The nature of the reaction between Ag+ and pyrite in 0.25 M H2SO4 solutions has been investigated in order to determine whether Ag+ can enhance the ferric sulfate leaching of this mineral. Analysis of reacted pyrite particles using scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), and low-angle X-ray diffraction (XRD) indicates that elemental silver and elemental sulfur are the primary surface species formed by this interaction. Rest potential measurements of a pyrite electrode immersed in a solution containing 10-2 M Ag+ are also consistent with what is expected for the deposition of metallic silver. Furthermore, the XRD data reveal that, at the most, only minor amounts of Ag2S are being produced. The presence of Ag2O has also been detected, but this is due to oxidation of silver after the experiment is complete and while the particles are being transferred for surface analysis. When 1 M ferric sulfate is contacted with pyrite which has been pretreated in a AgNO3 solution, most of the silver immediately redissolves and does not redeposit while ferric ions are present. This indicates that the kinetics of the transfer reaction between Ag+ and pyrite is slower than the reaction between Fe3+ and pyrite and suggests that Ag+ does not likely enhance the ferric sulfate leaching.
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