spectra of (a) vr and (b) vrs typical sem image of the viscose rayon which has a diameter of 9m, exhibits a characteristic serrated surface [12] in fig.2(a). a surface of the viscose rayon succinate is shown in fig.2(b). a slight difference of the viscose rayon succinate can be observed surface rougher than that of the viscose rayon. fig. 2, sem images of (a) viscose rayon and (b) viscose rayon succinate. ft-ir spectra of viscose rayon felt (a), the viscose rayon succinate (b), the viscose rayon succinate with metal complexes such as cu 2+ 4.2mmol/g at ph 5 (c), ni 2+ 0.91mmol/g at ph 6 (d), zn 2+ 0.69mmol/g at ph 6.3 (e), pb 2+ 0.83mmol/g at ph 5 (f), ag + 0.35mmol/g at ph 8 (g), and cr 3+ 1.42mmol/g at ph 4 (h) are shown in fig. 3. all of ir spectra exhibit a broad and intense band in the 3000-3700cm 1 region which is assigned to free and hydrogen bonded oh stretching vibration. in most hydrocarbons, the ch2 asymmetric stretch is near 2930 cm -1 . the ir spectra except viscose rayon are characterized by absorption a symmetrical band around 2930 cm -1 (ch2 and ch groups) and this band is switched from absorption peak at 2891cm -1 , which is assigned to symmetric band ch of viscose rayon. a peak at 1644 cm -1 was assigned to water absorption in viscose rayon. despite a peak of viscose rayon spectrum is observed at 1160 cm -1 , it should be mentioned that the very strong band at 1163 cm -1 is assigned to the c-o stretching in the esters (o(c=o)chch2) of viscose rayon succinate. carboxylic esters, and carboxylic acids show a strong c=o stretching absorption band in the region of 1870-1540cm -1 [22]. this sharp peak is not observed in spectra of viscose rayon. new strong peaks of viscose rayon succinate with metal ions such as ag + , cu 2+ , ni 2+ , pb 2+ , zn 2+ and cr 3+ , appeared at a range of 1721-1739 cm -1 . furthermore, not big intensity peaks were found at 1639cm -1 , 1623cm -1 , 1641cm -1 , 1546cm -1 , 1639 cm -1 , and 1737 cm -1 corresponded to ionic bonding formed between coo with ag + , cu 2+ , ni 2+ , pb 2+ , zn 2+ and cr 3+ , respectively. the bonds between carboxyl groups and metals can influence to the intensity of peak of carboxyl group of the viscose rayon succinate. it is explained that the band of carboxyl groups with metal shifted to low frequency because of this bond to hinder vibration of carboxyl groups. on the other hand, the absorption of the carboxyl group shifted to lower wavelength was attributed to the absorption of carboxyl group with metals according to the formation of the chelating complex which weakens the double bonding property of carbonyl groups owing the coordinate bond between oxygen atoms of carbonyl groups and metal ions [23]. in general, there is a 138 correlation between frequency of peak attributed to carboxyl-metal bond and the ionic radii. this result indicates that the ionic radius increases, the frequency decrease [24, 25]. definitely, the formation of the chelate ring and its resultant geometry has a direct effect on the coo bond. it is interesting to note that frequency of zn 2+ is higher than cu 2+ . the peak assigned at 1639cm -1 of viscose rayon succinate with zn 2+ corresponds to a syn-syn bridging carboxylate ligand [26]. (h) 4000 3000 2000 1500 1000 500 wavenumbers (cm -1 ) a b so rp ti o n s (a b s. u n it s) (a) (b) (c) (d) (e) (f) (g) fig. 3. ft-ir spectroscopy of (a) vr, (b) vrs, vrs with metal ion complexes: (c) cu 2+ 4.2mmol/g at ph 5, (d) ni 2+ 0.91mmol/g at ph 6, (e) zn 2+ 0.69mmol/g at ph 6.3, (f) pb 2+ 0.83mmol/g at ph 5, (g) ag + 0.35mmol/g at ph 8, and (h) cr 3+ 1.42mmol/g at ph 4. figure 4 shows quantitative analyses of heavy metals adsorbed on the viscose rayon succinate under increasing ph. the difference between heavy metal ions adsorbed on the viscose rayon succinate attributes with the chemical and physical properties of metal ions and chelating agent in ph range of 1.0-8. for increasing ph, the behavior of the viscose rayon succinate turns to more reactivity with metals. in acid medium, the viscose rayon succinate is highly protonated and it reduces the attracting effect of the metal ion due to lack of negative charge. the 4.28 mmol of cu 2+ in 1 liter aqueous solution adsorbed on a gram of the viscose rayon succinate at ph 5.01 is the maximum adsorption. as seen figure 4, the maximum adsorptions of metal ions can be ordered as cu 2+ >cr 3+ >ni 2+ >pb 2+ >zn 2+ >ag + . cu 2+ was much more quantity as compared from other metal ions under the same conditions. the values of kf , defined as the formation rate constants between coo and metal ions, increase with the charge of the metal ion. kf values of ag + , cu 2+ , ni 2+ , pb 2+ , zn 2+ and cr 3+ , were found to be 1.5x10 12 , 7.5x10 9 , and 3x10 7 for ch3coo , respectively [27]. moreover, the equilibrium quotients (logk) represent also the same order as 2.3, 2.01, and 1.08 [28] for cu 2+ , pb 2+ , and zn 2+ , respectively. the adsorptions under the ph range were also investigated through ft-ir spectroscopy. 1 2 3 4 5 6 7 8 0,0 0,5 1,0 1,5 2,0 2,5 a d so rp ti o n ( m m o l/ g ) ph ag + cu 2+ ni 2+ zn 2+ pb 2+ cr 3+ fig. 4. effect of ph on the adsorption of ag + , cu 2+ , ni 2+ , pb 2+ , zn 2+ and cr 3+ ft-ir spectra of cu 2+ , which is on behave of spectra of ag + , ni 2+ , pb 2+ , zn 2+ and cr 3+ ions, adsorbed on the viscose rayon succinate with increasing ph are shown in figure 5. the intensities observed at 1724 cm -1 , 3436cm -1 and attributed to ionic bonded between carboxyl and copper, and hydrogen bonded oh, respectively, decreased with decreasing ph. a reason of the decreased intensity at 3436cm -1 (o-h…o) is that the number of hydroxide carried by metal ions was decreased due to the reduced amount of metal ions bonded with the chelating fiber. at the same time by decreasing ph, the intensity of the peak assigned at 1736cm -1 (c=o) increased as switching from reduced amount of ionic bonds between carboxyl group and copper. the peak observed at 1656cm -1 assumed to the bond shown in fig.6. (b) due to oxygen of a single carboxyl do not depend each other through the metal ion. moreover, fig. 6 (a) they linked through the metal ion. in this case, their vibration is hindered and calculated to lower frequency. 139 (f) (e) (d) (c) (b) (a) 4000 3000 2000 1500 1000 500 a d s o rp ti o n ( a d s . u n it s ) wavenumbers (cm -1 ) fig.5. ft-ir spectra of vrs and vrs with cu 2+ increasing ph; (a) ph 2.5; (b) ph 3; (c) ph 3.5; (d) ph 4; (e) ph 4.5; (f) ph 5 conclusions in this study, viscose rayon succinate (chelating fiber) was synthesized from viscose rayon and succinic anhydrate in presence of dmso. the synthesis was successfully confirmed by 13 c nmr and ftir. moreover, a new very strong peak appearing at 1733cm -1 was attributed to c=o bonds. the general trends of decreasing frequency with increasing ionic radii, which were observed for the viscose rayon succinate metal ions complexes, were confirmed in the ft-ir spectra. an adsorption capacity of the viscose rayon succinate was 6.2meq/g. identical feature for each adsorptions frequency decreasing with decreasing ph were observed. the maximum metal ions adsorbed can be classified as cu 2+ >cr 3+ >ni 2+ >pb 2+ >zn 2+ >ag + and such as 4.2mmol/g, 1.42mmol/g, 0.91mmol/g, 0.83mmol/g, 0.69mmol/g, 0.35mmol/g, and respectively. amount of adsorption cu 2+ on viscose rayon succinate is much higher than other metal ions under the same conditions. acknowledgement the authors would like to acknowledge the financial support from korea institute of science and technology. references 1. kaiser, j. 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(1958) j. am. chem. soc. 81, 816. 26. william clegg, dale r. harbron, christopher d. homan, paul a. hunt, ian r. little and brian p. s, (1991) inorg. chim. acta. 186, 51. 27. martell, a. e. (1978) coordination chemistry volume 2, acs monograph 174. 28. martell, a. e., smith (1977) r. m. critical stability constants, volume 3: other organic ligands. 29. anita j. brandolini, deborah d. hills (2000) nmr spectra of polymers and polymer additives. 141 21 mongolian academy of sciences mongolian journal of chemistry the institute of chemistry & chemical technology mongolian journal of chemistry 15 (41), 2014, 21-26 introduction azo dyes comprise of almost half of global production (700000 t/y) and during dyeing operation process about 20% of them end up in wastewater. in ulaanbaatar, there are 27 cashmere treatment factories that 340 ton water per day for industrial usage. 11 of them are dyeing factories which conduct bleaching and dyeing process. these factories use acid and reactive dyes such as lanaset yellow, lanasol red, lanasol black etc. one of these organic dye is reactive blue 50 that is 1-amino-4-bromo-9,10-dioxo9,10-dihydroanthracene-2-sulfonic acid (fig. 1). it consists of sulfo group containing reactive dyes which have been especially developed for wool dyeing. its’ molecule contains two bromoacrylamide reactive groups which form a covalent bond with the nucleophilic groups of the wool’s amino acids during the dyeing process, resulting in outstanding wet fastness properties. however these organic dyes are stable, non-biodegradable, cancerogenic substances and negative impact on environment due to their complex aromatic molecular structure. there are many physical, chemical and biological methods used for the removal of dye from aqueous solution, including chemical coagulation, flocculation, chemical oxidation, photochemical degradation, membrane filtration, reverse osmosis, and aerobic/ anaerobic degradation. all of these techniques suffer from one or more limitation, and none of them is able to completely remove dyes from wastewater. thus, there is a need to find alternative methods that are effective in removing dyes from large volumes of effluent. zero valent iron nanoparticle technology is becoming an increasingly popular choice for treatment of hazardous and toxic wastes, and for remediation of contaminated sites. for many types of reactive dyes, various adsorbent materials have been investigated as an adsorbent materials. for example, adsorption behavior of reactive dyes (reactive blue 2, reactive red 2, reactive yellow 2) on activated carbon was studied at various experimental conditions. adsorption of these dyes was fitted with the langmuir and freundlich isotherm models and isotherm parameters were calculated [1]. r.hariharasuthan et.al. studied the adsorption of reactive blue 4 onto mgo in sorel’s cement and revealed the experimental data correlated reasonably well with the langmuir adsorption isotherm due to values of adsorption capacity and separation factor study of the adsorption of reactive blue 50 on zero valent iron d.sarangerel*, a.altangerel, b.munkhzaya, b.sukhbaatar department of chemistry, faculty of arts and sciences, national university of mongolia, ulaanbaatar 14201 article info: received 15 november 2014; revised 28 november 2014; accepted 01 december 2014 in this study, removal efficiency of the reactive blue 50 and adsorption mechanism on the zero valent iron were investigated. reactive blue 50 which is used to wool and cashmere dyeing were selected due its non-biodegradable and metabolic stability. zero valent iron particle has been synthesized by chemical method. a systematic characterization of zero valent iron was performed using x-ray diffractometer, scanning electron microscope and infrared spectrometer analysis. the optimal condition of adsorption was determined as initial reactive dye 50 concentration of 150 mg·l-1, zero valent iron mass of 0.2 g and solution ph of 6.0 at room temperature. at optimal condition, organic dye removal in a real wastewater sample from tsombon knit llc was 99.5%. keywords: adsorption, reactive dye, zero valent iron * corresponding author: e-mail: sarangerel@num.edu.mn doi: http://doi.dx.org/10.5564/mjc.v15i0.316 o o nh2 nhhn o br br s s o o -o oo ona+ na+ fig. 1. chemical structure of reactive blue 50 molecule mailto:sarangerel@num.edu.mn http://doi.dx.org/10.5564/mjc.v15i0.316 22 mongolian journal of chemistry 14 (40), 2013, 21-26 [2]. there are some studies on adsorption of reactive blue dyes on various adsorbent materials, almost all of them have studied that experimental data was fitted to the langmuir isotherm model [3, 4]. adsorption of different types of organic dye such as basic yellow, vat dye, acid dye and aniline blue dye onto zero valent iron were investigated in the basis of influence of ph, ratio of adsorbent and dye concentration, equilibrium isotherm and kinetics [5-8]. in this study, removal efficiency of reactive blue dye 50 in account of ph, initial concentration, adsorbent mass and the adsorption equilibrium were investigated. experimental preparation of zvi: zero valent iron (zvi) was synthesized through a chemical reduction method using sodium borohydride as a reducing agent. 2.703 g fecl3·6h2o was dissolved in 100 ml distilled water and stirred well. in another beaker 0.6053 g sodium borohydride was dissolved in 100 ml distilled water. the borohydride solution is added drop by drop into iron chloride solution with vigorous hand stirring in excess amount. ferric iron was reduced and zvi particles precipitated instantly according to the following reaction: 2fecl3 + 6nabh4 +18h2o ↓2fe o (хат) +6b(oh)3 +21h2 +6nacl after the first drop of sodium borohydride solution, black solid particles immediately appeared and then the remaining sodium borohydride is added completely to accelerate the reduction reaction. then the obtained mixture was conditioned in thermostat to separate the black iron nanoparticles from the liquid phase. the solid particles were washed with 25 ml pure ethanol to remove water. the synthesized nanoparticles were finally dried in oven at 323 k overnight. a scanning electron microscope (sem) and x-ray diffractometer (xrd) techniques were used to characterize the synthesized zvi. sem analysis was done using a semtrac mini with 30kv and high vacuum mode. particles were poly and randomly distributed [10]. it reveals that zvi particles were agglomerated due to drying process. powder xrd analysis was done using xrd panalytic. xrd of zvi samples was recorded over a 2θ range of 6-70 o . the characteristic broad peak at 2θ of 44.7 o indicated that the fe o and broad peak at 2θ of 35.8 o indicated that the feo and fe2o3 [5, 11]. adsorption studies: the adsorption experiments were carried out at the desired ph value, contact time, sorbent-zero valent iron mass and initial dye solution concentration level using the necessary sorbent in a 500 ml conical flask containing 250 ml dye solution at room temperature. zero valent iron mass from 0.1 g to 1 g of dry mass were used while the initial reactive blue 50 concentration varied from 100 mg·l -1 to 500 mg·l -1 and the ph from 2 to 12. before analysis, samples of solution were filtered through a filter paper (45mm). the solution ph in batch experiments was measured with a ph/conductivity meter (sanxin 521). the ph was adjusted to the range of 2-12 using 1.0 m naoh or 1.0 m hcl. different experimental parameter such as sorbent mass, ph and initial dye concentration were optimized to obtain maximum removal of reactive blue 50 using zvi. the batch sorption experiments were carried out in 300 ml erlenmeyer flasks where 0.20 g of the adsorbent and 250 ml of the reactive blue 50 solutions (100, 150, 200, 250 mg·l -1 ) were added. the ph of all solutions in contact with adsorbents was found to be 6.0. the erlenmeyer flasks were subsequently capped and agitated in an isothermal shaker at constant speed and 20 o c for 20 minutes to achieve equilibration. the amount of adsorption at equilibrium, qe (mg·g -1 ), was calculated by the following equation: results and discussion optimal condition effect of рн on reactive blue 50 sorption: the ph is a very important parameter that affects dye sorption process on zero valent iron [9, 12]. the sorption experiment was carried out for the removal of reactive blue 50 using zero valent iron in the ph range 2.0-12.0. solution with concentration of 150 mg·l -1 of reactive blue 50 and 0.5 g of sorbent mass were used for this study. the results are presented in figure 2.   w vcc qe e    where; c0 and ce dye concentration (mg×l -1) initially and at a given time t recpectively, v volume of dye soliution (l); w the weight of adsorbent (g). ph 0 2 4 6 8 10 12 14 r e m o v a l e ff ic ie n c y ,% 0 20 40 60 80 100 120 fig. 2. effect of ph on the sorption of reactive blue 50 (c0=150 mg·l -1, sorbent mass: 0.5 g) (1) 23 mongolian journal of chemistry 15 (41), 2014, 21-26 selected as optimum reactive blue 50 concentration. effect of zero valent iron mass on reactive blue 50 sorption: one of the important factors on sorption process is sorbent mass. the removal efficiency for reactive blue 50 as a function of zero valent iron mass was investigated in the range of 0.1-1.0 g and the results are presented in figure 4. during the experimental time, the removal efficiency was increased from 96.6% to 99.6% with increasing sorbent mass from 0.1 g to 1.0 g. this result can be explained by the fact that the sorption sites remain unsaturated during the process whereas the number of sites available for sorption sites increases by increasing the sorbent mass [6, 13]. however, the removal efficiency was stabilized with increasing sorbent mass from 0.5 g·l -1 to 1.0 g·l -1 . it higher sorbent mass, aggregates of sorbent mass can be formed. these may cause interference between binding sites at higher sorbent mass. therefore, 0.2 g for sorption of reactive blue 50 were selected as optimum zero valent iron mass for further experiments. therefore, the optimum sorption condition is selected as initial reactive dye 50 concentration of 150 mg·l -1 , zero valent iron mass of 0.2 g and solution ph of 6.0 at room temperature. organic dye of real wastewater sample from “tsombon knit” llc was removed with a percentage 99.5% through sorption by zero valent iron at this condition. adsorption isotherms: the experimental data of adsorption equilibrium between the amount of adsorbed dye (qe) on the zvi and the concentration of dye in solution (ce) at optimal condition were used to describe the appropriate isotherm model. the langmuir and freundlich isotherm models were used in this paper. the linearity and applicability of the models were evaluated by correlation coefficients. freundlich isotherm: freundlich isotherm model is assuming that the adsorption process takes place on a heterogeneous surface. the freundlich isotherm is expressed as: fig. 4. effect of sorbent mass on the adsorption of reactive blue 50 onto zero valent iron (c0=150 mg·l -1, ph=6.0, room temperature) during the experiments, the removal efficiency was from 98.29% to 21.41% and fas ph increased from 2 to 12. the sorption of reactive blue 50 depends on solution ph, which influences electrostatic binding of ions to corresponding groups. the sorption capacity of reactive blue 50 at low ph is better than that at higher ph. this result attributed to a phzpc (zero point charge) of zero valent iron. li et al. indicated that the phzpc of zero valent iron is at around 8.0 [6, 9, 12]. at low ph, the zero valent iron surface has positive charge and reactive blue 50 molecule has negative charge in aquatic dye solution. so the sorption of reactive blue 50 in the iron surface is improved at low ph. the removal efficiency was decreased at higher ph that is related to the formation of corrosion products such as oxide and hydroxide of fe(ii) and fe (iii) [6, 12]. the removal efficiency is higher (98.39%) at ph=6.0, so this result, the optimum ph is 6.0 for sorption of reactive blue 50 in zero valent iron. effect of initial concentration on reactive blue 50 sorption: the concentration of dye concentration is a significant factor to be considered for effective sorption process. the effect of reactive blue 50 concentration which was varied from 100 mg·l -1 to 500 mg·l -1 on the sorption capacity is shown in figure 3. the sorption capacity decreased as the initial concentration of reactive blue 50 concentration was increased from 100 to 500 mg·l -1 . after 5 minute, the sorption capacity was decreased from 92.09% to 93.82% with increasing initial reactive blue 50 of 100 to 500 mg·l -1 . however, reactive blue 50 concentration was 100 mg×l -1 and 150 mg×l -1 , sorption capacity was relatively stabilized. at lower concentrations, reactive blue 50 molecule present in the solution could interact with the binding sites and thus the sorption capacity was higher than those at higher reactive blue 50 concentrations. lower sorption yield is due to the saturation of sorption sites at higher concentrations [6, 13]. therefore, 150 mg·l -1 for sorption of reactive blue 50 were fig. 3. relationship between sorption capacity and sorption time (рн=6.0, sorbent mass: 0.2 g, room temperature) sorption time, minute 0 5 10 15 20 25 30 35 r e m o v a l e ff ic ie n c y , % 0 20 40 60 80 100 100 mg*l -1 150 mg*l -1 300 mg*l -1 400 mg*l -1 500 mg*l -1 sorbent mass, g 0.0 0.2 0.4 0.6 0.8 1.0 1.2 r e m o v a l e ff ic ie n c y , % 96.0 96.5 97.0 97.5 98.0 98.5 99.0 99.5 100.0 24 mongolian journal of chemistry 15 (41), 2014, 21-26 1/n indicates the adsorption intensity of the reactive blue dye onto zvi where 1/n=0 reversible, 1/n<0 unfavorable, 1/n>0 favorable adsoprtion. and also 1/n is a measure of surface heterogeneity then as its value gets closer to zero becomes more