The effect of ammonia activation on the desalination potential of natural zeolite published by Ural Federal University eISSN 2411-1414 chimicatechnoacta.ru LETTER 2023, vol. 10(4), No. 202310305 DOI: 10.15826/chimtech.2023.10.3.05 1 of 5 The effect of ammonia activation on the desalination potential of natural zeolite Aruzhan K. Kenessova ab * , Akmaral B. Rakhym ab , Bagashar B. Zhaksybay ab , Gulziya A. Seilkhanova ab a: Department of physical chemistry, catalysis and petrochemistry, Al-Farabi Kazakh National Univer- sity, Almaty 050040, Kazakhstan b: Center of Physicochemical Methods of Research and Analysis, Almaty 050012, Kazakhstan * Corresponding author: kenessova.aruzhan@gmail.com This paper belongs to the RKFM'23 Special Issue: https://chem.conf.nstu.ru/. Guest Editors: Prof. N. Uvarov and Prof. E. Aubakirov. Abstract Despite the abundance of water bodies on Earth, there is a limited amount of potable water. Therefore, the desalination process is of great interest. Adsorption of the main contaminants of saline water (Na+, K+, Cl– ions) is an alternative process of desalination. In the present work, a sorbent based on natural zeolite (NZ) modified with ammonium chloride (NH4Cl) is ob- tained and the effect of modification on the removal of Na+ and K+ ions from saline water is studied. According to the Brunauer-Emmett-Teller (BET) analysis, the modification of zeolite with NH4Cl leads to an increase in its surface area (7.85 to 8.09 m2/g). According to the results of the cati- on exchange capacity (CEC) determination, the modification leads to a de- crease in total CEC of zeolite (431.67±29.01 to 300.88±31.86 meq/100 g). According to the obtained results, ammonia modification enhances the ad- sorption ability of NZ to extract Na+ and K+ ions from saline water. The ex- traction degree (E) of Na+ ions by NH4-Z increases from 7.93±1.63 to 10.44±1.52%, while for K+ ions it increases about 2 times (27.69±2.45 to 56.46±3.71%). These results indicate that the ammonia-modified NZ can po- tentially be used as a desalination agent for the removal of Na+ and K+ ions from saline water. Keywords natural zeolite ammonia activation desalination sodium adsorption potassium adsorption Received: 30.06.23 Revised: 30.07.23 Accepted: 02.08.23 Available online: 04.08.23 Key findings ● Modification of zeolite with NH4Cl leads to an increase in its surface area, enhancing its adsorption capabilities. ● The modified zeolite, NH4-Z, shows higher selectivity for Na+ and K+ ions, resulting in increased extraction percentages. ● NH4Cl modification alters zeolite's cation-exchange capacity, favoring enhanced Na+ and K+ ion adsorption for desalination. © 2023, the Authors. This article is published in open access under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). 1. Introduction Water is one of the main vital human needs. It is one of the most abundant substances on Earth. But despite its abundance, there is only a limited amount of potable wa- ter available for human use. The scarcity of fresh water affects people’s daily lifes as well as agriculture, food pro- cessing, the economy, and other aspects of life [1]. As the population grows, the need for water becomes an urgent problem. According to recent investigations, 40% popula- tion of the Earth is already facing water shortages. These data are estimated to grow up to 60% by 2025 [2]. Vari- ous methods, such as disinfection, aeration, distillation, coagulation, etc., have been used to obtain fresh water [3]. These methods are aimed at removing contaminants from wastewater, such as inorganic and organic impurities, microbes, heavy metal ions, and radiological contami- nants. Despite the availability of different wastewater pu- rification techniques, they work better in combination by