Review on extraction and separation of valuable metal ions from aqueous solution by crown ether

doi:10.1016/j.cjche.2025.02.027

Abstract

Abstract: In recent years, with the rapid development of the economy and society, pollution of valuable metal ions in wastewater has become a major challenge to environmental sustainability. In order to solve the pollution caused by metal ions, researchers have conducted continuous researches and explored various remediation methods. Crown ether has attracted great attention because of its ionic radius and cavity size matching well with metal ions, which makes it have the ability to selectively complex metal ions. This unique property enables the directed removal and recovery of metal ions and makes crown ethers increasingly popular in extraction and separation processes. In this paper, the research progress of crown ethers in the extraction and separation of valuable metal ions was reviewed, with emphasis on the principles, extraction systems and the key factors affecting the extraction process. This study can provide some technical support for the application of separation and extraction of valuable metal ions by crown ether.

摘要： In recent years, with the rapid development of the economy and society, pollution of valuable metal ions in wastewater has become a major challenge to environmental sustainability. In order to solve the pollution caused by metal ions, researchers have conducted continuous researches and explored various remediation methods. Crown ether has attracted great attention because of its ionic radius and cavity size matching well with metal ions, which makes it have the ability to selectively complex metal ions. This unique property enables the directed removal and recovery of metal ions and makes crown ethers increasingly popular in extraction and separation processes. In this paper, the research progress of crown ethers in the extraction and separation of valuable metal ions was reviewed, with emphasis on the principles, extraction systems and the key factors affecting the extraction process. This study can provide some technical support for the application of separation and extraction of valuable metal ions by crown ether.

Jie Liu, Xin Zhang, Xingjie Lu, Qianting Li, Zhixiao Xue, Qiulu Zhang, Guizhi Wu, Wenxiang Xia. Review on extraction and separation of valuable metal ions from aqueous solution by crown ether[J]. Chinese Journal of Chemical Engineering, 2025, 85(9): 217-227.

References

[1] S.R. Dhokpande, S.M. Deshmukh, A. Khandekar, A. Sankhe, A review outlook on methods for removal of heavy metal ions from wastewater, Sep. Purif. Technol. 350 (2024) 127868.
[2] N.C. Joshi, P. Gururani, Advances of graphene oxide based nanocomposite materials in the treatment of wastewater containing heavy metal ions and dyes, Curr. Res. Green Sustain. Chem. 5 (2022) 100306.
[3] M.A. Martin-Lara, G. Blazquez, M.C. Trujillo, A. Perez, M. Calero, New treatment of real electroplating wastewater containing heavy metal ions by adsorption onto olive stone, J. Clean. Prod. 81 (2014) 120-129.
[4] X.Y. Wu, W.J. Xie, J. Ye, D. Sun, T. Ohnuki, M. Li, X.W. Zhang, Q. Fang, Q.Y. Tang, D.D. Li, Progress in heavy metals-containing wastewater treatment via microbial electrolysis cell: a review, J. Water Process Eng. 55 (2023) 104228.
[5] R. Amna, S.M. Alhassan, Exploring porous sulfur copolymers for efficient removal of heavy metal ions from wastewater: a computational study, J. Ind. Eng. Chem. 138 (2024) 365-379.
[6] A. Kagalkar, G. Som, S.A. Dharaskar, Metal recovery from municipal wastewater treatment plants, in: Resource Recovery in Municipal Waste Waters, Elsevier, Amsterdam, 2023, pp. 41-56.
[7] J.X. Du, T. David Waite, P.M. Biesheuvel, W.W. Tang, Recent advances and prospects in electrochemical coupling technologies for metal recovery from water, J. Hazard Mater. 442 (2023) 130023.
[8] A. Kaushik, A. Singh, Metal removal and recovery using bioelectrochemical technology: the major determinants and opportunities for synchronic wastewater treatment and energy production, J. Environ. Manag. 270 (2020) 110826.
[9] A. Abidli, Y.F. Huang, Z. Ben Rejeb, A. Zaoui, C.B. Park, Sustainable and efficient technologies for removal and recovery of toxic and valuable metals from wastewater: recent progress, challenges, and future perspectives, Chemosphere 292 (2022) 133102.
