Selective separation of Ni(II)/Co(II) ions from dilute aqueous solutions using continuous electrodeionization in the presence of EDTA

The selective separation of Ni2+/Co2+ ions from their dilute solution using continuous electrodeionization process, facilitated with complexing agent, was investigated in this study. In order to increase the selective removal of Ni2+ ion, EDTA was used as a complexing agent and Taguchi method was implemented for systematic design of the experiments. The statistical analysis of the experimental results showed that EDTA:Ni mole ratio and feed flow rate were the most influential parameters on performance of the process with contributions of 55.3% and 28.1%, respectively. The comparative experiments proved that the effective separation of Ni2+/Co2+ in the absence of EDTA was impossible. Also, electrodeionization process was more effective than electrodialysis process for selective separation of Ni2+/Co2+ when EDTA was used in both methods. Ni2+/Co2+ ions molar ratio increased from its initial value of 3 to a final value of 154.6 at optimum operating condition, as predicted by Taguchi method. Finally, obtained results showed that the applied procedure can be considered as a promising method for selective separation of Ni2+/Co2+ ions from their dilute aqueous solution.