heterogeneous [14]. equation (2) can be arranged to linear form: to describe the applicability of the freundlich isotherm model for the reactive blue 50 adsorption on zvi a linear plot of lnqe versus lnce is plotted and presented in figure 5 and the calculated parameters are shown in table 1. from the experimental results the freundlich isotherm fits quite well with the experimental data (correlation coefficient r 2 > 0.99) at room temperature (20 and 25 o c), however at 30 o c the freundlich isotherm fits poor with the experimental data. it is clear that the adsorption of reactive blue 50 onto zero valent iron is favorable because of value of 1/n<0. langmuir isotherm: the langmuir isotherm, one of the first theoretical treatments of non-linear adsorption has been successfully applied to a wide range of data that exhibit limiting or maximum adsorption capacities. the langmuir isotherm model is used to predict the sorption of aqueous compound onto a solid phase. this model assumes that a monolayer of adsorbed material is adsorbed over a uniform adsorbent surface. the langmuir isotherm model is assumed that once a dye molecule occupies a site no further adsorption can take place at that site and theoretically a saturation value is reached beyond which no further adsorption can take place. n efe ckq 1  (2) where; qe amount of dye adsorbed at equilibrium (mg g -1). ce equilibrium dye concentration in liquid phase (mg·l1). kf freundlich constant related to the bond energy and adsorption capacity, n is empirical constant (l·g-1). efe c n kq ln 1 lnln  (3) the distribution of these two phases is controlled by equilibrium constant. the langmuir isotherm is expressed as: the parameters qm (mg·g -1 ) and kl (l·mg -1 ) are the langmuir constants that relate the maximum adsorption capacity and energy of adsorption. the linear form of the langmuir isotherm equation (4) is expressed as follows: from the equation (5) maximum adsorption capacity, qm and the langmuir constant can be calculated from the slope (1/qm) and intercept 1/qmkl for the linear plot ce/qe versus ce. the calculated parameters are presented in table 1. the constants evaluated for langmuir isotherms by regressing the experimental data which is shown in figure 6 were kl (lmg 1)=0.2.5, qm (mg·g 1)=.16.64 with correlation coefficient r 2 =0.0400 at room temperature. it is clear that the langmuir adsorption isotherm is the best model for reactive blue 50 adsorption on to zvi. from the table 1 as increasing the temperature maximum adsorption capacity is decreasing due to desorption of reactive blue dye from surface of zero valent iron. in the langmuir equation, parameters qm and kl are used to evaluate dimensionless constant called separation factor or equilibrium parameter (rl). the value of the separation factor is a measure of adsorption behavior. if rl>1 the adsorption is fig. 5. linear form of freundlich isotherm model, experimental condition: рн= 6.0, room temperature 293k ck ckq q el elm e   1 (4) where q (mg·g -1 ) is the adsorbate amount adsorbed on adsorbent at equilibrium and c (mg·l 1 ) is equilibrium adsorbate concentration in solution. m e lme e q c kqq c  1 (5) fig. 6. linear form of langmuir isotherm model, experimental condition: рн= 6.0, room temperature 293 k (6) 25 mongolian journal of chemistry 15 (41), 2014, 21-26 unfavorable, rl=1 the langmuir isotherm is linear, rl=0 irreversible. when 0<rl<1 the adsorption process is favorable [14]. the calculated value of rl was 0.04 at 20 o c that is indicating adsorption of reactive blue 50 on zvi is favorable. considering the langmuir model monolayer of reactive blue 50 molecule was formed over a uniform adsorbent surface by intermolecular bonding. the correlation coefficients show that the adsorption process could be described by both langmuir and freundlich models. the experimental results show that the zero valent iron studied in this work has a very large adsorption capacity. conclusions: from this study, it is shown that the zero valent iron is efficient adsorbent material for reactive dyes. the optimal condition of batch adsorption process was evaluated as ph=2-8, mass of adsorbent was 0.2 g and temperature of adsorption found 20°c in 150 mg/l concentration of dye solution. at optimal condition, removal of efficiency of dye in real wastewater sample from tsombon knit llc was 99.5%. the correlation coefficients show that the adsorption process could be described by both langmuir and freundlich models. the experimental results show that the zero valent iron studied in this work has a very large adsorption capacity. it has been showed that assumed monolayer deposition of dye onto surface of zero valent iron by chemical sorption. it is clear that the surface of natural ores such as zeolite and bentonite can be modified by the zero valent iron due to its high adsorption capacity and high surface area. the modified natural ores presumably have high adsorption capacity and distribution constant. acknowledgements this work has been done within the framework of the project research for synthesis and characterization of natural clay mineral based adsorbent supported by the asia research center, mongolia and korea foundation for advanced studies, korea. references 1. yahya s., al-degs., musa i., el-barghouthi., amjad h., el-sheikh., gavin m.,walker, (2008) effect of solution ph, ionic strength, and temperature on adsorption behavior of reactive dyes on activated carbon. dyes and pigments, 77, 16-23 2. hariharasuthan r., nageswara rao a., bhaskaran a. (2013) adsorption studies on reactive blue 4 by varying the concentration of mgo in sorel’s cement. int. j. eng.&sc., 2(1), 287-292 3. mohammad taghi ghaneian., mohammad hassan ehrampoush and et.al. (2014) reactive blue 19 dye adsorption behavior on jujube stems powder from synthetic textile wastewater: isotherm and kinetic adsorption studies. j. community health res., 3(1), 67-78 4. sadiq j., baqir., ahmed f., halbus. (2014) removal reactive blue dye from wastewater by adsorption on white iraqi kaolin clay, j. pure and app. sc., 7(22), 1947-1954 5. poursaberi t., hassanisadi m. and et al. (2012) application of synthesized nanoscale zero valent iron in the treatment of dye solution containing basic yellow 28. prog. color colorants coat., 5, 35-40 6. arabi s., sohrabi m.r., khoravi m. (2013) adsorption kinetics and thermodynamics of vat dye onto nano zero – valent iron, ind. j. chem. tech., 20, 173-179 7. bangash f.kh., gul s. (2013) removal of acid dye from water by nano zero valent iron. tenside surf. det., 5, 346-359 8. pare brijesh pare., soni a., and bhagwat v.w. (2008) kinetics of reduction of aniline blue dye using zero valent iron. rasayan j. chem., 1(2), 413-420 9. chatterjee s., lim s.r., woo s.h., et al. (2010) removal of reactive black 5 by zero – valent iron modified with various surfactants. chem. eng. j., 160, 27-32 10. petala e., dimos k., and et al. (2013) nanoscale zero-valent iron supported on mesoporous silica: isotherm parameters value freundlich isotherm model 293 k 298 k 303 k kf l·mg -1 101.42 63.16 82.91 1/n 0.4693 0.3957 0.2958 r 2 0.9972 0.9933 0.8223 langmuir isotherm model 293 k 298 k 303 k qm, mg·g -1 416.67 322.58 285.71 kl, l·mg -1 0.245 0.101 0.141 rl 0.039 0.09 0.06 r 2 0.9799 0.9962 0.9517 table 1. isotherm parameters of adsorption of reactive blue dye on zvi 26 mongolian journal of chemistry 15 (41), 2014, 21-26 characterization and reactivity for cr (vi) removal from aqueous solution, j. haz. mat., 261, 295-306 11. prabu d., parthiban r. (2013) synthesis and characterization of nanoscale zero valent iron (nzvi) nanoparticles for environmental remediation, asian j. pharm. tech., 3(4), 181-184 12. li z., jones h.k., zang p., et al. (2007) chromate transport through columns packed with surfactant – modified zeolite/ zero valent iron pellets. chemosphere, 68, 1861-1866 13. akar t., anilan b., kaynak z., et al. (2008) batch and dynamic flow biosorption potential of agaricus bisporus/thuja orientals biomass mixture for decolorization of rr 45 dye. ind. eng. chem. res., 47, 9715-9723 14. kant rita. (2012) adsorption of yellow dye: acid yellow rr from its aqueous solution using two different samples of activated carbon by static batch method. natural science, 4(2), 112-115 mongolian academy of sciences mongolian journal of chemistry the institute of chemistry & chemical technology mongolian journal of chemistry 14 (40), 2013, p12-19 introduction coal is the major energy source and feedstock of chemical industry among fossil resources in the coming century because of its abundant reserves and easy availability. because of instability on world oil market, the diversification of energy carriers is practically implemented in many countries with involvement of various nontraditional types of organic raw materials, primarily, coal, whose reserves are much greater than oil and gas reserves. mongolia is the country of lack of oil source with relative rich in coal resource. mongolia has 20 billion tons of proven coal reserves and estimated resources totalling 163 billion tons, mostly of them is low-rank brown coal, but remains undeveloped due to a lack of infrastructure. such reserves include the huge tavan tolgoi deposit in the south gobi, which contains over 6.4 billion tons of high quality stone and coking coal, but lies more than 400 km from the nearest railway. there is a large brown coal basin (jurassic origin), which contains the baganuur, ovdogkhudag, aduunchuluun, tevshiin govi, khoot, tsaidam nuur and shivee ovoo deposits and this is located in the central economic region of mongolia [1]. the most important features of these deposits are accessed by opencast mining and coal can be transported using the nearby railway. in mongolia coal is currently the main energy carrier for thermal power plants and local boiler houses and there is almost no other form of large-scale coal utilization industry [2]. now mongolia exports about 15 million tons raw coal by trucks from the south gobi to china. however, coal samples from the tavan tolgoi deposit have been assessed for benefication [3] and coke production [4], samples from baganuur, bayanteeg and shivee ovoo deposits as fuel for pyrolysis [5], hydrogenation [6] and gasification [7, 8]. also samples from ovdogkhudag and aduunchuluun deposits have been assessed for their liquefaction potential using facilities in japan [9]. at present time mongolian government pays much more attention for the future development of coal processing industries such as coal benefication, coking, semicoking, gasification and liquefaction. there are already established several small scale semicoking factories in ulaanbaatar and in darkhan for production of smokeless fuel. the “energy resourses” company built a middlescale coal washing factory in south gobi. mongolian government is planning to establish a coking factory in the framework of “sainshand” industrial park and “mak” company a coal liquefaction factory on basis of aduunchuluun coal deposit. how to convert coal into oil and gas is a major issue in the country, which will affect the national safety and the economic sustainable development. therefore more detailed investigation of above mentioned most important coal deposits by using of modern instrumental analysis such as petrographic and different pyrolysis experimental sets is very important for the future development of coal processing industries in mongolia. investigation on characterization and liquefaction of coals from tavan tolgoi deposit b. purevsuren 1 , s. jargalmaa 1 , b. bat-ulzii 1 , b. avid 1 , t. gerelmaa 1 1 institute of chemistry and chemical technology, mas, peace avenue, ulaanbaatar 13330, mongolia article info: received 16 october 2013; revised 18 october 2013; accepted 21 october 2013 abstract: on the basis of proximate, ultimate, petrographic and ir analysis results have been confirmed that the tavan tolgoi coal is a high-rank g mark stone coal. the results of x-ray fluorescence analysis of coal ash show that the tavan tolgoi coal is a subbituminous coal. the ash of tavan tolgoi coal has an acidic character. the results of pyrolysis of tavan tolgoi coal at different heating temperatures show that a maximum yield 5.0% of liquid product can be obtained at 700 o c. the results of thermal dissolution of tavan tolgoi coal in tetralin with constant mass ratio between coal and tetralin (1:1.8) at 450 0 c show that 50.0% of liquid product can be obtained after thermal decomposition of the com (coal organic matter). keywords: coal, pyrolysis, petrographic analys, mineral compounds, thermal dissolution * corresponding author: e-mail: bpurevsuren.icct@gmail.com 12 mongolian journal of chemistry 14 (40), 2013, p2-3 experimental the type, resource and other information of the coals of tavan tolgoi deposit are given in table 1. the analytical samples of coals from these 2 deposits were prepared according to mongolian national standards (mns) and main technical specifications including moisture (mns 656-79), ash (mns 652-79), volatile matter (mns 654-79), caloric value (mns 669-87), sulphur content (mns 895-79) have been determined. table 1. some informations about coal samples of tavan tolgoi deposit name of deposit type location of the coal deposit approx. resources in million ton discovered in tavan tolgoi high rank bituminous and coking coal tsogttsetsi village of southgobi aimak,14 km from the tsogttsetsi soum to the south and 600 km from ulaanbaatar to the south gobi geological reserves 6.4 billion tones in 1966 the pyrolysis experiments of coal samples were performed in a laboratory small quarts retort (tube) which could contain air dried and powdered to a particle size < 0.2 mm 1 gof coal sample. the retort was placed in a horizontal electric tube furnace with a maximum heating temperature of 950 0 c. a chromealumel thermocouple was immersed in the tube furnace to measure the actual heating temperature.the pyrolysis experiments have been carried out at different heating temperatures 200 800 0 c with constant heating rate 20 0 c/min. first of all the quarts retort with coal sample was heated for example to 600 0 c with heating rate 20 o c/min. and kept at 600 0 c for 80 min. the retort was connected with a thermostable glass tube heated also in a tube furnace at 80 0 c for collecting of tars and this tube is also connected with a air-cooled glass vessel for collecting of pyrolysis water. the glass vessel for pyrolysis water is also connected with a thin glass tube for non-condensable gases [10]. the yields of pyrolysis products including solid residue (coal char), tar (condensed liquid product) and pyrolysis water determined by weighing, and the yield of gases by differences. for petrographic studies samples were embedded in a resin, ground flat and polished. all samples were cuttings which were embedded without any specific orientation. vitrinite reflectance was measured following the standard procedures [11]. it was attempted to measure 50 particles per sample. in addition, fluorescence microscopy was used for rapid qualitative information on maturity and organofacies. resedimented vitrinite particles are characterized by higher reflectivity than autochthonous vitrinite. usually, only the vitrinite population with the lowest reflectance values is measured and reported. for the determination of mineral content in both coals have been obtained completely burned ashes of coals during slowly and continuously burning in furnace at 200 850 0 c. the content of mineral elements in both coal samples and their oxides have been determined by using of x-ray fluorescence spectrometry. the thermal dissolution of coal samples have been carried out in a laboratory standard stainless steel autoclave by using tetralin as a hydrogen donor solvent. air dried for 24 h, and powdered to a particle size < 0.2 mm 1g coal sample mixed with 1.8g tetralin (mass ratio 1:1.8) in autoclave and heated in a laboratory furnace at temperatures of 350, 400, 450 o c for 2 h. after completion of experiment the autoclave with sample cooled at room temperature and removed all uncondensed gas and resulting liquid products were filtered, and the solid residue on filter was subjected to sequential extraction with chloroform in a soxhlet apparatus. an extract of liquid products of thermal dissolution of coal in tetralin was distilled by a laboratory rotary evaporation apparatus for complete removing of chloroform. the degree of coal conversion was determined from the loss of the organic matter of coal (omc) after extraction and also change in the ash contents of the initial coal samples and the insoluble residue. results and discussion the results of ultimate and proximate analysis of coal samples of boreholes no.4 and 8 from tavan tolgoi deposit are shown in table 2. the technical characteristics of tavan tolgoi coals in table 2 show that the content of ash in borehole viii is higher than in borehole iv. the content of sulfure in borehole viii is a little bit higher than in borehole iv and in generally both are comparatively lower which is good for environmental point of view. table 2. proximate and ultimate analyses of tavan tolgoi coals coal samples of tavan tolgoi proximate analysis, % ultimate analysis, % borehole iv w a а d v daf q daf stotal с daf % н daf % (n+o) daf , % 0.82 14.8 29.9 7524 0.98 84.0 5.42 10.25 borehole viii 0.94 18.4 35.7 7283 1.4 76.0 4.40 19.17 13 mongolian journal of chemistry 14 (40), 2013, p2-3 also the content of volatile matter in borehole iv is lower and caloric value is higher than in borehole viii. it means that the coal of borehole iv has a characteristic of a higher quality than borehole viii. the content of c is higher and o is lower in borehole iv coal than in borehole viii. first time these two coal samples have been characterized with petrographic analysis by microscopic photograph of specially prepared and polished samples and the petrographic photographs (two photographs from each samples) are presented in figure 1. fig. 1. the petrographic photographs of polished coal samples of tavan tolgoi deposit: photograph of coal from borehole iv; bphotograph of coal from borehole viii. there are clearly indicated bright segments (parts) in the petrographic photographs of two coal samples (figure 1, a, b) which is the specific petrographic characteristic of vitrinite maceral groups in the organic maturity of the high-rank coal. the next step of petrographic analysis is to measure the value of so called vitrinite reflectance (%rvt) of points as much as possible on these bright segments (parts) in the petrographic photographs. we have chosen about 50 points on more bright pattern of these photographs and the measured results of %rvt are given in table 3 and 4. table 3. the measured results of %rvt from the petrographic patterns of borehole iv coal samples. № ref, % time № ref, % time 1 0.872 28.9 26 1.004 285.6 2 0.891 32.8 27 1.007 287.8 3 0.838 127.8 28 0.998 289.8 4 0.659 130.5 29 0.875 292.0 5 0.755 133.5 30 0.870 338.7 6 0.876 146.2 31 0.834 342.9 7 0.931 148.7 32 0.801 348.9 8 0.831 151.5 33 0.822 350.5 9 0.856 157.5 34 0.890 353.9 10 0.943 179.5 35 0.951 355.9 11 0.848 181.1 36 0.948 357.8 12 0.761 183.2 37 0.957 359.3 13 0.847 186.5 38 0.904 361.8 14 0.953 210.6 39 0.890 422.0 15 0.941 213.7 40 0.897 425.1 16 0.965 216.4 41 0.883 426.3 17 1.022 221.0 42 0.828 428.0 18 1.016 223.9 43 0.835 430.5 19 0.988 226.4 44 0.880 433.2 20 0.958 228.7 45 0.902 449.0 21 0.890 230.5 46 0.809 451.7 22 0.971 232.7 47 0.873 453.5 23 0.886 235.9 48 0.849 454.2 24 0.910 240.9 49 0.773 455.0 25 1.047 283.7 50 0.899 457.5 14 mongolian journal of chemistry 14 (40), 2013, p2-3 the measured results of %rvt from the petrographic patterns of 2 coal samples in table 3 and 4 are summarized and shown as a diagrams (figure 2) for determination of averaged value of %rvt for each coal samples. table 4. the measured results of %rvt from the petrographic patterns of borehole viii coal samples. № ref, % time № ref,% time 1 0.843 74.7 26 0.731 295.3 2 0.680 77.6 27 0.932 320.1 3 0.749 80.0 28 0.969 322.2 4 0.724 83.6 29 1.005 323.3 5 0.904 120.9 30 0.990 325.3 6 0.917 123.2 31 1.006 329.4 7 0.855 125.0 32 0.917 339.9 8 0.851 127.4 33 0.891 377.8 9 0.836 128.7 34 0.927 379.8 10 0.863 129.6 35 0.936 383.7 11 0.814 131.1 36 1.030 399.1 12 0.875 132.6 37 0.740 428.8 13 0.821 143.2 38 0.735 446.6 14 0.813 145.6 39 0.670 448.4 15 0.812 149.8 40 0.830 462.6 16 0.773 152.5 41 0.875 464.6 17 0.791 163.9 42 0.815 465.6 18 0.822 278.1 43 0.835 467.4 19 0.751 280.0 44 0.814 468.1 20 0.772 280.9 45 0.853 510.5 21 0.782 283.2 46 0.847 512.4 22 0.746 285.1 47 0.792 519.7 23 0.792 287.2 48 1.009 527.8 24 0.809 289.7 49 0.985 537.2 25 0.677 292.7 50 0.974 537.8 a b fig. 2. the diagrams for determination of averaged value of %rvt for coal of tavan tolgoi deposit: a – for borehole iv; b for borehole viii. from the fig. 2 have been determined the averaged value of %r vt for coal of borehole iv(a) is 0.893% and for coal of borehole viii (b) is 0.844%. the determined averaged vitrinte reflectance (%rvt) of each coal samples confirm that the tavan tolgoi coal has a characteristic (%rvt = 0.893% 0.844%) of high-rank g mark coking coal [10 p.157]. for the characterization of two coals from tavan tolgoi deposit have been carried out ir analysis of each coal samples (ir spectra of borehole iv coal in figure 3 and ir spectra of borehole viii coal in figure 4). 