Waste Glycerol Addition to Reduce AMD Production in Unsaturated Mine Tailings

Abstract

A 20 month long column study was conducted to evaluate the surface application of waste glycerol (WG) to reduce release of acid mine drainage constituents from mine tailings. Beneficial characteristics of the WG include high aqueous solubility, high organic content, and high alkalinity. Four columns were packed with fine-grained sulfide rich tailings and incubated in the field under ambient temperature and precipitation conditions. In the two replicate untreated control columns, diffusion of oxygen into the tailings resulted in large increases in dissolved iron, sulfate, manganese, magnesium, aluminum, zinc, and hot acidity with an associated drop in pH. In the two replicate treated columns, WG was blended into the top 0.18 m of tailings 7 months after the columns were established, resulting in large reductions in iron, sulfate, hot acidity, aluminum, copper, and manganese. Observed pollutant reductions resulted from a combination of processes including: (a) neutralization of acidity by the KOH present in the WG (b) reduction of SO4 to H2S with subsequent precipitation of dissolved metals, and potentially (c) consumption of oxygen, slowing oxidation of the tailings.