{Removal of lithium from water by aminomethylphosphonic acid containing resin} J. Serb. Chem. Soc. 83 (9) 1059–1069 (2018) UDC 628.316.12+546.34:665.941:544.142.3: JSCS–5133 544.726 Original scientific paper 1059 Removal of lithium from water by aminomethylphosphonic acid-containing resin AYDIN ÇIÇEK, ONUR YILMAZ and ÖZGÜR ARAR* Ege University, Faculty of Science, Department of Chemistry, 35100, Izmir Turkey (Received 30 September 2017, revised 1 January, accepted 22 January 2018) Abstract: This paper gives an overview of the ability of an aminomethylphos- phonic acid-containing chelating resin for the removal of lithium from water. The studies were performed under various conditions, such as resin dose, initial Li+ concentration, solution pH and solution temperature. The results showed that the sorption of Li+ reached equilibrium within 15 min and the experimental data were well-fitted by the pseudo-second-order kinetic model. The Li+ sorp- tion was highly pH dependent, and the optimum pH for Li+ removal was ≥3. Isotherm sorption data displayed good correlation with the Langmuir model, and the maximum monolayer sorption capacity of the resin found to be 13.65 mg g-1. Thermodynamic studies suggested that Li+ sorption onto the chelating resin was an exothermic and spontaneous process in nature. The resin could be regenerated by 0.1 M HCl, NaCl or H2SO4 with > 99 % efficiency. Desorption of Li+ with 0.1 M NaCl resulted in no changes in the uptake capacity through four sequential sorption/desorption cycles. Keywords: chelating resin; ion exchange; lithium; Lewatit TP 260. INTRODUCTION Lithium is the 25th most abundant element (at 20 mg kg–1) in the earth’s crust.1 The major lithium minerals with commercial value are classified into three major groups, namely, silicates, micas, and phosphates.2 Lithium finds application in rechargeable lithium ion batteries (LIBs) because of its very high energy density by weight and high electrochemical potential (3.045 V).1 Besides batteries, lithium compounds are used in ceramics and special glass industries, in primary aluminum production, rocket propellants, nuclear and pharmaceutical industries, in the manufacture of lubricants and greases, synthesis of vitamin A, synthesis of organic compounds, silver solders, underwater buoyancy devices, and batteries. Lithium is alloyed with aluminum and magnesium as light metals to form stronger and lightweight alloys.3 It is recovered from mines and salt * Corresponding author. E-mails: ozgur.arar@ege.edu.tr, ozgurarar@gmail.com https://doi.org/10.2298/JSC170930020C ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. 1060 ÇIÇEK, YILMAZ and ARAR lakes, which contain about 17 million t of lithium in total, while seawater is also considered as a vast source of lithium (about 2.5×1014 kg), although the concen- tration of lithium is very low, i.e., 0.17 mg L–1.4 Various methods have been studied for the recovery of lithium from seawater, brine, and geothermal water. These can be classified into three groups: adsorption (ion-exchange), solvent extraction and co-precipitation.5 The efficiency and limits of such methods have been reviewed elsewhere.3 Problems in separation or in the concentration of trace constituents are sometimes encountered. Ion exchange resins with different cation-exchange groups may possess different selectivity coefficients. Among the factors that determine the ionic selectivity of resins, the most important ones are: a) the nature of the acidic functional group and b) the density of the structure, which is largely determined by the degree of cross linkage. Regarding the first point, it is characteristic that the affinity of alkali ions toward strongly acidic groups (sulfonic acid groups, etc.) decreases in the order K >> Na > Li, whereas the order is precisely the opposite on resins with carboxylic, phosphonous, and phosphonic acids (especially the latter) as the functional groups.6,7 The purpose of