Kinetics of hexavalent chromium removal with scrap iron in continuous-flow system [articol]

Abstract

The kinetics of hexavalent chromium removal by scrap iron was investigated in continuous system, using acidic (pH 2.5) aqueous Cr(VI) solution with low buffering capacity. Experimental data has been interpreted in terms of zeroorder, first-order and second-order integrated kinetic models. Kinetics of Cr(VI) removal process has been found to proceed in two stages, with Cr(VI) removal rates significantly decreasing with increasing the elapsed experimental time. Among the studied kinetic models, the first-order kinetic model was the best fit for the first time interval (first 48 hours), while for the second time interval the process of Cr(VI) removal by scrap iron was best described by a second-order kinetics. The observed deviations of Cr(VI) removal kinetics can be attributed to changes in scrap iron surface reactivity associated with passivation processes.