Preparation And Photocatalytic Performance Research Of Rare Earth Composite Doped Nano TiO₂

Nano titanium dioxide(TiO2) photocatalysis technology is a novel wastewater treatment technology, which has many advantages such as simple and easy control technological processes, without secondary pollution, cheap and non-toxic raw materials. Meanwhile, Ti O2 photocatalysis technology has its unique superiority for the degradation of organic matter in industrial wastewater. However, TiO2 also possesses drawbacks of composition of photogenerated electrons and holes, low utilization ratio of energy, and weak photocatalytic activity. To improve the catalytic efficiency, the composite doping modification technology of rare earth was applied in this study. A series of rare earth-TiO2 catalysts were prepared by using tetrabutyl titanate, yttrium nitrate, nitric acid neodymium and samarium nitrate as raw materials through sol-gel method, and the catalytic performance of earth-TiO2 catalysts was evaluated with the photocatalytic degradation of methylene blue.Nd/Y-TiO2 and Sm/Nd-TiO2 catalysts were prepared in this study. Meanwhile, the effects of preparation conditions, including ratio of rare earth, calcining temperature, the amount of rare earth and calcining time on catalytic activity were investigated. After the single factor experiments, response surface experiment and orthogonal experiment methods were applied to optimize the preparation conditions of Nd/Y-TiO2 and Sm/Nd-TiO2 catalyst, respectively.The results indicated that the optimal conditions of Nd/Y-TiO2 catalyst preparation were followings: x of NdxY(1-x) was 0.79, calcining temperature was 480℃, the rare earth content was 2.2%, and calcining time was 3h, respectively. The degradation rate reach to 94.82% under the reaction conditions of methylene blue concentration of 5mg/L, catalyst dosage of 0.6g/L, pH = 7, light source of 40 w and reaction time of 2h. On the other hand, the optimal conditions of Sm/Nd-TiO2 catalyst preparation were followings: x of SmxNd(1-x) was 0.3, calcining temperature was 500℃, the rare earth content was 2%, and calcining time was 3h, respectively, and the degradation rate could be up to 91.75% under such condtions.The reaction conditions of methylene blue and phenol photocatalytic degradation were also optimized in this investigation. The effects of phenol initial concentration, dosage of catalyst, solution pH on phenol photocatalytic degradation were investigated. Based on the above experiments, the catalytic reaction dynamics were preliminary discussed. The results indicated that the react model accorded with the first order reaction kinetic, and the reaction rate of phenol photocatalytic degradation linear correlated to the concentration of reaction substrates.The elements, crystal structure, surface morphology and the characteristic structure of the catalyst were investigated by technologies of X-ray diffractometer, environmental scanning electron microscope, infrared spectroscopy, UV-Vis spectrophotometer and thermogravimetric.