this study was to evaluate an aminomethylphosphonic acid- -containing chelating resin for Li+ sorption. The sorption process was optimized by varying different parameters, such as resin dose, initial solution pH, concen- tration of Li+ and temperature. Elution of Li+ from the resin was also examined. EXPERIMENTAL Materials Lewatit TP 260 resin was used in the experiments. It is a weak acidic, macroporous resin contains chelating aminomethylphosphonic acid groups. The properties of resin are listed in Table I.8 The resin was converted into the sodium form by treatment (100 mL wet resin) with 2 M NaCl (250 mL) solution for 24 h and then washing thoroughly with water. It was dried in an oven and used in the experiments. TABLE I. Physicochemical properties of Lewatit TP 260 Matrix Cross-linked polystyrene Functional Group Aminomethylphosphonic acid Ionic Form Na+ Total capacity (H-form) 2.3 eq. L-1 Water Retention 59–61 % Stable in pH range 0–14 Reagents Analytical grade reagents were used in the experimental studies. A stock solution of Li+ was prepared by dissolving appropriate quantities of Li2CO3 (Merck) salt. The weighed amount of Li2CO3 was transferred into a beaker containing pure water and then HCl was added for complete dissolution. The solution was heated and swirled to expel dissolved CO2. The prepared solution was cooled to room temperature then transferred to a volumetric flask and diluted to volume with water. ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. REMOVAL OF LITHIUM FROM WATER 1061 The pH of the solutions used in the batch test was adjusted to its optimum value by the addition of sufficient amounts of 0.1 M HCl and 0.1 M NaOH solutions. Lithium analysis The concentration of Li+ was determined using a flame photometer (Jenway PFP7). The concentration ranges of Li+ standards for the calibration curve were in the range of 0.1 to 5 mg L-1. High concentration of Li+ (which was used in the isotherm study) was measured after appropriate dilutions. Batch adsorption tests Experimental conditions for Li+ sorption were summarized in Table II. TABLE II. Experimental parameters for Li+ removal Investigated parameter Li+ concentration mg L-1 Amount of resin used, g Volume of solution, mL pH of solution Temperature °C Resin dose 5.0 0.02–0.5 25 6 25 pH of solution 5.0 0.3 25 1–6 25 Isotherm study from 25 to 300 0.3 25 6 25 Temperature effect 5.0 0.3 25 6 30,40, 50, 55 and 60 Kinetic study 5.0 12 1000 6 25 The removal efficiency (R) and capacity (q) of the resin were calculated according to Eqs. (1) and (2), respectively: 0 e 0 100 c c R c − = (1) 0 e c c q V m − = (2) where, c0 and ce (mg L-1) are the initial and equilibrium Li+ concentrations, respectively, V is the volume of solution (L) and m is the mass of the resin (g). RESULTS AND DISCUSSIONS Effect of resin dose The effect of resin dosage on the uptake of Li+ was studied to understand the efficacy of the resin for Li+ removal. The uptake of Li+ plotted as percent rem- oval vs. resin dose is illustrate in Fig. 1, from which it could be seen that on increasing the resin dose from 0.02 to 0.3 g per 25 mL, the removal efficiency improved from 53 to 98 %. This could be attributed to an increase in the avail- ability of more sorption sites as the dose of resin was increased.9 The optimum resin dose was found to be 0.3 g for 25 mL of solution and this amount was used in further experiments. Effect of solution pH The solution pH is a one of the important factor in sorption studies, because it can influence the structure of resin (for weak acidic and weak base), the struc- ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. 