Preparation And Performance Study Of TiO₂-based Multiple Complex Photocatalyst For Purification Of Dye Wastewater

At present,the output of various dyes in China has reached 900000 tons and accounted for more than 70%of the world.Dye wastewater has become one of the key pollution sources of environmental pollution.Nowadays,there are various methods for purifying dye wastewater and it had became the research hotspots in the world.Among various methods for purifying dye wastewater,the technology of photocatalytic purification of dye wastewater using semiconductor nanomaterials as catalysts has developed rapidly.Most of these nanomaterials are n-type semiconductor compounds such as TiO2,ZnO,CdS,ZnS,MoO3,WO3 and so on.Among these n-type semiconductor compounds,TiO2 is the most popular one because of its high catalytic activity,good stability and low cost.TiO2 has its own limitations,due to the wide band gap of TiO2,poor response to visible light,and the absorption capacity of sunlight has a certain limit,photogenerated holes and electrons are easily recombined,affecting the further application.Now more research is focused on improving its photocatalytic efficiency and synthesizing more efficient photocatalysts.In this paper,doping Cu,Fe and a series of carbon materials to improve the performance of photocatalytic purification of dye wastewater of TiO2.The specific experimental scheme was the hydrothermal synthesis of pure TiO2 and TiO2-MWCNTs,TiO2-RGO,TiO2-Graphite binary nanocomposites and TiO2-MWCNTs-Fe2O3,TiO2-MWCNTs-CuO,TiO2-RGO-Fe2O3,TiO2-RGO-CuO ternary nanocomposites,the effects of the hydrothermal temperature,the content of MWCNTs,RGO,Graphite and the content of Cu,Fe under the same carbon material content to the microstructure and photocatalytic performance of TiO2 were investigated.XRD,SEM,TEM,FTIR,XPS,UVVIS characterization and simulated photocatalysis experiment were used to determine its microstructure and performance of photocatalytic purification of dye wastewater.The results showed that the hydrothermal temperature has a certain effect on the performance of TiO2 photocatalytic purification of dye wastewater.When the hydrothermal temperature is 150?,the actual specific surface area of the photocatalyst is the largest and the photocatalytic activity is the best.The photocatalytic performance of the purification of dye wastewater of TiO2-MWCNTs,TiO2-RGO,TiO2-Graphite binary nanocomposites is higher than that of pure TiO2,and when the doping mass percentages of MWCNTs,GO and Graphite are 0.09%,0.15%and 0.3%,the TiO2-MWCNTs,TiO2-RGO and TiO2-Graphite nanocomposites have the best photocatalytic performance,and the best photocatalytic performance of TiO2-RGO is better than that of TiO2-MWCNTs and TiO2-Graphite.The photocatalytic performance of the purification of dye wastewater of TiO2-WCNTs-Fe2O3,TiO2-MWCNTs-CuO,TiO2-RGO-Fe2O3 and TiO2-RGO-CuO ternary nanocomposites were further improved than TiO2-MWCNTs and TiO2-RGO binary nanocomposites.The maximum photocatalytic performance of Fe-doped TiO2-MWCNTs and TiO2-RGO appeared when the doping content is 0.1%,and the maximum photocatalytic performance of Cu-doped TiO2-RGO appeared when the doping content is 0.075%,but the maximum photocatalytic performance of Cu-doped TiO2-MWCNTs appeared at the doping content of 0.05%under UV light and 0.075%under visible light conditions respectively.The improvement of the performance of MWCNTs,RGO,Graphite in the photocatalytic purification of dye wastewater by TiO2 was related to the heterojunOtion interface formed by TiO2 and these carbon materials and the reduction of TiO2 optical band gap.The presence of the heterojunction interface can make the photogenerated electrons generated on the surface of TiO2 were transferred to the surface of carbon material,thereby reducing the recombination rate of photogenerated electrons and holes on the surface of TiO2,and improving the utilization efficiency of the absorbed light energy of TiO2;the reduction of the optical band gap of TiO2 made the efficiency of it absorb light energy was improved,and these two aspects synergistically improved the photocatalytic performance of TiO2.The improvement of the photocatalytic performance of TiO2 by Cu and Fe was that the Cu2+and Fe3+were doped into the lattice of TiO2 instead of Ti4+thereby its optical band gap was reduced and caused TiO2 lattice defects to capture more light energy;it is also related to the fact that the generated Fe2O3 and CuO can transfer electrons generated by TiO2 absorbing photon energy,thereby reducing the recombination rate of photogenerated electrons and holes on the surface of TiO2.In addition,the performance of Cu-doped photocatalytic purification of dye wastewater is better than that of Fe,which may be related to the different ability of CuO and Fe2O3 to transfer electrons.