Electrocoagulation: A cleaner method for treatment of Cr(VI) from electroplating industrial effluents

Abstract

240-245Chromium contamination in waters are highly toxic even in very low concentrations and need to be completely removed from the effluents before they are discharged into a stream, sewer or on land. Electroplating industry is one of the industrial sectors producing chromium bearing wastewaters, mostly originating from chromium plating, anodizing, electroplating solutions and dip solutions like passivating dips, bright dips, etc. Chromium concentration in the effluents varies from 3 to 50 mg/L depending upon the care with which the plating operations are carried out. The results of this study have shown the applicability of electrocoagulation as a clean method for treatment of Cr(VI) containing wastewaters. The optimum removal of Cr(VI) was attained between pH 4-8. Increase in current density enhances the removal rate and the quickest treatment with an effective reduction of Cr(VI) concentrations was achieved below permissible level within 20 min. Iron electrodes were found to be more efficient in removing chromium in comparison to the aluminum and hydrid Al/Fe electrodes. This may be due to the formation of stable Fe-Cr complex which is more stable than Al-Cr complexes. On the other hand, 1 kg of Cr(VI) removal produces only 2,8 kg of sludge against 36 kg of sludge generated from iron sulphate precipitation method. The rate of removal is faster in comparison to the adsorption on activated carbon which is one of the most important requirement for practical application of this treatment method