The use in grass production of clinoptilolite as an ammonia adsorbent and a nitrogen carrier J. Serb. Chem. Soc. 80 (9) 1203–1214 (2015) UDC 546.171.1:541.183+549.67:537.872: JSCS–4791 504.53–035.22 Original scientific paper 1203 The use in grass production of clinoptilolite as an ammonia adsorbent and a nitrogen carrier JELENA MILOVANOVIĆ1, SUSANNE EICH-GREATOREX2, TORE KROGSTAD2, VESNA RAKIĆ3 and NEVENKA RAJIĆ4* 1Innovation Centre of the Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia, 2Faculty of Environmental Science and Technology, Norwegian University of Life Sciences, 1432 Aas, Norway, 3Faculty of Agriculture, University of Belgrade, Nemanjina 6, 11080 Zemun, Serbia and 4Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia (Received 17 March, revised 14 May, accepted 18 May 2015) Abstract: Clinoptilolite-rich tuff (NZ) from the Zlatokop deposit (Vranjska Banja, Serbia) was studied as a nitrogen carrier for grass production. The mechanism of binding ammonium cations present in aqueous solutions by NZ was examined, as well as the possibility of adsorption of ammonia released in fresh cattle manure during its fermentation. The NH4+ binding from solutions proceeded via an ion-exchange process that followed pseudo-second-order kinetics. Adsorption isotherms studied at 298–318 K followed the Freundlich isotherm equation. The NZ readily adsorbs ammonia liberated from manure and the addition of 10 wt. % of NZ to manure can preserve up to 90 % of ammonia. The potential benefit of this effect was examined in greenhouse pot experiments with Italian ryegrass (Lolium multiflorum, var. Macho) using three different types of soil (silty, clayey and sandy). The zeta potential measure- ments showed that the stability of their colloidal dispersions differed mutually and that the addition of NZ affected the stability and nitrogen cycling differ- ently. All results indicated that NZ could be applied in grass production. Keywords: zeolites; manure; Freundlich isotherm; soil; Italian ryegrass. INTRODUCTION Nitrogen is an essential nutrient for plant growth that has to be added to the soil to ensure the best growth and yield of crops. However, mineral nitrogen fer- tilizers have been implicated in various environmental issues. Ammonium and nitrate ions are readily lost from the soil by volatilization, leaching or surface run-off. As a result, different nitrogenous species are frequently present not only in agricultural wastewater, but also in groundwater. This may cause serious envi- * Corresponding author. E-mail: nena@tmf.bg.ac.rs doi: 10.2298/JSC150317042M _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 1204 MILOVANOVIĆ et al. ronmental problems such as eutrophication of water bodies and deterioration of water sources, also with possible consequences for humans, in particular for the health of small children.1 The removal of NH4+ from water through adsorption using various available sorbents was studied by many authors.2–7 Natural zeolites as non-toxic, eco- logically advantageous and affordable materials appear to be well suited for bind- ing NH4+ from aqueous media due to their ion exchange and adsorption pro- perties.8–11 Moreover, the use of natural zeolites for agricultural purposes is becoming widespread because zeolites are particularly useful for controlling agricultural soil fertilization and for preventing or retarding leaching and for increasing yields.12–14 Clinoptilolite is a very widespread zeolitic mineral in Serbia. The clino- ptilolite-rich tuff from the deposit Zlatokop (Vranjska Banja, Serbia) contains more than 70 wt. % of clinoptilolite and was found to exhibit good adsorptive and ion-exchange properties.15–17 In the present study, the tuff was investigated as a sorbent for ammonium ions and ammonia, and subsequently the ammonium- enriched zeolite was evaluated as a fertilizer. In particular, the present study examined: 1) the kinetics of binding of NH4+ from aqueous solution to NZ; 2) the