[10] M.Y. Zhu, Z.J. Cao, H. Yang, Z.L. Xu, C. Cheng, Improved dye and heavy metal ions removal in saline solutions by electric field-assisted gravity driven filtration using nanofiber membranes with asymmetric micro/nano channels, Sep. Purif. Technol. 300 (2022) 121775.
[11] M.S. Chauhan, A.K. Rahul, S. Shekhar, S. Kumar, Removal of heavy metal from wastewater using ion exchange with membrane filtration from Swarnamukhi river in Tirupati, Mater. Today Proc. 78 (2023) 1-6.
[12] A.Q. Jasim, S.K. Ajjam, Removal of heavy metal ions from wastewater using ion exchange resin in a batch process with kinetic isotherm, S. Afr. N. J. Chem. Eng. 49 (2024) 43-54.
[13] S. Tamizharasan, R. Muralidharan, N. Abirami, H. Leelavathi, A. Siva, A. Kumarasamy, R. Arulmozhi, Biomass derived carbon blended ion-exchange resins for the removal of toxic metal ions from waste water, Optik 283 (2023) 170930.
[14] D. Feng, C. Aldrich, H. Tan, Treatment of acid mine water by use of heavy metal precipitation and ion exchange, Miner. Eng. 13 (6) (2000) 623-642.
[15] H.Y. Wu, Y.F. Huang, B.B. Liu, G.H. Han, S.P. Su, W.J. Wang, S.Z. Yang, Y.B. Xue, S.Q. Li, An efficient separation for metal-ions from wastewater by ion precipitate flotation: probing formation and growth evolution of metal-reagent flocs, Chemosphere 263 (2021) 128363.
[16] J.A. Barragan, E.R. Larios-Duran, A.A. Peregrina-Lucano, E.P. Rivero, Paired electrochemical recovery of metal ions from emulated e-waste leached solutions in an RCE electrochemical reactor, Electrochim. Acta 471 (2023) 143419.
[17] L.M. Yang, W.B. Hu, Z.W. Chang, T. Liu, D.F. Fang, P.H. Shao, H. Shi, X.B. Luo, Electrochemical recovery and high value-added reutilization of heavy metal ions from wastewater: recent advances and future trends, Environ. Int. 152 (2021) 106512.
[18] K. Mabalane, N.D. Shooto, P.M. Thabede, A novel permanganate and peroxide carbon-based avocado seed waste for the adsorption of manganese and chromium ions from water, Case Stud. Chem. Environ. Eng. 10 (2024) 100782.
[19] Q.Y. Chen, Y. Wang, G. He, M. Yilmaz, S.J. Yuan, KMnO4-activated spinach waste biochar: an efficient adsorbent for adsorption of heavy metal ions in aqueous solution, Colloids Surf. A Physicochem. Eng. Aspects 684 (2024) 133174.
[20] A. Kovacevic, M. Tolazzi, M. Sanadar, A. Melchior, Hydrometallurgical recovery of metals from spent lithium-ion batteries with ionic liquids and deep eutectic solvents, J. Environ. Chem. Eng. 12 (4) (2024) 113248.
[21] T. Wesselborg, S. Virolainen, T. Sainio, Recovery of lithium from leach solutions of battery waste using direct solvent extraction with TBP and FeCl3, Hydrometallurgy 202 (2021) 105593.
[22] J. Chen, H.X. Zhong, S. Zhu, Study on Cu(II) extraction process optimization and mechanism from acidic leaching solution using the deep eutectic solvent P507/menthol, J. Mol. Liq. 396 (2024) 123968.
[23] H.J. Wang, Y.L. Feng, H.L. Li, H.R. Li, H. Wu, Recovery of vanadium from acid leaching solutions of spent oil hydrotreating catalyst using solvent extraction with D2EHPA (P204), Hydrometallurgy 195 (2020) 105404.
[24] Z.Z. Bian, Y.L. Feng, H.R. Li, R.Y. Zhang, New understanding of extraction and separation of vanadium(IV), iron and titanium using iron powder induction-leaching and P204-P507 synergistic extraction, Sep. Purif. Technol. 288 (2022) 120627.
