Galvanic effect of magnetite on electrochemical oxidation of arsenopyrite in acidic culture medium

The galvanic interaction of arsenopyrite—magnetite in acidic culture medium was investigated by electro- chemical measurements, X-ray photoelectron spectroscopy characterization and leaching experiments. The results indicated that the rest potential of magnetite was 321 mV, which was more anodic than 223 mV of arsenopyrite, and the galvanic current was 7.40 µA, verifying the existence of the galvanic interaction between arsenopyrite and magnetite. The galvanic potential and polarization curves suggested that the redox behaviors of arsenopyrite dominated the overall galvanic interaction. The galvanic interaction enhanced the electrochemical dissolution of arsenopyrite with the generation of more oxidation products (S⁰, SO₃^2—, SO₄^2— and AsO₃^3—) on arsenopyrite and an increase in the chemical reactivity of the surface. Leaching experiments of 6 days showed that the presence of magnetite improved the arsenic release from arsenopyrite by 30 mg/L, and further confirmed the enhanced oxidation of arsenopyrite when coupled with magnetite.