pH-Responsive Chitosan Sacrificial Layer for Simultaneous Enhancement of Ultrafiltration Performance and Sustainable Membrane Fouling Control

Membrane fouling is inevitable during ultrafiltration of natural surface waters. High-performance ultrafiltration membranes with sustainable antifouling abilities and regenerable properties are of great importance for water treatment. In this study, pH-responsive chitosan was used as a sacrificial and protective layer to enhance the ultrafiltration performance with a coating–decoating–recoating strategy. The resultant membranes were systematically characterized to determine the surface morphologies, separation, and antifouling capabilities. The results showed that the modified membranes exhibited enhanced hydrophilicity, reduced pore sizes, enhanced separation efficiencies, and improved antifouling behaviors at the expense of 3.4–18.8% reductions in the water fluxes. The atop chitosan layer served as the sacrificial layer for foulant deposition and protected the underlying support from fouling. Consequently, the fouled chitosan layer could be completely removed and regenerated by dissolution in an acid solution and recoated at the same time. During ultrafiltration of natural surface water, the flux recovery rate of the optimized membrane reached 95%, which was much higher than that of the control membrane (60.3%). The modified membranes exhibited excellent separation and antifouling capabilities in purifying real surface waters. Thus, the coating–decoating–recoating strategy is an economical and environmentally sound method for sustainable surface modifications of ultrafiltration membranes used to produce high-quality drinking water.