[25] W.H. Shi, J. Li, Y.B. Lai, H. Zhang, H.D. Zhang, X.X. Zhang, K.J. Liu, T. Qi, Simultaneous extraction of molybdenum and silicon from sulphate leach solution of spent catalyst using trialkylamine (N235) and recovery of pure ammonium molybdate, Hydrometallurgy 227 (2024) 106308.
[26] S.B. Yuan, Q. Liu, Y.D. Liang, K.G. Ning, X.Y. Yu, Y.J. He, Dual 3-D networked pickering emulsion hydrogels encapsulating copper extractants for the recovery of Cu2+ from water, J. Environ. Chem. Eng. 9 (2) (2021) 105154.
[27] C.J. Pedersen, Cyclic polyethers and their complexes with metal salts, J. Am. Chem. Soc. 89 (26) (1967) 7017-7036.
[28] H.K. Frensdorff, Salt complexes of cyclic polyethers. Distribution equilibriums, J. Am. Chem. Soc. 93 (19) (1971) 4684-4688.
[29] T. Iwachido, A. Sadakane, K. Toei, The extraction of alkali metal picrates into benzene by means of 18-crown-6, Bull. Chem. Soc. Jpn. 51 (2) (1978) 629-630.
[30] T. Sekine, H. Wakabayashi, Y. Hasegawa, The solvent extraction of thallium(I) as a dibenzo-18-crown-6 complex with the picrate ion, Bull. Chem. Soc. Jpn. 51 (2) (1978) 645-646.
[31] Y. Takeda, The solvent extraction of uni- and bivalent metal picrates by dibenzo-24-crown-8, Bull. Chem. Soc. Jpn. 52 (9) (1979) 2501-2504.
[32] P.R. Danesi, H. Meider-Gorican, R. Chiarizia, G. Scibona, Extraction selectivity of organic solutions of a cyclic polyether with respect to the alkali cations, J. Inorg. Nucl. Chem. 37 (6) (1975) 1479-1483.
[33] T.B. Lu, X.M. Gan, N. Tang, M.Y. Tan, Studies on rare earth complexes with crown ethers-XIX. Synthesis and characterization of the complexes of lanthanide thiocyanates with dibenzo-24-crown-8, Polyhedron 9 (19) (1990) 2371-2374.
[34] Y. Liu, B.H. Han, Z.H. Zhang, J.H. Guo, Y.T. Chen, Complexation thermodynamics of rare earth (III) with crown ethers. 3. Calorimetric titration of light lanthanoid (III) nitrates with dibenzo-18-crown-6 in acetonitrile, Thermochim. Acta 317 (1) (1998) 1-6.
[35] T.Z. Yu, J. Meng, Y.L. Zhao, H. Zhang, X.Q. Han, D.W. Fan, Synthesis and rare earth metal ion-sensing properties of aza-crown derivative incorporating with diaryl-1,3,4-oxadiazole, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 78 (1) (2011) 396-400.
[36] Q. Chen, L.X. Zhang, Deeply rooted crown ether chemistry, Chem. Eng. 31 (11) (2017) 44-47, (in Chinese).
[37] Y.S. Yang, J.Q. Zhu, Application of crown ether in metal ion separation, Chem. Reag. 3 (5) (1981) 39-44, (in Chinese).
[38] P. Xu, J. Hong, X.M. Qian, Z.W. Xu, H. Xia, X.C. Tao, Z.Z. Xu, Q.Q. Ni, Materials for lithium recovery from salt lake brine, J. Mater. Sci. 56 (1) (2021) 16-63.
[39] B. Swain, Separation and purification of lithium by solvent extraction and supported liquid membrane, analysis of their mechanism: a review, J. Chem. Technol. Biotechnol. 91 (10) (2016) 2549-2562.
[40] R.M. Izatt, K. Pawlak, J.S. Bradshaw, R.L. Bruening, Thermodynamic and kinetic data for macrocycle interactions with cations and anions, Chem. Rev. 91 (8) (1991) 1721-2085.
