Facile preparation of anti-biofouling reverse osmosis membrane embedded with polydopamine-nano copper functionality: Performance and mechanism

Abstract

In this study, we conducted a facile membrane modification process by mild electroless deposition of copper nanoparticles (CuNPs) integrating polydopamine (PDA) coating to combat biofouling of thin-film composite (TFC) reverse osmosis (RO) membranes. Various experimental tests and characterization techniques have been applied to reveal the anti-biofouling performance and underlying mechanism of prepared membranes (i.e., Cu/PDA/TFC membrane). The successful functionalization with PDA and CuNPs highly enhanced the anti-fouling properties of Cu/PDA/TFC membrane, as evidenced by 45%, 40% and 37% respectively lower adsorption of bovine serum albumin, humic acid, and lipopolysaccharide in static adhesion assays. A significant decreased membrane-foulant adhesion forces by 63% was observed for Cu/PDA/TFC membrane compared to control membrane, which is ascribed to enhanced membrane surface hydrophilicity after PDA coating. Moreover, The Cu/PDA/TFC membranes presented significantly decreased cell viability (E. coli from 90% to 22%, P. aeruginosa from 89% to 26%, and S. aureus from 84% to 18%), and reduced adenosine tri-phosphate (ATP) content after 3 h bacterial exposure (E. coli by 57%, P. aeruginosa by 50%, and S. aureus by 56%). Assessment on cell viability and metabolic activities of bacteria deposited on membrane indicate that contact-mediated toxicity contributed to the antibacterial mechanism of Cu/PDA//TFC membrane. In addition, the reduced viability of the planktonic cells at the membrane surroundings under durable copper leaching (∼17 mg/m2 to ∼9 mg/m2) suggest that release of antibacterial Cu2+ ions also played an important role in membrane antibacterial mechanism. Both contact-mediated and Cu2+ release-based antibacterial mechanisms endow Cu/PDA/TFC membrane with excellent anti-biofouling capacity under long-term dynamic condition, with 45% lower flux decline compared to the control membrane.