(339g) Photocatalyic Reduction of Cr(VI) by Fe-Ti Oxide

Although photocatalytic oxidation has been widely studied and practiced in industry, there have been far fewer reports of photocatalytic reduction, especially using visible light.  Among photocatalysts, titanium oxide is the most commonly used and is an excellent photocatalyst.  However, it requires UV light excitation.  Iron oxide, on the other hand, absorbs in the visible region, but it has low photocatalytic activity. Interestingly, composites of titanium oxide and iron oxide have been reported to possess activity for photo-oxidation of 2-propanol.  We found that titanium and iron oxide composites are also active for photoreduction of Cr(VI) to Cr(III), a common wastewater pollutant, using visible light.  Under the same conditions, hematite, magnetite, iron(II) titanate and iron(III) titanate were found to be inactive.  These results suggest that the formation of a heterojunction between these two oxides is essential for photocatalytic activity, and the chemical makeup of the chemical bonds formed at the heterojunction interface may also affect the overall efficiency of the process.