Abstract
Hexavalent chromium, a major contaminant in most wastewater sites, is a potential health threat inducing cancer to humans while trivalent chromium is an essential element for the metabolism of sugar. The radiation-induced reduction of Cr(VI) metal ion to Cr(III) by the perhydroxyl radical (HO(2) (aEuro cent)) and carboxyl radical anion (CO(2) (-aEuro cent)) produced by continuous radiolysis of water was investigated by steady state radiolysis of O(2), Ar and N(2)O-saturated pH 3 solutions in the presence of formate. In all cases the removed Cr(VI) was a linear function of the absorbed dose. The added formate was favorable for removing Cr(VI). Its presence protects the solution from reverse radiolytic oxidation of Cr(III) to Cr(VI). The measured and calculated yield of removal of Cr(VI) do agree quite well at low formate concentration but at high formate concentration the measured yield was higher than the expected. When all formate is exhausted no recovery of Cr(VI) from Cr(III) was observed in case of O(2)- and Ar-saturated solutions whilst in the case of N(2)O-saturated solutions Cr(VI) recovers. The results obtained in this study highlight the potential of this technology for industrial wastewater treatment.