Zhou Xuechen, Wang Zhangxin, Epsztein Razi, Zhan Cheng, Li Wenlu, Fortner John D, Pham Tuan Anh, Kim Jae-Hong, Elimelech Menachem
Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06511, USA.
Faculty of Civil and Environmental Engineering, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.
Sci Adv. 2020 Nov 25;6(48). doi: 10.1126/sciadv.abd9045. Print 2020 Nov.
State-of-the-art desalination membranes exhibit high water-salt selectivity, but their ability to discriminate between ions is limited. Elucidating the fundamental mechanisms underlying ion transport and selectivity in subnanometer pores is therefore imperative for the development of ion-selective membranes. Here, we compare the overall energy barrier for salt transport and energy barriers for individual ion transport, showing that cations and anions traverse the membrane pore in an independent manner. Supported by density functional theory simulations, we demonstrate that electrostatic interactions between permeating counterion and fixed charges on the membrane substantially hinder intrapore diffusion. Furthermore, using quartz crystal microbalance, we break down the contributions of partitioning at the pore mouth and intrapore diffusion to the overall energy barrier for salt transport. Overall, our results indicate that intrapore diffusion governs salt transport through subnanometer pores due to ion-pore wall interactions, providing the scientific base for the design of membranes with high ion-ion selectivity.
最先进的脱盐膜表现出高的水盐选择性，但其区分离子的能力有限。因此，阐明亚纳米孔中离子传输和选择性的基本机制对于离子选择性膜的开发至关重要。在这里，我们比较了盐传输的整体能量势垒和单个离子传输的能量势垒，表明阳离子和阴离子以独立的方式穿过膜孔。在密度泛函理论模拟的支持下，我们证明了渗透反离子与膜上固定电荷之间的静电相互作用极大地阻碍了孔内扩散。此外，我们使用石英晶体微天平，分解了孔口分配和孔内扩散对盐传输整体能量势垒的贡献。总体而言，我们的结果表明，由于离子与孔壁的相互作用，孔内扩散控制着盐通过亚纳米孔的传输，为设计具有高离子-离子选择性的膜提供了科学依据。