creating multi-stage purification. However, this method tends to be time and energy consuming. Saline water desalination is an alternative solution to the problem of freshwater scarcity. Desalination is the process of reducing the salinity of saline water [4, 5]. Ac- http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2023.10.3.05 https://orcid.org/0000-0001-5452-7543 http://creativecommons.org/licenses/by/4.0/ https://orcid.org/0000-0001-9532-4072 https://orcid.org/0009-0007-1654-5784 https://orcid.org/0000-0002-9939-8316 https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2023.10.3.05&domain=pdf&date_stamp=2023-08-04 Chimica Techno Acta 2023, vol. 10(4), No. 202310402 LETTER 2 of 5 DOI: 10.15826/chimtech.2023.10.3.05 cording to the World Health Organization (WHO), the sa- linity limit for drinking water is 500 ppm [5]. Currently, many countries provide fresh water to their the popula- tion by by desalting saline water reserves [6, 7]. The desalination process was invented in the 18th cen- tury. Since then, different desalination methods have been developed. They are reverse osmosis (RO), thermal desali- nation, multistage flash desalination (MSF), multi-effect distillation (MED), electrodialysis, and nanofiltration (NF) [8–12]. However, the commercialized desalination meth- ods have several drawbacks, such as the high cost of desal- ination plants for developing countries that are currently experiencing drinking water storage and high energy con- sumption [13]. Therefore, the existing methods still need to be improved. Adsorption is an alternative approach to solving the problem of freshwater scarcity. It is of interest due to its simplicity and effectiveness. Adsorption does not require energy consumption [14, 15]. The main contaminants of saline water are Na+, K+, and Cl– ions, which determine the salinity level of the water. The adsorption of these ions by adsorbent enables freshwater production. However, the use of the adsorption process by any adsorbent for desali- nation is a relatively new approach. The main challenge here is to develop an effective adsorbent that provides a high adsorption value for the removal of Na+, K+, Cl– ions. Aluminosilicate raw materials (zeolites, clays, etc.) are quite effective and widespread materials, with high sorp- tion activity towards various substances and relatively low cost [14]. Zeolites are well-known for their adsorption and ion exchange properties, especially towards various heavy metals and organic compounds [15, 16]. Various investiga- tions regarding saline water desalination by zeolites have been carried out. Zeolites, especially clinoptilolite, have high cation selectivity and cation exchange capacity (CEC), as well as they are non-toxic and low-cost. All these prop- erties make zeolites suitable for the adsorption of Na+, K+, Cl– ions, thus desalinating saline water [17, 18]. The use of zeolites in the desalination process is one of the promising ways to solve freshwater scarcity. Various works have been done to further enhance the adsorption properties of aluminosilicate and other raw materials for desalination purposes. Ahmed S. Alsaman et al. used HCl acid pretreatment in the preparation of com- posite silica-gel [19]. In another study, Alsaman et al. used acid pretreatment to enhance the adsorption properties of bentonite [20]. Moreover, Guo et al. investigated the use of zeolite modified with NaCl to remove K+ ions from sea- water and brackish water [21]. Acid treatment was also found to be effective for the use of natural zeolite in ad- sorption processes [22, 23]. This study is aimed at describ- ing the physicochemical characteristics of the natural zeo- lite (NZ) and modified NZ of the Shankanai deposit (Al- maty region, Kazakhstan). The key novelty of this study is the modification of NZ using NH4Cl to enhance its effec- tiveness in removing Na+ and K+ ions from saline water. 