Rapid attainment of full wettability through surface PEGylation of hydrophobic polyvinylidene fluoride membranes via spray-coating for enhanced anti-biofouling performances

Abstract

This manuscript explores the development of antifouling membranes fabricated by vapor-induced phase separation (VIPS) process and their spray-coating modification with an aqueous solution of a copolymer comprising butyl methacrylate and poly(ethylene glycol) methyl ether methacrylate, designated as poly(BMA-r-PEGMA). An initial optimization phase focused on improving the modification quality, with the aim of enhancing the wettability on both the top and bottom surfaces of the membranes, despite spraying on the top surface only. Our findings reveal that a sprayed solution concentration of 10 mg/mL, a pressure of 0.25 MPa, and a scan rate of 3000 mm/min achieved a decrease in water contact angle to 0 in less than 12 s for both membrane surfaces (the top surface directly exposed to the spray, and the bottom surface facing the instrument stage), suggesting that the spray-coating modifies the entire membrane’s bulk. The presence of the copolymer on both surfaces was also evidenced by FTIR and XPS tests. Further biofouling assessments demonstrated the performances of the optimized membrane (OM). In static attachment tests, the OM exhibited a high reduction in Escherichia coli adhesion, with less than 10 % adhering bacteria, compared to unmodified membranes. During the filtration of bacteria-containing wastewater, the OM boasted a flux recovery ratio approaching 60 % (against less than 40 % for a commercial hydrophilic membrane), a rejection rate of 99.3 %, and a water permeability of 2500 LMH/bar. Moreover, the OM was stable over a 4-week period, with a resistance to E. coli attachment remaining similar to prior immersion. These findings underscore the significant potential of spray-coating to develop stable and effective antifouling microfiltration membranes for the removal of microorganisms from wastewater.