Application of Doehlert matrix to the study of electrochemical oxidation of Cr(III) to Cr(VI) in order to recover chromium from wastewater tanning baths

The aim of this study was to optimize simultaneously the chemical and faradic yields of electrochemical oxidation of chromium(Ill) to chromium(VI) over a titanium-platinum anode in order to recover trivalent chromium from aqueous and tanning baths effluent. A Doehlert design was used to optimize the significant experimental variables: concentration of chloride ions [Cl-] (mol L-1); temperature of reactional media T ( C); pH of reactional media; intensity of electrolysis current I (A); time of electrolysis t (h). The quadratic models of second degree relate chemical (R-C) and faradic (R-F) yields to the different variables affecting the electrochemical reaction were determined by the NEMROD software program. Having to study simultaneously two responses, the Pareto graphic analysis of effects was used. The results obtained in this study have shown that the current intensity and the electrolysis time were the main influent parameters on the removal ratio of chemical oxygen demand (COD), total organic carbon (TOC) and electrochemical oxidation of trivalent chromium. (C) 2008 Elsevier B.V. All rights reserved.