Synthesis And Photocatalytic Effect Of TiO₂Nanoparticles By Improved Sol-gel Method

Titanium dioxide has great application prospects currently as photocatalytic functionalmaterials. Reactive oxygen species can be generated through photocatalysis, then throughredox reaction, various organic or inorganic compounds in environmental system can bedestroyed completely, and most substances can be degraded to carbon dioxide and water, orconverted into non-toxic and non-polluting substances.In this paper, the high photocatalytic active TiO2was prepared by improved sol-gelmethod in simple, mild reaction conditions, only by controlling the conditions of the reactionsystem, without high-temperature calcinations. On the basis, CdS/TiO2composite materialwas prepared. Samples prepared were characterized by scanning electron microscopy (SEM),X-ray diffraction (XRD), Fourier transform infrared spectroscopy. As simulated wastewater, acertain concentration of methyl orange solution was degraded through photocatalysis in thevisible and ultraviolet irradiation conditions. Preparation process and conditions wereoptimized by orthogonal test, which established a reaction system from preparation tostructure and then photocatalytic degradation. The results were as following.（1）Titanium dioxide with high photocatalytic property and good morphology wassynthesized, when temperature was60℃, water titanium mole ratio was80, pH was2,without high-temperature calcinations.（2）Photocatalytic degradation of methyl orange solution was carried out using nanotitanium dioxide samples prepared under different photocatalytic conditions. When titaniumdioxide dosage was1.8g/L, the degradation rate of10mg/L methyl orange solution reached74.15%after5h under visible light irradiation; at the same dosage of titanium dioxide, the degradation rate of10mg/L methyl orange solution reached99.84%after4h under ultravioletradiation. Photocatalytic degradation of methyl orange can be attributed to the synergisticeffect of adsorption and photocatalysis.（3）Samples prepared were analyzed by various characterization methods, such asscanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy.The results showed that samples were anatase TiO2with particle size less than100nm andthere was part of agglomeration.（4）Optimum preparation process of CdS/TiO2was obtained by tests at differentreagents and concentration; the effect of different doping amounts of CdS,1%,3%,5%,8%and10%(by mass scores) on photocatalytic activity of CdS/TiO2were studied byphotocatalytic degradation of methyl orange solution under visible and ultraviolet light.Samples were characterized using scanning electron microscopy and X-ray diffraction. Theresults showed that photocatalytic degradation effect of TiO2doped with1%CdS is better.When methyl orange solution was degraded for5h under visible light, the degradation ratereached65.73%; for4h under UV light, the degradation rate reached96.10%. Duringagitation and ultrasonic process, adsorption phenomenon of methyl orange happened, but inthe photocatalytic process CdS/TiO2adsorption of methyl orange didn’t happen. Afterphotocatalytic degradation methyl orange adsorbed on titanium dioxide was degraded. Thedoped samples characterized showed that there was hexagonal and cubic phase cadmiumsulfide (CdS).