efficiency of NZ in binding the NH3 rel- eased from fresh cattle manure; 3) whether the addition of ammonium-loaded NZ (AM–NZ) influences the ζ-potential of the soil and accordingly the availability of NH4+ for plants; 4) the effect of the use of NZ in herbage grass growth. EXPERIMENTAL Materials and methods The zeolite material (NZ) was obtained from a large sedimentary Zlatokop deposit in Vranjska Banja. The particle size of the samples used was in the range of 0.063–0.1 mm. A detailed X-ray powder diffraction analysis based on quantitative Rietveld refinement showed that the NZ contained 72.6 % clinoptilolite, 14.6 % feldspar plagioclase and 12.8 % quartz.18 Chemical analysis of the clinoptilolite phase present in the NZ obtained by scanning electron microscopy and X-ray microanalysis (JEOL JSM-6610LV) gave the following com- position expressed by corresponding oxides (wt. %): SiO2, 65.63; Al2O3, 12.97; Fe2O3, 1.48; Na2O, 0.95; K2O, 1.33; CaO and MgO. 1.41. The loss on ignition at 1073 K, obtained by thermal analysis (TA Instruments, SDT, Q600), was 12.9 wt. %. Furthermore, the porosity of NZ measured by nitrogen adsorption at 77 K (Hiden Isochema HTP1-V Volumetric Analyzer) gave for the BET specific surface area (SBET) and micropore volume (Vmic) 42 m2 g-1 and 0.0032 cm3 g-1, respectively. Prior to the experiments, the NZ was washed with deionised water and ethanol to remove soluble amorphous impurities, and then dried to a constant mass at 105 °C. Adsorption/desorption studies in solution The adsorption experiments were performed in the batch mode using NH4Cl solutions of different (initial) strengths, i.e., 5, 10, 25, 50 and 100 mg NH4+ dm-3. The study was realized by mixing 1 g of NZ with 100 cm3 of a solution of the chosen concentration. The suspension _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ CLINOPTILOLITE AS AN AMMONIA ADSPRBENT AND A NITROGEN CARRIER 1205 was shaken in a thermostated water bath (Memmert WNB22) for a period from 30 min to 24 h. The solid, ammonia-loaded NZ (AM–NZ) was separated by filtration. Three parameters were varied in the experiment: initial concentration of NH4+ in solution, temperature and contact time. Adsorption isotherms were determined at 298, 308 and 318 K. The NH4+ desorption experiments were conducted at 298 K by treating AM–NZ (con- taining 1.1 mg NH4+ g-1) with the KCl or NaCl solutions varying the salt concentration from 0.1 to 0.001 mol dm-3. Adsorption study in manure The capture of ammonia released during fermentation of fresh cattle manure (some of its chemical characteristics are given in Table I) was studied using a modified procedure des- cribed by Sharadqah and Al-Dwairi.19 Glass jars (volume 0.5 dm3) were filled with fresh cattle manure up to 2/3 their volume and tightly closed. Into four of the jars, a well homo- genized mixture of the fresh cattle manure and NZ was added in different 100:n weight ratios (n = 5, 10, 15 or 20). The fifth jar without NZ served as the system control. TABLE I. Chemical characteristics of the manure used in the experiments (g kg-1) pH Dry matter Loss on ignition Total Ca Total Na NO3-Nb NH4-Nb Total P Total K 7.60 28.5 713.2 390.0 18.9 0.08 27.01 8.9 67 aMeasured in dried sample; bmeasured in fresh sample In each jar, a porcelain crucible containing 10 cm3 of 0.1 M H2SO4 was placed on a tripod. After 24 h, the crucibles were replaced by new ones containing fresh H2SO4, and the solutions from the old ones were collected in a volumetric flask. The same process was repeated every day during 10 days, taking care that the jars were held open for the shortest possible time. The experiment was performed in triplicate. Zeta potential measurements Zeta (ζ) potentials of the soil samples and mixtures of the soil and AM–NZ suspended in water were measured. Prior to the measurements, a suspension of 5 g of the soil sample (or a homogenized mixture of 5 g of soil and 100 mg of AM–NZ) in 25 cm3 deionised water was homogenized by a standard