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.