The Study Of Several Questions In TiO₂-based Photocatalytic System

Ti02 Photocatalytic Oxidization, one of the advanced oxidization processes(AOP), has developed in recent 30 years. Because it can oxidize and degrade many organic contaminants which are hard to be degraded by other methods into CO2, H2O and other small molecules, this technology is increasingly becoming one of the popular research subjects in the field of photochemistry and environment protection. Now, the research on this technology is focused on the reaction mechanism, reaction kinetics, preparation of TiO2 with high catalytic activity and devising of photocatalytic reactor with high efficiency and large scale, etc. In order to do some basic things for the research on the reaction mechanism of TiO2 photocatalytic system, following problems are studied in this paper:1. The study on several factors which influence TiO2 aqueous suspension: by using COD of certain dye wastewater as the objective decomposition substance and using nanometer TiO2 as the photocatalyst, the effects of initial pH, dosages of Ti02 and reaction time on the photocatalytic efficiency of aqueous suspension were investigated in detail. The experimental results show that reaction time has greatest effect on the photocatalytic efficiency of this system, dosages of TiO2 takes second place and initial pH has the least effect on that. Furthermore, the optimal reaction condition is that initial pH is equal to 7.0, dosages of TiO2 is 3g/L and reaction time is 3 hours, under which the COD degradation rate of this wastewater is 89.5%.2. The study on several factors which influence the photocatalytic activity of TiO2 thin film: the TiO2 thin films deposited on the ektexine of quartz glass tubes was successfully prepared by sol-gel processing. By using those TiO2 thin films as photocatalyst and using COD of certain wastewater as the objective decomposition substance, effects of calcination temperature of the films, reaction time, soaking times and initial pH on photocatalytic efficiency of the fixed TiO2 film system were investigated in detail. The results show that COD degradation rate can reach the maximum 76.8% when calcination temperature of the films is 600℃, reaction time is 5 hours, soaking times is 5 and initial pH is 8.0.3. The comparison of photocatalytic efficiency of TiO2 aqueous suspension with that offixed TiO2 system: by using epoxy resins system as the bond, the nanometer TiO2 thin films deposited on the ektexine of common glass tubes was successfully prepared. Moreover, the photocatalytic efficiency of aqueous suspension and fixed nanometer Ti02 film system were compared under such conditions as the dosages of TiO2, initial pH and reaction time were all same. The results show that compared with that of the former system, the photocatalytic efficiency of the latter system is approximately reduced by 25%.In addition, a lot of problems which have been caused by those experiments were illuminated and analyzed in the last chapter of this paper. Moreover, further research direction was pointed out.