Closing the Loop in Ion Flotation: Recovery of Copper, Regeneration and Reuse of Collector from the Foam Phase by a Solvometallurgical Process

Ion flotation is an efficient separation technique for the recovery of metal ions from dilute aqueous solutions. Provided that both the collected metal and the surfactant are recovered from the foam phase, it could be considered as an alternative to ion exchange, adsorption or solvent extraction in hydrometallurgy. However, most studies are focusing only on the metal recovery by ion flotation and neglect the development of a closed-loop ion flotation flow sheet with regeneration of the collector. As a consequence, the industrial implementation of this technique to hydrometallurgical operations is limited. The objective of this paper was to develop a simple solvometallurgical process for the decomposition of copper(II) tetraamine dodecyl sulfate sublates from foams generated after the ion flotation of dilute copper-zinc ammoniacal solutions with sodium dodecyl sulfate (SDS). It was possible to recover copper almost quantitatively as a copper-bearing precipitate, after mixing the foam phase with a 8 g L-1 NaOH in methanol solution. The collector was regenerated from the solution by removal of methanol by distillation and its reusability was tested in five subsequent ion flotation cycles.The efficiency of the regenerated SDS for the recovery of copper from dilute copper-zinc ammoniacal solutions was similar (ca. 80%) to that of fresh SDS solution without make-up. Based on the experimental results, a conceptual closed-loop flow sheet is proposed for the recovery of copper from dilute ammoniacal leachates by ion flotation. [GRAPHICS]

Automated summary

Ion flotation is an efficient technique for recovering metal ions from dilute solutions, but its industrial implementation is limited due to neglecting collector regeneration. A solvometallurgical process was developed to decompose copper(II) tetraamine dodecyl sulfate sublates from foams generated after ion flotation, demonstrating almost quantitative copper recovery. In addition, a closed-loop flow sheet was proposed for copper recovery using regenerated SDS with similar efficiency to fresh SDS.