15 in the ir spectra of coal from borehole iv and viii can be recognized following absorption frequency regions: 700 900 cm -1 for car-h; 1000-1300 cm -1 for vibration of bonds in various oxygen-containing groups; 1350 1470 cm -1 for vibrations of –ch, ch2 and – ch3 groups; 1500 1630cm -1 for skeletal vibrations of aromatic rings, >c=o bonds in ketones, aldehydes and quinines; 2800 2950 cm -1 for stretching vibrations of –ch. -ch2 and – ch3 groups in saturated aliphatic structures; and 3030 -3350 cm -1 for stretching associated vibrations of – oh groups in aromatic rings and aliphatic structures. the both ir spectra are similar. in the case of tsaidamnuur coal ir spectra have very week and continous absorption bands (the absorption bands are not sharp). the content of mineral elements in both coal samples and their oxides has been determined by using of x-ray fluorescence spectrometry and the results are shown in figure 5 and 6 and table 5. mongolian journal of chemistry 14 (40), 2013, p2-3 fig. 3. the ir spectra of coal from borehole iv fig. 4. the ir spectrum of coal from borehole viii fig. 5. the x-ray fluorescence spectrogram of coal fig. 6. the x-ray fluorescence spectrogram of coal ash of viii from tavan tolgoi deposit ash of iv from tavan tolgoi deposit the dates in figure 5 6 and table 4 show that highest content of elements have si, o and sio2 in coal ash of both samples of tavan tolgoi deposit. in the case of al, fe, ca, s and al2o3, fe2o3, cao, so3 their contents are in a middle position in both samples. lowest contents have k, p, ti, mn, zn, sr and their oxides in both coal ashes. the sum of cao and mgo (cao+mgo<fe2o3=6.103-7.180) and the ratio (fe2o3+cao+mgo+na2o+k2o)/ (sio2+ai2o3+tio2)<1in both coal ash samples show that the tavan tolgoi coal is a high rank subbituminous coal and it’s ash has an acidic character. № elements, % elements, % borehole viii oxides,% borehole iv borehole viii 1 na 0.000 0.000 na2o 0.000 0.000 2 mg 0.000 0.000 mgo 0.000 0.000 3 ai 8.337 9.898 ai2o3 15.753 18.703 4 si 36.281 33.075 sio2 77.611 70.755 5 p 0.252 0.130 p2o5 0.578 0.299 6 s 0.774 0.482 so3 1.934 1.203 7 k 0.430 0.552 k2o 0.518 0.665 8 ca 1.348 0.844 cao 1.886 1.180 9 ti 0.553 0.535 tio2 0.923 0.893 10 fe 0.502 4.268 fe2o3 7.180 6.103 11 ni 0.009 nio 0.012 12 cu 0.011 cuo 0.014 13 zn 0.021 0.034 zno 0.027 0.043 14 sr 0.023 0.009 sro 0.028 0.011 15 mn 0.101 mn2o3 0.145 16 o 51.458 50.070 table 4. the mineral composition of coal ash of tavan tolgoi deposit 16 as it is known that subbituminous coals are useful raw material for a liquefaction technologies. the pyrolysis and thermal dissolution (hydrogen-donor solvent refining) are two different process of liquefaction for production of petroleum like liquid product (as main product) from solid fossil fuels. for this reason coals from tavan tolgoi deposit have been tested for a pyrolysis experiments aimed to determine an optimal heating temperature of coals in absent of oxygen and the determination of the yield of tar (liquid condensed petroleum like product) are chosen as the most important characteristic. the yields of pyrolysis products of borehole iv (table 6) and of borehole viii (table 7) from tavan tolgoi coals including hard residue, tar, pyrolysis water and gas after pyrolysis experiments at different temperatures of heating and constant heating rate (20 0 c/min) are given in figures 7 and 8. mongolian journal of chemistry 14 (40), 2013, p2-3 table 6. the yields of pyrolysis products of borehole iv from tavan tolgoi coals sample t 0 c t [min] hard residue, % tar, % pyrolysis water, % gas and loss, % borehole iv 200 80 99.09 0.6 0.3 300 80 98.76 0.31 0.9 0.03 400 80 97.86 0.33 1.32 0.75 500 80 92.29 2.53 2.86 2.32 600 80 89.6 2.89 2.32 5.19 700 80 84.58 3.5 4.4 7.4 800 80 78.9 4 4.61 12.4 fig. 7. the yields of pyrolysis products of borehole iv from tavan tolgoi coal at different heating temperature the yields of pyrolysis products of borehole iv and viii from tavan tolgoi coal at different heating temperature in table and figure and the results are very similar in both cases and show that the yield of hard residue is decreased by increasing of heating temperatures, because of increasing thermal decomposition of organic matter of coal at higher temperature. the yield of main product (tar) of pyrolysis of both coal from tavan tolgoi deposit increasing by the heating temperature until 700 0 c in which has a highest yield 4 5% which is lower than that of brown coal. also, as usually the yields of pyrolysis water and uncondensed gases increased by increasing of heating temperatures. table 7. the yields of pyrolysis products of borehole viii from tavan tolgoi coals sample t 0 c t [мin] hard residue, % tar. % pyrolysis water, % gas and loss, % borehol e viii 200 80 98.92 1.33 0.25 300 80 97.13 0.196 2.0 0.65 400 80 97.14 0.4 1.54 0.9 500 80 90.18 1.44 3.42 4.94 600 80 85.65 3.57 3.04 7.72 700 80 81.27 4.77 3.55 10.4 800 80 69.28 4.45 5.48 15.77 17 all above mentioned experimental results of boreholes iv and viii coal samples from tavan tolgoi deposit show that the coal of borehole iv from tavan tolgoi deposit characterizes with better results (more qualitative) than that of borehole viii. therefore the coal sample of borehole iv from tavan tolgoi deposit was chosen for next thermal dissolution experiments. the results of pyrolysis experiments of both coal samples from tavan tolgoi deposit show that these coals can be easily tested for thermal dissolution in mongolian journal of chemistry 14 (40), 2013, p2-3 fig. 8. the yields of pyrolysis products of borehole viii from tavan tolgoi coal at different heating temperature tetralin as a hydrogen donor solvent. the results of thermal dissolution of coal of borehole iv from tavan tolgoi is presented in figure 9. the yields of thermal dissolution products: hard residue, liquid and gas of this chosen tavan tolgoi coal sample (figure 9) at different heating temperatures show that the yield of hard residue is decreasing intensively against the increasing of heating temperatures, because of higher degree of thermal decomposition of coal organic matters at higher temperature. fig. 9. the yields of thermal dissolution products of tavan tolgoi coal (borehole iv) at different heating temperatures a confirmation of this the summarized yields of liquid and gas productions after thermal dissolution should increased, because of increasing weight loss of initial coal sample before the thermal dissolution process. such dependences already have observed in fig. 9 and the maximum yield of liquid product is 50.0% at 450 0 c. the results of thermal dissolution of tavan tolgoi coal in tetralin with constant mass ratio between coal and tetralin (1:1.8) at 450 0 c show that 50.0% of liquid product can be obtained after thermal decomposition of the com (coal organic matter). conclusions 1. on the basis of proximate, ultimate, petrographic and ir analysis results have been confirmed that the tavan tolgoi coal is a high-rank g mark stone coal. 2. the results of x-ray fluorescence analysis of coal ash show that the tavan tolgoi coal is a subbituminous coal. the ash of tavan tolgoi coal has an acidic character. 3. the results of pyrolysis of tavan tolgoi coal at different heating temperatures show that a maximum yield 5.0% of liquid product can be obtained at 700 0 c. 18 4. the results of thermal dissolution of tavan tolgoi coal in tetralin with constant mass ratio between coal and tetralin (1:1.8) at 450 0 c show that 50.0% of liquid product can be obtained after thermal decomposition of the com (coal organic matter). 5. purevsuren b., et al. (2009) thermal processing of baganuur coal from mongolia. annual scientific reports of the icct, mas, 10(36), 122-131. 6. tsedevsuren ts., et al. (1981) hydrogenation of bayanteeg coal of mongolia. chemistry of solid fuels, russian academy of sciences, 6, 17. 7. avid b., purevsuren b., paterson n., zhuo y., peralta d., herod a., dugwell d., kandiyoty r. (2004) an exploratory investigation on the perfomence of shivee-ovoo coal and khoot oil shale from mongolia, fuel, 83, 1105-1111. 8. avid b., purevsuren b et al. (2002) pyrolysis and tg analysis of the shivee ovoo coal mongolia. journal of thermal analysis and calorimetry, 68, 877-885. 9. ueda sh. (1994) preliminary survey on the mongolian coal. annual summary of coal liquefaction, 19, 140-150. 10. sklyar m.g., tyutyunnikov yu.b. (1985)khimiya tverdikh goruchikh iskopaemikh, kiev, visha shkola, p. 171 (in russian). 11. taylor g.h., teichmüller m., davis a., diessel c.f., littke r., robert p. (1998) organic petrology, gebr, borntraeger stuttgart, p. 704. mongolian journal of chemistry 14 (40), 2013, p2-3 references 1. purevsuren b., davaajav ya., erdenechimeg r. (2010) investigation on largest coal deposits in mongolia. monograph, toonot print, p. 165190. 2. purevsuren b. (2007). coal is the main source of energy. abstracts of papers, second korean and mongolian energy conference, seoul: yonsei univ., p. 13. 3. munkhjargal sh. (1985) the beneficiation of the tevshiin govi and tavan tolgoi coals. ph.d dissertation, praha, ugg, csw, p. 163 (in czech). 4. dugarjav j. (1995) coking properties of tavan tolgoi coal. reports of the institute of chemistry, mongolian academy of sciences, 17-22. 19 introduction the use of plants for culinary and ethno medicinal purposes can be dated back to ancient history, even as far back as the “stone age” era. plant leaves have been the most exploited for these purposes especially due to the proximate and phytochemical contents of these leaves. the proximate composition of these leaves reveal their nutritional status and make them suitable in food processing. the ethno medicinal uses of these leaves can be attributed to the phytochemical composition of the leaves which are also indicative of their antioxidant activities. hence, a study on these vital components reveals the usefulness of a plant’s leaves. diodia sarmentosa sw commonly known as “tropical buttomweed” [1], is a perennial herb without a true root system. it has a hairy leaf and stem which are about 7 cm and 4 m long respectively. it grows in bushy vegetation, riverine areas and on rocky grounds. it is majorly inhabited in tropical africa, asia, america and the mascarene islands. it is a dicot which belongs to the family rubiaceae and the genus diodia. in some parts of nigeria, especially the south western region, the leaves are crushed and used in preparing stew or soup and it is locally known as “ewe opaeyin” or “ewe ọhaigbo”. d. sarmentosa leaves are used in treating injuries, oedema [2] and haemorrhoids (pile). the whole plant is taken with pepper and salt for the treatment of dysentery in south western nigeria [3, 4]. the antiulcer potential of diodia sarmentosa (whole plant) [5] and its anti-inflammatory and analgesic activities [2] have been demonstrated. the anti-diabetic properties of d. sarmentosa has also been revealed [6]. this was determined using the n-hexane leaf extract of d. sarmentosa. other species belonging to the genus diodia has also gained wide applications. studies on diodia scandens revealed their use as poultry feed for ruminant animals [7]. there are also postulations that the plant has pharmacological properties, hence, could be used in the treatment of rheumatoid, oedema, inflammations [7] and brain thromboplastin [8]. d. scandens is also used traditionally in some parts of eastern nigeria to treat snake bites [8]. the plant also serves as a laxative and oxytocic agent in the treatment of uterine inertia and postpartum haemorrhage [9]. according to the same finding, the aqueous extracts are used to enhance micturition and sexual performance by rural inhabitants of ikwere and etche local government areas of rivers state, nigeria [9]. the anti-fungal properties of d. scandens have also been studied [10]. presently, there is no data showing a comprehensive proximate composition, phytochemical and antioxidant properties of d. sarmentosa leaves. okoroafor c et al., mong. j. chem., 21(47), 2020, 27-32 https://doi.org/10.5564/mjc.v21i47.1430 phytochemical and antioxidant properties of diodia sarmentosa swartz leaves okoroafor henry chinedu*, awagu fidelis emenike, azeke ehijie augusta perishable crops research department, nigerian stored products research institute, mile 4, rumueme, port harcourt, rivers state, 500262, nigeria * corresponding author: okoroaforchinedu@gmail.com; orcid id:0000-0001-7333-179x received: 26 november 2020; revised: 30 december 2020; accepted: 31 december 2020 abstract this research studied proximate, phytochemical and antioxidant properties of diodia sarmentosa leaves. the ethanol and aqueous extracts of the leaves significantly inhibited 2,2-diphenyl-1-picrylhydrazyl (dppho) radical formation with ic50 values of 10.994 and 10.121 μg/ml respectively, compared to the ascorbic acid standard (ic50 value = 17.916 μg/ml). the aqueous extract exhibited more inhibitory effect on thiobarbituric acid-reactive species (tbars) with ic50 values of 2.657 μg/ml while the ethanol extract had an ic50 value of 8.53 μg/ml compared to butylated hydroxytoluene standard (ic50 = 2.142 μg/ml). for the total antioxidant capacity assay, the aqueous extract had higher ascorbic acid equivalent values than the ethanol extract. however, the two solvent extracts showed antioxidant activity. diodia sarmentosa leaves possess useful phytochemicals which are indicative of its antioxidant properties. keywords: antioxidant; diodia sarmentosa; phytochemical; proximate mongolian journal of chemistry www.mongoliajol.info/index.php/mjc © the author(s). 2020 open access. this article is distributed under the terms of the creative commons attribution 4.0 international license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the creative commons license, and indicate if changes were made. 27 https://doi.org/10.5564/mjc.v20i46.1237 okoroafor c et al., mong. j. chem., 21(47), 2020, 27-32 experimental plant collection and identification: fresh samples of d. sarmentosa leaves were collected from farmlands and from natural vegetation within federal university of technology, owerri (futo) premises. it was identified by prof. iloegbulam i.i. of the department of crop science. a picture of a portion of d. sarmentosa plant is displayed in figure 1. preparation of plant extract and extraction: fresh leaves of d. sarmentosa were rinsed using distilled h2o, dried at room temperature and then in a laboratory oven at 40 °c. the dried plant material was grinded into fine powder and 160 g was weighed, soaked in ethanol (800 ml) for 48 h and placed on an orbital shaker. filtration was done using whatman no.1 filter paper placed inside a funnel, then dried at 40 °c using a rotary evaporator. proximate analysis of sample: determination of moisture content was carried out using a laboratory oven at 105 °c. ash was determined using an electric furnace at 550 °c. soxhlet apparatus was used in the determination of the crude fat. crude protein was determined using kjeldahl method. percentage carbohydrate was done by difference. these were all done using aoac method [11]. qualitative phytochemical screening: the test sample (0.2 g) was placed in separate test tubes to assay for phytochemicals as follows: saponin: frothing test was used in the detection of saponin, which was confirmed by constant foaming. flavonoid: ammonium test method was used in the determination of flavonoid. a yellowish colouration confirmed the presence of flavonoid. carbohydrate: molisch’s method was used in the determination of carbohydrate. this was confirmed by the formation of a brown ring. phenol: ferric chloride test was used in the determination of phenol. a greenish colouration was observed and this confirmed the presence of phenol. reducing sugar: reducing sugar was confirmed by a reddish colouration using fehling’s method. glycoside: fehling’s method was used in glycoside determination. glycoside was confirmed by a reddish colouration. tannins: ferric chloride method was used to determine the presence of tannins. a blue colouration was observed which confirmed the presence of tannins. alkaloid: presence of alkaloid was determined using wagner and dragendorff’s reagent. no precipitate was formed. steroids: to determine the presence of steroids, lieberman-buchard test was used. steroids were detected by a greenish colouration. terpenoid: a violet colouration after dissolution in ethanol and treatment with acetic anhydride and conc. h2so4 revealed the presence of terpenoids. quantitative phytochemical screening: determination of phenolics: total phenolics was determined using follin-ciocalteau reagent method. gallic acid was used as standard. folin-ciocalteu reagent was used in oxidizing d. sarmentosa leaves extract. this was then neutralized using na2co3. a portion (100 μl) of the different concentrations (15.63, 31.25, 62.5 µg/ml) of this extract was put into a mixture of 0.5 ml folin-ciocalteau reagent (0.1 dilution) and 1.5 ml sodium carbonate 2 % (w/v), then incubated for about 15 min at 25 °c. the absorbance of the blue coloured solution was read at 765 nm and results expressed in mg of gallic acid equivalent (gae)/100 g of dry weight of plant powder. determination of tannins: the leaves extract (1 ml) of d. sarmentosa was put into a solution containing 0.5 ml folin-ciocalteau reagent, 1 ml sodium carbonate and 8 ml of distilled water. this was kept at 25 °c for about 30 min. it was then centrifuged to get a supernatant and absorbance read at 765 nm. the results were expressed as mg tannic acid/100 g of dry weight of plant powder. determination of flavonoid: zhishen colorimetric method was used in the determination of flavonoid [12]. the diluted sample solution (0.5 ml) was put into a mixture containing 2 ml of distilled h2o and 0.15 ml of sodium nitrate (5 %) solution. after a short while, 0.15 ml of 10 % alcl3 (aq) was put into the solution and kept for about 6 min. diluted sodium hydroxide (4 %) solution (2 ml) was added to bring the total volume to 5 ml. the absorbance was taken after 15 min at 510 nm against water blank. the results were expressed as mg/100 g of dry weight of plant powder. determination of terpenoids: a portion of d. sarmentosa leaves (1 g) was extracted using ethanol (50 ml). the filtrate (2.5 ml) was mixed with 5% aqueous phosphomolybdic acid (2.5 ml) and 2.5 ml concentrated tetraoxosulphate (vi). after that, the volume of the solution was made up to 12.5 ml after 30 min using ethanol. the absorbance was read at 700 nm. the results were expressed as mg/100 g of dry weight of plant powder. determination of steroids: a portion of d. sarmentosa leaves (1 g) was extracted with 20 ml of ethanol. the filtrate (2 ml) was mixed with 2 ml of chromogen solution and kept at room temperature (25 °c) for about 30 min. 28 fig. 1. an aerial part of d. sarmentosa plant okoroafor c et al., mong. j. chem., 21(47), 2020, 27-32 then the absorbance was read at 550 nm. the results were expressed as mg/100 g of dry weight of plant powder. determination of saponin: extraction of the sample (1 g) was done using 10 ml petroleum ether. after that, an additional 10 ml of petroleum ether was mixed with the solution and then subjected to dryness by evaporation. the residue obtained after dryness was dissolved in 6 ml of ethanol. then, 2 ml of the solution was mixed with 2 ml of chromogen and left at room temperature for about 30 min. absorbance of the solution was read at 550 nm. the results were expressed as mg/100 g of dry weight of plant powder. determination of glycosides: a sample of d. sarmentosa leaves (1 g) was extracted with 50 ml of distilled water. alkaline picrate (4 ml) solution was mixed with 1 ml of the sample filtrate and heated for about 5 min. absorbance was read at a wavelength of 490 nm. the results were expressed as mg/100 g of dry weight of plant powder. reducing sugar: extraction of the sample (1 g) was carried out using 20 ml of distilled water. alkaline copper reagent (1 ml) was mixed with the filtrate (1 ml) and heated for about 5 min. then 1 ml of phosphomolybdic acid reagent and 2 ml of distilled water was mixed with the resultant solution and absorbance read at 420 nm. the results were expressed as mg/100 g of dry weight of plant powder. determination of soluble carbohydrates: extraction of the sample (1 g) was done using 50 ml of distilled water. the filtrate (i ml) was mixed with picric acid solution and the absorbance read at 580 nm. the results were expressed as mg/100 g of dry weight of plant powder. in vitro screening for antioxidant activities: quantitative dppho radical scavenging assay: quantitative dpphº was determined according to a modified gyamfi method [13]. the test was performed in triplicates. the sample extracts (1 ml each) were diluted 2-fold in 10 ml of water mixed with 0.5 ml of 0.076 mm dpphº. after that, it was mixed properly and kept away from sunlight at 25 °c for about 25 min. an aqueous solution (1 ml) of 0.076 mm dpphº was used as a negative control while the positive control was l-ascorbic acid. absorbance was read at 517 nm. thiobarbituric acid-reactive species (tbars): thiobarbituric acid-reactive species assay was carried out by a modified method of banerjee [14]. this aimed at quantifying the amount of lipid peroxide formed. egg yolk homogenate served as lipid-rich media [15]. the sample (100 μl) was mixed with egg homogenate (500 μl) in a test tube and distilled water was used to make up the volume to 1.0 ml. a mixture of 0.075 m feso4 (50 μl) and 0.1 m l-ascorbic acid (20 μl) were added to the solution, and kept at 37 °c for about an hour. then 0.2 ml edta (0.1 m) and 1.5 ml of tba reagent were put into each sample and heated for 15 min at 100 °c. after cooling, the samples were centrifuged for 10 min at 3000 rpm. the absorbance was read at 532 nm. butylated hydroxytoluene (bht) was used as the assay standard. total antioxidant capacity (tac) assay: phosphomolybdate method was used in assaying for total antioxidant capacity. a 0.1 ml aliquot of different concentrations (15.63, 31.25, 62.5, 125, 250, 500, 1000 μg/ml) of the extract and ascorbic acid (1000, 500, 250, 125, 62.5, 31.25, 15.63 μg/ml) was mixed with 1 ml of reagent solution (0.6 m h2so4, 0.028 m na2hpo4 and 0.004 m (nh4)2 moo4). the test tubes were heated in a water bath at 95 °c for 90 min. after cooling, the absorbance was read at 765 nm. the reagent solution (1 ml) was used as blank and ascorbic acid was used as standard. statistical analysis: pearson’s correlation coefficient at 95% confidence interval was used in the determination of correlation coefficient between analytes. one way analysis of variance (anova) was used in determining the standard deviation between means of values. results and discussion proximate analysis: the proximate analysis of d. sarmentosa leaves evaluated the moisture, ash, crude fat, crude fibre, crude protein and carbohydrate content. the percentage of carbohydrate was found to be (59.07 %); moisture content (10.66 %); crude protein (8.57 %); crude fibre (7.8 %); ash content (7.50 %) and crude fat (6.40 %). qualitative phytochemical analysis: d. sarmentosa leaves extract revealed the presence of saponin, flavonoid, and carbohydrate, phenol, reducing sugar, glycoside, tannin, steroid and terpenoid. however, alkaloid was absent (table 1). table 1. qualitative phytochemical analysis of d. sarmentosa leaves extract quantitative phytochemical analysis: quantitative phytochemical screening of the phytochemicals revealed a very high quantity of carbohydrate (3223 ± 3.95 mg/100 g) and reducing sugar (2410.87 ± 6.15 mg/100 g) in d. sarmentosa leaf extracts. 