Studies On The Preparation Of TiO₂ Doped By Lanthanide Ions And Its Application In Photocatalytic Degradation Of Imidazole

The treatment of deleterious heterocyclic compounds in industrial waste water is an important field. Based on the review of the preparation methods of TiO₂ and the photodegradation of organic waste water, the preparation of TiO₂ and lanthanide ions doped TiO₂ as well as their phototcatalytic application in the degradation of imidazole were studied systematically in this thesis. The results showed that photo-induced degradation of imidazole in the presence of TiO₂ photocatalysts has the prominent virtues, such as simple processing equipment and operation conditions controlled easily, effective degradation of organic pollutants and no secondary pollution. The main contents of the thesis were discussed as follows:(1)Titanium dioxide powder was prepared using TiCl₄ as precursor via sol-gel process. The influences of solvent system and calcination temperature on the catalytic performance of TiO₂ were investigated. It was found that the titanium dioxide powder prepared from ethanol solution and calcined at the temperature of 500℃ for two hours had high activity in the photocatalytic degradation of imidazole.(2)In order to improve the photocatalytic activity of TiO₂ photocatalyst, different lanthanide ions-doped TiO₂ including La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Tm³⁺ were prepared and characterized by X-ray diffraction(XRD), X-ray photoelectronspectroscopy(XPS), photoluminescence emission spectroscopy(PLS), surface photovoltage spectra(SPS). It was found that the lanthanide ions doped TiC>2 possessed more effective separation of the electron-hole pairs, giving higher photocatalytic activity in comparison with pure TiO2. Forthemore, the photocatalytic activity of Tb3+-doped TiO2 increased with an increase of concentration of Tb3+ less than 2%, and then decreased after the concentration of Tb3+ exceed 2%. The order of photocatalytic activity of various lanthanide ions doped TiC>2 samples was the same as the order of their SPS intensity, and the reverse as the order of their PLS intensity. Namely, stronger intensity of SPS and weaker intensity of PLS, mean that the doped-TiC>2 has higher photocatalytic activity. In conclusion, the intensity of SPS and PLS could be used as the criterion tocompare the photocatalytic activity of the semiconductors.(3)The kinetics of photocatalytic oxidation of imidazole over the2%Tb3+ doped TiC>2 photocatalyst were studied. The results indicated that oxidation of imidazole under UV light followed the first-order kinetic equation and that the rate of reaction was coincident with Langmuir-Hinshelwood equation. The kinetic equation obtained was l/r0=0.59122+83.088(l/C0), and the parent rate;constant of k and the adsorption balance constant of K were 1.8062 mg/(L*min) and 6.663xlO"3L-mg"1, respectively..,.