2. Experimental The following materials and reagents were used for the experiments: zeolite of Shankanai deposit (Almaty origin), NH4Cl, AgNO3, NaCl, KCl. 2.1. Natural zeolite modification Modified zeolite was obtained by treating dried and ground NZ with 1 M NH4Cl solution at a ratio of 1:5 for 24 hours and rinsing it with distilled water until the ex- cess Cl– ions were removed. The presence of Cl– ions was checked by qualitative analysis with 0.1 M AgNO3 solution. 2.2. Sample characterization The morphology of NZ and NH4-Z was studied, and the elemental analysis was performed using a scanning elec- tron microscope (SEM) (Quanta 3D 200i Dual system, FEI, USA) equipped with energy dispersive X-ray spectroscopy (EDX). The specific surface area of the zeolite samples was determined by the Brunauer-Emmett-Teller (BET) method. Fourier-transform infrared spectroscopy (FTIR) analysis was performed to identify the chemical bonds present in the zeolite samples. 2.3. Cation-exchange capacity determination For the determination of the cation-exchange capacity (CEC) of the samples, the standard method with NH4Cl was applied [24]. Zeolite samples were mixed with a 1 M NH4Cl solution in a ratio of 1:100 and stirred for 24 h on a laboratory shaker (Lauda, Germany). The suspensions were then centrifuged using a Z 306 Hermle Universal Centrifuge (Labnet, USA). The CEC was calculated as the sum of the concentrations of released Na+, K+, Mg2+, and Ca2+ ions which were calculated using the following formula: 𝑀𝑚𝑒𝑞/100 𝑔 = 𝐶𝑝𝑝𝑚 (𝑒𝑞. 𝑤𝑡 · 10), (1) where Mmeq/100 g is the concentration of released cation expressed in meq/100 g; Cppm is the concentration of re- leased cation expressed in ppm; eq.wt. is the equivalent weight of the released cation. 2.4. Adsorption study The ability of the obtained sorbents to absorb Na+ and K+ ions was studied at room temperature. For this purpose, the separate solutions containing Na+ and K+ ions with a concentration of 100 mg/L were prepared. 0.1 g of the sorbent was placed in a measuring beaker, filled with 10 mL of the solution, and stirred on the laboratory shaker at room temperature (25±5) °C for 24 hours. Then the solu- tion was filtered, and the adsorption value and extraction degree were calculated. The adsorption value was calculated using the follow- ing formula: 𝐴 = 𝑐0 − 𝑐𝑒𝑞 𝑚 · 𝑉, (2) where c0 and ceq are initial and equilibrium concentrations of the sorbate, mcg/cm3; V is a volume of the sorbate solu- https://doi.org/10.15826/chimtech.2023.10.3.05 Chimica Techno Acta 2023, vol. 10(4), No. 202310402 LETTER 3 of 5 DOI: 10.15826/chimtech.2023.10.3.05 tion, L; m is a sample mass, g. Extraction degree of the ions was calculated as follows: 𝐸 = 𝑐0 − 𝑐𝑒𝑞 𝑐0 ∗ 100 %. (3) The initial and equilibrium concentrations of ions were determined by laboratory ionometer “I-160MI” (Measur- ing equipment, Russia). 3. Results and Discussion 3.1. SEM The SEM images of zeolite samples are presented in Fig- ure 1. It can be seen from the SEM micrographs that after modifying NZ with NH4Cl the material becomes looser and a slight increase in the porosity of the surface of the parti- cles is observed. 3.2. Elemental analysis The results of the elemental analysis of the zeolite samples are presented in Table 1. All the samples contain mainly O, Si, and Al followed by minor amounts of Na, Mg, K, Ca, and Fe. Treatment of natural zeolite with 1 M NH4Cl leads to a slight increase in the amount of sodium, magnesium, potassium and iron. The changes in the content of ele- ments after modification could be because ammonium ions have a higher affinity for the zeolite’s framework com- pared to sodium and potassium ions. The selectivity of ammonium ions for those ions could possibly enable the NH4-Z to remove these ions from saline water by ion ex- change. 