Enhancement of arsenopyrite oxidation by pyrite through changing composition and structure of passivation layer

Abstract

Avoiding the formation of a passivation layer comprising intermediate products and secondary minerals is a principal challenge in preoxidizing arsenical gold ores. Due to the similar crystal, pyrite (Py) always coexists with arsenopyrite (Ap) and effects the oxidation, although its mechanism needs to be improved. Therefore, this study focuses on a mixed leaching system involving Py and Ap. The effects of refactoring the passivation layer structure through Ap oxidation using Py under various pH conditions is systematically investigated. The role of Py in the formation and regulation of the Ap passivation layer is clarified using advanced characterization techniques. The study results indicate that Py decreased the pH, causing the ferric arsenate in the passivation layer of Ap oxidation to become soluble. Furthermore, the addition of Py decreased the jarosite content in the passivation layer. These reconstruction effects of Py on the passivation layer of the Ap surface considerably enhanced Ap oxidation. The highest level of arsenic dissolution (821.43 mg/L) was observed at the mass ratio of Py and Ap at 2 (Py/Ap = 2), representing an obvious increase compared to the control group (520.96 mg/L). This study focuses on the reconstruction of the passivation layer by Py, and further elucidates the role of Py in enhancing Ap oxidation during the pretreatment of arsenical gold ores, thereby advancing our understanding of the interaction rules between gold-bearing minerals of arsenical gold ores.

Keywords

Arsenopyrite / Pyrite / Passivation layer / Preoxidation / Gold ores dearsenization

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