1062 ÇIÇEK, YILMAZ and ARAR ture of target molecule (especially if it has weak acidic or weak basic character) and H+ or OH– act as competing ions in the ion exchange process. The effect of initial solution pH values (1–6) on Li+ ion sorption onto TP 260 resin was inves- tigated, and the results are shown in Fig. 2. Li+ removal was unfavorable in acidic media (pH ≤ 1) but it increased with increasing pH value. There was only 4 % removal at pH 1 that increased to 99 % at pH ≥ 3. The pKa values of amino- methylphosphonic acid (AMPA) are 2.35 and 5.9.10 At pH 1, the functional group of the resin is in the molecular form, thus removal of Li+ was not possible. On the other hand, when the pH of solution was increased, the functional group of the resin ionized and sorption of Li+ was enabled. Fig. 1. Effect of resin dose on Li+ removal. Fig. 2. Effect of initial solution pH on Li+ removal. Isotherm analysis of Li+ removal The sorption isotherm is one of the important parameters for understanding sorption behavior and mechanism. The sorption capacity of the resin for Li+ removal was studied at different initial Li+ concentrations and the obtained results were applied to the Langmuir and Freundlich models. The Langmuir isotherm model is used to describe a monolayer adsorption process, and the model can be described in linear form by Eq. (3): ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. REMOVAL OF LITHIUM FROM WATER 1063 ce/qe = 1/bq0 + ce/q0 (3) In this equation, qe / mg g–1 is the amount of Li+ sorbed per gram of dry resin at equilibrium, q0 / mg g–1, and b / L mg–1 are the Langmuir constants related to the capacity and energy of sorption, respectively.11,12 The Freundlich isotherm model shows that a multilayer of the adsorption process occurs on heterogeneous surfaces, and is expressed by Eq. (4): log qe = log KF + (1/n)log ce (4) where KF / dm3 g–1 is the isotherm constant of the Freundlich model and n is the exponent of the Freundlich model. KF and n are characteristics of the system and are indicators of the sorbent capacity (or affinity for the solute) and sorption int- ensity, respectively.13 The related parameters of the two models were calculated and are summar- ized in Table III. From the values of the linear correlation coefficients (R2), the Langmuir model was found more suitable for describing the Li+ sorption than the Freundlich model. The results suggest that monolayer sorption of Li+ on such resin is the main mechanism. Additionally, the values of q0 calculated from the Langmuir model was 13.65 mg g–1. TABLE III. Calculated isotherm constants of Langmuir and Freundlich models Langmuir isotherm constants Freundlich isotherm constants q0 /mg g-1 b / L g-1 R2 KF / dm3 g-1 n R2 13.6553 0.0370 0.9914 2.4526 3.4710 0.9577 Dubinin–Radushkevich model The Dubinin–Radushkevich (D–R) model is another model that is used for clarification of the mechanism of sorption (i.e., physical or chemical). The linear D–R equation is given by Eq. (5): ln qe = ln Xm – βε2 (5) where β is a constant related to the sorption energy (mol2 J–2), Xm (mol g–1) is the D–R monolayer capacity, ε (mol L–1) is the Polanyi potential that is calcul- ated as shown in Eq. (6): ε = RTln (ce+1/ce) (6) The mean free energy, E (kJ mol–1), of sorption can be estimated by using β values as expressed in the following equations:14 E = 1/(β1/2) (7) For values of E < 8 kJ mol–1, physical forces may have an effect on the sorp- tion mechanism while E values between 8 and 16 kJ mol–1 depict sorption con- trolled by ion exchange and E > 16 kJ mol–1 signifies the process is chemi- sorption.15 ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. 1064 ÇIÇEK, YILMAZ and ARAR In the present case, Xm was found to be 0.0027 mol g–1, which is equal to 18.74 mg Li+ per g-resin, β was found to be 0.0050 mol2 J–2, and mean free energy, E, was 14.1 kJ mol–1, indicating that removal mechanism was ion exchange. The ion-exchange reaction of the resin with Li+ can be expressed as:16 2 2 2 2R CH PO(ONa) 2Li R CH PO(OLi) 2Na+ +⎯⎯→− + − +←⎯⎯ (8) Kinetics of Li+ removal Ion exchange time-dependent experiments were performed to evaluate the sorption kinetics. The kinetic data shown in Fig. 3 indicate that the sorption of Li+ increased rapidly within 5 