COMPARISON OF THE PHOTOCATALYTIC EFFICIENCY OF TIO2 IRON-OXIDES AND MIXED TI(IV) FE(III) OXIDES - PHOTODEGRADATION OF OLIGOCARBOXYLIC ACIDS

Comparative photo-oxidations of three oligocarboxylic acids, i.e. oxalic acid, EDTA and malonic acid, were performed with different catalysts, i.e. TiO2 (Degussa P-25), alpha-Fe2O3, gamma-Fe2O3, Fe3O4 and two samples of mixed Fe(III)-Ti(IV) oxides containing 0.5 wt.% and 5 wt.% Fe respectively. Different irradiation wavelengths were used. It was found that the photocatalytic efficiency depends mainly on the physicochemical properties of the catalyst, the irradiation wavelength, and the redox potential and adsorption ability of the substrate. The effect of surface complexes formed between the oxide and the organic compound was analysed. TiO2 was found to be the best catalyst. The relative utility and stability of iron oxides and mixed Fe-Ti oxides is discussed.