Study On The Preparation And Adsorption And Photocatalysis Properties Of Doped TiO₂

TiO2 nano-materials have promising potential in the application of photocatalysis and adsorption due to their advantages of being stable in chemical properties, their cheapness, as well as their strong property of oxidation-reduction. However, as photocatalyst, TiO2 still suffers from the following problems:in the catalytic reaction, the photo-generated electronic-hole pairs are unstable and prone to recombinate so that the photocatalytic activity will decrease; its ability to adsorpt organic dye is poor; the utilization rate of visible light is relatively low. To some extent, the above mentioned problems limit its practical application. In order to improve the photocatalytic properties of TiO2 as well as its adsorption performance, this article adopts the method of ionic doping to modify the prepared catalysts.The nanofibers of Titanate was prepared by solvothermal method with low concentration of alkali, and the N-doped TiO2 photocatalyst was prepared by double hydrothermal method. The catalysts were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectrum (FT-IR) etc. Methylene blue was used to simulat organic waste water to observe the influence of adsorption and catalysis with different amount of doped N to reveal the relationship of adsorption and catalysis. The result showed that doping nitrogen could change the crystal size and morphology of the catalysts. Furthermore, the adsorption and catalysis of nanofibers were improved dramatically. The degradation of methylene blue followed pseudo-first-order kinetics mechanism and the dye adsorption kinetics were in accordance with the pseudo second-order kinetic model under UV irradiation. In addition, the performance of adsorption and catalysis would be improved with higher amount of nitrogen doped, smaller grain size, and bigger specific surface area. The optimum percentage of N to Ti was 1:1.Titanate nanofibers prepared by solvothermal method with low concentration alkali solution were used as precursor. Silver nitrate was used as silver source, ammonium fluoride as fluoride source. And the series of titanium dioxide photocatalysts doped with silver and fluorine were prepared by impregnation and calcination method. The influence of calcination temperature, metal and nonmetal doping content and etc were observed. Methylene blue was used as the aimed degradation material to observe the property of photocatalysis. The catalysts were characterized by XRD, SEM, TG-DTG. The results showed:the optimum calcination temperature was 350 ℃; the doption of silver and fluorine failed to change the crystal type, but could change the size of crystal grain; the doption of these elements improved the photocatalytic activity and the optimum percentage existed.10% Ag-TiO2 and 50% F-TiO2 reached the best photocatalytic activity; Ag-TiO2 and F-TiO2 to the degradation of methylene blue curve followed pseudo-first-order kinetics mechanism.