Piperazine-functionalized porous anion exchange membranes for efficient acid recovery by diffusion dialysis

Diffusion dialysis employing anion exchange membranes (AEMs) as an energy-efficient and environmentally-friendly technology is highly desirable for acid recovery from acidic wastewater. Herein, porous AEMs with high acid permeability were tailored via a simple one-step route, in which porous chloromethyl polyethersulfone (CMPES) membrane substrate was modified by 1,4-dimethylpiperazine (DMP) to achieve simultaneous crosslinking and quaternization. The prepared piperazine-functionalized AEMs were characterized by morphology, ion exchange capacity, water uptake, water contact angle, stabilities and diffusion dialysis performance. Specifically, the optimal AEM (i.e., DPES-3h) applied in acid recovery from the simulated HCl (1.0 mol L−1)/FeCl2 (0.2 mol L−1) mixed solution at 25 °C possessed a proton dialysis coefficient (UH+) of 43.2 × 10−3 m h−1 and an acid/salt separation factor (S) of 29.6, remarkably outperforming the previously reported state-of-the-art AEMs. Furthermore, the DPES-3h AEM showed excellent thermal stability and acid resistance, suggesting considerable durability for long-term application. These results indicated that our piperazine-functionalized porous AEMs appear to be promising for acid recovery from the acidic waste streams via diffusion dialysis.