The study of the photocatalytic degradation kinetics for dichloroethylene in vapor phase

This investigation concerned the photocatalytic decomposition of cis-dichloroethylene (cis-DCE) with titanium dioxide under irradiation of 365 nm wavelength UV light. The feasibility studies involved initial concentration of reactant, humidity, oxygen content and light intensity on the effect of the heterogeneous photocatalytic reaction along with the development of reaction kinetic model based on above parameters. Under experimental conditions, the maximum reaction rate for decomposing DCE was 0.959 μmole/s-g and quantum yield of 0.297. The concentration effect was in proportion to reaction rate but inversely to conversion ratio. As oxygen being a good electron accepter, the reaction rate increased with increasing oxygen content, but for higher than 15%(v/v), the reaction rate no longer increased. The functions of water were twofold: one being the source of hydroxyl free radicals, and the other for competing with DCE on adsorption sites. For lower moisture content, reaction rate increased with increased moisture content, but reversed under high moisture content. Stronger light intensity increased reaction rate with proportion to 0.6 order of light intensity. The kinetic expression could be represented by Langmuir-Hinshelwood bimolecular reaction model.