Long-Term Evolution of Uranium Mobility within Sulfated Mill Tailings in Arid Regions: A Reactive Transport Study

Management of mill tailings is an important part mining operations that aims at preventing environmental dispersion contaminants concern. To this end, geochemical models and reactive transport modeling provide a quantitative assessment the mobility main contaminants. In arid regions with limited rainfall intense evaporation, solutes may significantly differ from usual gravity-driven vertical flow. uranium Cominak mine (Niger), these evaporative processes resulted in crystallization gypsum, to lesser extent jarosite, formation surface levels sulfated gypcrete, locally enriched uranium. We present fully coupled approach using HYTEC, encompassing quantitatively reproduce complex sequence observed hydrogeochemical processes. The gypcrete formation, porosity evolution solid content were successfully reproduced paleosurfaces tailing deposit. Simulations confirm high solubility uranyl-sulfate phase form atmospheric boundary where evaporation takes place, which would then be transformed into uranyl-phosphate phases after being watered or buried under fresh tailings. As usually exhibit lower solubility, transition beneficial for operators management.