Photochemical elimination of Cr(VI) from neutral–alkaline solutions

The elimination of Cr(VI) from aqueous solutions at neutral and low alkaline pH by photocatalytic reduction to Cr(III), using ZnO powder as catalyst, is investigated. The study has been performed by determination of the percentage of Cr(VI) eliminated in the presence of some species (i.e. Zn(II), Cd(II), Ni(II), Ca(II), CH3COO−, PO3‐4, CO2‐3, S2‐ and NH3) which usually are found in wastes together with Cr(VI). The results obtained show that the presence of some species prevents the alkalinization of the solution during irradiation, which increases the yield of Cr(VI) photoreduction. Other species, such as S2‐ and NH3, are oxidized during illumination: thus they prevent electron–hole recombination and, consequently, increase the yield of the Cr(VI) elimination. Copyright © 1990 Society of Chemical Industry