The surface of enargite after exposure to acidic ferric solutions: an XPS/XAES study

Abstract

Enargite surface reactivity in acidic ferric solutions simulating the acid mine drainage (AMD) environment has been investigated by X-ray photoelectron (XPS) and X-ray excited Auger electron spectroscopy (XAES) surface analysis. Natural enargite samples from a Peruvian mine with close to the nominal composition Based also on the quantitative XPS determinations, the surface of the reacted enargite can be described as a layered structure: a thin copper-deficient enargite layer (up to 0.7 nm) is formed on a slightly sulfurenriched enargite surface, the arsenic content remaining constant.

The oxidative dissolution of arsenopyrite (FeAsS) and enargite (Cu3AsS4) by Leptospirillum ferrooxidans

“…Data points for the four week abiotic control sample and for all samples incubated with cells of L. ferrooxidans fall on a line with an Auger parameter close to 1263 eV, similar to arsenic oxide compounds reported by Wagner et al (1979). Enargite data points all fall on an Auger line close to 1267 eV, similar to arsenide compounds and enargite samples reported by Fantauzzi et al (2006Fantauzzi et al ( , 2007. This indicates that oxidation of arsenopyrite at four weeks in the abiotic control is sufficient to create a shift in the Auger parameter from arsenide to arsenic oxide, and that oxidation by L. ferrooxidans demonstrates an arsenic oxide chemical state.…”

Copper isotope fractionation in acid mine drainage

“…For example, published results from X-ray photoelectron spectroscopy and SEM show that when oxidatively dissolved in acidic ferric solutions, chalcopyrite develops a leach layer that is deficient in Cu and enriched in sulfate (as a jarosite-like phase) Klauber, 2008), disulfide (S 2À ) (Klauber et al, 2001;Parker et al, 2003), and/or S 0 (Rimstidt et al, 1994;Klauber et al, 2001;Parker et al, 2003;Klauber, 2008). Freshly cleaved enargite surfaces exposed to acidic ferric solution also develop a Cu-deficient layer (Fantauzzi et al, 2007).…”

Exploiting XPS for the identification of sulfides and polysulfides

“…Sulfur speciation is of crucial importance for studies on portable storage devices (rechargeable Li-S batteries), [1][2][3] on mineral processing and oxidation processes, 4,5 on tribology, 6,7 on sorbents for desulfurization 8 and on corrosion phenomena. 9 Authors have been involved over the last decade in research on arsenic bearing sulde minerals oxidation [10][11][12][13][14] and biooxidation and particular attention was devoted to the investigation of the surface alteration of the minerals by means of surface analytical techniques (XPS and XAES) in order to clarify the mechanism of oxidative dissolution especially for enargite. In fact, it is acknowledged, that different sulde minerals follow different bio-oxidation paths.…”