[41] R.E.C. Torrejos, G.M. Nisola, H.S. Song, L.A. Limjuco, C.P. Lawagon, K.J. Parohinog, S. Koo, J.W. Han, W.J. Chung, Design of lithium selective crown ethers: synthesis, extraction and theoretical binding studies, Chem. Eng. J. 326 (2017) 921-933.
[42] W.J. McDowell, G.N. Case, D.W. Aldrup, Investigations of ion-size-selective synergism in solvent extraction, Separ. Sci. Technol. 18 (14-15) (1983) 1483-1507.
[43] G. Liu, Z.W. Zhao, A. Ghahreman, Novel approaches for lithium extraction from salt-lake brines: a review, Hydrometallurgy 187 (2019) 81-100.
[44] M.Z. Hong, X. Wang, W.J. You, Z.Y. Zhuang, Y. Yu, Adsorbents based on crown ether functionalized composite mesoporous silica for selective extraction of trace silver, Chem. Eng. J. 313 (2017) 1278-1287.
[45] H. Tian, M.L. Zhang, L.S. Wang, B.H. Tong, Z. Zhao, Synthesis of 4,13-dithio benzene and-18-crown-6 and its selective extractability on Ag+, Chem. Res. Chin. Univ. 39 (2018) 1191-1196.(in Chinese).
[46] Y. Kudo, Y. Kobayashi, S. Katsuta, Y. Takeda, Ion-pair formation of cadmium-18-crown-6 ethers complex ions with picrate and chloride ions in water and distribution of its picrate ion-pair complex into benzene, J. Mol. Liq. 146 (1-2) (2009) 60-65.
[47] N. Ghildiyal, Experimental investigations of complexes of some small ring fluorescent benzo oxa-crown ethers with alkali metal ions in solution phase: a review, J. Mol. Struct. 1312 (2024) 138603.
[48] Y.P. Tian, W.W. Chen, Z. Zhao, L. Xu, B.H. Tong, Interaction and selectivity of 14-crown-4 derivatives with Li+, Na+, and Mg2+ metal ions, J. Mol. Model. 26 (4) (2020) 67.
[49] T. Hayashita, J.H. Lee, M.G. Hankins, J.C. Lee, J.S. Kim, J.M. Knobeloch, R.A. Bartsch, Selective sorption and column concentration of alkali-metal cations by carboxylic acid resins with dibenzo-14-crown-4 subunits and their acyclic polyether analogs, Anal. Chem. 64 (7) (1992) 815-819.
[50] G.V. Jeffrey, Proceedings of the International Solvent Extraction Conference, Lyon, France, 1974.
[51] Z.F. Jing, G.G. Wang, Y.Q. Zhou, D.K. Pang, F.Y. Zhu, H.Y. Liu, Selectivity of 18-crown-6 ether to alkali ions by density functional theory and molecular dynamics simulation, J. Mol. Liq. 311 (2020) 113305.
[52] H. Yang, R. Gao, C.Y. Yang, H.B. Shan, T. Huang, Y.H. Wang, Y.D. Jin, S. Qin, X.C. Chen, C.Q. Xia, The mechanism insight into the cooperative coordination of aza-18-crown-6 ether with diglycolamide by p-benzyl as linkers enhancing the selectivity for heavy REEs(III), J. Mol. Liq. 407 (2024) 125281.
[53] O.A. Grad, M. Ciopec, A. Negrea, N. Duteanu, P. Negrea, R. Voda, Evaluation of performance of functionalized amberlite XAD7 with dibenzo-18-crown ether-6 for palladium recovery, Materials 14 (4) (2021) 1003.
[54] S.R. Dave, H. Kaur, S.K. Menon, Selective solid-phase extraction of rare earth elements by the chemically modified Amberlite XAD-4 resin with azacrown ether, React. Funct. Polym. 70 (9) (2010) 692-698.
[55] A.A. Bezdomnikov, V.E. Sharov, L.I. Demina, M.I. Skrebtsov, A.B. Ilyukhin, A.Y. Tsivadze, Specific features of lithium solvent extraction from perchlorate media with benzo-15-crown-5, Polyhedron 244 (2023) 116612.
