Understanding flotation processes at the atomic scale using density functional theory – A case study on adsorption of 2-Mercaptobenzothiazole on chalcopyrite and pyrite surfaces

Abstract

Detailed understanding of the mechanism of interaction between collector molecules and gold and copper bearing minerals is essential to design novel ligands for enhanced recovery of these precious metals from their ores. Density functional theory calculations reveal that while the (001) and (100) surfaces of chalcopyrite undergo significant reconstruction, only rearrangement of atoms occurs on the (110), (112) and pyrite (100) surfaces. The thione tautomer of the well-known ligand, 2-mercaptobenzothiazole (MBT), adsorbed stronger on both pyrite and chalcopyrite surfaces than the thiol form, consistent with the quantum chemical descriptors such as larger EHOMO, smaller ELUMO and smaller Egap of thione. However, the adsorption of thione was stronger on pyrite due to the formation of Fe-S bonds with both the endo and exo-cyclic sulphur atoms while only one Fe-S exocyclic bond was formed on chalcopyrite. Such differential binding explains the observed selectivity of MBT towards pyrite in flotation. Insights from this work not only aid in understanding the mechanism of interaction of ligands with mineral surfaces, but also provides us a way to rationally design ligands with enhanced efficiency for selective recognition and separation of target minerals.