min, followed by a relatively slow process, and then the sorption equilibrium was achieved within 15 min. In addition, no rem- arkable changes were observed from 15 to 45 min. Fig. 3. Removal of Li+ versus time. Reaction-based model The kinetic data were analyzed using pseudo-first-order, and pseudo-second- -order models. The equations for these models are given as Eqs. (9) and (10):17,18 log (qe–qt) = log qe – k1t/2.303 (9) t/qt = 1/k2qe2 + t/qe (10) Experimental results were applied to the kinetic models and the results are summarized in Table IV, from which it could be seen that the correlation coef- ficient (R2) obtained from the pseudo-second-order model was larger than that from the pseudo-first-order model. Diffusion-based model The intraparticle diffusion model proposed by Weber and Morris in 1963 was also taken into account in the experiments. They concluded that the sorption is proportional to the square root of the contact time:19 ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. REMOVAL OF LITHIUM FROM WATER 1065 qt =kidt1/2 (11) where kid is the intraparticle diffusion rate constant (mg g–1 min–0.5). When the intraparticle diffusion model controls the sorption, the graph of qt against t0.5 should be a straight line passing through the origin. The rate constant could be calculated from the slope of the line, The liquid film diffusion equation is given as: –ln (1–F) = kfdt (12) where F is the fractional attainment of equilibrium F  =  (qt/qe), kfd (1/min) is the rate constant. A linear plot of −ln (1 − F) vs. t with zero intercept would suggest that the adsorption process was controlled by liquid film diffusion.19 The experimental data were fitted in Eqs. (9)–(12) and the obtained results are summarized in Table IV. The R2 revealed that the retention process is the film diffusion controlled mechanism. TABLE IV. The calculated parameters of pseudo first and pseudo second order kinetic model Kinetic model Parameter Calculated value Pseudo first order k1 / min-1 0.4443 qe / mg g-1 0.782 R2 0.2594 Pseudo second order k2 / g mg-1 min-1 17.056 qe / mg g-1 0.6085 h / mg g-1min-1 0.6314 R2 0.9999 Intraparticle diffusion model R2 0.9756 kid 0.1998 Diffusion model R2 0.9890 kfd 0.4083 Thermodynamic parameters The effect of the temperature on the removal of Li+ from water was exam- ined by changing the solution temperature from 30 to 60 °C under the optimized conditions of resin dose and solution pH. Changes in the free energy (ΔG), entropy (ΔS) and enthalpy (ΔH) were estimated by the usual procedure.20 The calculated values are summarized in Table V. TABLE V. Thermodynamic parameters for Li+ sorption ΔS / J mol-1 K-1 ΔH / kJ mol-1 ΔG / kJ mol-1 (T / K) 10 –8.16 –12.1 (303) –12.2 (313) –12.4 (323) –12.4 (328) –12.5 (333) ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. 1066 ÇIÇEK, YILMAZ and ARAR The negative values of ΔG shows that ion exchange reaction is spontaneous. The negative value of ΔH suggests the exothermic nature of the sorption. The positive value of ΔS suggests increased randomness at the solid/solution interface during the sorption of Li+ onto the resin. Regeneration of the resin Regeneration experiments were performed as explained in the literature.21 Recovery of Li+ from the resin was checked with HCl, H2SO4 and NaCl sol- utions at various concentrations. The regeneration efficiency (RE / %) was cal- culated using Eq. (13): Desorbed amount of Li from the resin (%) 100 Sorbed amount of Li onto the resin RE + + = (13) The obtained results are summarized in Table VI, from which it could be seen that 0.1 mol dm–3 HCl, H2SO4 or NaCl was enough for complete regener- ation of the resin. TABLE VI. Effect of acid concentration on the desorption of Li+ from the resin Regenerant Concentration, mol dm-3 Desorbed amount of Li+, % HCl 0.01 75 0.05 88 0.1 >99 0.5 >99 H2SO4 0.01 85 0.05 96 0.1 >99 0.5 >99 NaCl 0.01 75 0.05 95 0.1 >99 0.5 >99 Multiple sorption/regeneration tests Multiple