Process for the recovery of cobalt and nickel in the presence of magnesium and calcium from sulphate solutions by Versatic 10 and Cyanex 272

Cobalt (II) and nickel (II) were simultaneously extracted from magnesium and calcium synthetic sulphate solutions using the carboxylic extractant Versatic 10. The two metals were then separated by extracting cobalt using the phosphinic acid Cyanex 272. Statistical design and analysis of experiments were used throughout in order to determine the main effects and interactions of the solvent extraction factors, which were the extraction pH at equilibrium, temperature, extractant concentration and organic to aqueous phase ratio. A statistically designed experiment was also carried out in order to study stripping of the loaded, with cobalt and nickel, Versatic 10 organic phase by using synthetic nickel spent electrolyte. Cobalt was recovered from the loaded Cyanex 272 by synthetic cobalt spent electrolyte, in order to produce a solution suitable for cobalt electrowinning. The slope analysis method was used to determine the nature of the cobalt and nickel complexes extracted with each of the extractants. The number of stages required for extraction and stripping processes of cobalt and nickel was also evaluated. The results of the continuous, counter current, mini plant tests clearly demonstrated the feasibility of the simultaneous recovery of cobalt and nickel from magnesium and calcium sulphate solutions by Versatic 10, as well as their separation by Cyanex 272.