Ultrathin asymmetric porous anion exchange membranes for high-efficiency electrodialysis desalination

Abstract

Freshwater scarcity has intensified the demand for energy-efficient desalination technologies. Among these, electrodialysis (ED) heavily depends on anion exchange membranes (AEMs) that exhibit low resistance and high permselectivity. However, conventional dense AEMs often suffer from thick structures and limited ion transport. This paper presents a structurally tunable ultrathin porous crosslinked AEM based on brominated poly(phenylene oxide) (BPPO). A non-solvent induced phase separation (NIPS) method is used to construct an asymmetric porous framework. Subsequent in situ crosslinking with piperazine and cationization with 1, 2-dimethylpiperazine stabilize the structure and introduce fixed piperazinium groups. The architecture combines high free volume for rapid counter-ion transport with sealed pores and a crosslinking network to suppress co-ion leakage. The membrane microstructure and electrochemical properties can be precisely tuned by adjusting the crosslinking duration. The optimized CCPPO-4 h membrane, with an ultrathin selective layer of only 0.84 μm, exhibits excellent desalination performance. Compared to the commercial AMV AEM, CCPPO-4 h achieves 24.5 % lower energy consumption (1.76 kWh kg⁻¹) and 15.4 % higher current efficiency (89.95 %). This work demonstrates the promise of tunable ultrathin porous AEMs fabricated via scalable processes for next-generation low-energy ED desalination.