procedure20 for 30 min by horizontal orbital shaking (120 rpm). The suspensions were left to settle overnight, and then a part of the colloid fraction was taken for the measurement. All measurements were performed in triplicate and expressed as mean values of the ζ-potential ± standard deviation. Pot experiments A greenhouse pot experiment was conducted under controlled conditions (20 °C, 18 h per day) with three different soil types and the Italian ryegrass (Lolium multiflorum, var. Macho) as the test crop. The soil types included a loam, a silt and a sandy soil. The former two were passed through a 5-mm mesh filter prior to being filled into pots of 3 dm3 volume. Some chemical parameters of the soils are given in Table II. The following treatments/fertilizers were used in the pots: a) control without any fertilizer, b) mineral fertilization with NH4NO3, c) fresh cattle manure, d) fresh cattle manure with the addition of 10 wt. % NZ, and in the silt soil only experiment and e) AM–NZ (con- taining 1.1 mg NH4+ g-1). All treatments were performed in triplicate. In all treatments, except in the control, the amounts of fertilizer corresponded to that typically used in grass production _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 1206 MILOVANOVIĆ et al. in Southern Norway (a nitrogen dose at the start of the experiment being equivalent to 120 kg N ha-1). The amount of manure was determined based on the NH4+ content in the wet sample and assuming that approximately 10 % of the organically bound N would be available over the experimental period, based on a previous mineralization study (results not shown). TABLE II. Some properties of the soils used in the pot experiments Soil Sand Silt Clay LOIa pH Total C Total N P-ALb K-ALb g kg-1 mg kg-1 Clay 450 380 170 61.0 5.2 23.1 2.1 58 195 Sand 940 30.0 30.0 13.0 5.1 2.8 0.1 16 10 Silt 20 930 50.0 37.0 6.5 14.5 1.0 49 200 aLoss on ignition; bammonium acetate lactate extractable In addition, an amount phosphorus equivalent to 20 kg ha-1 and an amount of potassium equivalent to approximately 100 kg ha-1, as well as all other macro- and micronutrients in appropriate amounts, were added in the case of the mineral fertilizer treatment. After the first cut, in all treatments except the one without nutrients, an additional amount of mineral N, equivalent to 60 kg N ha-1, was added. The pots were sown with 0.3 g of the seeds of Italian ryegrass. The moisture content in the soil was maintained at 60 % of the field capacity by irrigation with deionised water. The grass was cut three times after 5, 9 and 13 weeks of growth. Analytical methods and instrumentation The NH4+ concentration in the solutions was determined photometrically (Hach DR2800) using the Nessler reagent (Hach Method 8038). The cation concentrations of Na, K, Mg and Ca in solution ere determined by AAS using a Varian Spectra 55B instrument; at least five measurements were performed for each determination. Fourier transformed infrared (FTIR) spectra of NZ and AM–NZ were recorded in the 4000–400 cm-1 range on a Digilab-FTS-80 spectrophotometer, using the KBr pellet technique. Measurements of the ζ-potential were performed by electrophoresis using the laser Doppler method and a SZ-100 (Horiba Co. Ltd.) instrument in which a cell containing carbon electrodes is employed as a sample holder. The ζ-potential was calculated using the peak values of the mobility distributions detected by the Doppler shift in light scattering – the electrophoretic mobility of the particles was automatically calculated and converted to the ζ-potential using the Smoluchowski equation.21 The particle size distribution of the soils was determined by the pipette method.22 Soil and manure samples were ignited overnight at 823 K in order to determine the loss on igni- tion. The pH of the soil samples was measured by suspending the soil in H2O, with a soil to solution ratio of 1:2.5. The pH of the manure was measured directly in a wet sample. For