Research On The Photoelectrocatalytic Removal Of Organic Pollutants In Water With Three-dimensional TiO₂ Composite Electrode

With the accelerating process of industrialization in China,a large number of toxic and harmful organic pollutants enter the water body through multiple ways.Among them,industrial dyeing wastewater is one of the main sources of organic pollutants.The dyeing wastewater has complex water quality components,high content of refractory organic pollutants,poor biodegradability,and it contains groups such as benzene ring and azo.Once discharged into the environment,it will have a great impact on the ecological environment and human health.Traditional water treatment technology is difficult to achieve the desired treatment effect,so it is extremely urgent to develop an efficient,economical and environmentally friendly sewage treatment technology.Advanced oxidation process has become a research hotspot for researchers in recent years due to its strong oxidizing ability and high processing efficiency.Among them,TiO2 semiconductor-based photoelectrocatalytic oxidation technology is considered to be a promising environmental pollution deep treatment technology due to its green,environmentally friendly,energy-saving,efficient,and no secondary pollution.This paper is aimed at the problems that the traditional powder TiO2 is difficult to separate and recycling from water,powder TiO2 film has a small specific surface area and low catalytic efficiency.Therefore,the preparation of new and high-efficiency three-dimensional TiO2 nanotube arrays electrode and its visible light response extension are carried out.Meanwhile,the photoelectrocatalytic activity of the electrode materials was studied and the mechanism of photoelectrocatalytic degradation was proposed.The specific research results are as follows:1.The TiO2 nanotube arrays generated from the titanium sheet has low transparency,poor flexibility,and high requirements on the illumination angle.Therefore,in this thesis,TiO2 nanotube arrays electrode with three-dimensional configuration(3D-TNAs)were synthesized by anodizing using titanium mesh as the substrate.The experimental results show that the oxidation voltage is 20 V,the oxidation time is 90 min,and the calcination temperature is 500?,which are the best synthesis condition of TiO2 nanotube arrays under the system.The synthesized nanotubes are TiO2 anatase phase.2.This paper uses semiconductor composite method to modify TiO2 nanotube arrays due to the pure TiO2 nanotube arrays have high photogenerated electron-hole recombination rate and no visible light response.TiO2 nanotube arrays electrode loaded with TiO2 nanoparticles(3D-TNAs/TiO2)were prepared by sol-gel method and dielectrophoresis(DEP)/sol-gel method,respectively.Electrode materials with different photoelectrocatalytic performance are obtained by adjusting the reaction voltage and reaction time.The experimental results show that the electrode made by dielectrophoresis/sol-gel technology have short preparation time,more dense of the synthesized electrode,good surface morphology and uniform particle size,better photoelectrocatalytic performance and is a anatase and rutile heterojunction.Under the external bias of 0.8 V and simulated sunlight,the degradation rate of methylene blue in 210 min was 92%.Compared with unmodified 3D-TNAs and 3D-TNAs/TiO2 electrode prepared by traditional sol-gel method,the visible light photoelectrocatalytic activity of 3D-TNAs/TiO2(DEP/sol-gel)increased by 37%and 28%,respectively.3.The degradation rate of methylene blue by the 3D-TNAs/TiO2 electrode synthesized by evaporation induced self-assembly method was 64%,in order to further improve the photoelectrocatalytic activity of the electrode material,the 3D-INAs/TiO2 electrode was modified again by ion doping method in this paper.3D-TNAs/Gd-TiO2,3D-TNAs/N-TiO2 and 3D-TNAs/Gd-N-TiO2 composite electrodes were synthesized by evaporation induced self-assembly method.The photoelectrocatalytic performance of 3D-TNAs/Gd-N-TiO2 composite electrode was studied with dye methylene blue(MB)and plasticizer dimethyl phthalate(DMP)as target organic pollutants.The experimental results'show that the degradation rate of methylene blue by the 3D-TNAs/Gd-N-TiO2 composite electrode can reach 96%under the same experimental conditions,and the degradation of DMP can be mineralized into harmless substances,indicating that the electrode material has excellent visible light photoelectrocatalytic activity.