Kinetics of the photocatalytic oxidation of N(III) and S(IV) on different semiconductor oxides

The results of the nitrite and sulphite oxidation in aerated aqueous media in the presence of different semiconductor oxides acting as photocatalyst is investigated. Particular attention has been paid to the analysis of the kinetics of nitrite and sulphite oxidation over TiO2, ZnO and different Fe(III) oxides which are present in the natural environment. From the obtained experimental results it has been ascertained that nitrite photooxidation follows a Langmuir-Hinshelwood kinetics, the TiO2 with the higher anatase content being the most efficient photocatalyst. For sulphite photooxidation, the ferric oxides show a high photoactivity, along with an strong adsorption of reaction products. A kinetic law is derived taking into account the experimental results.