Optimization of porewater extraction techniques to evaluate thiosalts formation and mobility in unsaturated tailings

Large volumes of mineral waste are inevitably generated as mineral resources are critical for economic development, technology innovation and energy transition. Tailings storage facilities (TSF) store mineral waste that initially remain exposed to precipitation and atmospheric conditions. This leads to a series of geochemical reactions releasing dissolved constituents in tailings porewaters. Hydrogeological conditions play a key role in controlling tailings moisture content, oxygen diffusion, and the subsequent mobilization of dissolved constituents in tailings. In particular, sulfide minerals undergo oxidation in surface and partially saturated tailings, releasing metastable reduced S intermediates called thiosalts. Thiosalts can further oxidize to sulfate; however, this process increases porewater acidity with the release of protons (H+). The latent acidity of tailings porewaters in relation to elevated concentration of thiosalts represents a challenge for the mining sector which needs to be properly assessed for mine reclamation planning. This project aims at closing knowledge gaps on the formation and mobility of thiosalts in the active layer of TSFs undergoing freeze-thaw periods. Results from this study are beneficial for the partner and the mining sector working with Canada’s critical minerals, providing knowledge of the reactivity and S cycling within TSF under Arctic climate conditions.

Faculty Supervisor:

Maria Prieto-Espinoza

Student:

Partner:

Glencore Canada Corporation - Raglan Mine

Discipline:

Engineering

Sector:

Mining

University:

Polytechnique Montréal

Program: