Constructing crosslinked and cationized PIM-1-based anion exchange membranes for efficient acid recovery via diffusion dialysis

Diffusion dialysis (DD) shows strong potential for acid reclamation, yet standard anion exchange membranes (AEMs) with compact, low-free-volume matrices impede ion transport, leading to low acid permeability and poor selectivity. To overcome these barriers, we present a new class of PIM-1-based AEMs fabricated through liquid bromine (Br 2 ) bromination followed by simultaneous crosslinking and cationization with 1,4-Diazabicyclo[2.2.2]octane (DABCO). This approach mitigates radical-induced chain scission, thereby better preserving the rigid polymer backbone while introducing a high density of ion-conducting sites with enhanced structural reinforcement. The resulting membranes exhibit interconnected micropores narrowly distributed at 0.4–0.6 nm, enabling molecular sieving between protons and multivalent cations. The optimized PIM-D/10h membrane achieves a proton dialysis coefficient of 37.0 × 10 −3  m/h and a separation factor (H + /Fe 2+ ) of 54.3, exceeding the commercial DF-120 benchmark by more than fourfold and threefold, respectively, while maintaining a tensile strength around 19 MPa and strong acid resistance. These results demonstrate that combining free-volume design with matrix reinforcement resolves the canonical permeability-selectivity compromise, thereby enabling a scalable route to durable AEMs for rapid, selective acid recovery from industrial wastewater.