29 phytochemical observation bioavailability saponin persistent foaming ++ flavonoid a yellowish colouration ++ carbohydrate brown ring formation at the interface ++ phenol a greenish colouration +++ reducing sugar a brick red precipitate +++ glycoside a brick red colouration +++ tannin a blue black colouration +++ steroid colour change from violet to green +++ terpenoid colour change from pink to violet +++ alkaloid no ppt formed nd notice: + slightly available; ++ moderately available; +++ very much available; nd not detected okoroafor c et al., mong. j. chem., 21(47), 2020, 27-32 this suggest that the leaf extracts have high energy content and may be edible. high quantities of phenol (1121.02 ± 5.67 mg gae/100 g), a potent antiinflammatory phytochemical, was also observed. relatively high quantities of flavonoid (320.15 ± 1.83 mg/100 g) and terpenoids (149.41 ± 3.64 mg/100 g), potent anti-inflammators were observed. the results of the quantitative phytochemical constituents of d. sarmentosa leaves extract are shown in table 2. phytochemical mean ± std (mg/100 g) total phenolics 1121.02 ± 5.67 total tannins 64.68 ± 1.08 total flavonoid content 320.15 ± 1.83 terpenoids 149.41 ± 3.64 steroids 20.84 ± 0.13 saponins 5.07 ± 0.86 glycosides 50.38 ± 0.16 reducing sugar 2410.87 ± 6.15 soluble carbohydrates 3223 ± 3.95 in vitro antioxidant activities of leaves extracts of d. sarmentosa: dppho assay: a graph of inhibition (%) was plotted against dppho concentration (μg/ml) (fig. 2). there was a significant (r = -0.955, p < 0.05) negative pearson correlation between dppho aqueous and concentration while a significant (r = 0.704, p < 0.05) positive correlation was observed between dppho ethanol and concentration. dppho aqueous was negatively (r = -0.511, p < 0.05) correlated with the standard (ascorbic acid) while dppho ethanol was positively (r = 0.257, p < 0.05) correlated with the standard. tbars assay: a graph of inhibition (%) was plotted against concentration (μg/ml) (fig. 3). there was significant (r = 0.553, p < 0.05) positive pearson correlation between tbars aqueous and concentration and significant (r = -0.834, p < 0.05) negative pearson correlation between tbars ethanol and concentration. there was also significant (r = 0.824, p < 0.05) positive pearson correlation between tbars aqueous and bht standard while there was significant (r = -0.526, p < 0.05) negative pearson correlation between tbars ethanol and bht standard. total antioxidant capacity: a graph of ascorbic acid equivalent was plotted against concentration (fig. 4). there was significant (r = 0.987, p < 0.05) positive pearson correlation between total antioxidant capacity of aqueous extract and concentration. there was also significant (r = 0.424, p < 0.05) positive pearson correlation between total antioxidant capacity of ethanol extract and concentration. d. sarmentosa leaves contain protein (8.57 %), carbohydrate (59.07 %), fat (6.4 %), fibre (7.8 %), ash (7.50 %) and moisture (10.66 %). this reveals the nutritional composition of the leaves and suggest that it could be used as part of a healthy meal. qualitative phytochemical screening of 30 table 2. quantitative phytochemical analysis of d. sarmentosa leaves dppha dpph of aqueous extract; dpphe dpph of ethanol extract; dpph std dpph of ascorbic acid standard fig. 2. percentage dpphº inhibition of aqueous and ethanol extracts of d. sarmentosa leaves. fig. 3. percentage tbars inhibition of aqueous and ethanol extracts of d. sarmentosa leaves. tbarsa tbars for aqueous extract; tbarse tbars for ethanol extract; tbars (std) tbars for bht standard aaea ascorbic acid equivalent of aqueous extract; aaeeascorbic acid equivalent of ethanol extract. fig. 4. total antioxidant capacity of aqueous and ethanol extracts of d. sarmentosa leaves. okoroafor c et al., mong. j. chem., 21(47), 2020, 27-32 d. sarmentosa leaves revealed the presence of saponin, flavonoid, terpenoid, phenol, reducing sugar, glycoside, tannin, steroid and carbohydrate except alkaloid which was absent (table 1). presence of saponin indicates that the leaves can be useful in treating yeast and fungal infections [16]. this agrees with the findings of umoh [2] who reported the ability of d. sarmentosa leaves in preventing inflammation. flavonoids are natural antioxidants [17] which boost immune function, protect against microbial infections and prevent the formation of free radicals [18]. phenols prevent inflammation and also boost the body immune system [19, 20]. this supports the findings of umoh [2], who reported the anti-inflammatory properties of the leaves. presence of glycosides suggest that the leaves extract have the ability to lower blood pressure [21]. presence of tannins suggest that the leaves can be used in the treatment of wounds [22]. results of this study validates that of akah [5] regarding presence of tannins and of the antiulcer effect of d. sarmentosa leaves. dppho assay of the leaves extract of d. sarmentosa revealed significant antioxidant activity (fig. 2). the ic50 (inhibitory concentration at 50 %) value of aqueous and ethanol extracts of d. sarmentosa (10.121 and 10.994 μg/ml respectively) were significantly lower than the ic50 value of ascorbic acid (17.916 μg/ml). lower values reveal better antioxidant activity [23, 24]. in the thiobarbituric acid assay (tbars) (fig. 3), the aqueous extract showed a significantly higher percentage inhibition compared to the ethanol extract. the ic50 values for the aqueous and ethanol extracts were 2.657 and 8.53 μg/ml respectively compared to ic50 value of bht standard, which was 2.142 μg/ ml. this suggest that water soluble phytochemicals possess a stronger potential to reduce malondialdehyde (mda) formation. for the total antioxidant capacity assay (fig. 4), the aqueous extract had higher ascorbic acid equivalent values compared to the ethanol extract. this is quite normal since the solubility of ascorbic acid increase with increasing polarity [25]. however, the two solvent extracts showed antioxidant activity. conclusions the results of proximate assessment of d. sarmentosa leaves which revealed the edibility of the leaves, supports the 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mongolia *author to whom correspondence should be addressed jadambaa temuujin citi university denver street, 14190 ulaanbaatar, mongolia e-mail: temuujin.jadamba@citi.edu.mn orcid: https://orcid.org/0000-0003-0930-7271 this article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, and proofreading process, which may lead to differences between this version and the official version of record. please cite this article as: narantsogt n., narangarav l., bolortuya m, and jadambaa t. influence of comilling oxide physical properties on the structural changes of natural clinoptilolite zeolites. mongolian journal of chemistry, 24(50), 2023, xx-xx https://doi.org/10.5564/mjc.v24i50.1250 mailto:temuujin.jadamba@citi.edu.mn ac ce pt ed m an us cr ip t mongolian journal of chemistry page 2 of 13 influence of co-milling oxide physical properties on the structural changes of natural clinoptilolite zeolites narantsogt natsagdorj1, https://orcid.org/0000-0002-1040-1276 narangarav lkhagvasuren1, bolortuya munkhjargal1, jadambaa temuujin2*, https://orcid.org/0000-0003-0930-7271 1 school of mathematics and natural science, mongolian national university of education, 210648 ulaanbaatar, mongolia 2 citi university, denver street, 14190, ulaanbaatar, mongolia abstract 3 zeolites are a family of open-framework aluminosilicate minerals used in many diverse fields, including building materials, agriculture, water treatment, and catalysis. in this study, natural zeolites were mechano-chemically treated by co-milling with corundum and 6 cristobalite. the idea behind the study was that co-milling with high-hardness oxides would cause natural zeolite to undergo more structural distortion, potentially increasing its reactivity and sorption capabilities. corundum has a density of 3.95 g/cm3 and a hardness of 9, while 9 cristobalite has a density of 2.27 g/cm3 and a hardness of 6-7, according to the mohs hardness scale. in a planetary ball mill, the zeolites and 20 wt.% of various oxides were co-ground for 30 min. 12 the grinding media used were hardened steel balls with a weight ratio of 20:1 between the balls and the minerals. raw minerals and milled products were evaluated using x-ray diffraction, fourier-transform infrared spectroscopy and scanning electron microscopy. 15 it revealed that co-milling with different hardness oxides had a minor effect on the structural distortion of raw zeolite. crystallite size reduction and amorphization were observed in highhardness oxides rather than in zeolite particles. after milling, the amorphization of natural zeolite 18 milled alone was 30.4%, while no significant amorphization was observed when co-milled with corundum and cristobalite. preliminary results of cr(vi) adsorption tests on raw and milled zeolites indicate that co-milling with high-hardness oxides is not the preferred method to 21 enhance the activity of natural zeolite. keywords: natural zeolite, co-milling, mechano-chemical treatment, corundum, cristobalite, 24 ftir, xrd, adsorption, cr(vi) https://orcid.org/0000-0002-1040-1276 https://orcid.org/0000-0003-0930-7271 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 3 of 13 introduction 27 natural zeolites are microporous aluminosilicate minerals that have many uses in industry, agriculture, medicine, and the environment. they are formed when volcanic rocks and alkaline groundwater interact. natural zeolites are crystals that grow in the voids of sedimentary rocks 30 or basalt rocks that arise under various geological conditions [1, 2]. natural zeolites have received interest since the 1850s due to their base-exchange capabilities, which can be used in water softeners and agricultural applications [1, 3]. zeolites are used today primarily as 33 wastewater and gas pollution removers, catalysts, pesticides, and fertilizer carriers in food and agriculture, soil supplements, and animal feed additions [1, 2, 4]. due to the contamination of industrial wastewater discharges, which contain many toxic heavy metals such as cadmium, 36 chromium, lead, and mercury, the levels of toxic heavy metals in surface and ground waters have been rising recently [5]. chromium is regarded as a high-priority environmental pollutant among hazardous heavy metals. 39 the most prevalent chromium compounds have an oxidation state of (iii) or (vi) and are considered hazardous to the environment [6]. because of its solubility in practically the whole ph range, greater mobility than cr(iii), and chromium's carcinogenic state, cr(vi) is more 42 dangerous than cr(iii). cr(iii) is less poisonous and less mobile than cr(vi) [6]. although natural zeolites are used for many different things, their use is restricted because of their low purity and small channel diameter, which precludes the adsorption of larger gas 45 molecules and organic compounds. zeolites can be activated using a variety of techniques, such as mechanochemical activation, to improve their inherent qualities. the production of amorphous powders from elemental metals or powder mixes by ball milling, also known as 48 mechanical grinding (mg), has been shown to be an effective way of optimizing the properties of the powder [7-9]. mechanical activation of natural zeolite leads to amorphous products with a higher surface area and adsorption properties than raw zeolite [8, 9]. previous references [10, 51 11] provide contradictory results in the sorption research of mechanically milled clinoptilolite. the mechanically amorphized clinoptilolite's cation exchange capacity (cec) increased, according to zolzaya et al. [10]. in contrast, bohacs et al. discovered that methylene blue adsorption is 54 maintained in mechanically activated clinoptilolite [11]. mechanical amorphization can be accomplished by milling the crystalline compounds alone or in conjunction with other crystalline compounds; however, in the latter case, the mechanochemical production of a new amorphous 57 or crystalline compound is also possible. amorphization of the crystalline co-milling compounds is expected to rise if one of the compounds has a higher hardness than another. it was thought that the co-milled oxides' high hardness might also serve as a milling medium, accelerating the 60 amorphization of the softer co-milling compound. therefore, a study of the structures of ac ce pt ed m an us cr ip t mongolian journal of chemistry page 4 of 13 mechanically activated zeolite with the different oxides could clarify the influence of the hardness of the co-milled oxide on the sorption properties of the milled samples. this study aims to clarify 63 how co-milling oxide hardness affects the amorphization and adsorption characteristics of natural zeolite. in this study, x-ray diffraction (xrd), fourier transform infrared (ftir), and scanning electron microscopy (sem) were used to analyze the mechanochemical effects on 66 natural zeolites caused by co-milling with different hardness oxides using a planetary ball mill. the impact of co-milling natural zeolites with different hardness oxides on the reactivity of the original zeolite was checked using cr (vi) adsorption tests. 69 experimental materials: natural zeolite was obtained from the tsagaan tsav deposit in southern mongolia. 72 the zeolites were dried at room temperature before being pulverized by hand to reduce particle size with a ceramic pestle and mortar. mechanically activated zeolite preparation: corundum and cristobalite oxides were added to the 75 zeolite for co-milling. corundum has a density of 3.95 g/cm3 and a mohs hardness of 9. cristobalite has a density of 2.27 g/cm3 and a mohs hardness of 6. cristobalite was created by calcinating quartz oxide for 4 hours at 1300 ° c. quartz was converted to cristobalite to decrease 78 the hardness for a better comparison with corundum and to show the influence of hardness on the amorphization of natural zeolite. some raw zeolites were ground alone and used as a reference. 81 a planetary ball mill (nqm-0.4, china) was used to grind raw or mixed zeolites. natural zeolite 80% w/w + oxides 20% w/w make up co-milled zeolite samples. the grinding was carried out in a hardened steel pot with a volume of 121 cm3. the ball-to-powder weight ratio was 20:1 and 84 the grinding media was hardened steel balls with diameters of 0.6 cm. the samples (5.5 g) were milled at 1500 rpm at room temperature for 30 minutes. characterization: chemical analysis (xrf): chemical analyzes of the zeolite samples were 87 performed by xrf (shimadzu, primini-x-ray fluorescence, japan) using the pressed tablet. sem analysis: scanning electron microscope (sem) tm 1000 (hitachi, japan) was used to study the surface morphology of the raw and activated zeolites. before the analysis, the 90 aluminum stubs were coated with an adhesive. the samples were strewn across the stubs. to prevent static charge, the samples were gold coated with an emscope sc500 sputter coater. xrd analysis: mineralogical characterization was performed using powder xrd instruments 93 (shimadzu, maxima-x xrd-7000, japan). measurements were carried out with cu kα radiation wavelength of 1.54056 å, angle of 2 θ (5-60°) and scanning step size of 0.02°. after milling to determine the degree of amorphization, the following equation was used: 96 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 5 of 13 𝐴 = 100 − 𝐾, %; 𝐾 = 𝐼𝑎𝑐𝑡 𝐼𝑟𝑎𝑤 ∙ 100, % (1) -amorphization%, crystallinity%, iact-x-ray diffraction intensity of activated sample, iraw-x-ray diffraction intensity of the raw sample. for the calculation of the amorphization rate, the average 99 of the (020) and (131) peaks was used. for approximate crystallite size determination was used scherrer equation: 𝐷 = 𝐾 𝜆 𝛽 𝑐𝑜𝑠𝜃 (2) 102 d mean size of crystallites, k – shape factor constant roughly 0.90, depends on the shape of crystallites, β full width at half maximum in radians, λ x-ray wavelength, the non-overlapping (020, 131, 151) peaks were used to determine the crystallite size of the 105 zeolite. for the cristobalite (111, 102, 200) peaks and for corundum (012, 104, 113) peaks were used. ftir analysis: the shimadzu, fourier transform infrared spectrometer (ftir 8200pc, japan), 108 was used for the measurements by using 100 scans at 4 cm−1 resolutions, over the ir region of 400–4000 cm−1. an air background spectrum was collected at the start of the sample analysis. samples were diluted with spectroscopic purity kbr at powder weight ratio to kbr 1:200. the 111 zeolite samples were measured three times and averaged for further processing. a background spectrum was measured before every sample to compensate for atmospheric conditions around the ft-ir instrument. 114 adsorption test of cr(vi): only to determine whether the reactivity of the zeolites milled alone and in combination with other materials changed, a sorption test was conducted. a batch adsorption experiment was performed to determine the effectiveness of removing cr(vi). 117 according to a review of the literature, acidic media are preferred for the adsorption of cr(vi). to conduct the adsorption test, we utilized ph 2. the ph variation and adsorption terms were not explored because the adsorption was not the main objective of the investigation. at 23°c 120 +/2°c, batch studies were carried out in beakers at a batch rate of 0.5 g of zeolite per 50 ml of fluid. in glass beakers containing 50 ml of chromium standards, raw zeolite (clinoptilolite), milled zeolite, zeolite milled with corundum, and zeolite milled with cristobalite were added, 123 respectively. all the reagents used were analytical grade. the 1000 mg/l chromium standards were prepared from k2cr2o7 (sigma). after 30 minutes of reaction time, the sorbents were removed by filtration 126 through a laboratory filter paper for qualitative analysis and the residual concentration of chromate ions was determined by the uv-vis spectrophotometric method. the samples were tested for adsorption of cr (vi) and its removal %. 129 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 6 of 13 𝑄𝑒 = (𝐶𝑖 − 𝐶𝑒 ) 𝑤 ∗ v (3) 𝐶𝑟 (𝑉𝐼) 𝑟𝑒𝑚𝑜𝑣𝑎𝑙 % = (𝐶𝑖 − 𝐶𝑒 ) 𝐶𝑖 ∗ 100 (4) where qe is amount of adsorbed cr(vi), ci and ce are the initial and equilibrium cr(vi) 132 concentrations of the test solution (mg/l), v is the test solution at volume (l), and w is the amount of adsorbent (g). batch experiments were performed in duplicate and the average value was used. 135 results and discussion characterization of zeolite: table 1 shows the results of the chemical analysis of natural zeolite. 138 according to table 1, the main elements of natural zeolite are sio2, al2o3, k2o, na2o, and fe2o3. clinoptilolite is the primary crystalline phase of raw zeolite, according to the xrd pattern (fig. 141 2a) of the material. the si to al molar ratio is 5.44. k+>na+>ca2+>mg2+ are the primary exchangeable cations. illite and feldspar are examples of aluminosilicate minerals that may also be present based on chemical analysis. 