3.3. BET BET analysis allows us to define the specific surface area of the studied materials. Table 2 represents the the specif- ic surface area values of the initial and modified zeolite. Treatment with 1 M NH4Cl slightly increases the surface area of NZ from 7.85 to 8.09 m2/g, making it favorable for adsorption processes. 3.4. FTIR spectroscopy The spectra of NZ and NH4-Z are shown in Figure 2. The FTIR spectrum of NZ shows prominent peaks at 1025.40 cm–1, 1633.35 cm–1, and 3444.88 cm–1. In the IR spectrum of NZ, a strong band at 1025.40 cm–1 corresponds to the stretching vibrations of Si–O–Si and Si–O–Al bonds. The peak at 1633.35 cm–1 and 3444.88 cm–1 indicates the vibra- tions of present water and OH-groups in the structure of NZ, suggesting the presence of moisture in the zeolite structure. After the modification, a peak at 761.19 cm–1 appears on the spectrum. The peak at 761.19 cm–1 in the spectrum of NH4-Z may be related to the potential change in the tetrahedral structure of zeolite. 3.5. CEC The adsorption capacity of zeolites is usually explained by their ion-exchange properties. Therefore, an investigation of the CEC of zeolite samples is done. The results of CEC are presented in Table 3. From the CEC results of NZ, it can be seen that the zeolite contains more calcium ions than the other exchange cations. The second abundant element is sodium. This could be explained by the fact that sodium ions react more easily than magnesium in the ion- exchange processes. In the case of NH4Cl modification, the release of magnesium and calcium ions decreased signifi- cantly, while the sodium and potassium content only slightly decreased, making the total CEC to decrease. Figure 1 SEM images of NZ (a) and NH4-Z (b). Table 1 Results of the elemental analysis of the samples. Sample C, wt.% O, wt.% Na, wt.% Mg, wt.% Al, wt.% Si, wt.% K, wt.% Ca, wt.% Fe, wt.% NZ 3.13 44.97 2.53 2.23 10.18 27.51 1.02 2.99 4.78 NH4-Z 3.16 39.83 3.63 2.44 10.22 25.89 1.66 1.66 10.73 https://doi.org/10.15826/chimtech.2023.10.3.05 Chimica Techno Acta 2023, vol. 10(4), No. 202310402 LETTER 4 of 5 DOI: 10.15826/chimtech.2023.10.3.05 Figure 2 FTIR spectra of (a) NZ and (b) NH4-Z. Table 2 Specific surface area of sorbents. Sorbent Surface area, m2/g NZ 7.85 NH4-Z 8.09 3.6. Adsorption of Na+ and K+ ions The absorption capacity of the zeolite samples towards Na+ and K+ ions were investigated. The results of the study are presented in Table 4 below. From the data in the table, it can be concluded that the modification of NZ with NH4Cl enhances its adsorption capacities, increasing the extrac- tion degree of Na+ ions from 7.93 to 10.44 % and increas- ing the removal of K+ 2 times. Clearly, the modified zeolite has demonstrated a higher affinity for K+ ions compared to Na+ ions. This finding is significant and suggests that the obtained adsorbents could be promising materials for ap- plication in the desalination of potash brine-impacted groundwater. Table 4 Adsorption of Na+ and K+ ions by zeolite samples. Sample E(Na+), % E(K+), % NZ 7.93±1.63 27.69±2.45 NH4-Z 10.44±1.52 56.46±3.71 4. Limitations The modified zeolite shows a significant change in the ex- traction of potassium ions. However, there is no notable change in the extraction of sodium ions. Using the two- step modification (ammonia and acid activation) of NZ could possibly solve this problem. 