Preparation And Characterization Of RE～(3+)-TiO₂ And Their Photo-Degradation Of Orange I

A series of rare earth ion doping nanometer-TiO₂ catalysts were prepared by sol-gel method. The crystal structure, specific surface area, pore distribution, surface properties, optical absorption properties were characterized respectively by X-ray diffraction XRD), N2 adsorption, Fourier transform infrared spectra, UV-Vis diffuse reflectance spctroscopy DRS), etc. The degradation of Orange I was chosen as the probe reaction to examine the photo-catalytic activities of as prepared nanometer- TiO₂ materials. The adsorption of orange I were investigated in aqueous suspension using the pure TiO₂ and Rare earth ion-doped TiO₂ (RE³⁺-TiO₂) catalysts. Analyzing the relationship among the different dosage, different rare earth ion doping of TiO₂ catalysts and their photo-catalytic activities, the mechanism of Rare earth ion-doped TiO₂ was elucidated.1. Preparation and characterization of nanometer-rare-earth-ion-doped TiO₂ catalystsRare earth ion doping nanometer-TiO₂ catalysts were prepared by sol-gel method. The optimum preparation conditions were calcined of 2h at 500℃. The X-ray diffraction results of these catalysts showed that these nanometer- TiO₂ materials were all anatase and rare earth-ion doping could stabilize the anatase phase of TiO₂ and inhibit the increase of the crystallite size. The DRS results of catalysts showed that rare earth-ion doping could enhance optical adsorption in the ultraviolet region and result in the strong adsorption in visible region. The BET results of catalysts showed that Rare earth-ion doping could enhance surface area of catalysts.2. Adsorption and photo-catalytic properties of anometer-rare-earth-ion-doped TiO₂ catalystsThe adsorption results showed that RE³⁺-TiO₂ catalysts had better adsorption capacities and higher adsorption equilibrium constants than pure TiO₂ catalyst, due to the smaller crystallite and the RE³⁺ complex effect. The results showed that the degradation of orange I under UV radiation and visible light were better with RE³⁺-TiO₂ catalyst than with pure TiO₂. The experimental results also showed that there was an optimum rare earth ion doping amount for degradation of orange I under UV light and visible light, which related with the separation efficiency of interfacial charges by RE³⁺ doping and the competition of orange I and its degraded intermediates. The optical absorption of TiO₂ by RE³⁺ doping under visible light derived from the transitions of the 4f electrons of RE³⁺ and benefited to the enhancement of its visible light photo-catalytic activity.3. The mechanism of rare earth ion doping nanometer-TiO₂The photo-catalytic activity for orange I enhanced might be attributed reasons as follows: (1) rare-earth-ion doping leads to the increase of absorption capacity of orange I onto the surface of RE³⁺-TiO₂; (2) the light absorption of TiO₂ extend into the visible region rare-earth-ion doping; (3) the formation of a sensitization mechanism between rare-earth-ion and titanium oxide.In conclusion, our attention is mainly paid on the preparation modification of rare-earth-doped TiO₂ catalyst materials. They were characterized by various techniques and a series of adsorption and photo-catalytic activity experiments. From the research results above, we acquired comprehensive and systematic knowledge about rare-earth-doped TiO₂ catalyst materials and various properties of as RE³⁺-TiO₂ materials and explored a new way for decreasing pollutant of dye. The work will favor the development and modification of photo-catalysts for high efficient wastewater of pollution control, and provide the fundamental experimental data and theory bases. It will afford new thoughtfulness, new materials, new technology and new theory for resolving the environmental problems.