Zofchak Everett S, Zhang Zidan, Wheatle Bill K, Sujanani Rahul, Warnock Samuel J, Dilenschneider Theodore J, Hanson Kalin G, Zhao Shou, Mukherjee Sanjoy, Abu-Omar Mahdi M, Bates Christopher M, Freeman Benny D, Ganesan Venkat
McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States.
Materials Department, University of California, Santa Barbara, California 93106, United States.
ACS Macro Lett. 2021 Sep 21;10(9):1167-1173. doi: 10.1021/acsmacrolett.1c00243. Epub 2021 Sep 8.
Direct lithium extraction via membrane separations has been fundamentally limited by lack of monovalent ion selectivity exhibited by conventional polymeric membranes, particularly between sodium and lithium ions. Recently, a 12-Crown-4-functionalized polynorbornene membrane was shown to have the largest lithium/sodium permeability selectivity observed in a fully aqueous system to date. Using atomistic molecular dynamics simulations, we reveal that this selectivity is due to strong interactions between sodium ions and 12-Crown-4 moieties, which reduce sodium ion diffusivity while leaving lithium ion mobility relatively unaffected. Moreover, the ion diffusivities in the membrane, when scaled by their respective solution diffusivities and free ion fractions, can be collapsed to an almost universal relationship depending on solvent volume fraction.
通过膜分离直接提取锂，从根本上受到传统聚合物膜缺乏单价离子选择性的限制，特别是在钠离子和锂离子之间。最近，一种12-冠-4官能化的聚降冰片烯膜被证明具有迄今为止在完全水体系中观察到的最大锂/钠渗透选择性。通过原子分子动力学模拟，我们揭示这种选择性是由于钠离子与12-冠-4基团之间的强相互作用，这降低了钠离子的扩散率，而锂离子的迁移率相对不受影响。此外，当膜中的离子扩散率按其各自的溶液扩散率和游离离子分数进行缩放时，根据溶剂体积分数，它们可以归结为一种几乎通用的关系。
