Multiple Interface Reactions Enabled Zwitterionic Polyamide Composite Reverse Osmosis Membrane for Enhanced Permeability and Antifouling Property

Membrane fouling for polyamide composite reverse osmosis (RO) membranes is always one of the main bottleneck problems that limit its practical application. Herein, a novel zwitterionic polyamide composite membrane was prepared with a stepwise multiple interface reaction strategy, which combined the interfacial polymerization process with an interfacial grafting process to tailor an antifouling membrane surface. First, the polyamide composite membrane was prepared by conventional polyamide interface polymerization, and then N,N-dimethylethylenediamine was grafted to the polyamide composite layer via liquid interfacial amidation reaction to impart tertiary amine reactive sites, and finally 1,3-propane sultone underwent a vapor interfacial ring-opening reaction to induce quaternization of the tertiary amine reactive site and generate zwitterionic groups. Zwitterionic polyamide composite membrane showed higher hydrophilicity and lower surface roughness, which can facilitate water permeation and improve antifouling property. Compared to pristine RO membrane, the water flux of the zwitterionic RO membrane is promoted by ∼100%, and the NaCl rejection rate is maintained at 99%. Also note that the zwitterionic polyamide composite membrane exhibits outstanding antifouling property, compared to typical surfactants. The durability of the zwitterionic polyamide composite membrane during long-term operation was also demonstrated. This study provides a simple, effective, and novel method for the rational design and fabrication of antifouling RO membranes with excellent comprehensive separation performance.