Abstract: An extraction agent composition comprising in addition to one or more conventional extraction agents at least one agent, preferably a strong organic acid, affecting the phase interface tension for diminishing the drop size of the dispersed phase and for accelerating the conversion of the material from one phase to another for the separation of nickel (II) and cobalt (II) from each other from aqueous solutions containing both nickel and cobalt. By using said composition the separation can occur regardless of the type of counter-ion, i.e. said separation can take place from sulphate, nitrate and chloride solutions. Basing the separation on a high chloride content or on the necessity of oxidizing the cobalt being present into a trivalent state has been avoided by the addition of a small amount of strong organic acid.

Abstract: An improved liquid-liquid extraction process for separating metals from each other in which an aqueous solution containing metals is mixed with an organic solution containing an extraction agent that releases hydrogen ions. A mixture of aqueous dispersed phase and an organic continuous phase is formed and the pH of the aqueous dispersed phase is controlled by the addition of a neutralizing agent to the mixture of the aqueous dispersed phase and the organic continuous phase on the basis of pH measurements made with pH electrodes immersed in the mixture of the phases. These direct measurements permit accurate adaptation of the rate of addition of the neutralizing agent to the rate at which hydrogen ions are being released so that the pH of the aqueous dispersed phase is kept substantially constant. The phases are separated from each other after transfer of metal ions from the aqueous to the organic phase, and the separated metal values are recovered.

Abstract: A method of separating cobalt (II) and nickel (II) by extraction with an organic extraction solution from an aqueous solution containing these metal ions is disclosed, in which a water soluble magnesium compound is added to the aqueous solution prior to the extraction and after the extraction the extraction agent is regenerated to recover the cobalt.