sorption/regeneration tests were performed to determine the reus- ability of the ion exchange resin and the recovery of sorbed Li+. The sorption test was realized by contacting 0.3 g resin with 25 mL of Li+ solution (5 mg Li L–1, pH 6) for 2 h. After decantation of the solution, the resin was washed with pure water until the conductivity of the eluting water reached that of pure water con- ductivity value. The elution step was performed by contacting 0.1 mol dm–3 25 mL of regenerant solution with the washed resin for 2 h. At the end of this time, the solution was decanted and washed with pure water as explained above. This sorption/regeneration cycle was repeated 4 times and the obtained results are summarized in Table VII. ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. REMOVAL OF LITHIUM FROM WATER 1067 TABLE VII. Evaluation of sorption/regeneration cycle studies for Li+ removal, %, from water by Lewatit TP 260 resin Cycle number HCl NaCl 1 99 99 2 54 99 3 53 99 4 53 99 As can be seen from Table VII, the type of the regenerant influences the sorption capacity. When NaCl was used for regeneration, the sorption capacity of the resin did not change but when HCl was used, sorption capacity decreased. After regeneration with HCl, the resin was converted to the H-form and used in the next sorption cycle. In the second sorption process, Li+ replaces H+ and thus, the H+ concentration in the solution increased and the pH of the solution dec- reased. As explained in effect of solution pH section, when the pH of solution decreased and the sorption capacity of resin decreased. Previously in the litera- ture, various research studies were conducted for lithium removal/recovery. The results obtained in such research studies are summarized in Table VIII. The cap- acities of the sorbents vary from 4.07 to 62.5 mg g–1 sorbent. The removal per- formance of such materials strongly depended on the experimental conditions, particle size, and loaded metal. TABLE VIII. Capacities of sorbents used for Li+ removal/recovery Resin/Sorbent Capacity, mg g-1 Reference Manganese oxide adsorbent (H1.6Mn1.6O4) 40 22 Magnetic lithium ion-imprinted Polymer 4.07 23 MnO2 ion sieve 62.5 24 Nano-MnO2 28.2 25 Ion-sieve manganese oxide, HMnO(Mg) 8.5 5 Spinel lithium manganese oxide 27.62 26 λ-MnO2 31.55 27 Aminomethylphosphonic acid containing chelating resin 13.65 This study CONCLUSIONS In this study, the removal of lithium ions from aqueous solutions onto an ion-exchange resin was investigated under various experimental conditions, such as resin dose, initial solution pH, and temperature. The results clearly demon- strated that the phosphonic acid groups contributed to the sorption mechanism through electrostatic interactions between the phosphonic acid of the resin and the Li+. The ion exchange process was quite fast and equilibrium was established within 15 min. The percentage removal of Li+ was pH dependent, decreasing with decreasing initial pH of the solution. The equilibrium sorption behavior Li+ onto Lewatit TP 260 resin followed the Langmuir adsorption isotherm with a ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. 1068 ÇIÇEK, YILMAZ and ARAR maximum theoretical sorption capacity of 13.65 mg g–1 resin. The sorption of Li+ onto the resin was found to be mainly based on ion-exchange interactions, and these were confirmed by the Dubinin–Radushkevich model. Regeneration and reuse of resin work well for NaCl regenerant. Regener- ation of resin with acid solution decreased the removal efficiency of resin. Temperature variations were used to evaluate enthalpy, entropy and free energy changes. The negative value of free energy change showed the spont- aneous nature of the adsorption. In the temperature range 303–333 K, enthalpy change was negative, and the ion exchange reaction was exothermic. Acknowledgments. We would like to acknowledge Lanxess–Lewatit and their distributor in Turkey, Ökotek Environmental