Controllable cross‐linking of VA‐co‐VAm/PAN composite membranes for efficient pervaporation desalination under extreme pH conditions

Abstract Polyvinyl alcohol (PVA) is a promising membrane material for pervaporation (PV) desalination. However, the adjustment and control of the cross‐linking structure is still a challenge for PVA membrane. In this study, a novel pH‐resistant PVA‐based composite membrane for efficient pervaporation desalination was developed by precisely adjusting the cross‐linking behavior. Vinyl alcohol‐vinylamine copolymer (VA‐co‐VAm) containing both hydroxyl and amino groups was synthesized. Cross‐linking reaction was carried out based on the Schiff base reaction between amino groups (in VAm moiety) and glutaraldehyde (GA) under alkaline conditions. Cross‐linking degree of PVA selective layer was carefully controlled by adjusting the amino group content in copolymer. Results showed that membrane prepared with VA‐co‐VAm that containing 5 wt% N‐vinylformamide (NVF) displayed superior hydrophilicity and the largest free volume fraction. Pervaporation test indicated that the modified cross‐linking membrane showed good stability under extreme pH conditions. Specifically, under strong acid conditions (pH ~ 1) and alkaline conditions (pH ~ 14), the membrane showed excellent desalination performance with water flux over 12 kg/(m 2 h), and the salt rejection higher than 99.95%. Based on the above results, the prepared membrane offers a promising platform for desalination under extreme pH conditions, which shows great potential in industrial wastewater treatment.