144 table 1. chemical composition of natural zeolite, weight% sio2 al2o3 k2o na2o fe2o3 cao cl mgo tio2 sro p2o5 mno so3 72.6 14.8 4.2 3.54 2.16 1.51 0.0307 0.709 0.207 0.125 0.042 0.0094 0.066 sem micrographs (fig. 1) show that natural zeolite consists of particles with the main sizes of 50 to 300 m. the raw corundum represents chunky particles with varying sizes of 50-400 m, 147 while the cristobalite represents spherical morphology particles with sizes of 50 m. the particle sizes of the samples were substantially smaller after grinding. particles smaller than 100 m in size make up the milled samples. the larger particles with diameters of 100 m should 150 represent oxide particles, whereas the smaller particles should represent natural zeolites, because natural zeolites are considerably softer than oxide particles. this assertion might be supported by the fact that the milled zeolite contains smaller particles than those that were milled 153 along with the oxide particles. ac ce pt ed m an us cr ip t mongolian journal of chemistry page 7 of 13 (a) (b) (c) (d) (e) (f) fig. 1. sem images of raw zeolite (a), activated zeolite (b), raw corundum (c), raw cristobalite (d), zeolite activated (co-milled) with corundum (e) and zeolite activated with cristobalite (f) at 156 different magnification. the xrd patterns of raw, milled, and co-milled with oxides zeolite samples are shown in fig. 2. 159 clinoptilolite is the primary crystalline phase in raw samples, with illite and feldspar as minor impurities. the composition of tsagaan tsav natural zeolite is similar to that of natural zeolites from deposits in slovakia and ukraine [12]. 162 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 8 of 13 fig. 2. xrd pattern of zeolite (a-raw zeolite/clinoptilolite; b-milled zeolite; czeolite co-milled 165 with corundum; dzeolite co-milled with cristobalite), (cl – clinoptilolite; co – corundum; cr – cristobalite) 168 grinding of natural zeolite alters the structure of zeolite and lowers xrd intensity (fig.2b). formula (1) determined that the amorphization rate of clinoptilolite milled alone was approximately 30.4%. however, there are many overlapped peaks, making it difficult to 171 accurately characterize them. however, almost no amorphization of clinoptilolite was observed in the co-milled corundum and cristobalite oxide particles. milling, in general, reduces crystallite size while increasing strain to a particular limit of crystallite and strain. then, as the milling time 174 increases, the crystallite size is usually observed to increase as a result of agglomeration of the milled particles. it can be argued that the soft natural zeolite particles are agglomerating, consequently their crystallite size change is insignificant. 177 the estimated crystallite size of the raw zeolite, the raw oxides and the co-milled oxide and zeolite samples determined by formula (2) is shown in table 2. the crystallite size of the milled zeolite was dramatically reduced from 22.58 to 15.84 nm. however, the crystallite sizes of the 180 zeolites in co-milled samples were almost identical to those of the raw zeolites. the average crystallite size of zeolite co-milled with corundum was 22.63 nm and 18.02 nm with cristobalite. in other words, virtually little mechanically induced zeolite amorphization occurred during milling. 183 the amorphization of the oxide particles happens easier than that of the clinoptilolite particles, according to xrd patterns of the co-milled oxides zeolite samples. in other words, the structural integrity of the soft zeolite did not change significantly when it was co-milled with the high 186 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 9 of 13 hardness oxides. hard oxide particles experience preferential amorphization and a reduction in crystallite structure. unexpected data showed that our first hypothesis was wrong. 189 table 2. approximate crystallite size of the raw and milled samples determined by scherrer equation samples the miller indices (hkl) average d (nm) raw zeolite 020 22.58 131 151 milled zeolite 020 15.94 131 151 raw corundum 012 52.20 104 113 crystallite size of the corundum milled with zeolite 012 46.94 104 113 raw cristobalite 111 29.73 102 200 crystallite size of the cristobalite milled with zeolite 111 22.67 102 200 192 due to its extreme hardness, corundum is the mineral that is frequently used as an abrasive. the following are the used milling media and powders hardness: clinoptilolite < cristobalite < hardened steel < corundum. the following are the densities of the same materials: zeolite < 195 cristobalite < corundum <hardened steel. the current study reveals that the density of the milling media possibly has a greater impact on the microstructure of the milled powders than the hardness of the powders being employed. 198 the total alkali-silica (tas) diagram, which is based on the total alkali (k2o+na2o) and silica (sio2) ratio of volcanic rocks, indicates (not shown here) that the used zeolite is found in the rhyolite area or is the same as the idaho zeolite deposit of the tuff enriched in sio2 [12]. 201 according to one theory, clinoptilolite typically develops from tuffs as a devitrified byproduct of volcanic glass or appears in rhyolite holes [13]. the tas diagram supports this assertion. in fig. 3, the mid-ftir spectra of raw, milled, and co-milled zeolite with corundum and 204 cristobalite are shown in the lattice vibrations (4000-400 cm-1) area. ac ce pt ed m an us cr ip t mongolian journal of chemistry page 10 of 13 fig. 3. ftir spectrum of raw zeolite and milled zeolite (a) and zeolite milled with corundum 207 and cristobalite (b). the primary adsorption bands in raw clinoptilolite are located at 463, 601, 719, 785, 1041, 1635, 210 3443, and 3612 cm-1. the raw clinoptilolite ftir spectra closely resemble those provided by bohacs et al., putra and kusumawati, and mansouri et al. [11, 14, 15]. at 1040 cm-1, a large broadband was seen. at 1635, 3443, and 3612 cm-1, the bands are present. the hydroxyl of 213 illite [11], silanol, or aluminol (si-o(h)-al bridging hydroxyls) groups associated to broensted acidity [14] are assigned to the band over 3600 cm-1. the water molecules linked to the native zeolite structure are responsible for the bands at 3443 and 1635 cm-1 [11, 15]. near 1040, 785, 216 and 463 cm-1, additional bands can be seen. the 1040 cm-1 band corresponds to asymmetric stretching vibration modes of internal t–o bonds in to4 tetrahedra (t = si and al) as previous authors have always described [11, 15]. the 785 and 463 cm-1 bands are assigned to the 219 stretching vibration modes of o–t–o groups and the bending vibrations of t–o bonds [16]. some authors [11] described the appearance of the shoulder at wave number 860-920 cm-1 as a result of mechanically induced crystallite size decrease in the zeolite and a broadening band 222 at 1060 cm-1 as a result of mechanical amorphization. such alterations in the ftir spectrum were not observed in the current study of mechanically milled clinoptilolite. the zeolites co-milled with the corundum and cristobalite (fig. 3b) displays distinct bands for the zeolites, the typical 225 band of the corundum at 590 and 637 cm-1, and the cristobalite at 793 cm-1 [17, 18]. the water band centered at 1630, 3441, and 3661 cm-1 grew more in the zeolite sample co-milled with corundum than in the co-milled cristobalite sample. it implies that zeolite and corundum mixes 228 adsorb more water than zeolite and cristobalite blends. as a result, higher porosity and amorphization of zeolite in the co-milled with corundum than in the co-milled with cristobalite, which in agreement with the crystallite size data provided in table 2. 231 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 11 of 13 fig. 4. removal efficiency (%) of chromium (vi) adsorption by raw zeolite and milled zeolite with corundum and cristobalite. 234 fig. 4 demonstrates that the cr(vi) removal effectiveness of milled samples (eq. 4) is relatively similar each other. because the sorption test was not performed under optimal conditions, the 237 presented results should be interpreted as the comparative value of each sample under the conditions described in the characterization section. the removal efficiency of zeolites co-milled cristobalite and corundum is comparable to that of milled zeolite sample. minimal changes in 240 removal efficiency may indicate that structural changes in zeolite were not favorable in the mechanically milled zeolite's cation exchange capacity, confirming previous research [11]. the results of a preliminary study on the cr(vi) adsorption of raw, milled and co-milled with corundum 243 and cristobalite zeolites show that co-milling with high hardness oxides is not the best method for enhancing the reactivity of natural zeolite in terms of adsorption effectiveness. in comparison to zeolite milled alone, agglomeration and microstructural changes in soft and low-density 246 natural zeolites that are co-milled with high hardness oxides are minimal. as shown by the cr(vi) adsorption test, the reactivity of the co-milled natural zeolite was not improved. co-milling oxides should have a higher density than high hardness if the natural zeolite is required to undergo 249 greater structural changes. conclusions natural zeolites milled alone undergo mechanical amorphization which reduces crystallite size. 252 the rate of amorphization of the milled zeolites was not accelerated by co-milling with the highhardness oxides. however, the crystallite size of the milled samples has slightly decreased. the high-hardness corundum oxide initially becomes structurally distorted when they are co-milled 255 with soft zeolite using a high-density milling medium. it is preferred to mill with highac ce pt ed m an us cr ip t mongolian journal of chemistry page 12 of 13 density powders as opposed to high-hardness oxides, which could cause greater amorphization and considerable microstructural changes in the raw zeolite. when the clinoptilolite is milled 258 alone or in combination with other high hardness oxides, about 72-75% of the cr(vi) can be removed from the water solution. acknowledgments 261 this work has been supported by the research office of the mongolian national university of education. 264 references 1. margeta k., farkaš a. 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(2009) study of the thermoluminescence emission of a natural α-cristobalite. radiation effects & defects in solids, 164, 59-67. https://doi.org/10.1080/10420150802270995 https://doi.org/10.1016/j.micromeso.2014.04.006 https://doi.org/10.5564/mjc.v12i0.181 https://doi.org/10.1007/s10853-018-2502-2 https://doi.org/10.3390/min11101030 http://webmineral.com/data/clinoptilolite-na.shtml#.yflutbf19jk https://doi.org/10.22159/ajpcr.2018.v11i11.24366 https://doi.org/10.5277/epe130111 https://doi.org/10.1016/0584-8539(82)80070-6 https://doi.org/10.1080/10420150802270995 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 1 of 18 treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching nyamdelger shirchinnamjil, narangarav tumen-ulzii, nemekhbayar davaadorj, khulan byambasuren, sarantsetseg purevsuren, ulziibadrakh erdenebat, enkhtuul surenjav* institute of chemistry and chemical technology, mongolian academy of sciences, ulaanbaatar 13330, mongolia *author to whom correspondence should be addressed enkhtuul surenjav laboratory of inorganic chemistry institute of chemistry and chemical technology mongolian academy of sciences ulaanbaatar, mongolia e-mail: enkhtuul@mas.ac.mn orcid: https://orcid.org/0000-0002-2357-5339 this article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, and proofreading process, which may lead to differences between this version and the official version of record. please cite this article as: nyamdelger sh., narangarav t., nemekhbayar d., khulan b., sarantsetseg p., ulziibadrakh e., surenjav e. treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching. mongolian journal of chemistry, 24(50), 2023, xx-xx https://doi.org/10.5564/mjc.v24i50.1310 mailto:enkhtuul@mas.ac.mn https://orcid.org/0000-0002-2357-5339 https://doi.org/10.5564/mjc.v24i50.1310 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 2 of 18 treatment of copper-containing leaching residue by sulfation roasting followed by acid/water leaching nyamdelger shirchinnamjil, https://orcid.org/0000-0003-1242-7776 3 narangarav tumen-ulzii, https://orcid.org/0000-0003-0010-1402 nemekhbayar davaadorj, https://orcid.org/0000-0001-5484-1807 khulan byambasuren, https://orcid.org/0000-0002-5617-1605 6 sarantsetseg purevsuren, https://orcid.org/0009-0005-8860-0928 ulziibadrakh erdenebat, https://orcid.org/0000-0002-4397-9525 enkhtuul surenjav*, https://orcid.org/0000-0002-2357-5339 9 institute of chemistry and chemical technology, mongolian academy of sciences, ulaanbaatar 13330, mongolia 12 abstract 15 this research investigates the extraction of copper from copper-containing leaching residue, which includes 33.45% of copper, 14.14% of iron, 23.87% of sulfur and trace amounts of silver and other elements. roasting the copper-containing residue under air and oxygen flow convert 18 sulfides into sulfate, followed by water and acid leaching to extract copper. the process parameters, including leaching temperature, sulfuric acid concentration, leaching time, solid-toliquid ratio, and agitation speed, were optimized for both water and acid leaching methods. 21 results showed that the maximum copper dissolution efficiency was 93.12% with water leaching, and 97.16% with acid leaching. chemical analysis revealed that the water and acid leaching residue contained 48.13% and 31.64% of iron, respectively. this study provides 24 valuable insights into the process optimization for copper extraction from copper-containing leaching residue, which can inform the development of more efficient and sustainable methods for metal recovery. 27 keywords: copper technogen concentrate, thermal analysis, airand oxygen roasting, acid/water leaching 30 https://orcid.org/0000-0003-1242-7776 https://orcid.org/0000-0003-0010-1402 https://orcid.org/0000-0001-5484-1807 https://orcid.org/0000-0002-5617-1605 https://orcid.org/0009-0005-8860https://orcid.org/0000-0002-4397-9525 https://orcid.org/0000-0002-2357-5339 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 3 of 18 introduction the growing demand for copper has resulted in the depletion of copper ores with higher copper content, leading to the treatment of complex polysulfides or copper ore with higher contents of 33 impurities such as sb, pb, zn, as, hg, ni etc. among these impurities, arsenic is particularly challenging due to its toxicity. there are several significant polymetallic ore deposits in mongolia including tsav, boorchi, tolbo, kharmagtai and asgat. in recent years, there has been interest 36 in developing the asgat deposit as well as other mineral deposits in the country, to meet the growing demand for metals and minerals worldwide. asgat polymetallic deposit is estimated to hold approximately 6402.6 thousand of tonnes of ore, boasting a valuable metal reserve 39 including 2247.8 tonnes of silver, 7264.6 tonnes of copper, 31830.9 tonnes of antimony and 3319.8 tonnes of bismuth. although asgat is primarly known for its polymetallic ore composition, it can also be regarded as a potential source of copper due to the significant presence of 42 tetrahedrite, which constitutes 72% of the asgat concentrate [1-3]. processing of polymetallic concentrates is difficult task as it involves a variety of minerals such as enargite (cu3ass4), tennantite (cu12as4s13) and tetrahedrite (cu12sb4s13) associated with 45 other sulfide minerals [4]. to separate the target metals from the polymetallic ore concentrate, scientists have focused on removing harmful impurities. comprehensive study on thermal and kinetic study of polymetallic copper concentrate was conducted by mitovski et. al [5]. 48 tetrahedrite represents the main chemical source of copper (40-46%) and antimony (27-29%) along with other important elements including arsenic, bismuth, mercury, and silver. two main leaching methods for tetrahedrite have been identifiedalkaline and acidic leaching [6]. balaz 51 et.al studied leaching of mercury and antimony from tetrahedrites of different characteristics using an alkaline solution [7] while the leaching of tetrahedrite using hci in the presence of ozone was studied by ukasik et. al [8]. 54 the leaching residue can be further processed through an appropriate roasting process to convert the metals into extractable form by heating at high temperature [9-11]. three types of roasting methods are commonly used including oxidation roasting, chlorination roasting, and 57 sulfation roasting [12]. however, oxidation roasting requires high temperatures and may lead to copper loss as copper ferrite. chlorination roasting tends to generate toxic and corrosive oxychlorides [13]. on the other hand, sulfation roasting has been found to be quite suitable for 60 subsequent processing. nevertheless, during sulfation roasting, the reaction becomes complex when more than one sulfide is present in the sample. roasting is a surface reaction that results in the formation of an oxide layer. this layer remains 63 porous allowing oxygen to pass into the unreacted inner sulfide portion of the particle, while the resulting so2 gas is released [14]. the sulfuric gas then reacts with metal oxides and excess ac ce pt ed m an us cr ip t mongolian journal of chemistry page 4 of 18 oxygen to form sulfates, making the sulfation roasting process an environmentally friendly 66 technology. to produce a mixed oxidesulfate product sulfation roast is preferred, making it an ideal process for polysulfide compound. while there have been numerous investigations conducted, our study provides a comprehensive analysis of copper extraction from copper 69 technogen concentrate sourced from domestic ore deposits. this study aimed to assess the effectiveness of extracting copper from copper-containing leaching residue of polysulfide concentrate. the process involved sulfation roasting followed by 72 leaching with water and sulfuric acid. to determine the optimal conditions for sulfation roasting, the study examined the effects of roasting temperature and time under an air and oxygen atmosphere. after roasting, the resulting product was leached using water and sulfuric acid to 75 obtain a copper-bearing aqueous solution. copper sulfate was the predominant compound in the solution. experimental 78 materials: the raw material used in this study was the polysulfide concentrate obtained from the asgat mining ore in mongolia. the concentrate was initially subjected to alkaline-sulfide leaching (using naoh/na2s x 9h2o) to obtain a technogen concentrate also named copper containing 81 leaching residue, containing 33.45% copper, which was subsequently utilized for copper extraction. tg/dta analysis: thermal analysis of the copper technogen concentrate was carried out using 84 hitachi-tg/dta 7300. the tga/dta analysis was performed under air atmosphere, in the temperature range of 30-1000 oc, at a heating rate of 20.0 oc /min. sulfation roasting: sulfation roasting experiments were conducted under air atmosphere using 87 a temperature-controlled tube furnace equipped with a quartz tube. for comparison purposes, sulfation roasting experiments under oxygen were also carried out using a home-made tube furnace. the oxygen flow is controlled via brooks sho-rate flowmeter installed on the inlet. 90 sulfuric acid leaching: acid leaching experiments were conducted to evaluate the effect of various parameters, including acid concentration, temperature, leaching time, solid-to-liquid ratio and agitation speed. for each leaching experiment, 1.5-3 g of sample and 20 ml of acid with 93 appropriate concentration were placed in a round bottom flask. the leaching time was varied from 30 to 120 mins, while the acid concentration used were 0.4m, 0.8m, 1.2m and 1.6m. the leaching temperature ranged from 25 oc to 70 oc with solid-to-liquid ratio of 1:6.67 (15%), 1:8 96 (12.5%), 1:10 (10%), 1:13.33 (7.5%). agitation speeds of 200, 300 and, 400 rpm were used with magnetic stirrer. ac ce pt ed m an us cr ip t mongolian journal of chemistry page 5 of 18 water leaching: in the water leaching experiment 0.27-0.84 g sample and 20 ml of water were 99 placed in a conical flask and subjected to different temperature ranging from 25 oc to 70 oc, with agitation speeds ranging from 200 to 500 rpm at 100 rpm intervals. the leaching time varied between 30, 60 and 120 mins, with solid/liquid ratios of 1:25, 1:50 and 1:75. 102 after completion of the leaching process, the slurry was filtered and the leaching residue was washed continuously with distilled water and dried in an oven. the leachates and leach residue were analyzed using icp-oes, xrd, sem and chemical analysis to determine the constituents. 105 results and discussion asgat polymetallic ore concentrate is composed of several metals, including 0.91% silver, 18.2% copper, 19.4% antimony, 2.03% arsenic, and 1.6% bismuth, as well as other elements. in order 108 to remove toxic contaminants such as antimony, arsenic, and bismuth, the concentrate was subjected to alkaline-sulfide leaching. the activation energy for antimony leaching from the tetrahedrite by alkaline-sulfide leaching was calculated as 81.43 kj/mol which indicates the 111 leaching is controlled by surface chemical reaction [15]. these findings are consistent with those of other researchers [16]. the elemental composition of asgat concentrate and leaching residue are compared in table 1 114 [15]. the alkaline-sulfide leaching residue contains 33.45% of copper, 14.14% of iron, 23.87% of sulfur, 0.73% of silver and other trace elements such as silicon, aluminium and sodium. according to the xrd analysis, the leaching residue contains chalcopyrite (cufes2), covellite 117 (cus), chalcocite (cu2s), pyrite (fes) and argentite (ag2s) as well as non-ore sulfide minerals as shown in fig. 1 and table 2. 