Flotability of galena and pyrite using 2-mercaptobenzimidazole as a chelating agent: Adsorption characteristics and flotation mechanisms

Selective separation of pyrite and galena using 2-mercaptobenzimidazole (MBI) as a chelating collector, was investigated by flotation , scanning electron microscope (SEM), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Single-mineral flotation showed a significant flotability of pyrite at pH = 2–4 and galena at pH = 8–10 in the presence of MBI. The depressant effect of pyrite was observed to be more pronounced under alkaline conditions. Artificially mixed minerals flotation suggested the galena-pyrite could be separated under alkaline conditions, especially at pH = 10. SEM analysis indicates that the adsorption of MBI on galena surface is more intense than pyrite. However, the interaction between MBI and pyrite is stronger than that of MBI-galena. FT-IR analysis shows the iron and lead ions may chelate with -N = and -SH groups of MBI. Pyrite contains more iron hydroxide (or sulfate forms) in solution from XPS analysis, only half of the metallic ions on the surface function as active sites, thus reducing the amount of metal that can be chelated with MBI. DFT calculations revealed that MBI was often in the molecular form under acidic mediums and the ionic form under alkaline condition, while the ionic form of MBI was more active.