both the soil and manure analyses, the total C content was determined in crushed samples by dry combustion23 at 1323 K using a Leco CHN-1000 instrument (St. Joseph, MI, USA). The total N content was measured using the same instrument according to the Dumas method.24 The ammonium and nitrate contents in the manure (NH4-N, NO3-N) were measured by flow injecttion analysis (FIA, Tecator FIAstar 5010 Analyzer, Hillerød, Denmark) after extracting a fresh sample with 2 mol dm-3 KCl. The plant-available P and K in the soil were estimated by extraction with an ammonium acetate lactate solution (0.1 M ammonium lactate and 0.4 mol dm-3 acetic acid, pH 3.75),25 followed by inductively coupled plasma optical emission spec- trometry (ICP-OES, Perkin Elmer Optima 5300 DV, Waltham, MA, USA). The total P and K _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ CLINOPTILOLITE AS AN AMMONIA ADSPRBENT AND A NITROGEN CARRIER 1207 in the manure were determined on the same instrument after autoclave digestion in concen- trated HNO3 (0.25 g to 0.3 g sample in 5 cm3) and subsequent dilution to 50 cm3. The effect of different treatments on the yield in the pot experiments was tested statist- ically by analysis of the variance (General linear model). The Student–Newman–Keuls test was performed to identify the different means. Results with p < 0.05 were considered signi- ficant. The statistical analysis was realized using SAS 9.3 software (SAS Institute Inc., Cary, NC, USA). RESULTS AND DISCUSSION Adsorption study Adsorption capacity of the NZ increased with the initial NH4+ solution con- centration and slightly decreased with temperature. At 298 K, it varied from 0.37 mg NH4+ g–1 (for c0 = 5 mg NH4+ dm–3) to 6.45 mg NH4+ g–1 (for c0 = 100 mg NH4+ dm–3). A slight decrease in the adsorption capacity was found at 318 K: 0.32 mg NH4+ g–1 (for c0 = 5 mg NH4+ dm–3) and 6.10 mg NH4+ g–1 (for c0 = = 100 mg NH4+ dm–3). The results showed that the adsorption of NH4+ by NZ is an exothermic process, which agrees with the results obtained for a Turkish and clinoptilolite-rich tuff.26 The Langmuir and Freundlich models were used to describe the equilibrium isotherm data.27 The Langmuir model can be represented as: max L ee L e1 q b c q b c = + (1) where ce is the equilibrium concentration of the solute (mg dm–3), qe is the equilibrium concentration of the adsorbed solute (mg g–1), while qmax (mg g–1) and bL (dm3 mg–1) are Langmuir constants (qmax corresponding to the maximum achievable uptake by a system, and bL is related to the affinity between the ads- orbate and the adsorbent). The Freundlich model can be represented as: e F enq K c= (2) where qe (mg g–1) is the equilibrium solute uptake, KF (dm3 g–1) is the isotherm constant of the Freundlich model, ce (mg dm–3) is the equilibrium solution con- centration, and n is the exponent of the Freundlich model. KF and n are charac- teristics of the system and are indicators of the adsorbent capacity (or affinity for the solute) and adsorption intensity, respectively. For the Langmuir isotherm analysis, the value of the separation factor (RL) defined as: L L 0 1 1 R b c = + (3) _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 1208 MILOVANOVIĆ et al. is of special importance28 and for the Freundlich isotherm the value of the exp- onent (1/n) is significant. In all the experiments, the values of RL, which can be calculated using the bL values from Table III, and the 1/n values prove, according to the literature,16,28 that the adsorption was a favourable process (0< RL <1 and 1/n <1, Table III), in accord with the fact that NZ readily adsorbs NH4+ from aqueous solutions. As can be seen from Table III, the equilibrium adsorption data gave a better fit (higher values of R2) for the Freundlich than for the Langmuir model. TABLE III. Isotherm constants for the sorption of NH4+ from aqueous solution by NZ Temperature, K Langmuir isotherm Freundlich isotherm qmax a / mg g-1 bL b / dm3 mg-1 R2 KF c / dm3 mg-1 1/nd