Photocatalytic effect of iron corrosion products on reduction of hexavalent chromium by organic acids

• ICPs have significant photocatalytic effect on reduction of Cr(VI) by tartaric acid.
• The system allows simultaneous reduction of Cr(VI) and decolorization of OII.
• The photocatalytic effect of ICPs is related to the organic acid species.

Iron corrosion products (ICPs) were used as heterogeneous catalysts for reduction of hexavalent chromium (Cr(VI)) mainly by tartaric acid under photoirradation. The results indicate that ICPs have significant photocatalytic effect on reduction of Cr(VI) by tartaric acid. The percentage reduction of Cr(VI) depends on various factors such as pH value, tartaric acid concentration and ICPs dosage. Under the optimal conditions (tartaric acid concentration 1.6 mM, ICPs dosage 0.40 g/L and pH 3.0), the percentage reduction of Cr(VI) in a solution of 25 mL containing 0.2 mM Cr(VI) reaches 93% after 30 min. The percentage reduction of Cr(VI) is also influenced by co-existence of orange II (OII) and the system allows effective simultaneous reduction of Cr(VI) and decolorization of OII. Compared to tartaric acid, ICPs have lower photocatalytic effect on reduction of Cr(VI) by oxalic and citric acids.