Abstract
The gold mining industry faces several challenges due to the co-occurrence of gold and arseniferous minerals. The generation of contaminated neutral mine drainage (CND), despite the implementation of management methods limiting geochemical instability (desulfurization), has increasingly been recognized as an important environmental issue. The understanding of the geochemistry of low-sulfide and filtered tailings and the development of strategies for CND prevention are necessary to minimize the environmental impact of mining industry. This study aims to identify the sources and mechanisms of As mobility from low-sulfide and filtered tailings produced by Éléonore mine (QC) and evaluate the effectiveness of gravimetric separation for limiting As-CND. To do so, the geochemical behaviour of three particle size fractions of low-sulfide and filtered tailings (< 20 µm, 20-32 µm, > 32 µm) was studied in weathering cells. Tailings were reprocessed using a Knelson separator to recover As-bearing minerals. The influence of operating conditions on As recovery was investigated. The mobility of As in untreated vs reprocessed tailings was evaluated according to Field Leaching Tests (FLT). Physico-chemical characterization of low‑sulfide and filtered tailings (0.08% As) showed that 76% of As was concentrated in the fine fraction (< 20 µm), while well-liberated loellingite and, to a lesser extent, arsenopyrite were identified as the main As-bearing minerals. Results obtained from weathering cells showed a 10-times higher mobility of As from the fine fraction (< 20 µm). Less than 6% of As contained in tailings was leachable and induced neutral contaminated leachates. Gravimetric separation allowed to recover up to 46% of As-bearing minerals, although the mobility of As was not impacted by the retreatment due to the difficulty to recover fine particles (< 32 µm) containing easily leachable As.