Carrier-microencapsulation for preventing pyrite oxidation

摘要

The oxidation of pyrite causes the formation of acid mine drainage polluted by heavy metals. This paper proposes carrier-microencapsulation (CME) for preventing pyrite oxidation. In CME, an organic agent is used as an in-situ carrier for transporting Ti from Ti minerals to the pyrite surface through an aqueous phase. Then, the organic carrier is decomposed and Ti(OH)_4 or TiO_2 film is formed on the pyrite surface as a protective coating against oxidation. To demonstrate the effect of CME on pyrite oxidation, shaking-flask leaching experiments of ground pyrite were performed at 298 K in air for 25 days, with or without anatase (TiO_2) and catechol (1,2-dihydroxybenzene) as the organic carrier. The amounts of Fe and S extracted from the pyrite were lower with TiO_2 and catechol than without TiO_2 or catechol, indicating that CME using TiO_2 and catechol is effective in suppressing pyrite oxidation. When TiO_2 and catechol coexist, the Ti concentration in the solution phase increased initially and then decreased. SEM-EDX analysis of the CME-treated pyrite showed that Ti and O are present on the pyrite surface. Cyclic voltammogram of catechol showed that catechol was oxidized on pyrite electrode. These results indicate that Ti is extracted from TiO_2 by catechol as a Ti-catechol complex and that the complex is adsorbed and oxidized on pyrite to form a Ti (OH)_4 or TiO_2 coating suppressing pyrite oxidation.