G.E. Johnson, M. Sushko, E. Nakouzi, C. Subban, P. Valdez, A. Lines, V. Prabhakaran, P. Simonnin
Pacific Northwest National Laboratory,
United States
Keywords: critical minerals, rare earth elements, flow, field, precipitation
Summary:
Efficient and selective extraction of critical minerals, such as rare earth elements, from unconventional feedstocks like produced waters, geothermal brines, and leachates generated from recycled electronics and low-grade ores is vital for establishing and maintaining the domestic supply chains needed for energy dominance, economic growth, and national security. Traditional extraction from primary ores often involves energy- and chemical-intensive processes that produce large amounts of waste. More advanced separation techniques require specialty adsorbents, resins, and ligands that, while selective, are costly to manufacture, not always recyclable, and challenging to adapt across feedstock chemistries. We are developing a fundamentally different approach to critical mineral separations that utilizes non-equilibrium conditions to promote selective, low-energy precipitation with inexpensive commodity chemicals driven by hydrodynamic liquid flow and externally applied electric and magnetic fields. Notably, the distinct magnetic properties of rare earth elements offer a largely untapped opportunity to control the transport, speciation, and reactivity of these ions, as well as the nucleation and growth of crystals, and the handling of solid precipitates. Our holistic approach to critical mineral extraction integrates the fundamental science of separations with innovative characterization and modeling techniques, online sensing, and engineering/process design for eventual scale-up and deployment. We hypothesize that inhomogeneous electric and magnetic fields can be employed to manipulate interfacial potentials, local solvation environments, and concentration gradients at liquid–liquid interfaces, resulting in enrichment zones that promote nucleation pathways and facilitate field-driven fractional crystallization. To characterize the spatiotemporal enrichment of critical minerals in aqueous solutions driven by fields, we are developing spatially-resolved in situ multimodal visualization techniques, including Mach-Zehnder interferometry, fluorescence spectroscopy, and X-ray imaging. We are also developing highly sensitive and robust online spectroscopic sensors for real-time process monitoring and adaptive control, essential for extracting critical minerals from unconventional feedstocks with constantly changing compositions. To predict how electric and magnetic fields influence the transport and reactivity of solvated ions and precipitates, we are developing a new multi-scale modeling framework spanning from atomistic calculations to continuum fluid dynamics simulations. To ensure these scientific insights and capabilities lead to scalable, industrially relevant separation processes, we are conducting technoeconomic and life cycle analyses, along with process engineering, to compare our novel field-based separations to current industry methods. We demonstrate the selective separation of targeted critical minerals from various real-world feedstocks provided by domestic industry partners, including produced water from oil and gas extraction, polymetallic nodules, recycled electronics, and low-grade ores.