Investigation on solvometallurgical processes for extraction of metals from sulfides

Copper, nickel, iron, zinc, lead, and molybdenum are among the important metals commonly found as sulfide minerals in nature. Some of these metals are also found as sulfides in intermediate products like matte and mixed sulfide precipitates (MSP). The extraction processes of these metals from their sulfide forms through either pyrometallurgy or hydrometallurgy encounter various challenges. This study aimed to explore the viability of solvometallurgical processes (solvoleaching) as potential alternatives for the extraction of these metals from their sulfides (CuS, Ni₃S₂, FeS, ZnS, PbS and MoS₂). The solvometallurgical processes employed a range of solvoleaching systems, such as D2EHPA+MnO₂+H₂O, ammoniacal solvoleaching comprising of LIX 84-I+NH₄OH+H₂O₂, HCl-equilibrated TBP (TBP-HCl) and EG (ethylene glycol)-based solvents containing each of HCl, FeCl₃, ChCl and NH₄Cl. The solvoleaching mechanism of the metal sulfides in each solvoleaching system was discussed. The results were corroborated with thermodynamic tools like Eh-pH diagrams, Gibbs free energy change, and solvation properties of the metal ions, as well as the hard and soft acid-base (HSAB) theory. Analyses of the resulting leach solutions, utilizing suitable analytical techniques such as UV–Vis spectroscopy and FTIR, provided additional support for the results. A comparison made between the solvoleaching and classical aqueous leaching, showing comparable results, indicated the viability of solvoleaching processes as alternatives for the sustainable extraction of these metals from their sulfides.