Inhibition of photooxidation of iron(II) by some semiconductors

The photooxidation of iron(II) in aqueous ethanol is less in presence of TiO2, ZrO2, V2O5, CeO2, ZnO, Fe2O3, CdO, PbO, SnO2, CdS, ZnS and Al2O3 than in their absence. The photogeneration of iron(III) was studied at different [Fe2+], amounts of semiconductors suspended, airflow rates, light intensities, solvent compositions and wavelengths of illumination. The catalysts show sustainable photocatalytic activity. The metal oxides and sulfides reduce iron(III), formed by the homogeneous photooxidation of iron(II). TiO2, CeO2, ZnO, Fe2O3, CdO, PbO, SnO2 and Al2O3 effectively suppress the photooxidation of iron(II); ZrO2, ZnS and CdS also suppress but not completely. At high catalyst-loading V2O5 catalyses the photooxidation of iron(II). The mechanisms of the photocatalytic processes are discussed.