Reactions of aqueous Au (super 1+) sulfide species with pyrite as a function of pH and temperature

The reactivity of aqueous Au 1+ sulfides with FeS 2 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 Au 1+ and metallic Au are observed upon the FeS 2 surface. We show that Au deposition is increased at elevated pH or temperature; but the amount of Au deposited is far lower than in AuCl⁻ 4 solutions owing to the greater stability of Au(SH) 1-x x complexes. This is the first evidence of Au 1+ on pyrite from bisulfide solutions using XPS.