Designing a multifunctional TFC membrane with improved permeability and anti-biofouling performance using zwitterionic, quaternary ammonium, and fluorinated materials

A novel copolymer architecture integrating anti-fouling, bactericidal, and fouling-release functions has been developed for thin-film composite (TFC) membranes to effectively address biofouling concerns. The approach involves growing three functional polymers from membrane surface in sequence. The first polymer has low surface energy, the second has bactericidal properties, and the third has a strong hydration capacity. The presence of the multifunctional layer significantly increased water permeability, which is due to the swelling property of the functional polymer. The extended Derjauguin-Landau-Verway-Overbeek (XDLVO) theory analysis shows that the introduction of the multifunctional copolymer architecture increased membrane-foulant total interaction energy (Delta G(TOT)) from 22.6 to 35.6 mJ/m(2), indicating promising anti-adhesive properties. These properties have been confirmed by an 86 % decrease in E. coli adsorption during static bacteria assay. In addition, the fluoropolymer in modified membrane enhances its self-cleaning ability, which has been verified in static fouling-release assays where the TFC membrane can release attached cells under gentle agitation. Our long-term biofouling experiments further confirmed the superior multi-defense properties of the modified TFC membrane. Comparatively, the multifunctional membrane significantly reduced flux decline by 58 % and TOC biomass by 69 % during the dynamic biofouling process, and notably enhanced flux recovery of similar to 97 % after cleaning. Our new copolymer architecture highlights the potential to enhance the efficiency and longevity of TFC membranes in a variety of applications.