Process for selective extraction of metal ions from aqueous solutions and extracting agents suitable for that purpose

Claim 1

In a process for the selective extraction of copper and nickel ions from aqueous solution using a substantially immiscible organic extraction agent, the improvement wherein said extraction agent is essentially composed of a mixture of (1) oleic acid, or (2) oleic acid and at least one other unsaturated fatty acid and a (cyclo) aliphatic oxime, of from 6 to 12 carbon atoms, and wherein the (1) copper and nickel ions are first extracted with said extraction agent at a pH value of between 6 and 9 from an aqueous solution into said organic extraction agent, (2) thereafter extracting the copper and nickel ions from said organic phase into a second aqueous phase at a pH of between -2 and +1, and thereafter, (3) at a pH of between 4.0 and 6.0, selectively extracting said copper ions from said second aqueous phase with an extraction agent essentially composed of a mixture of (1) oleic acid, or (2) oleic acid and at least one other unsaturated fatty acid and a (cyclo) aliphatic oxime, of from 6 to 12 carbon atoms, and then (4) the copper ions in the organic phase are again reabsorbed into a third aqueous phase at a pH of between -2 and +1.