Mitigating contaminated mine drainage through mine waste rock decontamination: A strategy for promoting cleaner and sustainable management

Abstract

This study investigates the potential of reprocessing mine waste rock (WR) to mitigate acid generation, remove contaminants, and recover valuable resources. The WR, with a wide particle size distribution, was separated into a reactive fine fraction and an inert coarse fraction based on the diameter of physical locking of sulphides (DPLS). Through mineralogical characterization and geochemical analysis, the DPLS was determined to be 2.5 mm for the studied material. The primary objectives of the research were to evaluate the acid- and contamination-generating potential of the reactive fraction (<DPLS), assess the feasibility of reprocessing through various desulphurization/decontamination processes, and analyze the geochemical behavior of the desulphurized materials. Chemical and mineralogical analysis revealed that the feed sample was enriched in contaminant-bearing sulphides (e.g., pyrite, gersdorffite, pyrrhotite) and carbonates (e.g., calcite). Various decontamination processes, such as centrifugal dense medium separation (DMS), spiral/shaking table, and combined gravity-flotation techniques, were investigated. Results indicated that these processes reduced contamination risk due to WR oxidation (e.g., As leaching). Particularly, DMS and combined gravity-flotation processes proved effective, producing desulphurized material with low sulphur (0.28 wt%) and arsenic (0.026 wt%) contents alongside a high sulphur-bearing mineral recovery (88 wt%). Geochemical properties were evaluated using kinetic weathering cells, which showed that desulphurized materials from DMS and the combined gravity-flotation approach had the lowest leachate arsenic concentrations. However, leachates from material desulphurized using the spiral/shaking table slightly exceeded environmental limits for arsenic concentration (D019, Quebec, Canada). This study underscores the effectiveness of upstream environmental desulphurization in managing and valorizing WR, reducing its environmental impact, and recovering valuable resources.