Preparation And Performance Study Of Nitrogen-doped Titanium Dioxide/reduced Graphene Oxide Photocatalytic Composite Film

Membrane separation technology has the advantages of convenient operation,high separation efficiency,low environmental pollution and low energy consumption.It has been widely used in the treatment of drinking water,domestic sewage and industrial wastewater.However,problems such as membrane fouling and membrane flux decline during membrane separation hinder the further improvement of membrane separation technology.Photocatalytic technology has the advantages of low operating cost and environmental friendliness,but there are problems such as hard to reclaim,high energy consumption and low degradation rate,which limits the further development of photocatalytic technology.The photocatalytic composite membrane combines the photocatalytic technology with the membrane separation technology,the photocatalytic efficiency can be improved by the membrane entrapment and enrichment of the organic matter,and the photocatalytic degradation of the organic pollutant deposited on the membrane surface is also timely,which can effectively alleviate membrane fouling and increase membrane flux.In this study,a novel photocatalytic composite membrane of nitrogen-doped titanium dioxide reduced graphene oxide?N-TiO₂/RGO/PVDF?was prepared by surface coating method.Firstly,TiO₂ nanoparticles were prepared by high temperature calcination by sol-gel method,N-TiO₂/RGO nanoparticles were synthesized by hydrothermal method with urea?as nitrogen source?and graphene oxide?GO?.The morphology and structure were characterized by various methods,and the photocatalytic properties were investigated.Then,N-TiO₂/RGO nanoparticles were supported on the surface of the pretreated polyvinylidene fluoride?PVDF?microfiltration membrane by impregnation method and vacuum filtration method to prepare N-TiO₂/RGO/PVDF composite microfiltration membrane.The changes of photocatalyst loading on the morphology and properties of the membrane were analyzed.The results showed that compared with TiO₂,the doping of non-metallic nitrogen in N-TiO₂/RGO could reduce the band gap of TiO₂ and improve the utilization of visible light.The introduction of GO further expanded the photo-response range of TiO₂ and inhibited photo-generated electron cavities,the composite increased the contact area with the pollutants,thereby further improving the photocatalytic efficiency of TiO₂.The doping of N and GO had no obvious effect on the crystal structure of nano-TiO₂,TiO₂ still existed in the form of anatase.During the hydrothermal reaction,the doping of N and the reduction of GO proceeded simultaneously,TiO₂ and RGO were combined by electrostatic adsorption and chemical bonding.Combining N-TiO₂/RGO with PVDF microfiltration membrane,photocatalysis and membrane separation produced good synergistic effects.The introduction of the catalyst caused a significant change in membrane performance.Compared with the original PVDF membrane,the N-TiO₂/RGO/PVDF composite membrane had significantly increased hydrophilicity,increased flux,increased bovine serum albumin retention and significantly improved anti-pollution performance.The enrichment of membrane separation significantly improved the degradation efficiency of photocatalysis to organic matter.Photocatalytic composite membrane separation technology can provide an effective technical approach for the treatment of refractory high concentration organic wastewater.