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.