Fe(II)-initiated reduction of hexavalent chromium in heterogeneous iron oxide suspension

Abstract

The characteristics of Fe(II)-initiated reduction of Cr(VI) in iron oxide suspensions were investigated by conducting a series of kinetic experiments. A modified Langmuir-Hinshelwood kinetic model was used to provide a better description of Cr(VI) reduction kinetics which were believed to be occurring on the limited reactive site of reductant. The concentration of magnetite concentration as well as Cr(VI) concentration, significantly affected the reaction kinetics of Cr(VI). The reduction kinetics were improved with increasing magnetite and Cr(VI) concentration. Almost 95% of Cr(VI) reduction was achieved within 10 min at the condition of 8 g/L of magnetite and 80 mg/L of initial Cr(VI), respectively. The solution pH also affected the reaction rate in the range of 5.5 and 8.0 where a lower pH produced a faster reaction rate. The addition of Fe(II) on soil and magnetite showed the capability of improving Cr(VI) reduction kinetics, and their reduction kinetics was also well described by using a Langmuir-Hinshelwood kinetic model. The experimental results obtained in this research clearly show the advantage of additional reductant for reducing Cr(VI), and the), can provide basic knowledge for the development of remediation technology for the treatment of groundwater and soil contaminated with Cr(VI).