Study On Modified Mesoporous TiO₂ And It's Photocatalytic Activity

Titanium dioxide (TiO₂) is one of the green catalysts, which has attracted much attention due to its promising applications in the purification of air, the bactericidal action of water, and environmental photocatalytic degradation of organic pollutant compounds in waste water. The mesoporous TiO₂ has the better physical and chemical properties than TiO₂ because of its high specific surface area and well-regulated pore structure. Although most suitable, TiO₂ is active only in UV light and this limits the commercial viability of these processes. Large efforts have been made to dope titania with several metals as well as non-metals so as to make it photocatalytically active in visible light. Meanwhile, it is a challenge to synthesize anatase mesoporous TiO₂ with high photocatalytic activity. The photocatalytic activity and efficiency of TiO₂ can be enhanced obviously and the degradation of organic wastewater has a promising future by doping some transitional metal ions.In the present work, Ni doped and Si doped TiO₂ were prepared by a sol–gel process .The properties of the prepared TiO₂ materials were characterized by X–ray diffraction (XRD), Transmission electron microscopy (TEM), N2 adsorption-desorption and Fourier transform infrared spectrophotometer (FT–IR). The results indicated that these samples had honeycomb-like mesoporous structures with anatase framework. the crystalline forms and pore structer of the samples were greatly affected by doping of transitional metal ions.The photocatalytic activities of Ni doped mesoporous TiO₂ prepared here was measured by p-phenol and photodecomposition of papermaking wasterwater in ultra-violet light in aqueous solution. The influencing factors on the degradation of paper making wastewater including Ni doped ratio , light irradiation time, catalyst dosage, initial pH value and extra oxidant in the photocatalysis system were investigated. The results showed that the photocatalytic activity of Ni-doped TiO₂ was much better than the pure mesoporous TiO₂ in degradation of papermaking wastewater. the optimal ratio of nickel doping in mesoporous TiO₂ was 2%, the optimal degradation effect was achieved when the catalyst (2%Ni / TiO₂) dosage was 1.5 g/L, the initial pH was 4 with continuous aerating oxygen; the chroma of the wastewater was completely removed in 4 hours and after 12 h irradiation CODCr removal rate was 83.4%.The photocatalytic activities of Si doped mesoporous TiO₂ prepared here was measured by photodecomposition of methyl orange in UV as well as visible light, which showed excellent photocatalytic activity in both UV and visible light. The influencing factors on the degradation of methyl orange such as initial pH value, catalyst dosage, silicon doped ratio etc. in the photocatalysis system were investigated. When 3%Si/TiO₂ was used as the catalyst, initial pH was 4 and catalyst dosage was 2.0 g/L, complete photodegradation of the 30mg/L methyl orange was obtained in 4 h, in comparison, the degradation rate of methyl orange photocatalyzed by the pure TiO₂ was only 37.5% in same period of time.