R2 298 8.8879 0.0794 0.9943 0.9507 0.5531 0.9663 308 7.6329 0.1115 0.9836 1.2017 0.4663 0.9929 318 9.7514 0.0554 0.9906 0.7724 0.6150 0.9963 aMaximal monolayer adsorption capacity; bLangmuir constant; cFreundlich constant; dFreundlich model exponent The NH4+ adsorption kinetics were studied at 298, 308 and 318 K for sol- utions with c0 = 5, 10, 25, 50 and 100 mg NH4+ dm–3. The experimental data were analyzed by the Lagergren pseudo-first-order model and by the pseudo-sec- ond-order kinetics model.27 A linear dependence was obtained only for the pseudo-second-order model, indicating that the binding of NH4+ by NZ occurs by the pseudo-second-order reaction mechanism described by the following equation:25 ( )22 e d d t t q k q q t = − (4) where qe (mg g–1) is the adsorption capacity at equilibrium and k2 (g mg–1 min–1) is the rate constant of the pseudo-second-order adsorption. Integration between the limits t = 0 to t = t and q = 0 to q = qe, gives the following expression: 2 e2 e 1 1 t t t q qk q = + (5) The plot of t/qt vs. t is a straight line if the experimental data conform to this kinetic model, and the values of qe and k2 are obtained respectively from the slope and intercept of such a plot. As representative, the results obtained at dif- ferent temperatures for the initial concentration c0 = 25 mg NH4+ dm–3 are shown in Fig. 1. The adsorption capacity at equilibrium (qe) decreases with tem- perature whereas the rate constant changes irregularly with temperature. This was also observed for the other initial concentrations studied (data not presented). No acceptable explanation could be offered nor found in the literature for this pheno- menon. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ CLINOPTILOLITE AS AN AMMONIA ADSPRBENT AND A NITROGEN CARRIER 1209 Fig. 1. Kinetic curves at different tem- peratures obtained by fitting the exper- imental data to the pseudo-second-order rate model (c0 = 25 mg NH4+ dm-3). The FTIR spectrum of AM–NZ (not shown) confirmed the presence of NH4+ in the sample (vibration band at about 1400 cm–1 attributed to NH4+, which was not present in the spectrum of NZ), suggesting that the binding of NH4+ from aqueous solution by NZ proceeds by an ion-exchange reaction. This was proved further by elemental AAS analysis of the liquid phase after the ads- orption studies, i.e., after AM–NZ separation from the suspensions. The concen- trations of Na+, K+, Ca2+ and Mg2+ determined in the filtrate entirely corres- ponded to the amount of NH4+ bound by the NZ. In order to check whether the NH4+ in AM–NZ could be desorbed and thus become available as a nutrient in the soil, NH4+-desorption experiments were performed by treating AM–NZ with the NaCl or KCl solutions. The obtained results are given in Table IV. It is evident that the percentage of NH4+ desorption depended on the initial Na+/K+ concentration, showing that the desorption was _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 1210 MILOVANOVIĆ et al. also an ion-exchange process. It is interesting to note that desorption was more efficient in the KCl than in the NaCl solution. This could be explained by the fact that the radius of the NH4+ (151 pm) is very similar to that of the K+ (152 pm). Desorption in 0.1 M KCl was completed in 30 min. TABLE IV. Percentage NH4+ desorbed at 298 K from AM–NZ into solutions of NaCl or KCl in dependence on the salt concentration Concentration of NaCl/KCl, mol dm-3 Released NH4+, % in NaCl(aq) in KCl(aq) 0.100 64 100 0.010 42 50 0.005 24 42 0.001 17 18 It is well known that fresh cattle manure is rich in nitrogen, making it a good fertilizer. Nitrogen is present mainly in the organic matter, the content of which in the fresh manure being about 50 wt. %. However, during fermentation, manure looses significant amounts of nitrogen. Thus, the loss in four days may reach up to 90 % due to the extensive liberation of ammonia.29 In order to mitigate this loss, investigations were performed to determine: