Observations of Silicates in Both Retarding and Accelerating the Oxidation of Pyritic Sulfide in the Soil Environment

The effects of acidic ground water are a major worldwide problem. Investigations under controlled laboratory conditions can aid in the understanding of factors controlling pH in the wider environment. SEM studies of field samples have shown the surface of pyrite particles covered with smaller clay particles, particularly mica. This armoring phenomenon has been induced in laboratory testing.

Laboratory tests were also done to asses the ability of an alumino-silicate material (chloritic schist) to neutralize acidic leachate from earth with a high sulfidic pyrite content. The chloritic schist used had a significant Fe content. Testing with a layered column showed the material did indeed raise effluent pH compared with control column. In the column where the chloritic schist and the high sulfide material were mixed, some increase in pH, compared with the control column, was observed, but high levels of sulfate were measured in the effluent (compared with levels from the control column and the layered column). This implies increased oxidation of the pyrite.