Removal of heavy metals from Water Rinsing of Plating Baths by Electrodialysis

Abstract

During the chromic plating of parts, the baths become more and more poor in chromic acid and rich in metallic impurities such as Cu 2+ , Zn 2+ , Fe 3+ and Cr 3+ which makes the bath useless. Also, the water used to rinse parts contains chromic acid and metallic impurities. As it is known that chromic acid is relatively expensive and very toxic, so its recovery has double interest: economic and environmental. Its reuse is possible after removal of metallic impurities. In this work, we studied the possibility of metallic impurities elimination from the chromic acid. The influence of the current density and the circulating solution flow rate on the process efficiency has been studied. The elimination rates obtained in the presence of ion exchange textile are superior to those obtained in the absence of textile. The analysis of the results showed that for the three metallic impurities studied (Cu 2+ , Fe 3+ and Zn 2+ ), the purification rate increases versus the applied current density and solution flow rate. The importance of the elimination of the three metal cations is as the following order: Cu 2+ >Zn 2+ >Fe 3+ .