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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.