Separation of cobalt and nickel by solvent extraction

Abstract

This invention concerns the method of separation of Co from Ni in an aqueous solution containing Co from Ni salts, with an organic solvent containing 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and/or 3,5,5-trimethylhexyl phosphonic acid mono-3,5,5-trimethylhexyl ester and/or isodecyl phosphonic acid monoisodecyl ester as an effective extractant for the separation of Co from Ni, the method which requires fewer stages in the solvent extraction equipment and less organic solvent than the conventional method, and which can very effectively separate Co from Ni in high purity and in high yield. The continuous separation of Co from Ni according to this invention enables the separation of Co with purity above 99% in a yield above 99% and Ni with purity above 99% in a yield above 99%.

Description

Claims

1. A process for separating cobalt from nickel in an aqueous solution containing the above-mentioned metals, .[.with consists.]. .Iadd.consisting .Iaddend.essentially of.Iadd.: .Iaddend.

(A) contacting the said solution with an organic extraction solvent comprising a mono-alkyl alkylphosphonic acid as extractant and having the general formula: ##STR2## wherein R represents 2-ethylhexyl, 3,5,5-trimethylhexyl, or isodecyl, .Iadd.in one or more stages .Iaddend.whereby cobalt is extracted from the aqueous solution into the organic phase, and

(B) subsequently separating the resultant cobalt loaded organic phase from the aqueous phase.

2. The process of claim 1 wherein the said extractant is mono-2-ethylhexyl 2-ethylhexylphosphonic acid, mono-3,5,5-trimethylhexyl, 3,5,5-trimethylhexylphosphonic acid, or monoisodecyl isodecylphosphonic acid, or mixtures thereof.

3. The process of claim 1 wherein the extraction is performed within the pH range of from about 5 to 6.5.

4. The process of claims 1 or 2 wherein the organic extraction solvent comprises the said extractant in an amount of from 5 to 100% by volume.

5. The process of claims 1 and 2 wherein the organic extraction solvent comprises the said extractant in an amount of from 10 to 40% by volume.

6. The process of claim 4 wherein the said extractant further comprises an aliphatic hydrocarbon, aromatic hydrocarbon, or mixtures thereof.

7. The process of claims 1 to 3 wherein the organic extraction solvent contains an emulsion inhibitor.

8. The process of claims 1 to 3 wherein the emulsion inhibitor is tributyl phosphate or isodecanol.

9. The process of claims 1 to 3 wherein said cobalt loaded organic phase is scrubbed by contact with (a) diluted inorganic acid or (b) an aqueous solution containing cobalt salt. .Iadd.

10. The process of claims 1 or 2 wherein the extraction is performed by contacting said aqueous solution containing cobalt and nickel with said organic extraction solvent in two stages. .Iaddend. .Iadd.11. The process of claim 10 wherein the pH of said aqueous solution containing cobalt and nickel in the first of said two stages is 4.6. .Iaddend. .Iadd.12. The process of claim 11 wherein the pH of said aqueous solution containing cobalt and nickel in the second of said two stages is 5.8. .Iaddend. .Iadd.13. The process of claims 1 or 2 wherein the extraction is performed by contacting said aqueous solution containing cobalt and nickel with said organic extraction solvent in countercurrent extraction in two stages, and

the pH of said aqueous solution in the first of said two stages is 4.6, and

the pH of said aqueous solution in the second of said two stages is 5.8. .Iaddend. .Iadd.14. The process of claim 1 wherein the extraction is performed within the pH range of from 4.6 to 6.5. .Iaddend.