Research On Photocatalytic Oxidation Of Bioresistant Organic Compounds

Photocatalytic oxidation of water contaminants with semiconductors has been touted as one of the more promising remediation technologies for its complete mineralization of undesirable organic contaminants, particularly those toxic and bioresistant organic compound. TiC>2 has been shown to be an excellent photocatalyst owing to its stable chemical characteristics and low price, etc. However, photocatalytic oxidation is almost not industrially applied to wastewater treatment due to its low reaction rate and narrow range of available spectrum.In order to improve the photocatalytic activity of TiC>2 and extend energy range of photo-excitation, nanocrystalline TiO2 semiconductor as well as metal oxide/TiO2 photocatalysts MoO3/TiO2 > WO3/TiO2 were prepared by sol-gel method. The structure and morphology of catalysts were characterized by means of XRD^ TEM and IR. The results indicated that the mean particle size of catalysts was below 1 Onm and anatase TiO2 transformed to rutile TiO2 with increase of calcinations temperature. The percent of anatase TiO2 treated under 600 and 800 were respectively 93% and 15%. The addition of MoO3 or WO3 hindered phase transformation of TiO2 from anatase to rutile. The percent of anatase in MoO3/TiO2 and WO3/TiO2 were 96% and 94% respectively even at a calcination temperature of 800. The photocatalytic activity of nanosized TiO2 was evaluated by the photodegradation of Direct Fast Red 4BL and 2,4-dinitrophenol and the factors that affect the photocatalytic process were investigated. The results showed that degradation rates of 4BL and 2,4-dinitrophenolwere respectively 2.27 and 1.7 times as high as common TiO2 and nanosized TiO2 treated at 600 癈 showed a best photocatalytic activity. Both 4BL and 2,4-dinitrophenol disappearances approximately followed the first order kinetics and Langmuir-Hinshehwood model. The photocatalytic degradation of methyl orange with MoO3/TiO2 or WO3/TiO2 coupled nanopowder was investigated. The results showed that the photocatalytic activities of MoO3/TiO2 and WO3/TiO2 were better than that of MoO3 and WO3, respectively, but worse than that of nanosized TiO2. 2%WO/TiO2 showed approximately the same activity as TiO2, and the degradation rate of methyl orange was above 90%, while only 50% degradation rate was achieved with MoO3/TiO2 catalyst.