Facile fabrication of desalination NF membranes with enhanced chlorine resistance and antifouling performance by constructing zwitterionic polyester layer without chlorination sites

In water treatment, chlorination degradation and membrane fouling inevitably induce severe damage to polyamide nanofiltration (PA-NF) membranes, significantly shortening membrane service life. In this study, zwitterionic polyester layer without chlorination active site was constructed on the polyamide membranes by interfacial polymerization of 4,6-dihydroxypyrimidine (DHP) with 1,3,5-benzenetricarbonyl trichloride (TMC) and subsequent quaternization. Therefore, desalination NF membranes with enhanced chlorine resistance and antifouling performance were fabricated using a facile approach. ATR-FTIR and XPS characterizations confirmed the existence of zwitterionic polyester layer. After chlorination at 12,000 ppm·h under three pH conditions (4.0, 7.0, and 10.0), the salt rejection of zwitterionic polyester NF membrane (QPE-NF membrane) was all higher than 97.50 %. The chlorination treatment did not significantly alter the chemical structures and surface morphologies of QPE-NF membranes, as indicated by ATR-FTIR and SEM analyses. The flux recovery ratio (FRR) of QPE-NF membranes for bovine serum albumin (BSA) was 90.75 %, indicating good antifouling performance. The QPE-NF membranes possessed enhanced chlorine resistance and antifouling properties as well as improved desalination performance. This was ascribed to the absence of chlorination active sites in the zwitterionic polyester layer, serving as a barrier to chlorine attack. Meanwhile, the zwitterions formed an additional hydration layer by electrostatic interactions, which further enhanced surface hydrophilicity. This study presented a facile approach to fabricate polyester desalination NF membranes with chlorine resistance and antifouling properties.