Electrochemical study of arsenopyrite weathering

Abstract

Cyclic voltammograms and capacitance measurements are presented to characterize the mineral response at relatively moderate environmental conditions, pH 4.5 and T ¼ 25 C. The experiments involve examining the rates of oxidation and the surface morphology of arsenopyrite, which is oxidized abiotically. The semiconducting properties of the mineral have been investigated in attempt to gain additional information of FeAsS dissolution behavior in acidic solutions at potentials close to the open circuit potential of the mineral. A mechanistic pathway for the anodic dissolution of arsenopyrite in open circuit conditions is also suggested. At high overpotentials, anodic reactions produce mainly sulfate and arsenate ions and may be described as hole limited. The reduction of orpiment-like compounds at potentials more negative than the open circuit potential is discussed.

Dissolution of pyrite and other Fe–S–As minerals using deep eutectic solvents

“…There have been numerous studies which have described the electrochemical behaviour of metal sulfides in aqueous media, in addition to the effect of pH and temperature. [17][18][19][20][21][22] These studies demonstrate that the major products of oxidation of pyrite in aqueous solution are sulfate and ferrous ions, whilst other products are elemental sulfur, polysulfide, hydrogen sulfide, ferric hydroxide, iron oxide and iron(III). 23,24 In another study, the reduction of pyrite in aqueous solution produces FeS, S 2− and hydrogen.…”

“…Almeida and Giannetti studied arsenopyrite by mixing it with carbon powder and making it into an electrode and electrochemically oxidising it in an aqueous acetate buffer solution. 32 A relatively poorly resolved voltammogram was obtained which contained most of the redox processes shown in Fig. 7d.…”

Chemical and surface analysis during evolution of arsenopyrite oxidation by Acidithiobacillus thiooxidans in the presence and absence of supplementary arsenic

“…1b) and SEM-EDS (Fig. 3b) studies, as well as reports in the literature (Almeida and Giannetti, 2003). Accordingly, the signal augmentation of C1 and C2 during eMAE voltammetric analysis (Fig.…”

Carbon paste electrodes in the new millennium

“…In the case of carbon pastes, the most typical configuration is a carbon paste electroactive electrode (CPEE [17] [189,190], including mixtures with other oxides [191] or traces of toxic heavy metals [192]; (ii) metal-and metalloid sulphides: ZnS [193][194][195], PbS [196,197], CuFeS 2 [198], α-HgS and β-HgS [199], As 2 S 3 , As 4 S 4 , and FeAsS [197,200], or As III -and As V -contaminated soils [201], including a study with a series of sulphides [202] focused on more theoretical aspects of dissolution processes, including the individual redox-and phase transformations. Finally, the CPEE configuration has been employed to investigate (iii) other materials such as ground ores sampled in a mine [203], dried green sea-weed (as bio-sorbent [204]), Na-nitroprusside (analytical reagent [205]), solid derivatives of 9, 10-anthraquinones [206], or non-toxic thiadiazoles, whose electro-inhibiting capabilities could be utilised in corrosion studies of ancient bronze patina [207].…”