Biguanidine functional chitooligosaccharide modified reverse osmosis membrane with improved anti-biofouling property

In this work, a novel anti-biofouling reverse osmosis (RO) membrane was fabricated by second interfacial polymerization of synthesized cationic biguanidine functional chitooligosaccharide (COSG) with the acyl chloride groups on the nascent RO membrane surface. COSG fully combined the bioactivity of oligosaccharides and guanidine-based polymers. Meanwhile, the chitooligosaccharide (COS)-modified RO membranes were prepared for comparison. Both the COS and COSG modified membrane surface negative charge and roughness were reduced, and the hydrophilicity was significantly improved. The water flux of the COSG-modified membrane increased 16.61% than that of the virgin membrane, while the salt rejection exhibited slight decrease. Membrane fouling tests of lysozyme and bovine serum albumin illustrated that the COSG-modified membrane exhibited improved anti-fouling property with low flux decline ratios and high flux recovery ratios. Besides, the COSG-modified membranes exhibited excellent anti-bacterial property with mortalities of 99.9% against both Escherichia coli and Bacillus subtilis. Moreover, the COSG-modified membrane maintained high desalination performance after being immersed in the bacteria suspensions for seven days.