Abstract
The reduction of toxic chromium (VI) heavy metal from water to non-toxic Cr(Ill) using high dose and high dose rate continuous electron beam irradiation from a 2.5 MeV van de Graaff accelerator has been investigated in this work. More than 95% of Cr(VI) was removed after a dose of 5 kGy at near neutral pH buffered oxygen-saturated aqueous solutions containing formate as OH center dot radical scavenger. The reduction of the hexavalent chromium by the radiolytically produced superoxide radical anion (O2 center dot(-)) increased linearly with increasing radiation dose and was significantly boosted by the addition of formate. To explain the mechanise of this removal, a kinetic model was proposed where Cr(IV), rather than Cr(V), oxidizes O2(-)center dot in a one-electron reaction leading to the formation of the stable product Cr(III). This laboratory study shows that electron beam irradiation might open new possibilities for treatment of large volumes of industrial wastewater contaminated with chromium.