Dually-crosslinked anion exchange membranes with PVDF semi-interpenetrating polymer network for improved electrodialysis desalination

This study involves the development of a series of primary and secondary crosslinked anion exchange membranes (AEMs) within PVDF semi-interpenetrating networks, establishing a stable ion exchange structure. The optimal AEM, identified as DAEM-3, exhibits an ion exchange capacity (IEC) of 0.92 mmol·g−1, a solute diffusion rate of 0.0076 mmol/(cm2·h·mol/L). Remarkably, the desalination rate could reach 95.66 % within 180 min at a current density of 15 mA·cm−2, with the current efficiency of 81.12 %, surpassing the performance of the commercial membrane (AMX). Furthermore, the concentration rate reaches 17.00 % during a 390-minute process at a current density of 50 mA·cm−2, highlighting the ability of secondary cross-linking to simultaneously regulate IEC and the degree of cross-linking for improved densification and ion exchange performance. Moreover, the relatively tight cross-linked structure could be found to reduce water permeability and slow down the rate of spontaneous solute diffusion, making it a promising advancement in ED desalination and concentration technologies applied in zero liquid discharge.