• Low sulfide tailings were characterized to assess factors influencing As mobility. • The effect of salinity and particle size on As mobility from tailings was evaluated. • As was mainly associated with fine particles (<20 µm) of loellingite. • High salinity had limited effect on As mobility from loellingite-containing tailings. • Knelson separation was effective in concentrating 46% of As in concentrates. The geochemical and geotechnical stability of low sulfide filtered tailings (LFT) is enhanced relative to conventional slurry tailings. However, the residual occurrence of sulfides and sulfosalts can still generate As-rich neutral mine drainage (As-NMD). This study aimed to identify the sources of As mobility from LFT produced by an active gold mine in northern Québec, Canada, and then evaluate the performance of integrated management options as alternatives to restoration covers. The effects of water salinity and particle size on the mobility of As were evaluated using weathering cells over a 4-month period. Preliminary gravity separation tests using a lab-scale Knelson concentrator and prewashing steps were also conducted to evaluate their efficiencies to decrease As-NMD generation. Results showed that As was primarily associated with loellingite (0.04% − w/w) and, to a lesser extent, arsenopyrite (0.004% − w/w), with 75% of total As present in the fine particles (< 20 µm). Chloride (2,000‒2,500 mg/L) and sulfate (3,300–3,500 mg/L) salinity did not enhance As mobility under the conditions tested, which is inconsistent with previously reported findings on arsenopyrite-rich systems. Prewashing the tailings prior to weathering cells efficiently decreased by 60% the S content of LFT but had a limited effect on As mobility (factor 1.5). Particle size distribution influenced As mobility, with the fine fraction (<20 µm) releasing As at a rate that was 3-times higher than for coarser fractions. Gravity separation enabled the recovery of up to 46% of As-bearing minerals in the concentrate, which represent 3% of the total tailings mass. However, the mobility of As in Knelson tails was not enough mitigated due to the difficulty in recovering ultrafine particles of loellingite. These findings emphasize the need to develop stabilization rather than separation-based management strategies to efficiently prevent As-NMD from LFT dealing with the presence of fine and well-liberated As-bearing minerals.
Capelle et al. (Mon,) studied this question.