AN X-RAY PHOTOELECTRON SPECTROSCOPIC INVESTIGATION OF CHALCOPYRITE AND PYRITE SURFACES AFTER CONDITIONING IN SODIUM SULFIDE SOLUTIONS

The effects of sodium sulfide solutions at pH 9.2 on fresh fracture and oxidized fracture surfaces of chalcopyrite and pyrite have been investigated by X-ray photoelectron spectroscopy. At open circuit in the presence of oxygen, the mineral surfaces became enriched in sulfur at each sodium sulfide concentration used. In 3 X 10(-2) mol dm-3 solution, monolayer quantities of elemental sulfur were produced at the surface of pyrite whereas the sulfur-rich surface for chalcopyrite was a metal-deficient extension of the sulfide lattice. Multilayer quantities of elemental sulfur were produced at the surfaces of both minerals in 3 X 10(-3) and 3 x 10(-4) mol dm-3 sulfide solutions; however, for a given sulfide concentration, the coverage for pyrite was greater than that for chalcopyrite. Thick layers of elemental sulfur were deposited on both minerals from 3 x 10(-3) sodium sulfide solution at applied potentials more positive than the open circuit potential.