A facile strategy to develop highly stable antifouling NF membranes with chlorine resistance based on polyamide-sulfonamide active layer

In practical applications, Nanofiltration (NF) membranes are confronted with inevitable challenges, including the terrible fouling and the deterioration by chlorine, which hinders the wider application. In this study, 2-aminophenol-4-sulfonamide (APSA) was incorporated to form the polyamide-sulfonamide active layer, thus highly stable antifouling NF membranes with chlorine resistance were fabricated. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results showed APSA successfully grafted on the membrane surface. Scanning electron microscope (SEM) and atomic force microscope (AFM) images indicated a smooth membrane surface. Water contact angle of the PA-SA NF membranes declined to 19.7° compared with the PA NF membranes. Flux recovery rates (FRR) of bovine albumin (BSA), humic acid (HA), sodium alginate (SA) and oil/water emulsion were 96.4%, 96.8%, 96.0% and 94.6%, respectively. Besides, slight decline occurred to FRR value for BSA after three fouling cycles. No obvious decline of the rejection and water flux was observed on long-term stability. Notably, slight rejection rate decline and no obvious FRR value decline were observed after chlorination. Overall, the PA-SA NF membranes possessed highly stable antifouling property and chlorine resistance. It might be due to the fact that APSA including various hydrophilic groups grafted onto the active layer. N–H bonds of sulfonamide could act as a sacrificial unit against free chlorine. It is anticipated that this work could provide a facile strategy to develop NF membranes with highly stable antifouling property and chlorine resistance.