Visible light-induced crosslinking enables highly permeable and chlorine-resistant polyamide membranes for water purification

Nanofiltration (NF) based purification technology plays a growing role in water softening, wastewater reuse, and drinking water production, whose core component is the thin-film composite (TFC) polyamide (PA) surface separating layer with high water permeation and significant antifouling and chemical resistance. Strengthening water transport with simultaneously improving chemical tolerance and fouling resistance accords with the demands for sustainable water treatment. In this work, a photo-assisted crosslinked NF membrane with a regulated interlaced stripe surface morphology was fabricated through grafting 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) into the PA network during visible light irradiation. Surface structures and chemical features were characterized, and the NF performance, antifouling and chlorine resistance were systematically evaluated. The optimal membrane with AMPS molecules carrying sulfonyl groups crosslinked in the PA network was rendered electronegative charge, uniformly narrowed pore size, improved hydrophilicity, and higher crosslinking degree. The water permeation was augmented to 30.5 L m−2 h−1·bar−1 for the optimal membrane, four times more advanced than the pristine membrane with a water permeability of 5.9 L m−2 h−1·bar−1, and the divalent salt retention was improved to 99.7%. In addition, the optimal membrane also exhibited outstanding chlorine tolerance, fouling removal, and antifouling capacity. The flux recovery ratio (FRR) of the best membrane outperformed that of the pristine membrane and the flux declined more slowly in the whole fouling cycle testing. This work provides a novel avenue for fabricating high-efficiency TFC membranes with great water permeation and fouling resistance.