Silicate Coating on Pyrite to Prevent Acid Mine Drainage

2001

Pierre Bousquet,

Acid Mine Drainage (AMD) is the most serious environmental problem facing the Canadian Mineral Industry today. Acid Mine Drainage results from oxidation of sulfide minerals (eg. pyrite or pyrrhotite) contained in mine waste or tailings. It is characterised by low pH values and high concentrations of dissolved heavy metals and anions (such as SO42-). A new AMD remediation technology has recently been developed by which sulfide mineral particles of pyrite are coated with ferric hydroxide-silica coating that could prevent either O2 and Fe3+ from further oxidizing pyrite. The coating process involves reacting pyrite with soluble silicate in the presence of low concentrations of an oxidizer (such as H2O2 or hypochlorite). This ferric hydroxide-silica coating seems to inhibit pyrite oxidation under acid conditions. This paper presents the results of an investigation on the feasibility of ferric oxyhydroxide -silica coatings on pyrite contained in mine tailings from a Canadian mine. The eventual application of this technology by Canadian mining companies could result in significant savings on environmental protection costs.

Keywords: Pyrite, Mine drainage, Sulfides, Tailings, Silicate coating