120 table 1. the elemental composition of concentrate and the leaching residue sample elements, % ag sb as cu fe zn pb bi s concentrate 0.91 19.40 2.03 18.20 10.6 0.51 0.09 1.67 13.60 leaching residue 0.73 0.14 0.22 33.45 14.14 0.93 23.87 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 6 of 18 123 fig. 1. xrd analysis of copper-containing leaching residue table 2. phase identification by xrd analysis of copper-containing leaching residue 126 minerals formula contents, % chalcopyrite cufes2 43.24 chalcocite cu2s 6.03 covellite cus 3.51 argentite ag2s 6.95 albite naalsi3o8 38.47 tg/dta analysis: tga/dta thermogravimetric analysis was conducted to study the sample’s initial oxidation temperature, and mass change during the 30-1000 oc temperature range. the 129 comparison of tga/dta results with xrd phase identification of the sample will help to understand the complex reaction mechanism during the sulfation roasting. tga/dta analysis was done for copper-containing leaching residue at a heating rate of 20.0 oc/min in the 132 temperature range of 30-1000 oc under air atmosphere. as seen from the thermogravimetric curve cf. fig 2 when the sample is heated from room temperature till 315 oc there is slow weight loss of 2.9% was observed due to the evaporation of 135 moisture and organics as well as hydrates decomposition. eventually, the weight increase was observed and become 100.02% at 343.29 oc indicating the sulfides are oxidized and sulfates produced. roasting the sample further from 343 to 600 oc results in weight gain of a maximum 138 of 128.99% at 600.79 oc indicating the sulfation roasting fully occurred at this temperature range based on the theoretical calculation. the weight increase up to 600 oc is attributed to the production of copper sulfate. however, the iron sulfate production will also affect weight 141 increase. after 600 oc the weight loss occurs till 943.52 oc resulting the sulfur oxide which is associated with the decomposition of sulfates. to summarize, when copper-containing leaching residue is subjected to thermal analysis, weight gain of 28.7% occurs at a temperature range of 144 350-600 oc, whereas the total weight loss is 14% during the entire roasting at 25-1000 oc. ac ce pt ed m an us cr ip t mongolian journal of chemistry page 7 of 18 during the thermal treatment the following reactions are predicted. for example: 2cufes2 + 7.5o2 = 2cu2s + 2fes + 2so2 ∆g823,15к = 190 kj/mol (1) 147 3fes + 5o2 = fe3o4 + 3so2 ∆g823,15к = -1443.78 kj/mol (2) 2fes + 3.5o2 = fe2o3 + 2so2 ∆g823,15к = -1049.76 kj/mol (3) cu2s + so2 + 3o2 → 2cuso4 ∆g823,15к = -533.06 kj/mol (4) 150 2cus + so2 + 3o2 → 2cuso4 ∆g823,15к = -658.21 kj/mol (5) ag2s + 2o2 = ag2so4 ∆g823,15к = -392.71 kj/mol (6) fes2 + 3o2 = feso4 + so2 ∆g823,15к = -809.08 kj/mol (7) 153 fig. 2. thermogravimetric analysis of copper-containing leaching residue ∆got values for proposed reactions are calculated at 823.15k and it was found that all values 156 except for eq.1 are negative. this indicates that the reactions are thermodynamically feasible at the calculated temperature. roasting under air: the purpose of the roasting stage was to convert copper sulfide into easily 159 soluble copper sulfate. in comparison to conventional roasting processes, we have an advantage in using lower roasting temperature and eliminating the need for added sulfuric acid [9] or sodium sulfite as sulfation agent [12]. to achieve this, the copper-containing leaching 162 residue was underwent roasting in a nabertherm tube furnace under an air atmosphere at varying temperatures, ranging from 400 to 600 oc as determined by tg/dta analysis. roasting times varied from 15 minutes to 3 hours. 165 in this study, we examined the weight increase during sulfation roasting under varying times and temperatures. the results showed that the highest weight increase of 32.21% is occurred at 550 oc for one hour of roasting time under air atmosphere as shown in fig. 3. additionally, the color 168 difference of the roasted products can indicate whether sulfation roasting is complete. lighter ac ce pt ed m an us cr ip t mongolian journal of chemistry page 8 of 18 colors were observed at lower temperatures or shorter roasting times, whereas completed roasting resulted in darker colors due to copper sulfation. 171 the chemical composition of the roasted product is confirmed through an xrd study (refer fig. 4) revealing that 67.8% of the product was comprised of copper sulfate, while 27.2% composed goethite and 4.8% albite. this finding indicates that almost 95% of copper was successfully 174 converted to copper sulfate during the roasting process. the oxidation of chalcopyrite, covellite and chalcocite during roasting was responsible for this conversion [17]. furthermore, iron compounds were also present in the roasted product in addition to copper sulfate. 177 roasting under oxygen: the copper-containing residue was subjected to roasting under varying conditions of temperature, time, and oxygen flow rate. the results of the study, depicted in fig. 3, showed that the maximum weight gain for air roasting was 32.21% at one hour of roasting 180 time, while oxygen roasting produced a maximum weight gain of 29.85%. however, when the roasting time was increased to three hours, the maximum weight gain for oxygen roasting was found to be 33.15%. x-ray diffraction (xrd) data indicated that with roasting times less than 183 three hours at temperature less than 400 oc for oxygen roasting, fes2 and cus still existed, suggesting that the sulfation roasting was not complete. at three hours of roasting time, copper sulfates dominated, along with other minerals such as magnetite (fe3o4), goethite feo(oh), 186 and iron sulfates fe2(so4)3. therefore, the optimum conditions for oxygen roasting were determined to be a roasting temperature of 400 oc, a roasting time of 3 hours, and an oxygen flow rate of 20 ml/min (refer table 3). xrd analysis of the roasted sample revealed a 189 composition of 64.8% copper sulfate, 3.6% goethite, 4.5% hematite, 3.5% magnetite, and 18.7% albite with approximately 12% iron compounds present in the roasted product. 192 fig. 3. weight gain vs. the roasting temperature under the air and oxygen roasting (roasting time is 60 mins) ac ce pt ed m an us cr ip t mongolian journal of chemistry page 9 of 18 fig. 4. xrd analysis for effect of roasting time at optimum temperature (at 400 oc, o2 roasted for 180 195 min (a) 120 min (b) 60 min (c); and at 550 oc air roasted for 180 min (d) 120 min (e) 60 min (f)) table 3. phase identification by xrd analysis during the sulfation roasting sample temp./ oc gas time/min roasted product major phase minor phase 1 400 air 60 cuso4 feo(oh), fe2o3 2 450 air 60 cuso4 fe2o3 3 500 air 60 cuso4 cuso4x5h2o, feo(oh) 4 550 air 60 cuso4 cuso4x5h2o, feo(oh) 5 600 air 60 cuso4 feo(oh), fe2o3 6 650 air 60 cuso4 feo(oh), fe2o3 7 300 o2 60 cuso4 cufes2, fes2 8 350 o2 60 cuso4 cufes2, fes2 9 300 o2 180 cuso4 feo(oh), fes2 10 350 o2 180 cuso4 feo(oh), fes2, cus 11 400 o2 180 cuso4 feo(oh), fe3o4, fe2(so4)3 composition of our sample, which includes metal sulfides such as chalcopyrite (cufes2), 198 covellite (cus), chalcocite (cu2s), pyrite (fes) and argentite (ag2s), makes the reaction during the roasting process highly complex. the chemical and mineralogical composition of the concentrate, as well as the temperature, are crucial factors in determining the product 201 composition during sulfation roasting. however, other process parameters such as particle size, mixing, reaction time and roasting technique can also significantly impact the final product [18]. the sulfation roasting process is complete at 550 oc during the air roasting, but, when oxygen 204 roasting is used, a lower temperature of 400 oc is required for the sulfation process. leaching test with water: the copper technogen concentrate was roasted under optimum conditions and subsequently leached using water at various temperature to obtain a copper-207 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 10 of 18 bearing aqueous solution. the water leaching experiments were conducted by varying the leaching time, temperature, agitating speed and solid-to-liquid ratio. the dissolution efficiency (%), which is a measure of how much of the total copper is dissolved, 210 was calculated using the equation given below: 𝐷𝑖𝑠𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 (%) = 𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑑𝑖𝑠𝑠𝑜𝑙𝑣𝑒𝑑 𝑚𝑒𝑡𝑎𝑙𝑠 𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑚𝑒𝑡𝑎𝑙𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑠𝑎𝑚𝑝𝑙𝑒 ∗ 100 the copper dissolution efficiency was found to be at its highest with a rate of 91.68% at 60 213 minutes for the air roasted sample and 86.42% at 30 minutes for the oxygen roasted sample (refer to fig. 5). with increase of leaching time, copper dissolution decreased for the oxygen roasted sample. iron dissolution was generally lower, with about 12% in present in the leaching 216 solution and the majority remaining in the leaching residue. fig. 5. copper and iron dissolution efficiency as a function of leaching time 219 (s/l ratio 1:50, 500 rpm, 25 oc) ac ce pt ed m an us cr ip t mongolian journal of chemistry page 11 of 18 fig. 6. copper and iron dissolution efficiency as a function of agitation speed (air: 60 min, s/l ratio 222 1:50, 25 oc; oxygen: 30 min, s/l ratio 1:50, 25 oc) the agitation speed is an another important parameter in leaching experiments, and its effect on copper and iron dissolution was studied within the range of 200-500 rpm. for the air roasted 225 sample, the copper dissolution rate decreased slowly until 400 rpm but, increased to 91.68% at 500 rpm. the copper dissolution rate for the oxygen roasted sample increased gradually with the increase of agitation speed and reached a maximum value of 93.12% at 400 rpm. iron 228 dissolution was generally low for the air roasted sample, whereas for the oxygen roasted sample, high iron dissolution was observed, especially at 300 rpm (refer to fig. 6). this can be attributed to the increased molecular motion of iron sulfate as agitation speed increased, leading to a 231 corresponding increase in iron dissolution. the copper and iron dissolution rates were also studied as a function of solid-to-liquid ratio, as shown in fig. 7. for both air and oxygen roasted sample, the optimum solid-to-liquid phase ratio 234 was found to be 1:50 with copper dissolution rates of 91.68% and 93.12%, respectively. we assume that water-insoluble compounds were also present in the roasted sample. at the 1:50 phase ratio, the iron dissolution rate was low, at 16.49% indicating that most of the iron 237 compound was left in the leaching residue. ac ce pt ed m an us cr ip t mongolian journal of chemistry page 12 of 18 fig. 7. copper and iron dissolution efficiency as a function of solid-to-liquid phase ratio (air: 60 min, 500 240 rpm, 25 oc; oxygen: 30 min, 400 rpm, 25 oc) during the water leaching experiment, the solution temperature was varied from 25 to 70 degree celsius. there was no significant change observed both air and oxygen roasted samples, 243 therefore all other experiments were conducted at room temperature. (refer to fig. 8). the effect of temperature on iron dissolution was minimal, as most of iron was left in the water leaching residue. 246 fig. 8. copper and iron dissolution efficiency as a function of temperature (air: 60 min, s/l ratio 1:50, 500 rpm; oxygen: 30 min, s/l ratio 1:50, 400 rpm) 249 leaching test with sulfuric acid: to compare the effectiveness of acid versus water leaching, the roasted samples underwent acid leaching experiments with acid concentration, solid-to-liquid 252 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 13 of 18 ratio, and agitating speed varied. as depicted in fig. 9, copper dissolution was better with the oxygen roasted sample compared to the air roasted sample. both airand oxygenroasted samples achieved optimal copper dissolution rates with a sulfuric acid concentration of 1.6m. 255 copper dissolution decreased with lower acid concentrations. the leaching time of 30 minutes was determined to be sufficient for achieving a dissolution efficiency of 98.43% in the oxygen roasted sample. however, the air roasted sample required an extended leaching time of 60 258 minutes to attain a slightly lower dissolution efficiency of 96.01%. fig. 9. the effect of leaching time and acid concentration on copper dissolution (air: 25 oc, s/l ratio 261 1:10, 300 rpm; oxygen: 25 oc, s/l ratio 1:10, 300 rpm) fig. 10 shows that the solid-to-liquid ratio had no significant effect on copper dissolution both for 264 airand oxygenroasted samples. at an solid-to-liquid ratio of 1:8, the copper dissolution was approximately 90.37% for the air roasted sample and 98.43% for the oxygen roasted sample. however, the dissolution of iron is highest with lower solid-to-liquid ratio, particularly for the 267 oxygen roasted sample. fig. 11 illustrates the impact of agitation speed on copper dissolution. in the case of the air roasted sample, 200 rpm was determined to be the optimal agitation speed as it resulted in 270 97.16% copper dissolution. however, the iron dissolution rate was found to be relatively high. for the oxygen roasted sample, the highest copper dissolution rate (99.59%) was achieved at 300 rpm, with a lower amount of iron dissolved in the leachate. 273 leaching processes of copper compounds in the water and sulfuric acid proceeds via diffusion and activation energy were calculated as 6.05 and 8.70 kj/mol. ac ce pt ed m an us cr ip t mongolian journal of chemistry page 14 of 18 276 fig. 10. the effect of solid-to-liquid ratio on copper dissolution (air: 1.6m h2so4, 25 oc, 60 min, 300 rpm; oxygen: 1.6m h2so4, 25 oc, 30 min, 300 rpm) 279 fig. 11. the effect of agitation speed on copper dissolution (air: 1.6m h2so4, 25 oc, s/l ratio 1:8, 60 min; oxygen: 1.6m h2so4, 25 oc, s/l ratio 1:13.3, 30 min) 282 fig. 12 compares the water leaching residue and acid leaching residue obtained. the airand oxygenroasted samples (black and pink curves) primarily consist of chalcocyanite and goethite, 285 while the waterand acid-leached samples contain albite, anorthite, hematite, and goethite. the hard residue left after water leaching contains 33.4% albite (na[alsi3o8]), 7.1% anorthite (caal2si2o8), 13.7% goethite (feo(oh)) 14.5% maghemite (-fe2o3), and 31.0% hematite (-288 fe2o3) with total iron accounting for 48.13% according to chemical analysis. the sem-edx analysis of the leaching residue confirms the presence of a high amount of iron 44.77% along with 44.94% oxygen, 0.82% silicon at measured point (refer fig.13a). 291 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 15 of 18 this residue could be utilized as an iron resource and further processed to recover iron, thereby ensuring complete utilization of the raw material without generating any waste. the morphology of the leaching residue after the water and acid leaching both for air (a,b) and 294 oxygen (c,d) roasted samples were shown in fig. 13. sem-eds analysis confirmed the intensity of energy peaks corresponding to fe, o2 and si with about 44% of fe content. 297 fig. 12. xrd analysis of leaching residue compared with the roasted sample. a) acid leaching residue (o2 roasted), b) water leaching residue (o2 roasted), c) oxygen roasted sample, d) acid leaching 300 residue (air roasted), e) water leaching residue (air roasted), and f) air roasted sample 303 a b ac ce pt ed m an us cr ip t mongolian journal of chemistry page 16 of 18 fig. 13. sem micrographs of leaching residue; a) water leaching residue of air roasted sample b) acid leaching residue of air roasted sample; c) water leaching residue of oxygen roasted samples, d) acid 306 leaching residue of oxygen roasted samples copper bearing aqueous solution: the resulting leach liquor after the water/acid leaching will be 309 further utilized to produce a high-purity electrolyte with a high concentration of cu through solvent extraction. this electrolyte will then be used to electroplate a pure cathode copper. our study suggests a shorter flowsheet of extracting the copper from the polysulfide concentrate, 312 which includes a leaching process to remove the impurities such as arsenic, sulfation roasting, water/acid leaching and subsequent solvent extraction. 315 conclusions we systematically optimized the leaching processes for extracting copper from air and oxygen roasted samples using both water and sulfuric acid leaching methods. the parameters for water 318 leaching included a temperature of 25 oc, agitation speed of 500 rpm, solid-to-liquid ratio of 1:50 and a leaching time of 60 minutes. for acid leaching, we used a temperature of 25 oc, agitation speed of 200 rpm with a solid-to-liquid ratio of 1:8, and a leaching time of 30 minutes, with 1.6м 321 h2so4. our results indicated that acid leaching yielded a higher copper dissolution efficiency compared to water leaching, with values of 97.16% and 91.68%, respectively, for air roasted sample. 324 similarly, for the oxygen roasted sample, acid leaching achieved a copper dissolution efficiency of 95.53%, while water leaching resulted in 93.12%. notably, both methods exhibited a certain degree of iron dissolution efficiency, with approximately 15% and 30% present in the leachate 327 for the air roasted and oxygen roasted samples, respectively. xrd analysis confirmed the presence of hematite, goethite, magnetite and albite in the hard residue. after water and acid leaching, the hard residue contained 48.13% and 31.64%, total 330 iron, respectively. this indicates that water leaching was more effective in separating the iron compound, resulting in a higher concentration of iron in the hard residue. in conclusion, our c d ac ce pt ed m an us cr ip t mongolian journal of chemistry page 17 of 18 study highlights the optimized leaching processes for copper extraction from roasted samples. 333 acid leaching exhibited superior copper dissolution efficiency, while water leaching demonstrated better separation of iron compounds. these findings contribute to the understanding of efficient extraction methods and the potential for maximizing copper recovery 336 while minimizing the presence of unwanted elements like iron. acknowledgments 339 this research was supported by a fundamental research project from the ministry of education and science of mongolia funded by the mongolian foundation for science and technology under contract no. shuss. 2020/21. 342 references 1. javkhlan o., munkhtsengel b. 