| Photocatalysis is an attractive approach for environmental protection and energy transformation because of its advantage,such as low-temperature,non-energy intensity and non-pollution.Among semiconductor photocatalytic materials in recent years,titanium dioxide has been widely used for environmental application because of many advantages, such as better chemical stability,higher photocatalytic efficiency,cheapness and intoxicity. Photocatalyst is the key part in photocatalysis,and further improvement on its activity and efficiency by selective surface treatment by modifying the properties of the particles is an essential step to apply this novel technology.Complex semiconductor is the one of the most important modification and the most efficient method.WO3 doped siO2/TiO2(10/90)nano-particles were synthesized by sol-hydrothermal method from ammonium tungstate,tetraethylorthosilicate(TEOS)and tetrabutyl orthotitanate (Ti(OBu)4)as precursors,hydrochloric acid as catalyst.The samples are characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),Zeta potential, UV-Visible spectroscopy,BET,and transmission electron microscopy(TEM).The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange under high pressure mercury lamp.The effects of different conditions on the photocatalytic activity were investigated.For example,crystallization time,crystallization temperature,doped amount,surfactants,assistant catalyst,the pH units of the reactant,calcined temperature.The results are that synthethc time is 8h,synthetic temperature is 175℃,the doped amount is 1%, calcined temperature is 800C,the pH value is 3.WO3 can decrease the band gap energy of TiO2 and extend the light absorption edge.SiO2 can increase the stability of anatase TiO2,and inhibit the growth of crystalline.The size of particles is about 10-15nm.The samples can reuse while the photocatalytic efficiency is still high.WO3 doped SiO2/TiO2(20/20/80)powders have been prepared by sol-solvothermal method,and characterized by X-ray diffractometer,FT-IR spectrum,UV-vis spectrophotometer,BET and transmission electron microscope measurements.The structural characterization of samples shows that the titanium oxide is predominant anatase phase at 500-800℃treatment.The WO3 doped SiO2/TiO2 has far larger surface area than the surface area of pure TiO2.The size of elliptical particles is about 9-12nm.The effects of calcined temperature on the photocatalytic activity were investigated.The result is that the degradation of methyl orange enhances with the increase of the calcined temperature,and then decreases. The sample shows the highest photocatalytic activity for the degradation of methyl orange when calcined temperature is 1000℃.The study of the kinetics finds that the photocatalytic degradation of methyl orange is pseudo-first-order,which can be described by Langmuir-Hinshelwood equation.Adsorption has an important effect on the degradation of methyl orange.A volcano profiles is found between the intensity of adsorption and the photocatalytic activity.The efficiency is the highest when the intensity of adsorption is suitable.
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