5. Conclusions In the present work, the physicochemical properties of nat- ural and modified zeolites were studied. The modification of zeolite leads to an increase in its surface area, making it favorable for adsorption processes, but decreases its CEC. The removal of Na+ and K+ ions by NZ and NH4-Z shows that the modification of zeolite enables more high extrac- tion of ions to be achieved. From the study results it can be concluded that zeolite modified with NH4Cl can be used as potential sorbents for Na+ and K+ ions from saline water. ● Supplementary materials No supplementary materials are available. ● Funding This work has been funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (grant no. AP09260116). ● Acknowledgments None. ● Author contributions Conceptualization: A.B.R. Data curation: A.K.K., B.B.Zh. Investigation: B.B.Zh., A.K.K. Methodology: A.B.R., A.K.K., G.A.S. Supervision: G.A.S. Writing – original draft: A.K.K. Writing – review & editing: A.B.R. ● Conflict of interest The authors declare no conflict of interest. Table 3 CEC of zeolite samples (meq/100 g). Sample Na+ K+ Mg2+ Ca2+ Total NZ 152.94±9.34 15.19±1.57 32.91±3.61 230.62±14.49 431.67±29.01 NH4-Z 152.09±21.71 13.85±0.85 7.74±0.59 127.20±8.72 300.88±31.86 https://doi.org/10.15826/chimtech.2023.10.3.05 Chimica Techno Acta 2023, vol. 10(4), No. 202310402 LETTER 5 of 5 DOI: 10.15826/chimtech.2023.10.3.05 ● Additional information Author IDs: Aruzhan K. Kenessova, Scopus ID 57220024671; Akmaral B. Rakhym, Scopus ID 57208575069; Gulziya A. Seilkhanova, Scopus ID 56652160000. Websites: Al-Farabi Kazakh National University, https://www.kaznu.kz/en; Center of Physicochemical Methods of Research and Analysis, https://cfhma.kz/cfhma/. References 1. Burn S, Hoang M, Zarzo D, Olewniak F, Campos E, Bolto B, Barron O. Desalination techniques – A review of the opportu- nities for desalination in agriculture. Desalination. 2015;364:2–16. doi:10.1016/j.desal.2015.01.041 2. Jones E, Qadir M, van Vliet MTH, Smakhtin V, Kang S. The state of desalination and brine production: A global outlook. Sci Total Environ. 2019;657:1343–1356. doi:10.1016/j.scitotenv.2018.12.076 3. Sharma S, Bhattacharya A. Drinking water contamination and treatment techniques. Appl Water Sci. 2017;7:1043–1067. doi:10.1007/s13201-016-0455-7 4. Darre NC, Toor GS. Desalination of Water: a Review. Curr Pollution Rep. 2018;4:104–111. doi:10.1007/s40726-018-0085-9 5. Elsaid K, Kamil M, Sayed ET, Abdelkareem MA, Wilberforce T, Olabi A. Environmental impact of desalination technolo- gies: A review. Sci Total Environ. 2020;748. doi:10.1016/j.scitotenv.2020.141528 6. Zotalis K, Dialynas EG, Mamassis N, Angelakis AN. Desalina- tion technologies: Hellenic experience. Water. 2014;6:1134– 1150. doi:10.3390/w6051134 7. Curto D, Franzitta V, Guercio A. A review of the water desali- nation technologies. Appl Sci. 2021;11:1–36. doi:10.3390/app11020670 8. Pearce M, Brennan F. Novel findings in desalination. Desali- nation. 2015;360:13–18. doi:10.1016/j.desal.2014.12.020 9. Shah KM, Billinge IH, Chen X, Fan HQ, Huang YX, Winton RK, Yip NY. Drivers, challenges, and emerging technologies for desalination of high-salinity brines: A critical review. Desali- nation. 2022;538:115827. doi:10.1016/j.desal.2022.115827 10. Aende A, Gardy J, Hassanpour A. Seawater desalination: a review of forward osmosis technique, its challenges, and fu- ture prospects. 2020;8(8):901. doi:10.3390/pr8080901 11. Bone SE, Steinruck HG, Toney MF. Advanced characterization in clean water technologies. Joule. 2020;4(8):1637–1659. doi:10.1016/j.joule.2020.06.020 12. Ray SS, Chen SS, Sangeetha D, Chang HM, Thanh CND, Le QH, Ku HM. Developments in forward osmosis and membrane distillation for desalination of waters. Environ Chem Lett. 2018;16(4):1247–1265. doi:10.1007/s10311-018-0750-7 13. Ghalavanda Y, Hatamipoura MS, Rahimia A. A review on ener- gy consumption of desalination processes. Desalin Water Treat. 