Modification Of TiO₂ And Photocatalytic Degradation Of Gas-phase Aromatics

The volatile organic compounds (VOCs) in gas phase, especially aromatics, werevery harmful to the health of human being. The TiO₂, TiO₂-SiO₂, Cu2+/TiO₂-SiO₂,Fe3+/TiO₂-SiO₂, Ni2+/TiO₂-SiO₂ and TiO₂/ZnO-SiO₂ nanoparticles were prepared by asol-gel method starting from tetrabutyl titanate and n-ethyl silica as main materials.The properties of these catalysts were characterized by using X-Ray diffraction(XRD), surface area measurement(BET), transmission electron microscopy (TEM),UV–vis adsorption spectra and fourier transform infrared spectroscopy (FTIR)techniques. To evaluate the photocatalytic activity, the experiments of photocatalyticdegradation of p-xylene in gas-phase were performed, and the effects of doping ofSiO₂, ZnO and Cu2+, Fe3+, Ni2+ to the photocatalytic activity of catalysts werediscussed. In addition, the effect of water vapor on photocatalytic degradation ofgas-phase p-xylene over TiO₂/ZnO-SiO₂ was examined under different reactionconditions.The results revealed that Cu2+/TiO₂-SiO₂, Fe3+/TiO₂-SiO₂, Ni2+/TiO₂-SiO₂ andTiO₂/ZnO-SiO₂ catalysts had decreasing particle size of 9, 10, 12 and 11nm, whichwere favorable for increasing photoactivity. In addition, the doping Cu2+, Fe3+, Ni2+ toTiO₂-SiO₂ caused an adsorption shoulder evidently shift into visible-light region and astrong adsorption capacity for visible-light, accelerated the separation rate ofphotogenerated electron-hole pairs. The photocatalytic degradation rate of 100mg/Lgas-phase p-xylene was greatly increased from 67.5% of pure TiO₂ to 96.4% ofCu2+/TiO₂-SiO₂(nCu/nTi/ nSi =0.5%/1/0.25)and 97.6% of TiO₂/ZnO-SiO₂(n Ti/nZn/nSi=4/1/1) under ultraviolet light for 240 minutes. For the influence of water vapor inthe gas-phase on the photocatalytic degradation rate of p-xylene over TiO₂/ZnO-SiO₂,there was an optimum concentration of water vapor (500mg/L).photocatalysis, aromatics, p-xylene, Cu2+/TiO₂-SiO₂, Fe3+/TiO₂-SiO₂,Ni2+/TiO₂-SiO₂, TiO₂/ZnO-SiO₂...