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(1999) thermoanalytical studies on copper-iron sulphides. j. therm. anal. calorim., 58, 625-637. https://doi.org/10.1023/a:1010108729034 18. nyamdelger sh., narangarav t-u., nemekhbayar d., sarantsetseg p., surenjav e. et al., (2022) copper extraction from the sulphation roasted copper technogen concentrate. bulletin of the institute of chemistry and chemical technology, 10, 1-9. https://doi.org/10.5564/bicct.v10i10.1483 https://doi.org/10.5277/ppmp160134 https://doi.org/10.2320/matertrans.43.532 https://doi.org/10.4236/ijnm.2015.42002 https://doi.org/10.1007/s10311-020-01047-0 https://doi.org/10.1007/978-3-030-58069-8_2 https://doi.org/10.5564/bicct.v4i9.1814 https://www.sciencedirect.com/science/article/abs/pii/s0304386x10000824#! https://doi.org/10.1016/j.hydromet.2010.03.014 https://doi.org/10.1023/a:1010108729034 https://doi.org/10.5564/bicct.v10i10.1483 introduction today’s high-performance computers allow for the ground-state dft geometry optimization of molecules with about 100 atoms in a single day. according to moore’s law, in 25 years the computing power will increase by a factor of 106 [1], and algorithms will improve, so advances in experimental chemistry will not be comparable to advances in computing power. quantum chemical computing will become an essential tool for studying chemical problems, even surpassing experimental observations, and by 2050, chemical research methods will be very different. therefore, it is crucial to focus current research and future efforts on theory development. many chemical processes and biological systems operate based on weak intermolecular interactions [2], so weak intermolecular interactions have been of particular interest in chemistry [3-20], for example, in the field of gas chromatographic separations using capillary columns, where weak intermolecular interactions play an irreplaceable role [21], we found that hydrogen bonding plays a critical role in the retention time of acetic acid (aa) when using gas chromatography to analyze short-chain fatty acids (scfas) dissolved in dimethyl sulfoxide (dmso) [22, 23]. hydrogen bonding is a frequent weak intermolecular interaction, similar to chemical bonding in that it is directional and saturated, while the bond energy of hydrogen bonding is much smaller than that of chemical bonding. the bonding mechanism of hydrogen bonds is different from chemical bonds in that hydrogen bonds are a special type of the intermolecular force, dipole-dipole. the formation of hydrogen bonds involves electron donors and electron acceptors, where the electron acceptors mu r et al., mong. j. chem., 23(49), 2022, 19-26 https://doi.org/10.5564/mjc.v23i49.1407 a quantum chemical study of the interaction of carboxylic acids with dmso mu ren1, ao rigele2, na shun3, narantsogt natsagdorj1* 1department of chemistry school of mathematics and natural sciences, mongolian national university of education, ulaanbaatar, 14191, mongolia 2academic affairs, hulunbuir university, hulunbuir, 021108, china 3agilent technologies china co., ltd., beijing, 100102, china * corresponding author: narantsogt@msue.edu.mn; orcid id: 0000-0002-1040-1276 received: 23 march 2022; revised: 11 may; accepted: 19 may 2022 abstract quantum chemical computational methods, which use quantum mechanics and molecular dynamics theory, have developed rapidly in the past few decades, and quantum chemical computation has penetrated almost all fields of chemistry. hydrogen bonds are ubiquitously common weak intermolecular interactions. moreover, the bonding mechanism of hydrogen bonds is considered to be different from that of chemical bonding. because of the difficulty of experimental studies, a more accurate calculation of hydrogen bonding from theory is a more convenient and direct method to understand hydrogen bonding. density functional theory (dft) is the most widely used general function in quantum chemical calculations, giving accurate results for most chemical systems. in this paper, the geometries of the hydrogen-bonded dimer complex of acetic acid and dmso was structurally optimized and potential energy surface was determined. the geometries of four related hydrogen-bonded dimer complexes were fully optimized using the m06-2x/6-311++g (3d, 2p) exchangecorrelation functional with dft-d3(bj) empirical dispersion correction. we found that hydrogen bonding is a mixture of electrostatic interactions and covalent bonding, and that hydrogen bonding is a kind of force with different percentages of electrostatic and covalent character, rather than a special force independent of chemical bonding. thus, more clearly defining our inherent classification of forces between substances provides a new perspective for our future study of weak interactions such as hydrogen bonding. keywords: quantum chemistry, hydrogen bonding natures, acetic acid, dimethylsulfoxide mongolian journal of chemistry www.mongoliajol.info/index.php/mjc © the author(s). 2022 open access. this article is distributed under the terms of the creative commons attribution 4.0 international license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the creative commons license, and indicate if changes were made. 19 https://doi.org/10.5564/mjc.v23i49.1407 https://orcid.org/0000-0002-1040-1276 mu r et al., mong. j. chem., 23(49), 2022, 19-26 must be positively charged hydrogen atoms [5]. a more accurate calculation of hydrogen bonding from theory is an obvious way to understand hydrogen bonding, since experiments can be a complicating factor. liu et al. performed aimd calculations on the structure of hydrogen bonds in liquid water [24], dereka et al. investigated (hf)2 hydrogen bonding using quantum chemical calculations combined with experimental methods [25], and alkorta et al. described noncovalent interactions in detail using quantum chemical calculations [26]. however, the definition of hydrogen bonding still seems to be vague. the focus of this paper is to present the research methods of quantum chemistry and its utility for studying hydrogen bonds. the hydrogen-bonded dimer complexes were fully optimized using the m06-2x/6311++g (3d, 2p) exchange-correlation function with basis set superposition error (bsse) [27] of dft-d3(bj) empirical dispersion correction [28]. the hydrogen bonding in the active site was determined using the electrostatic potential (esp) results of the molecule; a quantum-chemical explanation of hydrogen bonding was derived using molecular orbital theory (mo) [29, 30]; confirmation of the directionality of hydrogen bonding was determined using a potential energy surface scan; estimates and comparisons of the energy of intermolecular hydrogen bonds in the geometries of the related 2 hydrogen-bonded dimer complexes (formic acid (fa)-dmso and trifluoroacetic acid (tfa)-dmso) were determined using the m06-2x/6311++g (3d, 2p) exchange-correlation function with dft-d3 (bj) empirical dispersion correction. based on the above calculations, we propose a supplement to the traditional understanding of hydrogen bonding. experimental methods of quantum chemistry: in classical mechanics, newton’s second law describes the motion of macroscopic objects. in quantum mechanics, schrödinger proposed the fluctuation equation to describe the state of motion of microscopic particles, which became the most fundamental equation of quantum mechanics and the theoretical basis of quantum chemical calculations [31, 32]. the time-independent schrödinger equation can be written as: where ĥ is a hamiltonian operator and includes all possible interactions within that system. ψ is the wave function of the system containing all measurable information. e is the energy of the system and the eigenvalue of the schrödinger equation. on this basis, the traditional hartree-fock equation [33] or the dft method [34-36] both seek approximations to solve the schrödinger equation. molecular modeling: molecular modeling is simply the theoretical methods and computational techniques used to model or simulate the behavior of molecules [37]. each model is an approximate solution of the schrödinger equation, which includes theoretical approaches and basis sets. the rapid development of computer technology and rapid advances in density general function theory and molecular dynamics theory have made theoretical calculations a powerful tool for studying intermolecular forces. in 1998, the nobel prize in chemistry honored quantum chemists pople and kohn for their contributions to quantum chemistry. pople’s approach to quantum chemical calculations and kohn’s density functional theory are significant milestones in computational chemistry. mhamad chrayteh et al. used second-order perturbation theory (mp2), where aldehyde hydrogen atoms strongly interact with water oxygen atoms, in the case of diand tri-hydrates [38]. chen jun et al. used density flooding theory (dft) and molecular dynamics (md) simulations to study the hydration mechanism of kaolinite surfaces [39]. bilonda and mammino performed calculations of intramolecular hydrogen bonding in matter using different theoretical approaches and basis sets [40]. quantum chemical calculations played an essential role in all these studies. theoretically, the use of higher-level theoretical methods and more sophisticated basis sets can lead to more accurate computational results. however, this can also make the computation costly or even unattainable. ultimately, a trade-off between computational cost and computational accuracy needs to be made when choosing molecular simulations. in this paper, the trend or qualitative forecast of hydrogen bonding in the aa-dmso hydrogen-bonded dimer complex was found using the gaussian16 quantum chemistry package [41] in the dft calculations because the quantitative structure is not predicted. results and discussion hydrogen bonding sites electrostatic natures: the carboxyl group in aa is a combination of two functional groups connected to a single carbon atom, the hydroxyl group (-oh) and the carbonyl group (=o). this combination imparts unique natures to each functional group, including polarity, high electronegativity, and weak acidity. these functional groups are capable of hydrogen bonding by providing and accepting protons [42] and will produce strong hydrogen bonds with the polar non-protic solvent dmso. quantum chemical computations provide a good characterization of the intermolecular interactions and the sites of action. in this paper, structure-optimization and frequency calculations were performed separately for the aa molecule and the dmso molecule using the m062x/6-311++g(3d,2p) [43, 44] method and the dftd3bj [28] dispersion correction, which includes nbo [45] analysis and characterization of the hydrogen bonding sites between the solvent aa molecule and the dmso molecule. 20 ĥ ψ = e ψ # (1) mu r et al., mong. j. chem., 23(49), 2022, 19-26 the absence of imaginary frequencies is the end of the structural optimization-stable structure. in fig. 1, the different colors on the molecular surface correspond to the qualitative size of the surface electrostatic potential (esp). regions colored in red indicate the esp is negative: electrons concentrate more in these locations and positively charged particles have stronger interactions. regions colored in blue indicate the esp is positive: negatively charged particles more favorably interact in these locations [46]. the maximum positive esp value of the aa molecule concentrates in the upper portion of the carboxyl functional group (-oh), while the upper region of the s=o in the dmso molecule has a negative esp value; these two regions produce hydrogen bonding [47]. using the esp results, the aa molecule and dmso molecule follow the placement of fig. 1. esp has been a popular function for revealing electrostatic interactions between substances [48]. we chose the fa-dmso hydrogen-bonded dimer complex, which is similar to the aa-dmso hydrogen-bonded dimer complex. we performed esp computations, and the results were in concordance with the results of rohmann’s study [49]. we also performed esp calculations for hydrogen-bonded dimer complexes of aa with n-methyl-pyrrolidone (nmp) and aa dimethylformamide (dmf) (fig. 2), both of which are polar, non-protic solvents with similar dipole moments to dmso [50]. the results and hydrogen bonding interaction sites are consistent with the results of mu [51] and safonova [52] et al. esp accurately shows the hydrogen bonding action sites and effectively illustrates the electrostatic nature of hydrogen bonding. covalent nature of hydrogen bonds: homo/lumo interaction: hf is a typical hydrogen bonding system, and the structure-optimized geometry of the (hf)2 hydrogen bonding system according to previous reports [53-55] and using the computations of section 0 is shown in fig. 3(b). the angles of f-h...f-h are θ1 = 113° and θ2 = 7.6°, and the four atoms not in a straight line, which matches the action site characterized by the esp results of hf. however, the angle of action does not follow the results of the esp (fig. 3 (a)), and our computations are consistent with the studies of řezac [55] and howard [56]. frontier molecular orbital theory, which incorporates highest occupied molecular orbital (homo) and lowest unoccupied molecular orbital (lumo) calculations, is an important indicator for chemical reactions [57]. the formation of covalent bonds is the redistribution of electrons in the orbitals of frontier molecules when satisfying certain conditions [58, 59]. following the arrangement of the aa-dmso hydrogen-bonded dimer complex according to the hydrogen bonding sites, we used the calculation method in section 0 for structure optimization and frequency calculations. during the mapping of its molecular orbitals, we were able to determine the covalent natures of the aa-dmso hydrogen bonding: the redistribution of electrons in the aa molecule lumo+3 (fig. 4(a)) and the dmso molecule homo-1 (fig. 4(c)) forms homo-4 in the aadmso hydrogen-bonded dimer complex (fig. 4(b)). according to the above results, we cannot explain the hydrogen bonding energy by van der waals gravity and 21 fig. 1. the hydrogen bonding site of aa with dmso fig. 2. hydrogen bonding sites for similar hydrogen-bonded dimer complex of aa and dmso fig. 3. hydrogen bonding of (hf)2 (a) site and direction of (hf)2 interaction presumed by esp, (b) hydrogen bonding angle of (hf)2 fig. 4. hydrogen bonding associated molecular orbials of the aa-dmso hydr gen-bon ed dimer complex (a) lumo+3 of the aa molecule, (b) homo-4 of the aa-dso hydrogen-bonded dimer complex mu r et al., mong. j. chem., 23(49), 2022, 19-26 chemical bonding gravity alone [60], nor can we explain the hydrogen bonding angle of (hf)2 by electrostatic interactions alone, since the van der waals force is also an electrostatic interaction, and electrostatic interactions will only place the four atoms of (hf)2 in a straight line. the results of wolters [61] for hydrogen bonding between compounds containing halogens and our quantum chemical calculations indicate the involvement of covalent bonds in the hydrogen bonding interaction. directionality of hydrogen bonding: potential energy surface (pes) determination is one of the central concepts in quantum chemical calculations. according to the born-oppenheimer approximation, a pes is a mathematical or graphical relationship between the energy of a molecule (or collection of molecules) and its geometry [62], and we can represent the energy of a system as a function of geometric coordinates. we performed a pes scan of the aa-dmso hydrogenbonded dimer complex using the calculation method in section 0. in order to obtain the surface in threedimensional space to identify the directionality of the hydrogen bonds, the quantum chemical calculation selects only two variables: the hydrogen bond length l and its angle θ (fig. 5(a)), so the energy e of the system is a function of l and θ. fig. 5(b) shows the 3d pes of the system energy variation with hydrogen bond length l and angle θ. when the angle θ tends to 180° and the bond length l tends to 1.6 å, the energy of the aa-dmso hydrogenbonded dimer complex decreases, indicating that the aa-dmso hydrogen-bonded dimer complex is more stable and the hydrogen bond strength is stronger [6366], further indicating the hydrogen bond is directional. directionality is an essential indicator of covalent bonds. the strength of covalent bonds between atoms is strongly dependent on an angle [67]. the threedimensional pes of the aa-dmso hydrogen-bonded dimer complex demonstrate the directionality of hydrogen bonds and also indicate that hydrogen bonds have covalent nature. estimates of the energy of intermolecular hydrogen bonds: estimates of the energy of intermolecular hydrogen bonds can be characterized in several ways, of which the binding energy (be) is one of the most important quantities. the be, as used herein, is equivalent to the “interaction energy” between two monomers in complex geometry. quantum chemistry has become a routine and reliable method for estimating the be of various hydrogen bonds [68]. for example, a study evaluated the performance of dft generalized functions in calculating the binding energy of furan clusters. the results showed that the functionals m05-2x and m06 are recommended for further affordable investigations of the furan clusters [69]. in this section, the geometries of all three hydrogenbonded dimer complexes (table 1) were fully optimized using the m06-2x exchange-correlation functional with dft-d3(bj) empirical dispersion correction. 22 fig. 5. hydrogen bonding and three-dimensional pes of the aa-dmso hydrogen-bonded dimer complex (a) hydrogen bond length l and angle θ of the aa-dmso hydrogen-bonded dimer complex (b) hydrogen bonding pes of the aa-dmso hydrogen-bonded dimer complex fig. 6. esp for fa, aa, and tfa and the npa charge of the hydrogen atoms of fa, aa, and tfa involved in hydrogen bonding fig. 7. hydrogen bond lengths of fa-dmao, aa-dmso, and tfa-dmso project fa-dmso aa-dmso tfa-dmso npa charge (h atom)* 0.490 0.492 0.502 npa charge (o atom)* -1.015 -1.015 -1.015 hydrogen bond length (å) 1.587 1.618 1.490 hydrogen bond be (kj/mol) -61.743 -59.079 -73.955 table 1. npa charges of hydrogen bond atoms, hydrogen bond length, and energy notice: * npa charge (h atom) is the npa charge of the hydrogen atoms of fa, aa and tfa involved in hydrogen bonding. * npa charge (o atom) is the npa charge of the oxygen atoms of dmso involved in hydrogen bonding. mu r et al., mong. j. chem., 23(49), 2022, 19-26 for fully characterizing hydrogen bond interactions, we have utilized many other quantum chemical calculations in addition to bes, such as the hydrogen bond length, the npa charges of the atoms at the ends of the hydrogen bonds, and esp. using correlations between various well-known hydrogen bond-related quantum chemical calculations and estimated be values, we have shown that each of these quantum chemical calculations has its own ability to characterize the strength of hydrogen bond interactions. our calculations have revealed that the higher the npa charge difference of the hydrogen bond terminal atoms, the shorter the bond length. additionally, larger hydrogen bond energy is observed with lower electron density of the electron acceptor as determined by esp. we found from the strong hydrogen-bonded dimeric complexes that the electron acceptor of the hydrogen atom all contain atoms or groups of atoms with high electronegativity. conclusions in the work presented here, we have performed dft calculations for the aa-dmso hydrogen-bonded dimer complex using esp, homo/lumo, pes, and estimated and compared the energy of hydrogen bonds of four related hydrogen-bonded dimer complexes. the quantum chemical calculations have revealed the natures of hydrogen bonding in the aa-dmso hydrogenbonded dimer complex: electrostatic interaction is the main factor in the generation of hydrogen bonds, and the esp can characterize the site of action of hydrogen bonds; the redistribution of electrons in molecular orbitals provides hydrogen bonding with a significant degree of chemical bonding character, which is one of the reasons why the hydrogen bonding energy is between chemical bonding and van der waals forces, and the directionality of hydrogen bonding revealed by pes, and estimates of the energy of intermolecular hydrogen bonds is also consistent with this finding. different interactions link the atoms in a compound, and these links do not have a clear demarcation line, but can be considered a mixture of multiple interactions. therefore, on the premise that hydrogen bonding is a mixture of electrostatic interactions and 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hydrothermal treatment; cellulose recovery; biomass 24 digestibility https://orcid.org/0000-0002-0894-9929 https://orcid.org/0000-0002-0479-6179 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 3 of 15 introduction 27 increasing energy usage and the rapid depletion of fossil fuels require renewable energy development to reduce pollutions generated by fossil fuels. according to the energy information administration of the united states (eia), worldwide energy demand will 30 increase by 40% by 2040, reaching about 800 quadrillion british thermal unit, with the rising countries accounting for the majority of the demand increases [1]. due to its use as a fuel and other value-added chemical production, biomass or biofuel has attracted increasing 33 attention among the numerous renewable energy sources such as geothermal, hydro, wind, and solar [2]. the fact that lignocellulosic biomass makes up a large portion of plant matter makes it the 36 most plentiful renewable resource on earth. it is a desirable feedstock for making chemicals and fuels since it is accessible and affordable. the three main components of lignocellulosic biomass are cellulose (40–50%), lignin (15–20%), and hemicellulose (25–35%). rice 39 straw’s recalcitrant nature is one of the challenges for its biochemical conversion to bioethanol and methane. to convert biomass to biofuel, cellulose and hemicellulose molecules must be broken down into monomers or simple sugars. rice straw fermentation 42 is difficult in practice, which creates a significant barrier for lignocellulosic biomass in the bioconversion process [3]. in a sugar platform bio refinery, pretreatment is an important step in increasing biomass digestibility. several criteria define the goal of any pretreatment 45 procedure: (1) maximizing the final yield such as ethanol and other valuable products; (2) high amount lignin removal; and (3) reducing the formation of degradation products that can inhibit the action of produce biofuels [3, 4]. there are four main types of treatments, i.e., 48 physical, chemical, physicochemical, and biological methods in the hydrolysis of lignocellulosic biomass, and some of these treatment methods are very effective. many chemical, thermal, and biological pretreatment procedures have been extensively 51 researched to increase lignocellulosic biomass susceptibility to later enzymatic hydrolysis [5]. the use of water as the primary reaction medium with no other chemical additives makes hydrothermal pretreatment one of the most effective pretreatment techniques in terms of 54 both practical and environmental considerations [6]. hydrothermal (ht) processing of lignocellulosic materials has been studied under a variety of operational conditions in the past. ht treatment operating temperatures are typically 57 between 100 and 230 °c, though higher temperatures can be used. the efficiencies vary depending on the applied temperature and time, which are co-related factors. generally, 180 – 210 °c with a short holding time (1-15 minutes) can achieve the best sugar refinery 60 [7, 8]. some researchers suggested ht treatment with some chemicals such as acid and ac ce pt ed m an us cr ip t mongolian journal of chemistry page 4 of 15 alkali addition. according to imman et al. [9], the carbohydrate yield from ht treatment with acid and alkali were about 30 40% higher than that without chemical addition. however, 63 adding chemicals is not regarded as environmentally friendly. the liquid to solid ratio (lsr) of solid concentrations can range from 2 to 100 (w/w), with the most typical values being around 10 [5]. the interaction between ht temperature and holding time has a significant 66 impact on the selection of both the liquid and solid phases. it is widely assumed that ht treatment at a higher temperature for a short time will result in slightly better pentoses yield and less inhibitor formation [10, 11]. ht treatment at 200 210 °c for a short period is 69 effective: when corn stover was hydrothermally treated at 210 °c for 0 and 10 minutes, more than 90% of the xylan was solubilized [12, 13]. one of the most critical aspects in the process economics of commercializing lignocellulosic biomass conversion is energy 72 consumption. that’s why energy balance analysis is very important. according to he et al. [13], ht pretreatment gained energy about 2741 mj/t-rice straw when the process was performed at 150 °c for 20 minutes, which was 300 mj/t-rice straw more compared to the 75 methane production from no pretreatment group. in addition, the energy recovery from the ht and microwave pretreatment was 43 53% and 57 79%, respectively [14]. many researchers investigated the ht treatment on various types of lignocellulosic 78 materials, but there is little information about ht reactor head space's influence on sugar recovery. this research aimed to determine the suitable ht treatment conditions for rice straw to achieve digestible sugars which can be used for maximal ethanol production. 