2014;54(6):1526–1541. doi:10.1080/19443994.2014.892837 14. Shahmirzadi MAA, Hosseini SS, Luo JQ, Ortiz I. Significance, evolution and recent advances in adsorption technology, ma- terials and processes for desalination, water softening and salt removal. J Environ Manage. 2018;215:324–344. doi:10.1016/j.jenvman.2018.03.040 15. Ng KC, Thu K, Kim Y, Chakraborty A, Amy G. Adsorption desali- nation: An emerging low-cost thermal desalination method. De- salination. 2013;318:161–179. doi:10.1016/j.desal.2012.07.030 16. Baile P, Fernandez E, Vidal L, Canals A. Zeolites and zeolite- based materials in extraction and microextraction techniques. Analyst. 2019;144(2):366–387. doi:10.1039/c8an01194j 17. Wibowo E, Rokhmat M, Khairurrijal S, Abdullah M. Reduction of seawater salinity by natural zeolite (Clinoptilolite): Ad- sorption isotherms, thermodynamics and kinetics. Desalina- tion. 2017;409:146–156. doi:10.1016/j.desal.2017.01.026 18. Paul B, Dynes JJ, Chang W. Modified zeolite adsorbents for the remediation of potash brine-impacted groundwater: Built-in dual functions for desalination and pH neutralization. Desali- nation. 2017;419:141–151. doi:10.1016/j.desal.2017.06.009 19. Alsaman AS, Askalany AA, Ibrahim EMM, Farid AM, Ali ES, Ahmed MS. Characterization and cost analysis of a modified silica gel-based adsorption desalination application. J Clean Prod. 2022;379:134614. doi:10.1016/j.jclepro.2022.134614 20. Alsaman AS, Ibrahim EMM, Askalany AA, Farid AM, Ali ES, Ahmed MS. Composite material-based a clay for adsorption desalination and cooling applications. Chem Eng Res Des. 2022;188:417–432. doi:10.1016/j.cherd.2022.09.017 21. Guo XF, Ji ZY, Yuan JS, Zhao YY, Liu J. Recovery of K+ from concentrates from brackish and seawater desalination with modified clinoptilolite. Desalin Water Treat. 2016;579160:6829–6837. doi:10.1080/19443994.2015.1010590 22. Paul B, Dynes JJ, Chang W. Modified zeolite adsorbents for the remediation of potash brine-impacted groundwater: Built-in dual functions for desalination and pH neutralization. Desali- nation. 2017;419:141–151. doi:10.1016/j.desal.2017.06.009 23. Gibb NP, Dynes JJ, Chang W. Synergistic desalination of potash brine-impacted groundwater using a dual adsorbent. Sci Total En- viron. 2017:593–594:99–108. doi:10.1016/j.scitotenv.2017.03.139 24. Kragovic M, Pasalic S, Markovic M, Petrovic M, Nedeljkovic B, Momcilovic M, Stojmenovic M. Natural and modified zeolite- alginate composites. Application for removal of heavy metal Cations from contaminated water solutions. Minerals. 2018;8(1):11. doi:10.3390/min8010011 https://doi.org/10.15826/chimtech.2023.10.3.05 https://www.scopus.com/authid/detail.uri?authorId=57220024671 https://www.scopus.com/authid/detail.uri?authorId=57208575069 https://www.scopus.com/authid/detail.uri?authorId=56652160000 https://www.kaznu.kz/en https://cfhma.kz/cfhma/ https://doi.org/10.1016/j.desal.2015.01.041 https://doi.org/10.1016/j.scitotenv.2018.12.076 https://doi.org/10.1007/s13201-016-0455-7 https://doi.org/10.1007/s40726-018-0085-9 https://doi.org/10.1016/j.scitotenv.2020.141528 https://doi.org/10.3390/w6051134 https://doi.org/10.3390/app11020670 https://doi.org/10.1016/j.desal.2014.12.020 https://doi.org/10.1016/j.desal.2022.115827 https://doi.org/10.3390/pr8080901 https://doi.org/10.1016/j.joule.2020.06.020 https://doi.org/10.1007/s10311-018-0750-7 https://doi.org/10.1080/19443994.2014.892837 https://doi.org/10.1016/j.jenvman.2018.03.040 https://doi.org/10.1016/j.desal.2012.07.030 https://doi.org/10.1039/c8an01194j https://doi.org/10.1016/j.desal.2017.01.026 https://doi.org/10.1016/j.desal.2017.06.009 https://doi.org/10.1016/j.jclepro.2022.134614 https://doi.org/10.1016/j.cherd.2022.09.017 https://doi.org/10.1080/19443994.2015.1010590 https://doi.org/10.1016/j.desal.2017.06.009 https://doi.org/10.1016/j.scitotenv.2017.03.139 https://doi.org/10.3390/min8010011