Fabrication Of Novel Hydrophilic PTFE/TiO₂ Membrane And Its Performance

Self-assembly of TiO₂ is a well-studied approach to preparing the hydrophilic,antifouling and self-cleaning composite membranes.In order to improve the surface antifouling ability and the photocatalysis activity of PTFE/TiO₂ membrane in both UV light and visible light region,three different structural modification methods of facet coupling with TiO₂ and graphite carbon nitride?g-C₃N₄?have been done in this study.According to the SEM images,it is obvious that the roundish TiO₂nanoparticles are well distributed on a layered structure of g-C₃N₄ via a heterojunction formed at the interface along boundaries.Results from UV-vis diffuse reflectance spectra?DRS?and photo luminescence?PL?show a decrease in the band gap energy of the CNTO composites from the pure TiO₂.Since the CB potential energy of g-C₃N₄?-1.15 eV?was more negative than that of TiO₂?-0.29 eV?,the photo-excited electrons on the g-C₃N₄ surface could transfer easily to TiO₂,enhancing the photoinduced electron-hole separation and effective interfacial electron transfer,which lead to a better visible light response and satisfactory photocatalytic efficiency.Among the CNTO composites prepared by three different methods,CNTO-b displayed the best photocatalytic ability in which the degradation rate of MB reached 95.2% after 80 min of UV-visible light irradiation and 82%after 3 hours of visible light irradiation.The CNTO-b composite was then introduced to the PTFE membrane surface via plasma-induced graft polymerization of polyacrylic acid?PAA?to prepare the CNTO/PAA/PTFE membrane.After modification,the water contact angle could be obviously lowered from 115.8°to 62.3°,the flux was maintained at about 800 L·m^-2·h^-1 after 20-minute filtration.What's more,compared to the TiO₂/PAA/PTFE membrane made by TiO₂ sol,the CNTO/PAA/PTFE membrane owned a better performance of antifouling and photocatalytic activity.After 100 min of irradiation under visible light,CNTO/PAA/PTFE membrane could degrade 78% concentration of MB pollutant.Also,the CNTO/PAA/PTFE composite membrane showed a good resistance to fouling in the 1g/L BSA solution.The water flux of the fouled membrane could have 100% flux recovery after 30 min of UV-visible and visible light irradiation,respectively.In this sense,this approach successfully prepared a kind of hydrophilic modified PTFE/TiO₂ membrane by combining the g-C₃N₄ with TiO₂ to enhance its surface photocatalytic activity,which showed a promising application case of CNTO composites in membrane hydrophilic modification.