Abstract
The mineralogical characteristics of Copperbelt ores undergo continuous stratigraphic changes due to ongoing mining activities and weathering changes. These variabilities in mineralogy lead to drastically different behaviors in hydrometallurgical processing during the recovery of Cu and Co. Consequently, the technologies currently used in several hydrometallurgical industries have demonstrated their limitation in the effective processing of these ores. This paper focuses on the thermodynamic approach to assess the possibility of extracting Co and Cu from a mixture of ores characterized by Cu-Co oxide and Cu sulfide streams. To achieve the purpose of this investigation, the first phase consisted of thermodynamic predictions, while the second focused on experimental analysis. The thermodynamic feasibility of simultaneous Co and Cu extraction was assessed using potential-pH predominance and speciation diagrams of an actual leaching system. Thermodynamic calculations were used to construct Eh-pH and species distribution diagrams for the Co-Cu-Fe-SO42--H2O system under standard leaching conditions. Software tools such as Hydra-Medusa, HSC Chemistry, Phreeqc, and Geochemist's Workbench were employed to calculate thermodynamic equilibria. The redox behavior of Fe species at pH 1.5 was also investigated to account for the chemistry and potential mechanisms of minerals during the leaching of the mixed system. Results revealed that experiments conducted under a free and average redox potential of 440 mV, pH of 1.5, solid percentage of 10%, stirring speed of 600 rpm, and temperature of 50 degrees C for 2 h led to a leaching efficiency of 86 and 70% Co and Cu, respectively. The dissolution of Co and Cu in the mixed system was promoted by the impact of chemical reactions involving the contribution of H+, HSO4-, and H2SO4, as well as redox reactions involving the Fe2+/Fe3+ redox couple and the galvanic interactions between oxidized and sulfidic minerals.