Technologies and Chemical Industries, for providing the resin sample. We thank the Mr. Emre Seyyal and Mr. Ekrem Kandemir for their kind suggest- ions to improve this paper. И З В О Д УКЛАЊАЊЕ ЛИТИЈУМА ИЗ ВОДЕ СМОЛОМ КОЈА САДРЖИ АМИНОМЕТИЛФОСФОНСКУ КИСЕЛИНУ AYDIN ÇIÇEK, ONUR YILMAZ и ÖZGÜR ARAR Ege University, Faculty of Science, Department of Chemistry, 35100, Izmir Turkey Ова студија даје увид у способност аминометилфосфонске киселине која садржи хелатну смолу да уклони литијум из воде. Испитивања су изведена под различитим условима као што су количина смоле, почетна концентрација Li+, pH раствора и његова температура. Резултати су показали да сорпција литијума достиже равнотежу за 15 min, а експериментални подаци су добро корелисани кинетиком псеудо-другог реда. Сорп- ција Li+ је показала велику зависност од pH, а оптимална pH за уклањање Li+ била је изнад 3. Подаци за изотермну сорпцију показали су добру корелацију са Лeнгмировим моделом, а максимални капацитет монослојне сорпције у смолу је био 13,65 mg/g. Тер- модинамичка испитивања су указала на егзотермност односно спонтаност процеса ове сорпције. Смола се може регенерисати из 0,1 M HCl, NaCl или H2SO4 са ефикасношћу преко 99 %. Десорпција Li+ у 0,1 M NaCl није дала никакве промене у капацитету пре- узимања у четири узастопна сорпциона/десорпциона циклуса. (Примљено 30. септембра 2017, ревидирано 1. јануара, прихваћено 22. јануара 2018) REFERENCES 1. P. Meshram, B. D. Pandey, T. R. Mankhand, Hydrometallurgy 150 (2014) 192 2. H. Aral, A. Vecchio-Sadus, Ecotoxicol. Environ. Saf. 70 (2008) 349 3. B. Swain, Sep. Purif. Technol. 172 (2017) 388 4. L. Wang, C. G. Meng, W. Ma, Colloids Surfaces, A 334 (2009) 34 5. Y. Miyai, K. Ooi, S. Katoh, Sep. Sci. Technol. 23 (1988) 179 6. H. H. Ussing, P. Kruhoffer, H. J. Thaysen, N. H. Thorn, The Alkali Metal Ions in Biology: I. The Alkali Metal Ions in Isolated Systems and Tissues, Springer, Berlin, 2013 7. W. G. Berl, Physical Methods in Chemical Analysis, Elsevier, Amsterdam, 1961 8. G. Coşkun, İ. Şimşek, Ö. Arar, Ü. Yüksel, M. Yüksel, Desalin. Water Treat. 57 (2016) 25739 9. E. Özbunar, S. Kırca, Ö. Arar, Ü. Yüksel, Anal. Lett. 50 (2017) 1657 ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. REMOVAL OF LITHIUM FROM WATER 1069 10. Handbook of Biochemistry and Molecular Biology, R. L. Lundblad, F. M. Macdonald, Eds., CRC Press, Taylor & Francis, Boca Raton, FL, 2010 11. B. Alyüz, S. Veli, J. Hazard. Mater. 167 (2009) 482 12. S. Deniz, N. Taşci, E. Yetimoğlu, M. Kahraman, J. Serb. Chem. Soc. 82 (2017) 215 13. J. Milovanović, S. Eich-Greatorex, T. Krogstad, V. Rakić, N. Rajić, J. Serb. Chem. Soc. 80 (2015) 1203 14. R. M. Alosmanov, J. Serb. Chem. Soc. 81 (2016) 907 15. A. Altinisik, Y. Seki, S. Ertas, E. Akar, E. Bozacı, Y. Seki, Fibers Polym. 16 (2015) 370 16. A. A. Zagorodni, Ion Exchange Materials: Properties and Applications, Elsevier, Oxford, 2007 17. Y. S. Ho, J. Hazard. Mater. 136 (2006) 681 18. Y. S. Ho, G. McKay, Process Biochem. 34 (1999) 451 19. Y. Aşçi, Ş. Kaya, Desalin. Water Treat. 52 (2014) 267 20. Z. Aksu, Process Biochem. 38 (2002) 89 21. Ö. Arar, Anadolu Univ. J. Sci. Technol. Appl. Sci. Eng. 17 (2016) 530 22. R. Chitrakar, H. Kanoh, Y. Miyai, K. Ooi, Ind. Eng. Chem. Res. 40 (2001) 2054 23. X. Luo, B. Guo, J. Luo, F. Deng, S. Zhang, S. Luo, J. Crittenden, ACS Sustain. Chem. Eng. 3 (2015) 460 24. S. Zandevakili, M. Ranjbar, M. Ehteshamzadeh, Hydrometallurgy 149 (2014) 148 25. K. S. Chung, J. C. Lee, E. J. Kim, K. C. Lee, Y. S. Kim, K. Ooi, Mater. Sci. Forum 449– –452 (2004) 277 26. T. Ryu, J. Shin, J. Ryu, I. Park, H. Hong, B.-G. Kim, K.-S. Chung, Mater. Trans. 