Doping Modified Nano Tio <sub> 2 </ Sub> Photocatalyst Preparation, Characterization And Photocatalytic Activity

Nano-titanium dioxide is an important green material with broad band-gap, which can be moderate, strong adsorption of pollutants, high photocatalytic efficiency, can catalyze a variety of pollutants, nontoxic, mild reaction conditions and the operation is simple and could reduce secondary pollution. Nano-titanium dioxide is attracting the people's growing concern in wastewater treatment, air purification, disinfection antibacterial, skin care, Ceramics and it will have potential applications in many other fields.In our study, nano-titanium dioxide catalysts is prepared by sol-gel method with tetrabutyl titanate as titanium source, anhydrous alcohol as solvent and the concentrated nitric acid as inhibitor. Factors affecting nano-TiO₂ crystal composition, morphology, particle size and photocatalytic activity such as the mole ratio, pH value, the natural aging time, drying, calcination temperature and time of calcinations are investigated.In this paper, the formation mechanism of agglomeration of TiO₂ nanoparticles is researched. Colloide formed in the preparation using heterogeneous azeotropic distillation process to prevent aggregating in the drying and calcining process. Characterization of nanopowder is obtained with X-ray diffraction, scanning electron microscopy, differential thermal analysis. Results show that heterogeneous azeotropic distillation process effectively removes the water in the preparation of titanium dioxide powder. As a result, particle dispersion is very good and loose TiO₂ powder is obtained.Through experiments in the laboratory the process and conditions of preparation of TiO₂ powder is determined. The X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, differential thermal analysis and UV-Vis absorption spectra are use to characterize the titania nanopowder. Meanwhile, the variation of particle diameter and crystal phase and the photocatalytic activity of TiO₂ powders in the process of calcination are researched. To further enhance photocatalytic activity of nano TiO₂, on the base of in-depth analysis of the mechanism of photocatalytic TiO₂, the metal ion-doped titanium dioxide catalyst is prepared by sol-gel method and selected metal ions such as Fe³⁺, Pb²⁺, Ni²⁺, Zn²⁺ and Sr²⁺ is used as dopent. With X-ray diffraction and scanning electron microscopy analysis the impact of the various metal ions on crystal structure and grain size of the doped-titanium dioxide is inspected. Through the degradation of simulated omethoate wastewater the effect of ion doping on the photocatalytic activity of TiO₂ is studied and the optimum calcination temperature and doping ratio is determined. Preliminary study of metal ion doping on the photocatalytic activity of TiO₂ powder mechanism is made.On the basis of a single metal ion doped modification, in this paper, the first use of three kinds of Pb-N, Ni-N and Fe-N co-doping is made to modify titanium dioxide. UV-Vis absorption spectra were inspected for visible-doped nanocrystalline titanium dioxide absorption capacity. In visible light (350<λ<450 nm), photocatalytic Degradation of methyl orange solution is made and its photocatalytic activity is inspected to determine the best ratio of co-doping, and to preliminarily explore the mechanism of photocatalytic activity of co-doped TiO₂ powder. Research shows that the absorption edges of the three systems of co-doped nanocrystalline TiO₂ have varying degrees of red shift and the absorption ability of visible light is noticeably improved; For Photocatalytic Degradation of methyl orange in visible light, catalytic activity of co-doped nanocrystalline is higher than the single-doped TiO₂ powder because co-doping elements played a good synergistic effect to promote the improvement of its photocatalytic activity.