Accelerated Carbonation of Mine Tailings for Acid Mine Drainage Treatment and Carbon Dioxide Sequestration

The mining industry not only consumes intensive energy and produces large carbon dioxide (CO2) emissions, but also generates significant amounts of mine tailings (MT). As a waste, MT can weather and produce acid mine drainage (AMD) when exposed to oxygen and water. AMD is a serious environmental hazard because of the heavy metals in it, which if not properly managed, may adversely affect the environment and human health. This paper presents an experimental study of accelerated carbonation of MT for treating AMD and sequestering CO2 simultaneously. By first injecting AMD and then injecting CO2 into the MT, the already dissolved Ca, Mg, and Fe in the AMD are simply available for carbonation. Furthermore, the acidic AMD promotes the dissolution of Ca, Mg, and Fe from the MT, adjusts the pH of the MT to a condition ideal for carbonation, and thus enhances carbonation. The generated carbonates, as a binder, also increase the strength of the MT and improve the geotechnical safety of the MT storage facility.