Surface functionalization of nanofiltration membrane with sulfonic groups for enhanced water permeance and antifouling performance

Sodium p-styrene sulfonate was grafted onto polyamide layer of nanofiltration membranes by UV irradiation. • The modified membrane had higher specific surface area, excellent hydrophilicity and negative surface charge. • The membrane exhibited enlarged pore size and uniform pore distribution. • The membrane improved water permeance (increased by 34.02%) and Cl − /SO 4 2− selectivity simultaneously. • The membrane possessed favorable anti-silica scaling property and robust organic fouling resistance. Conventional polyamide nanofiltration membranes suffer from severe fouling, including organic and silica scaling, and low water permeability. A highly hydrophilic, antifouling layer was constructed by grafting sodium p-styrene sulfonate (SSS) onto the separation layer via UV irradiation. After optimizing SSS dosage and UV grafting time, the modified membrane exhibited enlarged pore size and more uniform pore distribution due to photodegradation and photodecarboxylation‌ induced by UV radiation, as well as a more negative charge and high hydrophilicity due to SSS grafting. Its water flux reached 63.47 L m −2  h −1 , increased by 34.02% compared to the pristine membrane, with Na 2 SO 4 rejection over 95% via synergistic Donnan and size exclusion effects. The membrane exhibited enhanced antifouling performance. The flux decline ratio of modified membrane was only 10.49% and flux recovery ratio reached to 95.34% for bovine serum albumin fouling, while those of virgin membrane was 16.00% and 83.47%, respectively. The two values of modified membrane were 30.87% and 74.11%, respectively for humic acid fouling, while those of original membrane were 45.66% and 60.05%, respectively. Further, the membrane also exhibited excellent silica scaling resistance, the flux decline ratio was only 0.55%. The modified membrane showed stable continue performance and superior acid resistance. Overall, UV-initiated SSS grafting directly functionalizes the membrane separation layer to simultaneously boost water permeability and antifouling capacity, offering a facile and effective strategy for high-performance polyamide NF membranes. Download: Download high-res image (132KB) Download: Download full-size image