Based On The Preparation And Performance Of TiO₂ And Bi₁₂O₁₇Cl₂ Photocatalytic Composite Membranes

Membrane separation technology has attracted much attention in water treatment because of its low energy consumption,easy control,and strong stability.It can be used in the field of water treatment,but its main problem is the decrease of membrane separation efficiency and shortened service life caused by membrane fouling.Photoeatalytie technology is a green renewable environmental remediation technology that removes organic or inorganic contaminants through a light-driven oxidation process without secondary pollution.The anti-fouling,hydrophilic and photocatalytic properties of the photocatalytic membrane prepared by the combination of membrane technology and photocatalytic technology have strong wastewater treatment and self-cleaning ability,which can effectively solve the problem of membrane fouling,photocatalyst recovery and reuse.TiO2 has superior hydrophilicity and excellent self-cleaning properties,but its own forbidden band defects make its practical application limited.To overcome the shortcomings of TiO2,the researchers explored many modification methods,such as the preparation of new morphologies of TiO2,in combination with other metal oxides or non-metal oxides.As a novel visible light catalyst with a layered structure,Bi12O17Cl2 has a unique electronic structure and has good photocatalytic activity and stability in photocatalytic reactions.Based on TiO2 and Bi12O17Cl2,a series of new high-efficiency photocatalytic membranes were prepared.In this thesis,nanowire TiO2(TiO2NW),Bi12O17Cl2 nanosheets,and Bi12O17Cl2-TiO2NW were prepared by hydrothermal method,and graphene oxide(GO)was prepared by Hummers modification method.On this basis,the GO was mixed with TiO2NW,TiO2NP,Bi12O17Cl2 and Bi12O17C2l-TiO2,and modified by dopamine(PDA)to prepare RGO/PDA/TiO2NP,RGO/PDA/TiO2NW,RGO/PDA/Bi12O17Cl2 and RGO/PDA/Bi12O17Cl2-TiO2NW composite material,then deposited on the CA membrane by vacuum filtration to prepare a photocatalytic composite membrane,respectively.The composites and membranes were characterized by XRD,FTIR,XPS,SEM,TEM and UV-Vis,and evaluate their performance through experiments.The composites and membranes were characterized by FTIR,XPS,SEM,TEM and UV-Vis,and their correlation properties were evaluated experimentally.The results show that TiO2NW has better dispersibility and photocatalytic performance than TiO2NP.RGO/PDA/TiO2NW-CA composite membrane has better anti-staining property than RGO/PDA/TiO2NP-CA composite membrane.The RGO/PDA/TiO2NW-CA composite membrane prepared by TiO2 has high water flux(273 L/m2·h·bar)and rejection(about 98%)for dye-oil-water emulsion,and can be irradiated under visible light.A relatively stable dye-oil-water permeation flux and high rejection were maintained for the next 5 cycles.For the composite material RGO/PDA/Bi12O17Cl2,the introduction of Bi12O17Cl2 not only increaseed the interlayer spacing of the reduced graphene oxide(RGO),but also improved the distribution of Bi12O17Cl2 among the graphene oxide nanosheets.Under visible light irradiation,the RGO/PDA/Bi12O17C12-CA composite membrane achieved continuous flow separation of oil/water emulsion and degradation of soluble organic pollutants methylene blue(MB)and p-chlorophenol(4-CP).With the increase of Bi12O17Cl2 content,the membrane flux was gradually increased,and the oil/water emulsion separation rate was above 97%.After visible light irradiation,the MB degradation efficiency was about 98.5%,and the degradation rate of p-chlorophenol(4-CP)was about 96%.Under visible light irradiation,the composite membrane maintains high flux and high rejection after 10 cycles.In addition,in order to improve the hydrophilicity and flux of RGO/PDA/Bi12O17C12-CA composite membrane and the photocatalytic effect of RGO/PDA/TiO2NW-CA membrane,combined with the narrow band gap of Bi12O17C12,TiO2 hydrophilicity,heterojunction It is beneficial to separate the characteristics of electron-hole pairs and prepare Bi12O17Cl2-TiO2NW heterojunction materials.The results showed that compared with RGO/PDA/Bi2O17Cl2-CA,the prepared RGO/PDA/Bi12O17Cl2-TiO2NW-CA membrane not only increaseed the membrane flux but also retained the interception effect on the oil-water emulsion,and its pure water fluxwasincreased by 3 times.The water tentacles were reduced by about 20°,and the retention rate of the oil-containing emulsion was maintained above 95%,and the reaction rate constant of the membrane for MB and 4-CP was increased by about 30%.