Solvent extraction and separation of zinc and cobalt from ammoniacal solution

Abstract

A process was developed to recover Zn and Co by solvent extraction from the raffinate generated during processing of sea nodules. From a model ammoniacal solution containing 0.2 g/L Zn or 0.2 g/L Co, extraction of Zn and Co by Versatic acid was studied. A maximum of 87% Zn was extracted with 1M Versatic acid in single stage, whereas extraction of Co was negligible due to its higher oxidation state. When Co(III) was reduced to Co(II) by the addition of cobalt powder, 1M Versatic acid extracted 76% Co in a single stage. From the McCabe Thiele diagram number of counter current extraction stages required for complete recovery of Zn and Co from ammoniacal solution was determined. Simulation of counter current extraction of Zn and Co was also carried out. Thus, this process can be used to recover Zn, leaving Co in the raffinate. Then Co can be recovered by solvent extraction with Versatic acid after reducing Co(III) to Co(II) state.