Investigation On Modification Of Nano-TiO₂and Its Photocatalytic Activity

Heterogeneous photocatalysis has shown a high efficiency in the photooxidation ofmany organic pollutants present in liquid effluents. Among various semiconductors,TiO₂is considered as the most promising photocatalyst due to its high photocatalyticactivity, photochemical stability, non-toxicity and low cost. However, TiO₂is activeonly in UV light and this limits the commercial viability of these processes. Thephotocatalytic activity and efficient of TiO₂can be enhanced obviously, meanwhile, thedegradation of organic wastewater and usage of sunlight has a promising future bydoping some non-mental ions, transitional metal ions and SiO₂to titania.In the present work，N/Co co-doped TiO₂was prepared by a sol-gel process. Theproperties of the catalysts were characterized by X-ray diffraction （XRD）, Highresolution transmission electron microscopy （HRTEM）, UV-vis diffuse reflectancespectra （UV-vis DRS）, N2adsorption-desorption isotherms, and energy-dispersive X-rayspectrometer （EDS）. Characteristic results indicated that the predominant phase ofprepared TiO₂was anatase. The TEM indicated that most of the particles are regularcubic and the grain size is uniform at approximately10nm. EDS showed that nitrogenand cobalt had have been effectively doped into the titania lattice. UV-vis diffusereflectance spectra showed an extension of light absorption into the visible region forthe modified TiO₂.The photocatalytic activities of N and transitional metal co-doped TiO₂wasmeasured by photodecomposition of papermaking wastewater and domestic wastewaterin both UV and visible light, which showed excellent photocatalytic activity in both UVand visible light. The influencing factors on the degradation of wastewater such asdoping amount, catalyst dosage and initial pH value etc. in the photocatalysis systemwere investigated. When the catalyst2%N2%Yb/TiO₂usage is1.0g L–1and the initialpH is4，the degradation rate of CODCrof domestic wastewater was about79.6%. Whenthe catalyst3%N2%Co/TiO₂usage is1.0g L–1and the initial pH is3，the degradationrate of CODCrof papermaking wastewater was about59.8%.Furthermore, a series of nitrogen-doped TiO₂-SiO₂composite materials wereprepared by a sol-gel method through different TiO₂/SiO₂molar ratio. The productstructure and optical properties were characterized by various techniques includingX-ray diffraction （XRD）, UV-Vis diffuse reflectance spectroscopy （UV-Vis DRS）, and energy-dispersive X-ray spectrometer （EDS）. The result of XRD revealed a decrease inthe size of TiO₂particles with increasing the SiO₂content. UV-Vis diffuse reflectancespectroscopy revealed that the absorbing band edges have a red shift. The photocatalyticactivities of N-TiO₂-SiO₂samples prepared here were measured by photodecompositionof domestic sewage in UV light, which showed excellent photocatalytic activity in UVlight. CODCrdegradation rate was60.2%under ultra-violet light irradiation whenN-TiO₂-SiO₂sample prepared with TiO₂:SiO₂molar ratio of2:1was used as thecatalyst, the initial pH is4and catalyst dosage was1.5g L–1.