Phase distribution and release of heavy metal in pyrite using sequential extraction procedure and diffuse reflectance Fourier transform infrared Spectroscopy

Phase distributions of heavy metals in pyrite were analyzed by inductively coupled plasma mass spectrum with sequential extraction procedure. The result showed that Pb was the main heavy metal in pyrite and its total content was 830 mg/kg. Pb of exchangeable state by acid existed mostly in galena (PbS) or carbonate phase of pyrite and this proportion was 56. 9%, Pb of reducible state existed in iron oxides by 29. 7% in proportion, Pb of oxidable and residual state existed in sulfide and silicate by 3. 5% and 9. 9% respectively. The release of Pb in pyrite was primary, but the release of Cr and Cd should not be neglected. The surface reaction in pyrite was investigated by the diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and it was found that the surface hydroxyls in pyrite were strengthened in the process of surface oxidation; moreover, the surface dissolution and surface acidification were existed. A release mechanism of heavy metal was proposed that the dissolution-adsorption equilibrium occurred, and further the equilibrium was under the control of both surface oxidation in pyrite and neutralization reaction by carbonate, and finally induced heavy metal release and migration.