Polyamide-Based Electronanofiltration Membranes for Efficient Anion Separation

Monovalent anion (i.e., Cl–/SO42–) permselective membranes with high permselectivity, low cost, and excellent stability are urgently desired in the chlor-alkali industry. Herein, a facile interfacial polymerization strategy is employed to fabricate polyamide-based electronanofiltration (ENF) membranes for efficient anion separation. The densely cross-linked network structure and the strong electrostatic repulsion to anions of high valence by a high density of carboxylic residuals lead to the low permeation of SO42– and high permselectivity of Cl–. Specifically, the optimized ENF membranes show a Cl– flux of 2.31 mol h–1 m–2 and Cl–/SO42– selectivity of 98 at a current density of 10 mA cm–2. The Cl– selectivity of ENF membranes is 20 times higher than that of the commercial monovalent anion-selective membrane (ACS), while the Cl– flux is of a similar value. Moreover, the ENF membranes show excellent cycle stability as the permselectivity remains stable in a 10-consecutive electrodialysis process. Therefore, polyamide-based ENF membranes can be promising candidates for practical Cl–/SO42– separation in industry.