Reactions of aqueous Au1+ sulfide species with pyrite as a function of pH and temperature

The reactivity of aqueous Au1+ sulfides with FeS2 at pH = 3 and 6 for temperatures of 25 and 90°C has been investigated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDXA), and static secondary ion mass spectrometry (SSIMS). The presence of both Au1+ and metallic Au are observed upon the FeS2 surface. We show that Au deposition is increased at elevated pH or temperature; but the amount of Au deposited is far lower than in AuCl4- solutions owing to the greater stability of Au(SH)1-xx complexes. This is the first evidence of Au1+ on pyrite from bisulfide solutions using XPS.