Assessment of the Biogeochemistry of Rare Earth Elements and Distribution of Other Elements in Oil Sands Tailings

Rare earth elements (REEs) are crucial components in a wide range of modern technologies, from renewable energy systems to advanced electronics and defense applications. Due to their growing global demand and limited primary sources, there is an urgent need to explore alternative sources for REEs recovery. Oil sand tailings, a major byproduct of bitumen extraction processes, represent an underexplored source of REEs and other valuable metals. In this study, we investigated the mineralogical and biogeochemical characteristics of three distinct oil sands tailing streams to assess their potential as a secondary source of REEs and to better understand their speciation and distribution mechanisms. Chemical analyses of these tailings indicated elevated concentrations of several metals, such as aluminum (≈94,490 mg/kg), titanium (≈10,210 mg/kg), magnesium (≈5891 mg/kg), and manganese (≈1060 mg/kg). REEs concentrations ranged from 442.72 to 797.79 mg/kg, highlighting the tailings' potential for resource recovery. The extraction of REEs from such waste streams aligns with the "waste-to-resource" concept, offering an environmentally sustainable route to strategic material supply diversification. This study provides critical insights into the complex interplay among mineralogy, geochemistry, and microbiology of REEs and other valuable elements in oil sands tailings. By assessing the mechanisms of metal association and mobilization, our findings aim to contribute to the development of targeted extraction strategies and support the broader goal of sustainable resource recovery from industrial waste streams.