[56] L. Xu, Y.H. Xiong, L. Wang, Y.P. Tian, B.H. Tong, J.L. You, Z. Zhao, A novel method for selective recovery of indium from end-of-life liquid crystal displays by 15-crown-5 ether and its derivatives, Hydrometallurgy 202 (2021) 105601.
[57] Y. Sun, M.Y. Zhu, Y.L. Yao, H.W. Wang, B.H. Tong, Z. Zhao, A novel approach for the selective extraction of Li+ from the leaching solution of spent lithium-ion batteries using benzo-15-crown-5 ether as extractant, Sep. Purif. Technol. 237 (2020) 116325.
[58] A.D. Zubenko, B.V. Egorova, L.S. Zamurueva, S.N. Kalmykov, O.A. Fedorova, Synthesis of benzoaza-15(18)-crown-5(6) ethers and study of their complexes with lead(II), Mendeleev Commun. 31 (2) (2021) 194-196.
[59] J.H. Wu, D.C. Zhang, T.Z. Yang, D.S. Xia, Selective recovery of low-concentration light rare earth ions from high-concentration ammonium sulfate system by coordination ability, J. Sustain. Metall. 10 (1) (2024) 206-223.
[60] Y. Luo, N. Marets, T. Kato, Selective lithium ion recognition in self-assembled columnar liquid crystals based on a lithium receptor, Chem. Sci. 9 (3) (2018) 608-616.
[61] M.H. Mashahadizadeh, R. Mohyaddini, M. Shamsipur, Selective and efficient liquid membrane transport of Au(III) by tetrathia-12-crown-4 as a specific carrier, Sep. Purif. Technol. 39 (3) (2004) 161-166.
[62] X. Bai, J.D. Dai, Y. Ma, W.B. Bian, J.M. Pan, 2-(Allyloxy) methylol-12-crown-4 ether functionalized polymer brushes from porous PolyHIPE using UV-initiated surface polymerization for recognition and recovery of lithium, Chem. Eng. J. 380 (2020) 122386.
[63] E.Z. Li, J. Kang, P.Y. Ye, W.J. Zhang, F.Q. Cheng, C.X. Yin, A prospective material for the highly selective extraction of lithium ions based on a photochromic crowned spirobenzopyran, J. Mater. Chem. B 7 (6) (2019) 903-907.
[64] J. Wang, reportPreparation and Properties of Sr(Ⅱ) high-efficiency Extraction Separation Materials, M.D. Thesis, Southwest University of Science and Technology, China, 2024, (in Chinese).
[65] T.T. Yong, C.X. Zhao, C.J. Zhao, H.L. Liu, Separation of Rb+ and Cs+ from aqueous solution by ionic liquid extraction with crown ether, J. East China Univ. Sci. Technol., Nat. Sci. Ed. 45 (2019) 58-66, (in Chinese).
[66] A.E. Visser, R.P. Swatloski, W.M. Reichert, S.T. Griffin, R.D. Rogers, Traditional extractants in nontraditional solvents: groups 1 and 2 extraction by crown ethers in room-temperature ionic liquids, Ind. Eng. Chem. Res. 39 (10) (2000) 3596-3604.
[67] N. Islam, S.S. Chimni, Binding and selectivity of phenazino-18-crown-6-ether with alkali, alkaline earth and toxic metal species: a DFT study, J. Mol. Struct. 1130 (2017) 781-790.
[68] K.S. Diao, H.J. Wang, Z.M. Qiu, A DFT study on the metal binding selectivity of 12-crown-4 and its heterocyclic analogs, J. Mol. Struct. THEOCHEM 901 (1-3) (2009) 157-162.
[69] R. Behjatmanesh-Ardakani, NBO-NEDA, NPA, and QTAIM studies on the interactions between aza-, diaza-, and triaza-12-crown-4 (An-12-crown-4, n =1, 2, 3) and Li+, Na+, and K+ ions, Comput. Theor. Chem. 1051 (2015) 62-71.
[70] I. Oral, S. Tamm, C. Herrmann, V. Abetz, Lithium selectivity of crown ethers: the effect of heteroatoms and cavity size, Sep. Purif. Technol. 294 (2022) 121142.
