Bioleaching of ultramafic tailings by acidithiobacillus spp. for CO2 sequestration.

Bioleaching experiments using various acid-generating substances, i.e., metal sulfides and elemental sulfur, were conducted to demonstrate the accelerated dissolution of chrysotile tailings collected from an asbestos mine near Clinton Creek, Yukon, Canada. Columns, possessing an acid-generating substance colonized with Acidithiobacillus sp., produced leachates with magnesium concentrations that were an order of magnitude greater than mine site waters or control column leachates. In addition, chrysotile tailings were efficient at neutralizing acidity, which resulted in the immobilization of metals (Fe, Cu, Zn) associated with the metal sulfide mine tailings that were used to generate acid. This suggests that tailings from acid mine drainage environments may be utilized to enhance chrysotile dissolution without polluting "downstream" ecosystems. These results demonstrate that the addition of an acid-generating substance in conjunction with a microbial catalyst can significantly enhance the release of magnesium ions, which are then available for the precipitation of carbonate minerals. This process, as part of a carbon dioxide sequestration program, has implications for reducing net greenhouse gas emissions in the mining industry.