The interaction of aqueous silver species with sulphur-containing minerals as studied by XPS, AES, SEM, and electrochemistry

Abstract

The interaction of aqueous silver ions with pyrite, galena, and sphalerite and of silver chloride complexes with pyrite and galena has been investigated using X-ray photoelectron and Auger electron spectroscopies, scanning electron microscopy, and open circuit potentials. For the interactions with silver ions, silver sulphide was observed as the first surface product on all mineral surfaces. At longer reaction times, the occurrence of polysulphide species and metallic silver was also observed. For interactions of the aqueous silver chloride complexes with galena, the same surface products were observed as in the chloride-free system, with the amount of total silver present on the surface increasing with increasing chloride ion concentration. In the case of pyrite, the uptake of silver by the mineral decreases at elevated concentrations of chloride which causes a decrease in the concentration of total free silver ion in solution. Differences in reactions of the minerals with silver species in solution are attributed to the differences in the change in the oxidation state of sulphur. In galena and sphalerite, no change in oxidation state of sulphur occurs on dissolution, while S− in pyrite forms S2−.