Influence of photoirradation on reduction of hexavalent chromium by zero-valent iron in the presence of organic acids

Reduction of hexavalent chromium (Cr(VI)) by zero-valent iron (Fe 0) was investigated systematically in the present study. No change in Cr(VI) concentration occurs using untreated Fe 0 powders even after a long contact time. The Fe 0 powders treated with acid washing shows a weak activity and a poor long-term performance to reduction of Cr(VI). The activity and long-term performance of treated Fe 0 powders is not effectively improved in the presence of citric acid. In contrast, introduction of photoirradiation not only dramatically increases the reduction rate of Cr(VI) in the presence of citric acid but also effectively stabilizes the activity of Fe 0 powders and films. Such enhancement should be attributed to photoreductive dissolution of the oxide layer on Fe 0 surface. For this newly developed system, effective reduction of Cr(VI) is favored at low pH values and oxalic and tartaric acid are also effective as complex reagents. ► Investigation of influence of organic acid on longevity of Fe 0. ► Development of an efficient system for reduction of Cr(VI) by Fe 0. ► Consideration of effect of nature of organic acid and pH on reduction rate.