Hexavalent chromium removal in an electrocoagulation column reactor: Process optimization using CCD, adsorption kinetics and pH modulated sludge formation

In this study, hexavalent chromium [Cr(VI)] removal from aqueous solutions by electrocoagulation, using iron electrodes, was optimized for process variables: applied current, initial pH, initial chromium concentration and application time. A four-factor central composite design (CCD) together with response surface methodology (RSM) was used for investigating the effects of the process parameters on response variables: hexavalent chromium removal efficiency and energy consumed per gram removal of chromium. The optimum conditions were determined to be pH 3.0, 1.48A applied current, 49.96 ppm initial Cr(VI) concentration and application time of 21.47 min for 100% Cr (VI) removal. The corresponding value of energy consumption was found to be 12.97 W-hour per gram removal of Cr (VI). Adsorption kinetics study showed that the removal followed pseudo-first order kinetics and the adsoption fitted the langmuir isotherm very well. Moreover, the sludge generated under the optimized conditions showed the best settling characteristics between the pH range of 6-9. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.