a) whether the addition of NZ to fresh cattle manure could retain the liberated NH3, and b) the optimal amount of NZ that has to be used for NH3 capture. Addition of the NZ to fresh manure conserved the NH3 released during fermentation, and the percentage of the captured NH3 ranged between 67 and 98 % depending on the applied amount of NZ (5–20 wt. %). Since about 90 % of NH3 was captured on addition of 10 wt. % NZ in comparison to the control, this amount of NZ was chosen as the optimal amount for the pot experiments (vide infra). ζ-potential values The zeta potential is an important parameter for soil/zeolite suspensions in water since it could be interpreted as an indicator of the stability of the suspended colloidal dispersions with respect to particle aggregation.30 For most soils, the ζ potential has a negative value because the ground surface is usually negatively charged. Moreover, the soil stability is a qualitative indicator of biological acti- vity, energy flow and nutrient cycling. A dispersion is regarded as stable, when the ζ-potential is < –30 mV.31 The results of the ζ-potential measurements are listed in Table V. It is evident that the clayey soil showed the lowest value of ζ, which could be explained by the strong electronegativity of the clays present in the soil sample. The sandy soil also showed a very low ζ-potential, which could be attributed to the presence of organic matter in which carboxyl groups are ionized.31 The silty soil exhibited the highest ζ-potential, implying a lower sta- _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ CLINOPTILOLITE AS AN AMMONIA ADSPRBENT AND A NITROGEN CARRIER 1211 bility. The addition of AM–NZ influenced the ζ-potential of all three types of soil but the changes were most pronounced for the clayey and sandy soils. The sta- bility of clayey soil decreased on addition of AM–NZ in contrast to sandy soil in which the colloidal fraction became more stable. TABLE V. The values of ζ-potentials, mV Soil sample System Soil/water Soil+AM–NZ/water Clay –45.0±0.7 –38.0±0.8 Silt –23.6±1.1 –22.3±1.6 Sand –37.0±0.9 –40.6±0.7 Pot experiments To obtain an insight into a possible use of NZ in grass production, pot exp- eriments were performed with Italian ryegrass, Lolium multiflorum, var. Macho. Italian ryegrass was used because it is fast-growing and responds to high N fertil- ization by yielding an abundance of vegetative matter. The results for the three cuts in the pot experiment are given in Fig. 2, exp- ressed as tones of dry matter (DM) per hectare. Fig. 2. Yields of ryegrass for differ- ent treatments and different types of soil. Statistically significant dif- ferences are indicated by different letters (p < 0.001). Figure 2 reveals similar overall yields for the mineral fertilizer, the manure and the manure+NZ treatments, with the exception of the sandy soil where con- _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 1212 MILOVANOVIĆ et al. siderably less biomass was produced in the control than in the other two treat- ments. In general, there was little difference between the amounts of biomass harvested at different cuts for these three treatments. A slight but significant dif- ference (statistics for the separate cuts are not shown) was found in the silt, with a somewhat lower biomass in the first cut in the manure+NZ treatment compared to mineral fertilizer and manure alone. However, this slower growth at the begin- ning was compensated for by a good yield in the second cut. It seems that NZ added to the silt binds NH4+ strongly at least in the initial phase of the growing period. This could, at least partly, have been due to the rel- atively high pH value of the silty soil (6.5), at which value cations are strongly adsorbed and hence less available than in the clayey and sandy soils. This sug- gestion is in accordance with the zeta potential measurement, which showed that the stability of colloidal fractions of the silty soil is not influenced by the