Grafting bis-siloxane anion-exchange membranes: Investigating sulfuric acid concentration and solvent resistance

Electrodialysis (ED) was widely use for sulfuric acid (H 2 SO 4 ) recovery. However, challenges such as proton leakage during ED processes and the presence of large amounts of organic solvents in the wastewater have limited the recovered acid concentration to less than 30 wt% and shortened membrane lifespan. In this study, we prepared a series of anion exchange membranes (AEMs) using 3-aminopropyltrimethoxysilane (APTMS) and phenyltriethoxysilane (phTES) as cross-linking agents aimed at concentrating H 2 SO 4 through the ED process. As the content of bis-siloxane crosslinkers increased, the ion exchange capacity (IEC) of the membranes decreased from 1.86 to 1.27 mmol g −1 , resulting in lower water flux and membrane conductivity. However, the increased crosslinker content significantly enhanced membrane hydrophobicity, thereby improving its acid-blocking properties. During ED operations at a current density of 10 mA cm −2 , the BPPO-10APTMS-10phTES membrane achieved a H + concentration of 2.15 mol/L (from an initial concentration of 1.00 mol/L), outperforming AEMs without cross-linking structure. Additionally, the BPPO-xAPTMS-xphTES membranes (x = 5, 10, and 15) exhibited strong resistance to organic solvents. This research offers valuable theoretical guidance for developing AEMs with enhanced acid concentration capabilities and solvent resistance.