Separation of calcium and cadmium by electrodialysis in the presence of ethylenediaminetetraacetic acid

The separation of calcium and cadmium ions in a system containing ethylenediaminetetraacetic (EDTA) as the complexing agent has been studied using a laboratory-scale batch electrodialyzer, The theoretical distribution diagram constructed for the Ca-Cd-EDTA system suggested that cadmium preferably formed negatively charged complexes while calcium remained in the positively charged uncomplexed form. The experimental results confirmed that under the influence of an electric field, calcium was exclusively transported to the cathode while more than 90% of cadmium totally removed from the middle compartment of the batch electrodialyzer migrated toward the anode. The separation effect resulting from EDTA complexation was studied within the 1.5-4.0 pH range.