Suppression of Pyrite Oxidation by Carrier Microencapsulation Using Silicon and Catechol

Abstract

Acid mine drainage (AMD) is formed from the natural oxidation of sulfide minerals such as pyrite and FeS₂. Prevention of AMD is very important and several techniques are currently being investigated for the treatment and abatement of AMD. This paper proposes carrier-microencapsulation (CME) using Si–catechol complex – for preventing pyrite oxidation. In CME, the water soluble organic carrier, catechol, and metal ion, Si, make a complex, e.g., tris-catecholato complex of Si⁴⁺, which oxidatively decomposes on pyrite surface and forms a stable oxide or hydroxide, e.g., Si(OH)₄ or SiO₂ layer on the pyrite surface as a protective coating against pyrite oxidation. To demonstrate the effect of CME using on pyrite oxidation, shaking flask leaching experiments of pyrite without and with CME treatment were performed. Significant halt in pH drop was observed after the CME treatment of pyrite. The CME coating was found very effective even at low concentration of 1 and 5 mol m⁻³. The amount of Fe and S leached were lower from the pyrite with CME treatment than without CME treatment, indicating that CME using Si and catechol is effective in suppressing pyrite oxidation. The effect of pH and presence of microorganism were also evaluated. The CME coating was found very effective even in acidic pH range. The CME treatment suppressed pyrite oxidation even in the presence of iron oxidizing microorganism. Presence of Si and O on the residue pyrite surface in energy-dispersive X-ray spectroscopy analysis supported the sustainability of CME coating at acidic pH.

Keywords:

• acid mine drainage
• carrier micro encapsulation
• pyrite oxidation