Self-healing polyamide reverse osmosis membranes with temperature-responsive intelligent nanocontainers for chlorine resistance

Improving the performance of reverse osmosis membranes remains great challenge to ensure excellent NaCl rejection while maintaining high water permeability and chlorine resistance. Herein, temperature-responsive intelligent nanocontainers are designed and constructed to improve water permeability and chlorine resistance of polyamide membranes. The nanocontainer is synthesized by layer-by-layer self-assembly with silver nanoparticles as the core, sodium alginate and chitosan as the repair materials, and polyvinyl alcohol as the shell. When the polyamide layer is damaged by chlorine attack, the polyvinyl alcohol shell layer dissolves under temperature stimulation of 37 °C, releasing inner sodium alginate and chitosan to repair broken amide bonds. The polyvinyl alcohol shell responds to temperature in line with actual operating environment, which can effectively synchronize the chlorination of membranes with temperature response and release inner materials to achieve self-healing properties. With adding temperature-responsive intelligent nanocontainers, the NaCl rejection of thin film composite membrane decreased by 15.64%, while that of thin film nanocomposite membrane decreased by only 8.35% after 9 chlorination cycles. Effective repair treatment and outstanding chlorine resistance as well as satisfactory stability suggest that temperature-responsive intelligent nanocontainer has great potential as membrane-doping material for the targeted repair of polyamide reverse osmosis membranes.