Study On Kintics Of Photocatalysis Oxidation Of Organic Pollutants With Nano-TiO₂ In Water

There are four parts in this dissertation. In the first part, the history, application, mechanism and kinetics of photocatalysis were introduced. The research methods of photocatalytic kinetics and the different kinetic models of photocatalysis were introduced in classification and the defects in this field were evaluated.In the second part, a novel photocatalytic reactor of annulus, which allows the in-situ monitoring of experimental data, has been designed and constructed by us (and validated using formic acid as the model reactant) and a new kinetic model (Langmuir-Freundlich-Hinshelwood) was developed on the basis of the L-H model. The results show that the calculated results obtained from the new kinetic model are in good agreement with experimental data (R²>0.9).In the third part, the photocatalytic kinetic characteristics of seven carboxylic acids (acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, tartaric acid, malic acid) were investigated, including the dependency of the reaction rate constant k on initial concentration, TiO₂ amount, light intensity and pH. The results showed that their kinetic characteristics under different conditions were successfully described in terms of Langmuir-Freundlich-Hinshelwood model. The relationship between the corresponding parameters and the rate constant k were also determined. The experimental results showed that different adsorption modes were the key factors for the photocatalytic degradation rates. The strong adsorption modes would be favorable to the photocatalytic degradation. TiO₂ amount and pH directly influenced the rate and the optimal reaction conditions were different according to different reaction systems. The influence of light intensity on the chang trend of reaction rate constant k was similar and they had a good linear relationship. Although the heterogeneity of catalysis surface and the adsorption molecules interaction were considered in the new kinetic model and the heterogeneity coefficient n could directly reflect the influence of the bonding force between the catalysis and adsorbs on the rate constant k, there were still some defects in it.In the fourth part, future research direction was pointed out.