The electrochemical behavior of arsenopyrite (FeAsS) electrodes in alkaline cyanide solutions has been investigated in an attempt to gain a better understanding of its dissolution chemistry. Surface oxidation reactions of arsenopyrite have been studied using cyclic voltammetry for pH values between 8.1 and 12.0 and for cyanide concentration from 10-4 to 10-2 M. Anodic oxidation of FeAsS appears to be sensitive to both pH and cyanide, as indicated by a characteristic peak at 0.30 V vs SHE for pH 11.3 and 10-2 M CN-. The anodic process corresponding to the main peak is described by the reaction: FeAsS + 9H2O = FeOOH + H2AsO3 - + SO4 2- + 15H+ + 12 e - The oxidation of the H2AsO3 -to HAsO4 2- is detected by a second wave at higher potentials under quiescent conditions. At high pH, the main peak is insensitive to the presence of cyanide, whereas at low-alkalinity this peak is sensitive to cyanide.
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