Preparation Of Supported TiO₂ Photocatalyst And The Application Of It In Treatment Of Organic Pollutants

In this work, a new type of nanometer TiO2/AC catalyst was prepared. The structure characteristics and adsorption behavior of this novel catalyst were investigated. The photodegradation of p-chlorophenol by using this catalyst was studied. The silver-modified TiO2/zeolite catalyst was also prepared in order to improve the photodegradation efficiency of methyl orange waste water.The atmospheric pressure metal-organic chemical vapor deposition (MOCVD) technology was used to load TiO2 onto the surface of active carbon. XRD results showed that TiO2 calcined at 773K is in anatase phase and rutile phase at 873K. The results of TEM suggested that TiO2 particles were in the range 10 to 20 nm when the amount of titania supported was 8%(wt). BET surface area was only reduced by 6% with the loading amount was 8%(wt), so it can be concluded that the framework of active carbon was not destructured strongly. The degradation of 4-CP was enhanced with the samples of TiO2-AC added to the photocatalytic system.To some organic contaminations such as methyl orange, the photodegradation performance of supported TiO2 catalyst is not satisfied. Catalysts of silver-modified TiO2/zeolite containing different amounts of Ag via a two-step dipping of AgNO3 solution and UV-irradiation process were examined for their improved catalytic activity towards photodegradation of methyl orange. The silver modified TiO2/zeolite catalysts present enhanced photocatalytic efficiency one time more than non-silver modified TiO2/zeolite catalysts did. The optimum silver nitrate concentration of the dipping solution was found to be 10-3M, whose photodegradation efficiency is approximate to that of titanium dioxide powder (Degussa P25). While with the Ag+-ion concentration further increased in dipping solution, the photocatalyst efficiency of the silver-modified catalysts decreased. The silver-modified catalysts were characterized with XRD and TEM. In addition, the presence of metallic silver always produces an increase in activity in comparison with Ag+ ions. This can be explained by the increase in the electron-hole pair separation efficiency induced bytrapping of electrons by metallic silver.The adsorption characteristics of 4-cp on TiO2/AC catalyst system have been investigated. The result shows that The adsorption isotherm forms of 4-cp adsorbed on TiO2/AC catalyst follows Langmuir adsorption model. The relationship of the photodegradation of 4-cp and the adsorption behavior of 4-cp on TiCVAC catalyst can be described by the Langmuir-Hinshelwood kinetics model, we can conclude the reaction rate of the photodegradation of 4-cp by this model. The adsorption equlibrium constant calculated by Langmuir adsorption isotherms under dark adsorption conditions is smaller than calculated by L-H kinetics model under UV-light photodegradation, which shows that the adsorption of 4-cp on TiO2/AC catalyst has increased when under UV-light photodegradation.