The Deposition of Sulfur on Pyrite and Chalcopyrite From Sodium Sulfide Solutions

Abstract

The deposition of sulfur from oxygenated sodium sulfide solutions on to fracture surfaces of massive natural pyrite from two different locations has been studied by X-ray photoelectron spectroscopy. For both samples an overlayer of elemental sulfur was formed from sulfide concentrations between 10^-5 and 5×10^-2 mol dm^-3 with a maximum near 10^-2   mol dm^-3; the decrease in sulfur coverage at the higher concentrations is accounted for by polysulfide formation. However, under the same conditions, the sulfur coverage on pyrite from Spain was double that on pyrite from Elba. Although the two minerals contain different levels of trace elements, it was not possible to identify the cause of the difference in behaviour. The incorporation of copper into the surface of the Spanish pyrite decreased the sulfur coverage by a factor of two, indicating that foreign atoms can have a significant effect. The sulfur layer formed on chalcopyrite after immersion in sodium sulfide solutions was about half that on Spanish pyrite treated simultaneously. The significance of these findings to the selective collectorless flotation of chalcopyrite/pyrite ores is discussed.