54 (2013) 1029 27. Y. K. Recepoğlu, N. Kabay, İ. Yılmaz-Ipek, M. Arda, K. Yoshizuka, S. Nishihama, M. Yüksel, Solvent Extr. Ion Exch. 6299 (2017) 1. ________________________________________________________________________________________________________________________Available on line at www.shd.org.rs/JSCS/ (CC) 2018 SCS. << /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /None /Binding /Left /CalGrayProfile (Dot Gain 20%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (U.S. Web Coated \050SWOP\051 v2) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Error /CompatibilityLevel 1.4 /CompressObjects /Tags /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages true /CreateJobTicket false /DefaultRenderingIntent /Default /DetectBlends true /DetectCurves 0.0000 /ColorConversionStrategy /CMYK /DoThumbnails false /EmbedAllFonts true /EmbedOpenType false /ParseICCProfilesInComments true /EmbedJobOptions true /DSCReportingLevel 0 /EmitDSCWarnings false /EndPage -1 /ImageMemory 1048576 /LockDistillerParams false /MaxSubsetPct 100 /Optimize true /OPM 1 /ParseDSCComments true /ParseDSCCommentsForDocInfo true /PreserveCopyPage true /PreserveDICMYKValues true /PreserveEPSInfo true /PreserveFlatness true /PreserveHalftoneInfo false /PreserveOPIComments true /PreserveOverprintSettings true /StartPage 1 /SubsetFonts true /TransferFunctionInfo /Apply /UCRandBGInfo /Preserve /UsePrologue false /ColorSettingsFile () /AlwaysEmbed [ true ] /NeverEmbed [ true ] /AntiAliasColorImages false /CropColorImages true /ColorImageMinResolution 300 /ColorImageMinResolutionPolicy /OK /DownsampleColorImages true /ColorImageDownsampleType /Bicubic /ColorImageResolution 300 /ColorImageDepth -1 /ColorImageMinDownsampleDepth 1 /ColorImageDownsampleThreshold 1.50000 /EncodeColorImages true /ColorImageFilter /DCTEncode /AutoFilterColorImages true /ColorImageAutoFilterStrategy /JPEG /ColorACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /ColorImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000ColorACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000ColorImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 300 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /GrayImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000GrayACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000GrayImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict << /K -1 >> /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False /CreateJDFFile false /Description << /ARA /BGR /CHS /CHT /CZE /DAN /DEU /ESP /ETI /FRA /GRE /HEB /HRV (Za stvaranje Adobe PDF dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. Stvoreni PDF dokumenti mogu se otvoriti Acrobat i Adobe Reader 5.0 i kasnijim verzijama.) /HUN /ITA /JPN /KOR /LTH /LVI /NLD (Gebruik deze instellingen om Adobe PDF-documenten te maken die zijn geoptimaliseerd voor prepress-afdrukken van hoge kwaliteit. De gemaakte PDF-documenten kunnen worden geopend met Acrobat en Adobe Reader 5.0 en hoger.) /NOR /POL /PTB /RUM /RUS /SKY /SLV /SUO /SVE /TUR /UKR /ENU (Use these settings to create Adobe PDF documents best suited for high-quality prepress printing. Created PDF documents can be opened with Acrobat and Adobe Reader 5.0 and later.) >> /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ << /AsReaderSpreads false /CropImagesToFrames true /ErrorControl /WarnAndContinue /FlattenerIgnoreSpreadOverrides false /IncludeGuidesGrids false /IncludeNonPrinting false /IncludeSlug false /Namespace [ (Adobe) (InDesign) (4.0) ] /OmitPlacedBitmaps false /OmitPlacedEPS false /OmitPlacedPDF false /SimulateOverprint /Legacy >> << /AddBleedMarks false /AddColorBars false /AddCropMarks false /AddPageInfo false /AddRegMarks false /ConvertColors /ConvertToCMYK /DestinationProfileName () /DestinationProfileSelector /DocumentCMYK /Downsample16BitImages true /FlattenerPreset << /PresetSelector /MediumResolution >> /FormElements false /GenerateStructure false /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles false /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /DocumentCMYK /PreserveEditing true /UntaggedCMYKHandling /LeaveUntagged /UntaggedRGBHandling /UseDocumentProfile /UseDocumentBleed false >> ] >> setdistillerparams << /HWResolution [2400 2400] /PageSize [612.000 792.000] >> setpagedevice