Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155.
Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155
Proc Natl Acad Sci U S A. 2021 Sep 14;118(37). doi: 10.1073/pnas.2022198118.
Water filtration membranes with advanced ion selectivity are urgently needed for resource recovery and the production of clean drinking water. This work investigates the separation capabilities of cross-linked zwitterionic copolymer membranes, a self-assembled membrane system featuring subnanometer zwitterionic nanochannels. We demonstrate that selective zwitterion-anion interactions simultaneously control salt partitioning and diffusivity, with the permeabilities of NaClO, NaI, NaBr, NaCl, NaF, and NaSO spanning roughly three orders of magnitude over a wide range of feed concentrations. We model salt flux using a one-dimensional transport model based on the Maxwell-Stefan equations and show that diffusion is the dominant mode of transport for 1:1 sodium salts. Differences in zwitterion-Cl and zwitterion-F interactions granted these membranes with the ultrahigh Cl/F permselectivity ( = 24), enabling high fluoride retention and high chloride passage even from saline mixtures of NaCl and NaF.
对于资源回收和清洁饮用水的生产，具有先进离子选择性的水过滤膜是迫切需要的。本工作研究了交联两性离子共聚物膜的分离性能，这是一种具有亚纳米级两性离子纳米通道的自组装膜系统。我们证明，选择性的两性离子-阴离子相互作用可以同时控制盐的分配和扩散性，在很宽的进料浓度范围内，NaClO、NaI、NaBr、NaCl、NaF 和 NaSO 的渗透率跨越了大约三个数量级。我们使用基于 Maxwell-Stefan 方程的一维输运模型来模拟盐通量，并表明对于 1:1 的钠盐，扩散是主要的输运方式。两性离子-Cl 和两性离子-F 相互作用的差异使这些膜具有超高的 Cl/F 选择性（=24），即使从 NaCl 和 NaF 的盐水混合物中，也能实现高氟化物保留和高氯化物透过率。
