Abstract:Oxidation of arsenopyrite with Acidithiobacillus ferrooxidans was studied. The electrochemical results show that arsenopyrite is firstly oxidized to As₂S₂ at the potential of 0.2−0.3 V (vs SHE) and As₂S₂ covers the electrode and retards the process continuously. While at higher potential over 0.3 V (vs SHE), As₂S₂ is oxidized to H₃AsO₃, and H₃AsO₃ is then oxidized to H₃AsO₄ at 0.8 V (vs SHE). The leaching results show that the addition of FeS₂ can promote the oxidation of As³⁺ to As⁵⁺ and increase the activity of the bacteria. The best bio-oxidation technical parameters are the initial pH of 1.8−2.0, particle sizes less than 0.074 mm, temperature in the range of 25−30 ℃ and rotating speed of the orbital incubator of 100−160 r/min. The results provide theoretical and technological supports of bio-oxidation arsenopyrite for pretreating refractory arsenic gold ores.

Key words: arsenopyrite; electrochemistry; bio-oxidation; Acidithiobacillus ferrooxidans