Reprocessing of the Cantung Mine Tailings
flotation , tailings , reprocessing , desulphurization , chalcopyrite , scheelite , copper , tungsten , sulphur
Tailings, a waste product generated from the processing of ore, constitute a large, long-lasting portion of a mine’s environmental footprint. The Cantung Mine, located in Northwest Territories, Canada, is a defunct mine with over 4 million tonnes of tailings. The tailings contain sulphide minerals, which can oxidize and produce acid rock drainage if left in their current state. Due to the mine’s proximity to the Flat River, any acid rock drainage produced by the tailings has the potential to impact the surrounding environment. This thesis investigates methods to reprocess and separate the Cantung tailings into two distinct fractions: a high-mass fraction of tailings that are not acid generating and an acid-generating low-mass concentrate containing sulphide minerals that can be handled and stored separately. By separating the mine’s tailings, benign waste might be filtered and stored in dry-stacks, reducing the environmental and structural risks posed by sub-aqueous tailings storage units. Mineralogical work determined that pyrrhotite was the main sulphide mineral present in the tailings. Scoping level flotation tests determined that the reagents sodium isopropyl xanthate, sodium hexametaphosphate, and Aero 6493 had the greatest influence on flotation results. A Box-Behnken experimental design was conducted to optimize the flowsheet. Grinding, magnetic separation, and flotation were employed to recover up to 86.5% of the total sulphur in a concentrate weighing 29.8% of the initial mass. The low-sulphide tailings contained 1.96% sulphur, which would reduce the impact of acid rock drainage if implemented. Analysis of the low-sulphide tailings determined that the remaining sulphur was primarily found in the -38 micron fraction, which is difficult to recover by flotation. Preliminary flotation tests were completed in an attempt to recover copper and tungsten in the tailings not recovered during the mine’s operation. Both metals were unable to be recovered at high grades, with further research required to determine appropriate recovery methods. The findings of this thesis demonstrate the effectiveness of reprocessing mine waste from the Cantung Mine to reduce the potential of future environmental impacts.