Electrochemical oxidation of arsenopyrite in acidic media

Oxidation of arsenopyrite and deposition of gold on the oxidized surfaces: A scanning probe microscopy, tunneling spectroscopy and XPS study

“…Two weak cathodic maxima at approximately 0.15 and À0.25 V, and a current surge at potentials more negative than À0.3 V are observed on the negative-going sweep; the charge associated with the reduction is much less than that passed in the electrooxidation processes. Similar data have previously been acquired at different arsenopyrite electrodes (Kostina and Chernyak, 1976;Cruz et al, 1997;Lázaro et al, 1997;Lin and Zheng, 1997;Costa et al, 2002); they are consistent with the idea that a passivating layer decomposes at high enough overpotentials, thereby accelerating the oxidation of underlying mineral. In the second cycle, the surges of cathodic and anodic currents are shifted to more negative and more positive potentials, respectively, extending the passivity region; the cathodic maximum arising at about +0.4 V is due to the reduction of Fe(III) species.…”

“…The mechanisms of relevant reactions are still insufficiently understood, particularly because the processes in aqueous media, usually electrochemical in nature, are deeply complicated by semiconducting properties of sulfide minerals, so the interfacial transfer of electrons and the transport of charge carriers between different sites at which the various reactions occur are critically dependent upon the precise composition and local characteristics of the appropriate spatial regions (Rimstidt and Vaughan, 2003). The electrochemical oxidation of arsenopyrite occurs in two steps associated with passivation at moderate positive potentials and ''transpassive'' behavior at higher ones (Kostina and Chernyak, 1976;Cruz et al, 1997;Lázaro et al, 1997;Lin and Zheng, 1997;Costa et al, 2002). Lin and Zheng (1997) proposed that the dissolution of arsenopyrite in acidic chloride solutions is retarded by elemental sulfur that is oxidized to sulfate at the second step.…”

Pretreatment of a refractory arsenopyritic gold ore using hydroxyl ion

“…2 shows a typical electrochemical response of pure arsenopyrite mineral without pretreatment, the sweep potential was initiated from the open circuit potential (OCP) in the anodic direction, with a sweep rate of 20 mV/s. Diverse voltammetric studies reported in the literature found that electro-oxidation of arsenopyrite in acidic medium takes place in two stages (Nava and González, 2007;Cruz et al, 2005;Lázaro et al, 1997). Initially, arsenopyrite is oxidized to realgar (As 2 S 2 ) and Fe (II) (A); after these species are interfacially formed, the second stage of the process begins (B): Fe (II) is oxidized to Fe (III).…”

Pb–Zn–Cd–As Pollution in Soils Affected by Mining Activities in Central and Southern Spain: A Scattered Legacy Posing Potential Environmental and Health Concerns

“…239 Arsenopyrite is present in many Pb-Zn deposits (e.g., the Mazarrón district), 240 and therefore it is worth showing here how the oxidation of this mineral occurs 241 [32] (8-11):…”