Rare Earth Doped Nano-tio <sub> 2 </ Sub> Preparation And Photocatalytic Properties

Improving water pollution treatment is one of the hot spots in environmental protection field. Photocatalytic oxidation method has many advantages such as high activity, stabilization and complete mineralization of undersirable organic contaminants, particularly toxic and unbiodegradable organic compounds. For the moment, this technology is limited in the laboratory level in China.In this thesis La³⁺, Ce³⁺ single doped TiO₂ and La-Fe, Ce-Fe co-doped TiO₂ were prepared by sol-gel method. The structure, shape and spectrum characteristic were characterized by XRD, FE-SEM, EDS, FT-IR and UV-vis. The photocatalytic activities were evaluated by degradation of methyl orange and chloramine phosphorus. At the same time, we investigated the influence of process parameters on the fabrication of doping TiO₂. Furthermore, we analyed the reaction kinetic of organics photocatalytic degradation process.The results show that the particle size of the powder is homogeneous, the particle size is varied with the change of doped amount and element. With the annealing temperatures increasing, the particle grown. The particle size of rare-earth doped TiO₂ is smaller than pure TiO₂, we consider that doping restrain the growth of crystal. The doping with optimum rare-earth could restrain the crystal structure changing. The co-doping with optimum rare-earth and metal can restrain the transform of anatase structure to rutile structure and the growth of crystal more effectively. FT-IR results show that Infrared absorption bands of rare-earth doped TiO₂ has been broaden, and characteristic vibration peak of Ti-O is red-shift. UV-vis results show that the absorption sideband of La³⁺ doped TiO₂ has red-shift and widen the spectrum absorption range.The results show that the photocatalytic of TiO₂ has been highly improved by rare-earth doping. The optimal doping of La³⁺ is 0.5mol%, Ce³⁺ is lmol%, and annealing temperature is 500℃. The co-doping of rare-earth and metal show a synergistic effect for photocatalytic activity of TiO₂. The co-doped TiO₂ show higher photocatalytic activity in degradation of methyl orange than that of single doped TiO₂. Titania co-doped with La-Fe for n(La):n(TiO₂)=0.5%, n(Fe):n(TiO₂)=0.05% have the highest photocatalytic efficiency. In the same condition, organics photocatalytic process is difference. Degradation rate of methyl orange is higher than chloramine phosphorus. Fitting cuve of methyl orange photocatalytic degradation show that the reaction kinetics of rare-earth doped TiO₂ is according with the first order reaction equation of Langmuir-hinshelwood. Photocatalytic degradation cure of chloramine phosphorus is fit for conic. The form of equation is Y=A+B₁*t+B₂*t².