Separation of nickel from cobalt using electrodialysis in the presence of EDTA

Optimum conditions are determined for the removal of nickel from cobalt solutions by electrodialysis exploiting the greater stability of the EDTA complex with nickel. The Ni–(EDTA)^2– complex and hydrated Co²⁺ ions are transferred from the feed solution to the electrodialysis anolyte and catholyte chambers, respectively. A three compartment cell is required to prevent the transfer of hydrated Ni²⁺ from the anolyte chamber as the EDTA present is destroyed at the anode. Complete removal of nickel from cobalt can be achieved but there is a compromise between cobalt purity and the percentage of cobalt transferred to the catholyte chamber for recovery.