Biophytometallurgy: biomining metals from plant resources

The physicochemical controls governing metal acquisition, release, and redistribution across biological interfaces remain poorly understood. Biophytometallurgy--the microbially assisted release and recovery of plant-associated metals--was used to probe the directionality of the mechanisms controlling nickel (Ni) and rare earth element (REE) release from plants of the genus Phytolacca during solid-liquid extraction. Ni, an established phytomining target, was included as a comparator for chemical extraction. Bulk characterization did not support a detectable dominant crystalline REE-phosphate-like compartment in hydroponically enriched shoots. Dissolution and rebinding experiments instead revealed chemically accessible nickel and REE compartments, the latter of which had behaviors consistent with apparent equilibrium-like partitioning under mildly acidic conditions. During sulfur biooxidation, Acidithiobacillus ferrooxidans promoted REE release while providing a competing cell-associated REE sink. Consequently, aqueous REE concentrations reflected net redistribution among the separable plant, solution, and microbial phases instead of dissolution alone. These results establish a framework for studying metal partitioning across complex and coupled biological systems and support a route for aqueous REE recovery from plants without thermochemical conversion to ash.