Preparation Of TiO₂ Photocatalysts And Their Application In Degradation Of Formic Acid And Methyl Orange

In recent years, semiconductor photocatalysts have evoked tremendous interest in the light-stimulated degradation of aqueous pollutants and atmospheric pollutants. Titanium dioxideCTiOa) photocatalysis has been the focus of the investigations, particularly because of its high photocatalytic activity and its stability with respect to photocorrosion and chemical corrosion.In this paper, the methods of preparing TiOi nano-particles and TiO2 thin film coated on glass-plate were investigated. It is suggested that sol-gel method using TiCU is the best method for preparation of TiO2 particles; Acetic acid is a good reagent for decreasing aggregation of Ti02 crystallite; Uniform transparent TiO2 films were prepared by sol-gel process using spinning technique.For each method, the temperature and the duration of the treatment were studied. TG/DTA, XRD and TEM of the calcined samples were recorded and heat treatment conditions were based on these analysises. UV-vis absorption spectra of TiO2 colloidal suspensions were recorded on spectrophotometer. The photocatalytic activities of catalysts for degradation of formic acid and methyl orange were examined and the factors of degradation were discussed in detail.For the more, to enhance the photocatalytic activity of TiO2, modifications have been introduced to the crystalline matrix by selective doping of foreign metal ions. A serials of TiO2 particles and TiO2 thin film catalysts doped with Zr, Sn, Fe and Ag were prepared and their photocatalytic activities were investigated. It is suggested that theactivities of doped TiO2 photocatalysts appear to be a complex function of the dopant concentration, the mechanisms of doped TiO2 are not well understood. The photocatalytic activities of some doped system increased while others decreased. In all of the doped TiO2 system, Ag-doped TiO2 showes the best photocatalytic activity. It is due to the morphosis of Ag doped and its facility for O2 capturing electron.We also discussed the advantages of reactions carried out by suspensions of powdered TiO2 and immobilized TiO2 thin film. The filtration of the slurries and inactivation of the catalysts is the most difficulty for suspensions system. The immobilization system could avoid the filtration step and would be of great practical benefits.