Silicate micro-encapsulation of pyrite

CIM Bulletin, Vol. 95, No. 1063, 2002

K. Fytas and P. Bousquet

Acid mine drainage (AMD) is a serious environmental problem that preoccupies the Canadian mining industry. Considerable amounts of money are spent every year in an effort to prevent or reduce the acid mine drainage phenomenon. AMD occurs when sulphide minerals (e.g., pyrite) contained in rock are exposed to air and water and subsequently oxidize to produce low pH water. This acid effluent has the potential to mobilize any heavy metals contained in the rock. Coating the sulphide minerals with silicates is a new promising technology to reduce AMD. Pyrite is treated with a solution containing H2O2, sodium silicate and a buffering agent. H2O2 oxidizes a small part of pyrite producing ferric iron (Fe3+) ions. These ions subsequently react with the silicate ions to produce ferric hydroxide-silica that precipitates on the pyrite surface producing a passive coating. This silicate coating can protect the grains of pyrite from oxidation. This paper presents a series of experiments that confirm that silicate coating can considerably reduce AMD.
Keywords: Acid mine drainage, Silicates, Tailings, Leaching, Oxidation.