Mechanism and kinetics of Cr(VI) reduction by waste slag generated from iron making industry

Iron making industry has generated a large amount of waste slag containing iron. Feasibility of utilizing the slag to remove toxic Cr(VI) from aqueous phase was investigated in a batch system. Main mechanism of Cr(VI) removal by the slag was its reduction into Cr(III) by the Fe(II) released from the slag under acidic condition. One gram of the slag could remove 56.1 (± 0.5) mg of Cr(VI) at pH 2. The removal rate of Cr(VI) increased with a decrease in pH or increase of slag dosage. A simple kinetic model in the form of −d[Cr(VI)]/dt = k[slag]n was developed to predict the time-dependent concentration of Cr(VI) in aqueous phase. At pH 2, the model successfully described the Cr(VI) removal behaviors in aqueous phase under various slag dosages and initial Cr(VI) concentrations.