Enhanced Mono/Divalent Ion Separation via Charged Interlayer Channels in Montmorillonite-Based Membranes
Bo Han, Xuejin Sun, Zuoming Fan, Haicheng Jiang, Ziyue Wang, Wenjuan Zhang, Mingrui He, Jun Ma
Abstract
Efficient mono- and divalent ion separation is pivotal for environmental conservation and energy utilization. Two-dimensional (2D) materials featuring interlayer nanochannels exhibit unique water and ion transport properties, rendering them highly suitable for water treatment membranes. In this work, we incorporated polydopamine/polyethylenimine (PDA/PEI) copolymers into 2D montmorillonite (MMT) nanosheet interlayer channels through electrostatic interactions and bioinspired bonding. A modified laminar structure was formed on the substrate surface via a straightforward vacuum filtration. The electrodialysis experiments reveal that these membranes could achieve monovalent permselectivity of 11.06 and Na + flux of 2.09 × 10 –8 mol cm –2 s –1 . The enhanced permselectivity results from the synergistic effect of electrostatic and steric hindrance effect. In addition, the interaction between the PDA/PEI copolymer and the MMT nanosheet ensures the long-term operational stability of the membranes. Theoretical simulations reveal that Na + has a lower migration energy barrier and higher migration rate for the modified MMT-based membrane compared to Mg 2+ . This work presents a novel approach for the development of monovalent permselective membranes.