Anti-biofouling nanofiltration membrane constructed by in-situ photo-grafting bactericidal and hydrophilic polymers

Membrane biofouling is a serious constraint to lifespan of polyamide thin film composite (PA TFC) membranes. However, improving the anti-biofouling ability of membranes with traditional surface modification technologies has negative effects on its performance. Herein, we designed a composite membrane bearing photoreactive PA (PPA) layer via introducing benzophenone acyl chloride (Bp-COCl) into interfacial polymerization (IP) at first. Then, the bactericidal and hydrophilic polymers, polyhexamethylene biguanide (PHMB) and polyethylene glycol (PEG), were in-situ photo-grafted on the membrane surface to form a polymer grafting (PG) layer. The conditions of Bp-COCl content and UV irradiation time were investigated, the optimum modified membrane showed high water permeability of 18.6 L m(-2) h(-1) bar(-1) and outstanding divalent ions rejection ability of 91.7% as well as long-term operation stability. Besides, in the anti-biofouling tests, the bacterial inhibition rate of membrane reached up to 98.6% and the flux recovery ratio (after four biofouling cycles) increased from 44.7% to 70.8% compared to pristine membrane. This work paves a novel way to fabricate anti-biofouling PA TFC nanofiltration (NF) membrane with high performance. Meanwhile, the PPA layer provides a universal platform for membrane surface modification.