Geochemical modelling of coupled sulfide–silicate systems during sulfuric acid leaching of Ni-, Co-, and Mn-bearing minerals

Abstract The increasing demand for critical metals such as nickel (Ni), cobalt (Co), and manganese (Mn) has highlighted the need for efficient hydrometallurgical recovery from low-grade sulfide resources and mine wastes. Although sulfuric acid leaching is widely used for metal extraction, the coupled geochemical behaviour of sulfide and silicate minerals during leaching remains poorly understood. This study developed and demonstrated a reaction-path geochemical modelling framework using The Geochemist’s Workbench (GWB) for evaluating coupled sulfide-silicate systems during sulfuric acid leaching, using heazlewoodite (Ni 3 S 2 ), alabandite (MnS), and linnaeite (Co 3 S 4 ) in association with chrysotile, forsterite, brucite, and enstatite as representative mineral assemblages. The framework integrates mineral stability analysis, aqueous metal evolution, speciation modelling, and saturation index evaluation over a pH range of approximately 9 to 0. The modelling revealed that the thermodynamic stability sequence, Alabandite < Heazlewoodite < Linnaeite, governs the dissolution sequence of Mn → Ni → Co, while Mg-bearing silicate minerals preferentially consume acidity and delay sulfide dissolution. These results provide a thermodynamic explanation for the experimentally observed early release of Mg, delayed Ni mobilization, and the comparatively refractory behaviour of Co during sulfuric acid leaching. Comparison with published and previous experimental studies showed good qualitative agreement with the predicted mineral stability and metal release behaviour. These findings improve the understanding of coupled sulfide–silicate interactions and provide thermodynamic insights that may inform future sulfuric acid leaching and critical metal recovery studies involving low-grade ores and mine tailings. More broadly, the framework demonstrates how coupled sulfide-silicate interactions can be systematically evaluated in whole-ore systems, providing a transferable methodology for investigating acid consumption, metal release, and mineral stability during hydrometallurgical process development.