Constructing dual-resistant nanofiltration membranes with superior antifouling and chlorine tolerance through a synergistic modification approach

Tailoring nanofiltration membranes capable of simultaneously achieving high water permeance, exceptional selectivity, and chlorine resistance for safe drinking water purification remains a critical challenge in membrane science. This study presents a sodium citrate (SC)-assisted interfacial polymerization strategy combined with oxalyl chloride (OC) grafting modification to address these limitations. By precisely regulating the selective acylation reaction between oxalyl chloride and residual amine groups within the polyamide active layer, the surface charge density and pore structure of the membrane were systematically tuned. The resulting active layer exhibited a dense, uniform nodular morphology, accompanied by enhanced surface hydrophilicity and electronegativity. The optimized membrane demonstrated a high water permeance of 20.7 L·m −2 ·h −1 ·bar −1 while maintaining a NOM/mineral separation selectivity of 47.6. Furthermore, the SC6-OC1 membrane exhibited superior antifouling performance and long-term stability. The reduction of chlorine-sensitive amine sites, coupled with reinforced inter-chain crosslinking, significantly improved chlorine resistance. This SC-OC strategy offers a mechanistic pathway to simultaneously enhance membrane selectivity and durability, providing a promising solution for NF membranes-based sustainable, high-performance drinking water purification.