addition of zeolite. The yields in the treatments without fertilizer are, as expected, much smaller than in the other treatments, especially in the sandy soil, which contained the smallest amount of nutrients. Even when the sandy soil was treated with the min- eral fertilizer, the plants grew poorly – most likely due to the low original pH of the soil (i.e., 5.1, Table II). Treatments including both manure and manure+NZ improved the growing conditions in the sandy soil, which was reflected in the much higher yields. In the silty soil, the treatment with AM–NZ resulted in slightly higher over- all yields than in the manure+NZ and the mineral fertilizer treatment but not compared to the manure alone. The may be explained by the fact that the AM– NZ was obtained by the ion-exchange reaction using a NH4+-solution of well- -defined strength as opposed to the NZ exposed to manure. In the latter case, less NH4+ was bound by NZ because the manure used possessed not only NH4+ pre- sent in the liquid phase, but also organically bound N. It should be stressed that the available N from manure cannot be determined accurately in comparison to the available N in AM–NZ. Accordingly, the resulting differences are likely to have caused the small differences in growth between the different treatments in the silty soil. CONCLUSIONS This study evaluated the adsorption ability of zeolitic tuff from the Zlatokop deposit towards NH4+ present in liquid medium and towards NH3 liberated in manure, as well as its capability to be a nitrogen reservoir for plant growth. The adsorption studies show that the process proceeded via an ion-exchange mechanism, which followed the pseudo-second-order kinetic model (R2 > 0.99). The adsorption isotherms studied at 25–45 °C followed the Freundlich isotherm model. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ CLINOPTILOLITE AS AN AMMONIA ADSPRBENT AND A NITROGEN CARRIER 1213 The addition of 10 wt. % of the tuff to fresh cattle manure conserved about 90 % of ammonia and preserved its nutritive value. Greenhouse pot experiments with Italian ryegrass suggested that the plants utilize the NH4+ bound by the tuff in a similar manner to the NH4+ in easily soluble mineral fertilizers. Further work will be directed towards exploitation of the tuff in odour control as well as towards its potential use in the reduction of the nitrogen oxide emission during manure application in agriculture. The results of such work could be expected to significantly contribute not only to a less odoriferous, but also to a healthier envi- ronment. Acknowledgements. This research was supported by the Norwegian Programme in Higher Education, Research and Development HERD (Project “The use of natural zeolite (clinoptilolite) for the treatment of farm slurry and as a fertilizer carrier”) and by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Project No. 172018). И З В О Д ПРИМЕНА КЛИНОПТИЛОЛИТА КАО АДСОРБЕНТА АМОНИЈАКА И НОСАЧА АЗОТА ЗА ПРИМЕНУ У УЗГОЈУ ТРАВЊАКА JEЛЕНA MИЛОВАНОВИЋ1, SUSANNE EICH-GREATOREX2, TORE KROGSTAD2, ВЕСНА РАКИЋ3 и НЕВЕНКА РАЈИЋ4 1Иновациони центар Технолошко–металуршког факултета,Универзитет у Београду, Карнегијева 4, 11000 Београд, 2Faculty of Environmental Science and Technology, Norwegian University of Life Sciences, 1432 Aas, Norway, 3Пољопривредни факултет, Универзитет у Београду, Немањина 6, 11080 Земун и 4Технолошко-металуршки факултет, Универзитет у Београду, Карнегијева 4, 11000 Београд Зеолитски туф (NZ) са великим садржајем клиноптиолита из рудника Златокоп (Врањска Бања) испитиван је као носач азота за потребе гајења траве. Проучен је меха- низам и кинетика везивања амонијум-јона из водених раствора за NZ као и могућност везивања амонијака који настаје ферментацијом свежег стајњака. Везивање амонијум- -јона је реакција јонске измене која следи кинетику псеудо-другог реда. Адсорпционе изотерме испитане на 298–318 K следе Фројндлихову једначину. NZ лако везује амо- нијак који се ослобађа у стајњаку