Effect of pH and chloride concentration on the removal of hexavalent chromium in a batch electrocoagulation reactor

In this work, the effect of pH and chloride ions concentration on the removal of Cr(VI) from wastewater by batch electrocoagulation using iron plate electrodes has been investigated. The initial solution pH was adjusted with different concentrations of H2SO4. The presence of chloride ions enhances the anode dissolution due to pitting corrosion. Fe2+ ions formed during the anode dissolution cause the reduction of Cr(VI) to form Cr(III). which are co-precipitated with Fe3+ ions at relatively low pH. The reduction degree of Cr(VI) to Cr(III) and the solubility of metal hydroxide species (both chromic and iron hydroxides) depend on pH. At higher concentrations of H2SO4, the reduction of Cr(VI) to Cr(III) by Fe2+ ions is preferred, but the coagulation of Fe3+ and Cr(III) is favoured at the lower H2SO4 concentrations. (C) 2009 Elsevier B.V. All rights reserved.