| Heterogeneous photocatalysis can degrade organic pollutants in water efficiently by oxidation utilizing TiO2 as a catalyst, and has been the subject of extensive research in the field of environmental science recently. However, TiO2 has several disadvantages as follow:①The high rate of electron-hole recombination on particles results in a low efficiency of photocatalysis.②TiO2 may show photocatalytic activity by irradiation of ultra violet light for its wide band gap (Eg=3.2eV), but the proportion of UV light to the sun light is very small.③The suspensed TiO2 powder is easy to agglomerate and difficult to recover from solution. Those disadvantages have the photocatalytic oxidation technique of TiO2 limited practice. Considering the problems above, the research work has been carried out as follow.The cross experiment design is used to investigate the effect of four factors on photocatalytic properties of nanosized TiO2 prepared in sol-gel. The effect order of four factors is calcinated temperature (500℃),the amount of acetic acid(20ml),the amount of distilled water(7.2 ml),the amount of anhydrous ethanol (58.32 ml). It is founded that the photocatalytic activity of the TiO2 sample calcined at 500℃is the highest of the TiO2 samples calcined at different temperatures, and its structure consisted of anatase crystallites about 18.5nm in size. The research results show that calcined temperature has great effect on the crystal structure and crystal size of nano-TiO2 particles, and anatase crystal grows during the process of calcination treatment.The photocatalytic activity of Mo doped TiO2 and Cr doped TiO2 nanoparticles are studied systematically. The research results show that the introduction of Mo ion and Cr ion can inhibit the growing of crystal size, and there is a small shift toward longer wavelengths in absorption band edge. It is founded that calcined temperature,kind doped element and its concentration has great effect on photocatalytic activities of TiO2 nanoparticles. And the introduction of Mo ion and Cr ion both improves obviously the photocatalytic activity, and the photocatalytic activity of 0.05mol% Mo doped TiO2 sample calcined at 500℃is the highest of Mo doped TiO2 photocatalysts, and it is higher than that of Cr doped TiO2 samples. The improvement of the photocatalytic activity contributes to formation of doped energy and the decrease of crystal size.TiO2 doped with Sm3+,Eu3+,Ce3+和Y3+ nanoparticles are prepared by sol-gel method and characterized by XRD,UV-Vis/DRS,TEM,BET and XPS. The results show that the introduction of four kind of rare earth inhibits the phase of transformation process and the growing of the crystal size and produces lattice expansion. It is founded that there is a small shift toward longer wavelengths in absorption band edge and the absorption strength becomes bigger than that of pure TiO2 sample. A part of Sm2O3 exists on the surface of TiO2 monitored by XPS spectra. Ln-TiO2(Ln= Sm3+,Eu3+,Ce3+和Y3+)exhibited higher activity than pure TiO2, and there is a photocatalysis downtrend of Ln-TiO2, namely, Sm-TiO2> Eu-TiO2 >Y-TiO2 >Ce-TiO2. The best concentration of four doped rare earth is 0.05mol%, and the best calcined temperature is 500℃. It is founded that the photocatalyic activity is related to the electronic number on 4f orbit of rare earth. The photocatalytic activity irradiated by simulated sunlight of 0.05mol% Sm doped TiO2 nanoparticle calcined at 500℃is the highest of Sm doped TiO2 photocatalysts.The photocatalytic activity of the Sm doped TiO2 film loaded ACF prepared by sol-gel method calcined at 600℃and 800℃were studied systematically. The results show that the photocatalytic activity of the sample calcined at 600℃is higher than that of the sample calcined at 800℃because of phenomena of fraction on the film and the degradation of combination strength. It is founded that after used, the photocatalytic activity of the sample calcined at 600℃is lower than without used.
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