[71] J.T. He, J.Y. Hua, X.H. Ma, R. Wickramasinghe, J.X. Li, A mixed solvent system of amino crown ether and ionic liquids for a high-efficient extraction of cesium, J. Mol. Liq. 412 (2024) 125868.
[72] Y.P. Tian, Z.L. Liu, Z.S. Jia, F. Zhang, C. Yang, L. Xu, Z. Zhao, Mechanism for lithium extraction with ether and ester oxygens in armed crown ethers, J. Mol. Liq. 400 (2024) 124350.
[73] S.K. Sahu, V. Chakravortty, M.L. Reddy, T.R. Ramamohan, The synergistic extraction of thorium(IV) and uranium(VI) with mixtures of 3-phenyl-4-benzoyl-5-isoxazolone and crown ethers, Talanta 51 (3) (2000) 523-530.
[74] Y. Meguro, Y. Kitatsuji, T. Kimura, Z. Yoshida, Steric effect of β-diketone in synergistic extraction of actinide(III) and lanthanide(III) with β-diketone +18-crown-6 ether/1, 2-dichloroethane, J. Alloys Compd. 271 (1998) 790-793.
[75] F. Abdollahzadeh Khanghah, J. Karimi-Sabet, C. Ghotbi, Optimization of synergistic extraction of calcium ion via an emulsion liquid membrane using dicyclohexano-18-crown-6 and D2EHPA carriers: a design of experiment study, J. Clean. Prod. 432 (2023) 139663.
[76] S.M.S. Hussain, A.A. Adewunmi, O.S. Alade, M. Murtaza, A. Mahboob, H.J. Khan, M. Mahmoud, M.S. Kamal, A review of ionic liquids: recent synthetic advances and oilfield applications, J. Taiwan Inst. Chem. Eng. 153 (2023) 105195.
[77] J. Houzar, K. Cubova, M. Semelova, M. Nemec, Solvent extraction of radiostrontium into ionic liquids using crown ethers, J. Radioanal. Nucl. Chem. 332 (5) (2023) 1515-1519.
[78] Z.Z. Zhang, Y.Z. Jia, B. Liu, H.X. Sun, Y. Jing, Q.Y. Zhang, F. Shao, M.X. Qi, Y. Yao, Extraction and separation of lithium isotopes by using organic liquid film extraction system of crown ether-ionic liquid, Fusion Eng. Des. 161 (2020) 112015.
[79] B. Liu, S. Wang, Y.Z. Jia, W.B. Zhu, Q.Y. Zhang, X.Q. Wang, Y. Yao, Y. Jing, Lithium isotope separation by crown ethers of different nitrogen-containing derivatives in the ionic liquid-anisole system, J. Mol. Liq. 272 (2018) 548-553.
[80] Y.T. Du, P.H. Rao, Y.S. Li, J.P. Qiu, W.G. Qiu, H. Tang, M.A. Potter, Toxicological responses of the earthworm Eisenia fetida to 18-crown-6 under laboratory conditions, Bull. Environ. Contam. Toxicol. 93 (4) (2014) 452-455.
[81] M. Jawaid, F. Ingman, Ion-pair extraction of Na+, K+ and Ca2+ with some organic counter-ions and dicyclohexyl-18-crown-6 as adduct-forming reagent, Talanta 25 (2) (1978) 91-95.
[82] R.Z. Zhao, F.Q. Wei, X.L. Ren, Research status and prospect of extraction and separation of lithium from salt lake, Appl. Chem. Ind. 50 (2021) 1690-1693+1703, (in Chinese).
[83] W.B. Zhu, Studies on the separation of lithium isotopes in different ionic liquid-crown ether systems, M.D. Thesis, Qinghai Institute of Salt Lake Research, Chinese Academy of Sciences, China, 2019, (in Chinese).
[84] Y.H. Xiong, T. Ge, L. Xu, L. Wang, J.D. He, X.W. Zhou, Y.P. Tian, Z. Zhao, A fundamental study on selective extraction of Li+ with dibenzo-14-crown-4 ether: toward new technology development for lithium recovery from brines, J. Environ. Manag. 310 (2022) 114705.
