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

Membrane fouling is inevitable duringultrafiltrationof naturalsurface waters. High-performance ultrafiltration membranes with sustainableantifouling abilities and regenerable properties are of great importancefor water treatment. In this study, pH-responsive chitosan was usedas a sacrificial and protective layer to enhance the ultrafiltrationperformance with a coating-decoating-recoating strategy.The resultant membranes were systematically characterized to determinethe surface morphologies, separation, and antifouling capabilities.The results showed that the modified membranes exhibited enhancedhydrophilicity, 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 asthe sacrificial layer for foulant deposition and protected the underlyingsupport from fouling. Consequently, the fouled chitosan layer couldbe completely removed and regenerated by dissolution in an acid solutionand recoated at the same time. During ultrafiltration of natural surfacewater, the flux recovery rate of the optimized membrane reached 95%,which was much higher than that of the control membrane (60.3%). Themodified membranes exhibited excellent separation and antifoulingcapabilities in purifying real surface waters. Thus, the coating-decoating-recoatingstrategy is an economical and environmentally sound method for sustainablesurface modifications of ultrafiltration membranes used to producehigh-quality drinking water.