Zhao Chen, Feng Fan, Hou Jue, Hu Jian, Su Yuyu, Liu Jefferson Zhe, Hill Matthew, Freeman Benny D, Wang Huanting, Zhang Huacheng
Chemical and Environmental Engineering, School of Engineering, RMIT University, Melbourne, Victoria 3000, Australia.
Department of Mechanical Engineering, The University of Melbourne, Parkville, VIC 3010, Australia.
J Am Chem Soc. 2024 May 22;146(20):14058-14066. doi: 10.1021/jacs.4c02477. Epub 2024 May 11.
Metal-organic framework (MOF) membranes with high ion selectivity are highly desirable for direct lithium-ion (Li) separation from industrial brines. However, very few MOF membranes can efficiently separate Li from brines of high Mg/Li concentration ratios and keep stable in ultrahigh Mg-concentrated brines. This work reports a type of MOF-channel membranes (MOFCMs) by growing UiO-66-(SH) into the nanochannels of polymer substrates to improve the efficiency of MOF membranes for challenging Li extraction. The resulting membranes demonstrate excellent monovalent metal ion selectivity over divalent metal ions, with Li/Mg selectivity up to 10 since Mg should overcome a higher energy barrier than Li when transported through the MOF pores, as confirmed by molecular dynamics simulations. Under dual-ion diffusion, as the Mg/Li mole ratio of the feed solution increases from 0.2 to 30, the membrane Li/Mg selectivity decreases from 1516 to 19, corresponding to the purity of lithium products between 99.9 and 95.0%. Further research on multi-ion diffusion that involves Mg and three monovalent metal ions (K, Na, and Li, referred to as M) in the feed solutions shows a significant improvement in Li/Mg separation efficiency. The Li/Mg selectivity can go up to 1114 when the Mg/M molar concentration ratio is 1:1, and it remains at 19 when the ratio is 30:1. The membrane selectivity is also stable for 30 days in a highly concentrated solution with a high Mg/Li concentration ratio. These results indicate the feasibility of the MOFCMs for direct lithium extraction from brines with Mg concentrations up to 3.5 M. This study provides an alternative strategy for designing efficient MOF membranes in extracting valuable minerals in the future.
具有高离子选择性的金属有机框架（MOF）膜对于从工业卤水中直接分离锂离子（Li）非常理想。然而，很少有MOF膜能够有效地从高镁锂浓度比的卤水中分离锂，并在超高镁浓度的卤水中保持稳定。这项工作报道了一种MOF通道膜（MOFCM），通过将UiO-66-(SH)生长到聚合物基底的纳米通道中，以提高MOF膜在具有挑战性的锂提取方面的效率。所得膜表现出对二价金属离子优异的单价金属离子选择性，锂/镁选择性高达10，因为分子动力学模拟证实，镁在通过MOF孔传输时应克服比锂更高的能垒。在双离子扩散下，随着进料溶液中镁/锂摩尔比从0.2增加到30，膜的锂/镁选择性从1516降低到19，对应锂产品的纯度在99.9%至95.0%之间。对进料溶液中涉及镁和三种单价金属离子（钾、钠和锂，称为M）的多离子扩散的进一步研究表明，锂/镁分离效率有显著提高。当镁/M摩尔浓度比为1:1时，锂/镁选择性可高达1114，当该比例为30:1时，仍保持在19。在高镁锂浓度比的高浓度溶液中，膜的选择性也能稳定30天。这些结果表明MOFCM从镁浓度高达3.5 M的卤水中直接提取锂的可行性。本研究为未来设计高效MOF膜提取有价值矿物提供了一种替代策略。
