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 i s investigated. Particular attention has been paid to the analysis of the k inetics of nitrite and sulphite oxidation over TiO2, ZnO and different Fe(I II) oxides which are present in the natural environment. From the obtained experimental results it has been ascertained that nitrite photooxidation fo llows a Langmuir-Hinshelwood kinetics, the TiO2 with the higher anatase con tent being the most efficient photocatalyst. For sulphite photooxidation, t he ferric oxides show a high photoactivity, along with an strong adsorption of reaction products. A kinetic law is derived taking into account the exp erimental results.