The increasing global demand for critical minerals, driven by rapid population growth and the widespread adoption of low-carbon technologies, electric vehicles, and clean energy systems, highlights the urgent need for sustainable resource management. Mine tailings, traditionally considered waste, are now being recognized as valuable secondary sources for mineral recovery. This paper compiles a comprehensive review of the four short- and mid-term critical minerals (lithium, cobalt, nickel, and rare earth elements) and provides insights regarding their recovery with a focus on the latest technological advancements. By exploring key innovations in separation processes, the review demonstrates how these technologies are addressing supply chain bottlenecks while simultaneously reducing the environmental footprint of mining operations. The paper also advocates for a holistic approach to mine waste management, integrating mineral recovery with environmental remediation. It emphasizes the dual benefits of recovering valuable resources while purifying contaminated water and mitigating pollution risks. The proposed circular economy model suggests a sustainable blueprint for managing mine tailings, emphasizing resource reuse, waste reduction, and economic viability.

The increasing industrial demand for rare earths requires new or alternative sources to be found. Within this context, there have been studies validating the technical feasibility of coal and coal byproducts as alternative sources for rare earth elements. Nonetheless, radioactive materials, such as thorium and uranium, are frequently seen in the rare earths’ mineralization, and causes environmental and health concerns. Consequently, there exists an urgent need to remove these radionuclides in order to produce high purity rare earths to diversify the supply chain, as well as maintain an environmentally-favorable extraction process for the surroundings. In this study, an experimental design was generated to examine the effect of zeolite particle size, feed solution pH, zeolite amount, and contact time of solid and aqueous phases on the removal of thorium and uranium from the solution. The best separation performance was achieved using 2.50 g of 12-µm zeolite sample at a pH value of 3 with a contact time of 2 h. Under these conditions, the adsorption recovery of rare earths, thorium, and uranium into the solid phase was found to be 20.43 wt%, 99.20 wt%, and 89.60 wt%, respectively. The Freundlich adsorption isotherm was determined to be the best-fit model, and the adsorption mechanism of rare earths and thorium was identified as multilayer physisorption. Further, the separation efficiency was assessed using the response surface methodology based on the development of a statistically significant model.

Increasing disruption in the rare earth supply chain creates an urgency to develop alternative resources, in which utilization of coal-based materials presents great potential. Nevertheless, environmental control is a significant challenge in rare earth extraction processes. This study was conducted to contribute to the limited information on removing thorium and uranium from rare earths while coal-based products are used as feedstock. The laboratory studies suggested that the selective precipitation and solvent extraction approach yields the most favorable separation performance. Complete thorium precipitation was achieved around a pH value of 4.8. Due to the close precipitation pH ranges of uranium and rare earths, further separation by solvent extraction was applied to achieve an enhanced separation. Based on a Box-Behnken experimental design, the effect of extractant concentration, pH, strippant concentration, and O/A ratio was investigated. Best separation performance was achieved using 50 v% TBP at a pH of 3.5 with an O/A ratio of 3 and 1 mol/L H₂SO₄, which resulted in 1.8% uranium and 73.4% rare earth extraction. The extraction and precipitation behavior of the elements were further assessed with the distribution ratio, separation factor, thermodynamic parameters, and species distribution diagrams to provide a thorough understanding of the separation mechanisms. The results were statistically analyzed, and a model was developed to predict uranium recovery. The developed experimental protocol was validated using a rare earth oxalate sample produced at the pilot-scale processing facility. Finally, a conceptual process flowsheet was developed to effectively separate radionuclides while producing rare earth oxide products.

To reduce reliance on foreign nations, it is essential for the United States to identify domestic sources of rare earth elements (REEs) and develop sustainable technologies to effectively recover them. Acid mine drainage (AMD) is one such source that has attracted interest because of the presence of a wide range of REEs. The concentration of REEs in these sources is, however, dilute (at the ppb level), and while conventional processes, such as solvent extraction, effectively recover them, they are associated with high energy and chemical usage. In this work, a hardwood biochar-based adsorption process is described for REE recovery from AMD. A number of adsorption parameters were tuned to identify the optimal operating conditions, and the biochar was characterized using various morphological and transport-based techniques, using La3+ as a representative REE. The thermodynamic and kinetic interactions of the REEs with the biochar are evaluated based on equilibrium adsorption uptakes and adsorption kinetics, using selected ions with similar size and charge as probe ions. These results demonstrate that intra-REE separation is possible due to differences in the adsorption kinetics of these ions, highlighting the synergistic roles of ion size and charge on overall performance. Beyond ideal single-ion solutions, the biochar performance was also evaluated for synthetic multi-ion solutions and real AMD solutions. Finally, preliminary results on weak-acid-induced desorption behavior and its effects on biochar reusability were included. Overall, this study shows that biochar adsorption offers an effective, sustainable method for REE recovery from AMD, supporting efforts to develop the domestic REE supply chain while addressing environmental challenges posed by AMD.