Co-deposition enhances electrodialysis of thin film composite (TFC) membranes for efficient separation of Cl−/SO42-

The increasing demand for monovalent anion separation necessitates the development of highly efficient and cost-effective monovalent selective membrane. In this study, thin-film composite (TFC) membranes were fabricated via a co-deposition method and applied in an electrodialysis system for Cl − /SO 4 2− separation. The high density of amine groups in the membrane enhances ion exchange performance, while the dense cross-linked structure and residual carboxyl groups formed after the interfacial polymerization (IP) reaction restrict SO 4 2− transport due to limited pore size and strong electrostatic repulsion . In contrast, the membrane exhibits high permeability for Cl − , enabling efficient separation of the two anions. The TFC membrane prepared by IP followed by co-deposition of 0.2 wt% Polyethyleneimine (PEI) and 0.2 wt% dopamine (DA) demonstrated excellent separation performance. At a current density of 100 A m −2 , the flux of Cl − was 24.62 × 10 −7 (mol·cm −2 ·min −1 ), while the flux of SO 4 2− was only 0.31 × 10 −7 (mol·cm −2 ·min −1 ), with a selection factor of 80.5, the selection factor is 17 times higher than that of commercial monovalent anion exchange membranes . The prepared TFC membranes exhibited excellent stability, maintaining consistent ionic fluxes of 23.79 × 10 −7 mol cm −2 ·min −1 for Cl − and 0.27 × 10 −7 mol cm −2 ·min −1 for SO 4 2− , respectively. Seven consecutive cycling experiments proves good stability of the membrane. This demonstrates their great potential for industrial applications. • The TFC membrane was modified by co-deposition method and applied in electrodialysis . • Separation factor for Cl − /SO 4 2− is 80.5, 17 times higher than commercial membrane. • Seven consecutive cycles operation demonstrate excellent stability of the membrane.