Triethanolamine-Modified CMPSF Anion Exchange Membranes for High-Efficiency Acid Recovery via Diffusion Dialysis

Anion exchange membranes (AEMs) serve as critical components in diffusion dialysis (DD) systems due to their unique permselectivity. This study developed a series of triethanolamine (TEA)-functionalized chloromethylated polysulfone (CMPSF) AEMs via solution casting. The physical and chemical structural characterization through 1H NMR, XPS, FTIR, and SEM proved successful membrane synthesis. The performances of the membranes, such as ion exchange capacity (IEC), water contact angle (WCA), water uptake (WU), chemical stability, and mechanical stability, were systematically evaluated. For HCl/FeCl2 acid recovery (1 mol L−1 HCl + 0.25 mol L−1 FeCl2), the optimal membrane (TEA-CMPSF-M50) demonstrated exceptional DD performance, with an acid dialysis coefficient (UH+) of 47.9 × 10−3 m h−1 and separation factor (S) of 3.87. Crucially, after 7-day immersion in acidic solution at 65 °C, the membrane maintained UH+ and S values of CMPSF-M50 AEM of 45.4 × 10−3 m h−1 and 4.02, respectively, confirming the outstanding acid resistance and thermal stability of TEA-CMPSF-M50 AEM. These results indicated that the TEA-functionalized AEMs developed in this work hold great promise for industrial acid recovery applications.