Electroseparation of cobalt and nickel from a simulated wastewater

A study of the electrodeposition at sheet electrodes was carried out under potentiostatic control for solutions containing either 0.1 M Co(II) or 0.1 M Ni(II) and a 1:1 mixture of both 0.1 M Co(II) and 0.1 M Ni(II). From the linear sweep voltammetry of solutions containing only either Co(II) or Ni(II), a potential region in which cobalt would be expected to be electrodeposited without the simultaneous electrodeposition of nickel was identified and a theoretical deposit composition against potential plot was constructed. Deposition from a 1:1 Ni(II): Co(II) mixture at the optimum potential for separation produced a 90% cobalt /10% Ni alloy. Long term, potentio-selective extraction from a 1:1 Ni(II): Co(II) mixture showed that when the stainless steel cathode was predeposited with pure cobalt, the cobalt level in the solution could be reduced to less than 5% of its original value whilst leaving the Ni(II) at 85% of its original value.