SOLVENT EXTRACTION PROCESS FOR THE SEPARATION OF COBALT FROM NICKEL IN AQUEOUS SULPHATE-CONTAINING SOLUTIONS

摘要

An improved process for separating cobalt values from nickel values in anaqueous nickel and cobalt sulphate-containingsolution in which the solution is contacted with a water-immiscible organicsolution containing an organophosphorous acidin a cobalt extraction circuit. The process is particularly useful for aqueoussolutions containing high total metals content andelevated cobalt concentrations, while avoiding the formation and precipitationof ammonium sulphate containing double salts duringthe solvent extraction of the cobalt. The improvement includes contacting aportion or all of the water-immiscible organic solutionrequired for cobalt extraction with a nickel-containing ammoniacal solution toproduce a nickel-loaded organic phase and a partiallynickel-depleted raffinate. The nickel-loaded organic phase is then passed tothe cobalt extraction circuit for selective cobaltextraction in which nickel is displaced from the organic phase by cobalt, toproduce a cobalt-depleted, nickel-enriched, raffinateand a cobalt-loaded organic phase. Advantageously, the nickel-containingammoniacal solution is generated by adjustment of thenickel-containing raffinate from the cobalt extraction circuit, by additionsof ammonia, preferably as ammonium hydroxide, andammonium sulphate.