Hydrometallurgical recovery of copper and cobalt from reduction-roasted copper converter slag

The paper is concerned with a simple hydrometallurgical method for selective recovery of copper and cobalt from industrial copper converter slag. The following consecutive stages are proposed: roasting of the slag in reduction conditions to produce Cu–Co–Fe–Pb alloy, electrolytic dissolution of the alloy in an ammonia–ammonium chloride solution, ammoniacal leaching of the slime, selective copper and cobalt electrowinning. Cu27–Co6–Fe64–Pb1.5 alloy was a five-phase system and did not dissolve uniformly during electrolysis. This resulted in the separation of the metals, wherein iron remained in the slime, while copper and cobalt were components of slime, electrolyte and cathodic deposit. A mechanism of the alloy dissolution was developed. A series of secondary processes took place in the system: precipitation of iron compounds, copper cementation with cobalt and iron; adsorption of copper and cobalt ions on the iron precipitates. Final products were metals of high purity (99.9% Cu, 92% Co).