Environmental desulfurization of mine tailings using froth flotation: The case of Amaruq Mine (Nunavut, Canada);

This research examined the the desulfurization of tailings from the Amaruq mine at a laboratory scale using froth flotation. Optimization of the flotation process was carried out by testing the conventional potassium amyl-xanthate collector (PAX) and three alternative collectors from the mercaptobenzothiazole (MBT) and dithiophosphate (DTP) families. The main goal was to assess the efficiency of the desulfurization process as a sustainable tailings management approach to prevent contaminated mine drainage generation. Mineralogical characterization of the Amaruq tailings using automated scanning microscopy (QEMSCAN®) revealed that the total sulfide and carbonate contents were about 8 wt% and 3 wt%, respectively; 63.39 % of the sulfur occurred as pyrrhotite, 30.17 % as pyrite, 3.63 % as gersdorffite, and 2.61 % as arsenopyrite. To compare the collector flotation yields, response surface methodology (RSM) was used for statistical design, analysis, and modelling of froth flotation experiments using three key-parameters: pH, activator (CuSO4) dosage, and collector dosage. Four quadratic mathematical models were developed for each collector to calculate sulfide recovery. Variance analysis (ANOVA) revealed that the factors that most affected sulfide recovery were collector type/dosage and pH. Process optimization yielded a maximum sulfide recovery of 96.73 % using 300 g/t PAX and 300 g/t CuSO4 at pH 11. A similar recovery of 95.83 % was achieved using an MBT-MTP based collector under the same conditions. The maximum recovery obtained using MTP and MTP-DTP based collectors while operating at optimal conditions (alkaline pH and maximum collector dosage at 350 g/t) was 88.65 %. The desulfurization process succeeded in decreasing the sulfur content in the tailings to<0.11 wt%. The final tailings were not acid-forming, as confirmed by the acid-base accounting (ABA) and net acid generation (NAG) static tests, compared to the highly acid-forming feed samples. Kinetic testing on the benign desulfurized tailings was also performed to predict and validate their acid generating potential, as well as their contaminant release rates (particularly As, Ni, Cu, Fe, and Zn). The Amaruq desulfurized material did not present any significant risk of contaminated mine drainage generation, and the leached contaminants did not exceed the criteria set by Quebec provincial legislation.

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