Abstract
Underground backfilling allows for effective disposal of mine waste, however the backfill must also be able to withstand a certain load, since in most cases it is used as an underground construction material, such as in cut-and-fill mining methods. Therefore, the composition of the mill tailings must be such that when combined with a binding agent and pumped underground, the slurry or paste is then able to withstand specific loads within a certain period of time. High-pyrrhotite content tailings are commonly found at mine sites in Ontario and Quebec. The high-pyrrhotite tailings are reactive and can easily oxidize and produce acidity and/or metal-laden drainage under some disposal conditions. This means that the pyrrhotite in the tailings can lead to acid mine drainage if stored on surface, however it can also cause strength degradation if used in too high a concentration in underground mine backfill. Bioleaching processes can be used in an attempt to neutralize the tailings to reduce the strength degradation. These bioleaching processes can provide another benefit by transforming the mine waste from environmental hazard to economic opportunity, since the tailings may contain significant metal values. CanmetMINING developed a novel stirred-tank bioleaching process for recovering nickel and cobalt (both critical for vehicle electrification) that incorporates partial neutralization and iron removal in the bioleaching circuit; bench-scale tests resulted in excellent Ni and Co recovery over a range of temperatures. The resulting process residue contains a significant proportion of jarosite, which can be problematic for long-term disposal. This presentation reports on research designed to evaluate different options for disposal of the high-jarosite residue into a suitable underground mine backfill material.