Simultaneous Removal of Greases and Hexavalent Chromium from Electroplating and Chromate Conversion Coating Waste Solution by Electrocoagulation

Simultaneous removal of oil droplets and hexavalent chromium from synthetic wastewater of chromium plating and chromate conversion coating plants by electrocoagulation in a new cell design was studied under different conditions of pH, initial Cr6+ concentration, NaCl concentration, and current density. Under optimum conditions, more than 90% of oil content and Cr6+ were removed. Percent removal was found to increase with decreasing Cr6+; high Cr6+ concentrations tend to passivate the aluminum anode and decrease the percent removal of Cr6+ and oil. The effect of NaCl concentration shows a maximum percent removal at 1.5%. The pH range 4-5 was found to give the highest percent removal. Increase of current density was found to improve the percent removal of Cr6+ and oil droplets. The favorable effect the combined oil and Cr6+ removal on the capital and operating costs of wastewater remediation was pointed out. Potential merits of the present cell design compared to the traditional parallel plate cell were highlighted.