Modification Of Nitrogen Doped TiO₂ And Kinetic Study

The titania(TiO₂) which has the properties of better steady of chemistry, resisting erosion, low cost, nontoxicity etc is becoming the best potential appliance in the photocatalysts. The dissertation firstly introduced recent developments in titania photocatalysis and its application prospects for the treatment of organics and poisonous bacteria in the air or wastewater. Then the mechanism of titania photocatalytic process, influencing factors of photacataytic activity, classes of modification and various methods of preparation were systematically reviewed.In the research, nitrogen doped TiO₂ nanosize particles were prepared under hydrothermal condition with tetra-n-butyl titanate and ammonia as the precursors, the colour of this photocatalyst was yellowlish. The products obtained under different conditions were characterized by means of X-ray diffraction(XRD) , X-ray photoelectron spectroscopy(XPS) and ultraviolet-visible diffuse reflection spectrum(UV-Vis DRS). The influences of various proportion by volume, hydrothermal temperature, hydrothermal time and calcination temperature to the structure and activities of catalysts were investigated. Photocatalytic activities of the nitrogen doped catalysts were evaluated under ultraviolet and visible light irradiation by photodegradation of methylic-orange and phenol respectively.In order to research the kinetics of TiO₂ photocatalysis, choosing the TiO₂ on sale as the catalyst, and using the direct fast scarlet(4BS) as the model pollutant. The dependence of initial degradation rates on the incident light intensity and kinetic model were discussed. The results showed that neither in high nor low light intensity, in all cases 4BS degradation models seriously observed the L-H zero kinetics, that was to say the initial rates were constants. It was also found that, in the case of lower light intensity, the higher light intensity the quicker rate, when it exceeded 3.08mw/cm², the change of degradation rate was little. To account for the experimental finding, the rates are linearly proportional to the square root of the intensity in a large range, it is also proved that the high light intensity irradiation will decrease the quantum yield.