Application of ionizing radiation to environmental protection: removal of toxic Cr(VI) metal ion in industrial wastewater: preliminary study

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 (HO2 • ) and carboxyl radical anion (CO2 -• ) pro- duced by continuous radiolysis of water was investigated by steady state radiolysis of O2, Ar and N2O-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 oxi- dation 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 O2- and Ar-saturated solutions whilst in the case of N2O-saturated solutions Cr(VI) recovers. The results obtained in this study highlight the potential of this technology for industrial wastewater treatment.