Redox reactions of arsenopyrite in aqueous electrolyte solutions

The state of the arsenopyrite (FeAsS) surface in aqueous electrolyte solutions was studied by cyclic voltammetry and with the rotating disk electrode. It could be concluded when comparing the experimental steady-state potentials established at arsenopyrite in solutions of different pH with the mineral's phase diagram that a protective film is formed at the FeAsS surface which protects the mineral against further oxidation. In acidic solutions this film consists of elemental sulfur alone, while in neutral and alkaline solutions iron hydroxide also is present in it. The degree of dispersion of the mineral has no effect on surface film composition or on the position of the cathodic maxima in the I vs E curves of arsenopyrite.