Development of silica protective layer on pyrite surface: a column study.

An appealing technique to prevent and/or minimize pyrite oxidation and subsequent acid generation in mine waste sites is the formation of a protective coating on the surface of sulfide grains. To investigate the conditions for the formation of an efficient coating on pyritic tailings, column tests were performed. These tests involved the treatment with a coating solution, which was continuously recycled through the packed bed of tailings. The coating solution was consisted of SiO4-4 oxyanions, an oxidant (H2O2), and adjusted to pH 6. The effect of the volume of coating solution per mass of material (L/S ratio), Si concentration and treatment duration on coating formation was studied. Based on the results, a protective coating can be developed on the pyrite particles following treatment with a solution of 0.1 mM Si concentration, which resulted in the reduction of sulfate release by 84% compared to non-treated pyrite samples.