81 experimental materials: in this investigation, rice straw was collected from a farm area in tsukuba 84 (ibaraki-ken, japan) and cut up into small pieces and then be air-dried. the air-dried rice straw particles were milled for the experiment, with particle sizes ranging from 0.27 to 0.56 mm. before use, the milled straw was kept in a plastic container in the dark at ambient 87 temperature. the original rice straw used in this study contains 92.56% total solids, 50.3% total carbohydrates, 27.8% lignin and 10.44% ash. apparatus and procedure: in a 200 ml stainless-steel reactor, ht treatment was 90 performed. rice straw was treated at 4 temperature levels in the range of 180 – 210 °c for 0 min, 5 min, 10 min, and 15 min, respectively. the temperature in the ht reactor was increased at 12 °c/min on average, and the pressure was around 1 bar. in addition, when it 93 reached the holding time, the heater was powered off, and a table fan was used to cool it. the average cooling rate was 2 °c/min. nine different ht treatment conditions were performed in this study, which were labelled as ht180-10, ht180-15, ht190-10, ht200-5, 96 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 5 of 15 ht200-10, ht210-0, htp210-0(5), htp210-0(9), htp210-0(15). the first six experimental tests were to find out the suitable ht condition, and the last three experiments were to check whether the reactor pressure had any influence on the sugar yield. the installed pressure 99 meter was used to read the reactor pressure, which was around 1 2 mpa depending on ht conditions. the treated rice straw was centrifuged after ht treatment, and the solid ht residue was rinsed with distilled water. the ph value, total organic carbon (toc), volatile 102 fatty acids (vfas), and total carbohydrate of the isolated supernatant were all measured. after being washed with deionized water, the solid residue from ht was dried at 105 ºc for 24 hours and used to calculate the total yield based on the weight difference [15]. for future 105 usage, the pretreated dry biomass was packaged in plastic bags and stored in the dark. analytical methods: the national renewable energy laboratory (nrel) method was used to determine total solid (ts), volatile solid (vs), and calculate yield [15]. the concentration 108 of total soluble carbohydrates was measured using the phenol sulfuric acid technique with glucose as reference [16]. a ph meter was used to determine the ph value. individual vfa species in the liquid from rice straw during ht treatment was determined using gas 111 chromatography with a flame ionized detector (gc-8a, shimadzu corporation, japan). vfas were calculated as the sum of acetic, propionic, iso-butyric, n-butyric, iso-valeric, and n-valeric acids. a toc analyzer was used to determine the total organic carbon (toc) of 114 the ht liquid component (toc-v csn, shimadzu, japan). the modified method was used to determine the amounts of lignin, cellulose, and hemicellulose in ht treated dry biomass [15, 17]. in brief, 0.3 g of solid residue was mixed 117 with 3 ml of 72% w/w h2so4 on a laboratory shaker for 4.5 hours at ambient temperature (25 °c). the solution was then diluted to 4% and hydrolyzed overnight to convert cellulose to glucose. the liquid and solid components were then separated using vacuum filtration, 120 and the solid part was dried at 105 °c for lignin analysis. acid-soluble lignin and total carbohydrate were determined in the separated liquid. all the trials were done three times and the average results were presented. the structural 123 morphology of ht treated biomass and the raw rice straw were observed by optical microscopy. the structural modifications during the ht treatment were also investigated using an ft-ir spectrophotometer. 126 the energy consumption was estimated according to eq. 1 [13]. the rice straw disposal capacity was expected to be 1 ton in this study. 129 𝐸𝐻𝑇 = 𝑚𝑤𝑎 𝛾𝑤𝑎(𝑇𝐻𝑇 − 𝑇𝑎𝑡 ) + 𝑚𝑟𝑠 𝛾𝑟𝑠(𝑇𝐻𝑇 − 𝑇𝑎𝑡 ) (1) ac ce pt ed m an us cr ip t mongolian journal of chemistry page 6 of 15 where eht (mj) is the heat consumption by ht reactor; mrs (t) is the disposal capacity of rice straw; mwa (t) is the water usage; γwa is the specific heat capacity of water (4.18 kj/kg 132 °c); γrs is the specific heat capacity of rice straw (1.67 kj/kg °c); tht (°c) is the ht treatment temperature (180-210 °c in this study); tat is the temperature of the environment (25 °c in this study). 135 the out wall of the ht reactor would be supplied with thermal insulation material if it were implemented in practice; however, heat loss through the reactor wall during the ht process was ignored in this study. 138 results and discussion soluble products from ht treatment of rice straw 141 changes of ph value and extraction yield: ht treatment is an effective approach for the solubilization of biomass because the breakdown of macromolecular components is temperature-dependent. the ht extraction yield and ph value of the liquid fraction from ht 144 treatment are shown in fig. 1. the extraction yield reflects the amount of all dissolved components, including dissolved hemicellulose, cellulose, lignin, protein and other soluble compounds. the extraction yield varied from 31% (ht180-10) to 44% (ht210-0), and it was 147 slightly declined to 39% under htp210-0(5). as can be observed from the findings, increasing the peak temperature helped dissolve rice straw. the maximum extraction yield was achieved at 210 °c. under this ht temperature, an additional experiment was 150 conducted to check the influence of headspace pressure and it was adjusted by amount of straw. as the additional experiment`s result shows, the maximum ht treatment extraction yields were 44.3% in htp210-0(15), 39% in htp210-0(5), and 40% in htp-210-0(9), 153 respectively. this observation agrees with yu et al. [22] who found that the soluble yield was ~36% under 180 °c for 10 minute, which could be a little bit increased (~40%) at 200 °c. the ph values varied from 3.31 (ht200-5) to 4.31 (ht180-10). from fig.1, the ph value 156 was decreased from 4.31 to 3.31 (ht200-5), then slightly increased to 3.55 at ht210, probably due to a higher temperature especially > 200°c can break down some organic acids [18]. generally, when compared to the total extraction yield and ph value, a reverse 159 tendency was noticed: the increased extraction yield was accompanied by a decreased ph value, probably owing to the production of organic acids from the dissolved hemicellulose. ac ce pt ed m an us cr ip t mongolian journal of chemistry page 7 of 15 162 when the reactor headspace was changed, the ph values were also detected to change under 210 °c, which were degreased to 3.84, and 3.56 under htp210-0(5) and htp210-165 0(15), respectively. the results show that htp210-0(5) and htp210-0(9) conditions cannot substantially break down hemicellulose to organic acids when compared to ht210-0(15). this means that the reactor headspace or pressure may influence the extraction yield and 168 the liquid ph value. dissolved carbohydrate and toc from rice straw by ht treatment: the total dissolved carbohydrate was determined using the phenol-sulfuric acid method. this method can 171 reflect all types of sugars such as xylose, glucose and others. fig. 2 shows the production of total sugars in the liquid fraction from ht treatment, including monomeric and oligomeric sugars. the total carbohydrate concentration varied depending on the ht temperature and 174 holding time. the lowest value was 8.3% from ht180-10, which was increased up to 17.1% under ht210-0. the total carbohydrate in rice straw is mostly made up of easily soluble polysaccharides (hemicellulose and mono sugar), rather than crystalline cellulose that is 177 usually degraded at temperatures above 230 °c [19]. it means under ht210, the obtained dissolved total carbohydrate was mainly from the dissolved hemicellulose. total toc concentration in the liquid part of ht treated rice straw followed a similar pattern to total 180 carbohydrate concentration. the lowest value was 4927 mg/l from ht180-10, and the highest value was 7849 mg/l obtained under ht210-0. 31 36.3 42.9 43.9 43.6 44 39 40 44.3 4.31 3.93 3.85 3.31 3.35 3.55 3.84 3.85 3.56 3.0 4.0 5.0 6.0 7.0 10 20 30 40 50 p h v a lu e e x tr a c ti o n y ie ld ( % , w /w ) ht conditions extract yields, % extract ph value fig. 1. extraction yield and ph value of ht liquid fraction ac ce pt ed m an us cr ip t mongolian journal of chemistry page 8 of 15 183 based on the above results, the most suitable condition was determined as ht210-0, under which the highest carbohydrate yield and toc were achieved. for the headspace experiment, the amount of total carbohydrate and toc were lower in htp-210-0(5) and 186 htp-210-0(9), when compared to htp-210-0(15). more specifically, the total carbohydrates were 12.9% and 15.1% with toc being 6060 mg/l and 6156 mg/l when the ht treatment was conducted under htp-210-0(5) and htp-210-0(9), respectively. in contrast, the total 189 carbohydrate was 17.7% with toc being 7024 mg/l under htp-210-0(15). this observation also suggests that the reactor headspace effected on the extraction yield and liquid products. 192 dissolved organic acids in liquid fraction from ht treatments: under the hydrothermal condition, xylose molecules can be broken down with organic acid production, which can influence the liquid ph value [18]. the vfas obtained by ht treatment of rice straw at the 195 appropriate peak temperatures are shown in fig. 3. the total concentration of vfas was increased with the increase in ht temperature, while it was slightly degreased when prolonging the holding time. a longer holding time might break down some organic acids. 198 the dominant acid was acetic acid from all test conditions, accounting for 43% or 333 mg/l in ht180-10 to 96% or 847 mg/l in htp210-0 of the total vfas in the ht liquid fraction. ht210-0 produced the most successful solubilization of rice straw of all the test conditions, 201 mainly to the degradation of hemicellulose into xylose, which was then degraded into acetic acid. 4927 5612 7127 6999 6787 7849 6060 6156 7024 8.3 12.4 15.9 16.1 16.8 17.1 12.9 15.1 17.7 6 11 16 21 26 0 2000 4000 6000 8000 10000 t o ta l c a rb o h y d ra te ( % , w /w ) t o c ( m g /l , v /w ) ht conditions toc total carbohydrate fig. 2. soluble carbohydrate production and dissolved total organic carbons (toc) from ht liquid fraction ac ce pt ed m an us cr ip t mongolian journal of chemistry page 9 of 15 other vfa species were also detected. in the ht treatment liquid from ht180-10, there 204 were 93 mg/l propionic acid, 95 mg/l n-butyric acid, 70 mg/l iso butyric acid, 83 mg/l iso valeric acid and 92 mg/l valeric acid. the concentrations of these vfas were detected to decrease when the ht temperature increased over 200 °c. under ht200-5 condition, only 207 two vfas were detected, i.e., acetic acid (829 mg/l) and n-butyric acid (37 mg/l), suggesting that a higher temperature is beneficial for vfas decomposition. in addition, a lower vfas was detected in the liquid from htp210-0(5) and htp210-0(9) in 210 comparison to htp210-0(15). there were 3 noticeable unknown peaks from the gas chromatography results that need further confirmation by additional vfa standards. these unknown vfa products were observed to increase when ht treatment was conducted at 213 temperature over 200°c. they could be levulinic acid and formic acid, which are produced at high temperatures from furfural and 5-hmf. this observation agrees with the statement by liu et al. [20, 18] who detected the increase of these acids in the ht liquid part when 216 temperature was increased to 200 °c. the effect of ht treatment on the solubilization of rice straw was studied. the ht treatment yielded various amounts of carbohydrate and other products from rice straw. ht210 was 219 found to have a considerable impact on rice straw solubilization, boosting dissolved carbohydrate production with lower ph while also increasing vfa production. this observation suggests that this ht temperature is more suitable for hemicellulose 222 decomposition from rice straw. the reactor headspace experiment found that a smaller fig. 3. changes in individual volatile fatty acids (vfas) during hydrothermal treatment of rice straw at peak temperatures 0 200 400 600 800 1000 v f a ( m g /l ) ht conditions n valeric acid iso valeric acid n butyric acid iso butyric acid propionic acid acetic acid ac ce pt ed m an us cr ip t mongolian journal of chemistry page 10 of 15 headspace (htp210-0(15)) is more effective compared to htp210-0(5) and htp210-0(9), yielding higher extraction rate, total carbohydrate and toc concentrations. 225 solid residue fraction from rice straw by ht pretreatment lignin and total carbohydrates: the solid fraction from rice straw by ht treatment was dried at 105 °c for 24 hours after being separated by centrifuge. this dry residue is important as 228 it becomes a cellulose-rich biomass that could be used to produce ethanol and other useful products after hydrolysis. fig. 4 shows the contents of lignin and total carbohydrate in the ht treated dry biomass. the lignin content was detected as 27.8 to 48.0 % (w/w) in rice 231 straw and ht210-0, respectively. the breakdown of hemicellulose resulted in an increase in lignin content as the ht temperature goes up. results show that ht210 condition can remove most of the hemicellulose. 234 fig. 4. changes in lignin and total carbohydrate contents in the ht treated dry biomass the total carbohydrates varied from 29.3 to 50.3%. the highest carbohydrate content was 237 detected in the raw rice straw that contains all types of sugars such as hemicellulose, cellulose and soluble sugars. the lowest total carbohydrate content was 29.3 % in the treated dry biomass after 210 °c for holding 0 minute. this observation may indicate that 240 much hemicellulose has been removed and the remained carbohydrate might be only glucose. due to a lack of suitable conditions for the hplc, the contents of xylose, glucose, galactose, and arabinose were not measured in this study. 243 the reactor headspace experiments also have some difference on lignin and total carbohydrate contents. the highest lignin content was 47.1% in htp210-0(15) condition compared to other 2 conditions, indicating that condition is more efficient to decompose 246 hemicellulose. however, the carbohydrates of htp210-0(5), htp210-0(9) were higher than htp210-0(15) and they were 32.3%, 34.9%, respectively. it might be due to some amount ac ce pt ed m an us cr ip t mongolian journal of chemistry page 11 of 15 of hemicellulose residue without breakdown. from the headspace experiments, amount of 249 loaded sample including water should be greater than 80% of the reactor capacity. under this condition, a higher pressure would be created to break down the lignocellulosic materials compared to the lower filled (like 50 70%) reactor. 252 morphological changes of treated biomass: the morphological changes were observed by optic microscopy. the rice straw without treatment looks so smooth and without any significant damage. during the ht treatment process, the surface of the treated rice straw 255 particles became more open, considerably rougher, and displayed clearly porous structures, likely resulting in much more contact between water molecules and carbohydrates inside the straw particles. the most suitable conditions were ht210-0 and ht200-10 because the 258 smooth structure looked broken down. ft-ir analysis: under various ht treatment conditions, the ft-ir spectrum were recorded to investigate chemical structural changes in rice straw. as illustrated in fig. 5, the changes 261 in functional groups in the treated rice straw were particularly noticeable between the wavenumbers 600 cm-1 and 1800 cm-1. the signal at 1720 cm-1, corresponding to the c=o functional group, is a typical peak of ester connected acetyl, feruloyl, and ρ-coumaroyl 264 groups between hemicellulose and lignin. the disappearance of this peak above 200 °c shows that ht treatment may have eliminated hemicellulose by cleaving the ligninhemicellulose ester link. the signal observed at approximately 1432 cm−1 corresponds to -267 ch2 bending of cellulose [21]. the lignin-hemicellulose bond`s peaks at 1320 cm-1 (c-o of syringyl ring) and 1245 cm-1 (c-o of guaiacyl ring) were diminished in ht210-0. the peak at 1245 cm-1 (assigned to β-ether bonds in lignin and between lignin and carbohydrates [20] 270 was declined in the ft-ir spectrum of treated rice straw above 200 °c. these observations support the chemical components and optical microscopy findings. 273 fig. 5. ft-ir spectrum of original and treated rice straw ac ce pt ed m an us cr ip t mongolian journal of chemistry page 12 of 15 energy consumption by ht treatment: the energy consumption by ht treatment is one of the important factors that influence the energy efficiency of the whole system. a higher ht 276 temperature can easily break down the rice straw complex structure, while it may be economically infeasible when compared to lower temperature ht treatment in terms of energy efficiency. energy input was calculated based on per ton of extraction yield, meaning 279 how much energy was required for per ton of extract from ht treatment of rice straw. the energy input was calculated from the results obtained under htp210-0(5), htp210-0(9), and htp210-0(15) in order to well understand the effect of the ht reactor headspace. table 282 1 summarizes the required energy for per ton extract when ht treatment was conducted under the above conditions. 285 table 1. the energy input of ht treatment for the headspace experiment ht conditions water used (ton) rice straw used (ton) ht extraction yield (%) ht yield (ton) energy input (mj) for ht extraction energy input for per ton extract (mj) htp210-0(5) 5 0.5 39.0 0.195 4021 20620 htp210-0(9) 9 0.9 40.0 0.360 7238 20104 htp210-(15) 15 1.5 44.3 0.665 12063 18153 these data did not include the energy needed for drying after ht treatment. the energy 288 consumption was calculated as 20,620 mj, 20,104 mj and 18,153 mj by htp-210-0(5), htp-210-0(9) and htp-210-0(15), respectively. the lowest energy was consumed under htp210-0(15) condition due to its higher extraction yield than the other two ht210 291 conditions. this result also suggests that the ht reactor headspace is critically essential for the enhanced breakdown of rice straw when energy consumption is taken into consideration. however, a more detailed energy balance analysis is necessary when the final products 294 such as ethanol, methane and other useful products are considered, which might be different when different final products being concerned. 297 conclusions in this study, we investigated the effects of ht treatment on rice straw solubilization and residue changes. in terms of achieving optimal results, the ht treatment conducted at 210 300 °c for 0 minutes yielded the best outcome, with a soluble carbohydrate yield of 44% and a total organic carbon (toc) content of 17.1%. the temperature of ht treatment was found to exert a significant influence on the production of volatile fatty acids (vfas), with acetic 303 ac ce pt ed m an us cr ip t mongolian journal of chemistry page 13 of 15 acid being the predominant species in this condition. moreover, this study showed that ht treatment demonstrated higher efficiency at temperatures above 200 °c and short holding times, which was supported 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