и додатак 10 мас. % NZ може да сачува 90 % амони- јака. Потенцијална корист овог ефекта испитивана је праћењем раста Италијанског љуља (Italian ryegrass, Lolium multiflorum, var. Macho) у саксијама у стакленој башти применом три различите врсте земљишта (прашина, глина, песак). Мерењем цета потен- цијала утврђено је да се стабилност колоидних дисперзија земљишта међусобно разли- кује и да додатак NZ утиче различито на стабилност, а тиме и на кружење азота у зем- љишту. На основу укупних резултата закључено је да се NZ може користити при узгоју травњака. (Примљено 17. марта, ревидирано 14. маја, прихваћено 18. маја 2015) REFERENCES 1. K. G. Cassman, A. Dobermann, D. T. Walters, AMBIO 31 (2002) 132 2. H. Liu, Y. Dong, H. Wang, Y. Liu, Desalination 263 (2010) 70 3. M. Khan, N. Yoshida, Bioresource Technol. 99 (2008) 575 4. P. Vassileva, P. Tzvetkova, R. Nickolov, Fuel 88 (2009) 387 _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. Available on line at www.shd.org.rs/JSCS/ 1214 MILOVANOVIĆ et al. 5. P. Vassileva, D. Voikova, J. Hazard. Mater. 170 (2009) 948 6. T. C. Jogensen, L. R. Weatherley, Water. Res. 37 (2003) 1723 7. W. M. Rostron, D. Stuckey, A. A. Young, Water Res. 35 (2001) 1169 8. M. Reháková, S. Cuvanová, M. Dyivák, J. Rimár, Z. Gaval’ová, Solid State Mater. Sci. 8 (2004) 397 9. P. J. Leggo, B. Ledésert, G. Christie, Sci. Total Environ. 363 (2006) 1 10. S. Leung, S. Barringtin, Y. Wan, X. Zhao, B. El-Husseini, Bioresource Technol. 98 (2007) 3309 11. J. Venglovsky, N. Sasakova, M. Vargova, Z. Pacajova, I. Placha, M. Petrovsky, D. Harichova, Bioresource Technol. 96 (2005) 181 12. A. C. de Campos Bernardi, P. P. Anchão Oliviera, M. B. de Melo Monte, F. Souza- Barros, Micropor. Mesopor. Mater. 167 (2013) 16 13. H. V. Der Stok, T. Sofyan, DE and WO2013119108 A1 (2013) 14. S. Belboom, A. Leonard, in Plant Sciences Reviews, D. Hemming, Ed., CABI, Walling- ford, 2011, p. 52 15. Dj. Stojakovic, J. Milenkovic, N. Daneu, N. Rajic, Clay Clay Miner. 59 (2012) 277 16. Dj. Stojakovic, J. Hrenovic, M. Mazaj, N. Rajic, J. Hazard. Mater. 185 (2011) 408 17. N. Rajic, Dj. Stojakovic, M. Jovanovic, N. Z. Logar, M. Mazaj, V. Kaucic, Appl. Surf. Sci. 257 (2010) 1524 18. Š. Cerjan Stefanović, N. Zabukovec Logar, K. Margeta, N. Novak Tušar, I. Arčon, K. Maver, J. Kovač, V. Kaučič, Micropor. Mesopor. Mater. 105 (2007) 251 19. S. I. Sharadqah, R. A. Al-Dwairi, Jordan J. Civ. Eng. 4 (2010) 378 20. M. W. I. Schmidt, C. Rumpel, I. Kogel-Knabner, Eur. J. Soil Sci. 50 (1999) 87 21. R. J. Hunter, Zeta Potential in Colloidal Science: Principles and Applications, Academic Press, London, 1981 22. P. Elonen, Acta Agralia Fenn. 122 (1971) 1 23. D. W. Nelson, L. E. Sommers, in Methods of Soil Analysis Part 2, A. L. Page, R. H. Miller, D. R. Keeney, Eds., American Society of Agronomy Inc., Soil Science Society of America Inc., Madison, WI, 1982, pp. 539–579 24. J. M. Bremner, C. S. Mulvaney, in Methods of Soil Analysis Part 2, A. L. Page, R. H, Miller, Eds., Vol. 9 of Agronomy Monograph, American Society of Agronomy, Madison, WI, 1982, pp. 595–624 25. H. Egnér, H. Riehm, W. R. Domingo, Lantbrukshögskolans Annaler 26 (1960) 199 26. A. Mishra, J. H. Clark, G. A. Kraus, P. R. Seidl, A. Stankiewicz, Y. Kou, Green Mater- ials for Sustainable Water Remediation and Treatment, The Royal Society of Chemistry, Cambridge, 2013, p. 93 27. S. Sen Gupta, K. G. Bhattacharyya, Adv. Colloid Interface Sci. 162 (2011) 39 28. A. M. Yusof, L. K. Keat, Z. Ibrahim, Z. A. Majid, N. A. Nizam, J. Hazard. Mater. 174 (2010) 380 29. K. A. Rabai, O. H. Ahmed, S. Kasim, Afr. J. Biotechnol. 11 (2012) 12825 30. Y. Yukselen, A. Kaya, Water Air Soil Poll. 145 (2003) 155 31. J. P. Mendez, F. P. Garcia, O. A. A. Sandoval, M. A. M. Marzo, Acta Montan. Slovaca 18 (2013) 17. _________________________________________________________________________________________________________________________ (CC) 2015 SCS. All rights reserved. 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