[85] S.V. Nesterov, O.A. Zakurdaeva, Targeted preparation of highly efficient lithium extractants based on 14-membered crown ethers, Mendeleev Commun. 32 (5) (2022) 670-671.
[86] S. Wang, Study on the separation of lithium isotopes by ionic liquid extraction with different side chain crown ethers, M.D. Thesis, Qinghai Institute of Salt Lake Research, Chinese Academy of Sciences, China, 2018, (in Chinese).
[87] M. Ciopec, O. Grad, A. Negrea, N. Duteanu, P. Negrea, C. Paul, C. Iana?i, G. Mosoarca, C. Vancea, A new perspective on adsorbent materials based impregnated MgSiO3 with crown ethers for palladium recovery, Int. J. Mol. Sci. 22 (19) (2021) 10718.
[88] J.Y. Hua, J.T. He, H.C. Pei, J.H. Du, X.H. Ma, J.X. Li, A remarkable improved Li+/Mg2+ selectivity and Li+ recovery simultaneously by adding crown ether to tributyl phosphate-ionic liquid extraction system as co-extractant, Sep. Purif. Technol. 335 (2024) 126162.
[89] J.L. Wang, S.T. Zhuang, Cesium separation from radioactive waste by extraction and adsorption based on crown ethers and calixarenes, Nucl. Eng. Technol. 52 (2) (2020) 328-336.
[90] P.R. Zhang, Z.X. Xue, C.M. Wang, J.H. Sun, F. Shao, X.W. Zou, B. Li, M.X. Qi, Y. Jing, Y.Z. Jia, Mechanisms of ionic liquids on the enhancement of interfacial transport of lithium ions in crown ether system, J. Clean. Prod. 366 (2022) 132782.
[91] G.S. Tsebrikova, I.S. Ivanova, A.B. Ilyukhin, I.A. Yakushev, P.V. Dorovatovskii, V.P. Solov’ev, V.E. Baulin, A.Y. Tsivadze, Co2+, Ni2+ and Cu2+ complexes with phosphorylated derivatives of cyclen and diaza-18-crown-6: effect of anion on the structure of complexes and their stability in solution, Inorg. Chim. Acta. 549 (2023) 121410.
[92] I.A. Kuz’mina, M.A. Kovanova, A.S. Udalova, Solvation of dibenzo-18-crown-6 ether in water-aprotic solvents, J. Mol. Liq. 367 (2022) 120393.
[93] M. Jozwiak, L. Madej-Kielbik, H. Piekarski, Effect of temperature on the solvation of 15-crown-5 ether in water-methanol mixtures, Thermochim. Acta 533 (2012) 22-27.
[94] M. Jozwiak, L. Madej-Kielbik, H. Piekarski, Effect of temperature on the solvation of 15-crown-5 ether in water-ethanol and water-propan-1-ol mixtures, Thermochim. Acta 568 (2013) 122-129.
[95] M. Jozwiak, M.A. Kosiorowska, Effect of temperature on the process of preferential solvation of 1,4-dioxane and 12-crown-4 ethers in the mixture of water with formamide, Thermochim. Acta 539 (2012) 62-66.
[96] L. Zhang, Q. Yang, Application of crown ether in extraction and separation of metal ions, Acad. Forum Nandu. 9 (1) (1989) 101-103, (in Chinese).
[97] M. Cao, J. Peng, S.W. Hu, Theoretical calculation of conformation transformation, selectivity and isotopic effects of crown ether-metal ion complexes, J. Isot. 35 (6) (2022) 525-534, (in Chinese).
[98] B.D. Zheng, H.Z. Chen, Application of crown ether in extraction and separation, Mar. Sci. Bull. 5 (1) (1986) 86-91, (in Chinese).
[99] J. Strzelbicki, B. Strzelbicka, E. Lubboch, R.A. Bartsch, Separation of alkali metal cations by polymer-supported liquid membranes using ionizable crown ethers, Process. Metall. 7 (1992) 1517-1522.
[100] L.N. Wei, J. Kang, H. Li, E.Z. Li, H.G. Chen, F.Q. Chen, Research progress of extraction agent and extraction system for extracting lithium from salt lake, Inorg. Chem. Ind. 53 (2021) 21-25, (in Chinese).