Cadmium electroplating wastewater treatment using a laboratory-scale electrodialysis system

A study of the treatment of synthetic wastewater containing cadmium and cyanide using a laboratory-scale five-compartment electrodialysis cell is presented. Cadmium and cyanide removal is limited by a cadmium compound precipitation on the cation-exchange membrane. Successive changes of synthetic wastewater on the diluate compartment of the electrodialysis cell avoids the cadmium compound precipitation. This indicates the possibility of obtaining a solution with high cadmium and cyanide concentration. This solution can then be reused in the cadmium electroplating bath. When the wastewater contains other metals (copper, chromium or iron), reuse of cadmium and cyanide in the deposition bath is not possible, since transport of these former metal ions occurs with cadmium and cyanide ions. The results demonstrate that the percent extraction (pe) of cadmium and cyanide and the current efficiency (ce) depends on the ions concentration in the wastewater. (C) 2003 Elsevier B.V. All rights reserved.