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Advancing active brine extraction
One area where the economics may eventually shift is rare earth extraction from brines. Geothermal fluids, oilfield-produced waters, and other subsurface brines can contain dissolved rare earth elements, creating the possibility of recovering critical minerals alongside existing energy operations. Unlike conventional hard-rock deposits, these resources are contained within fluid systems that in some cases are already being produced and managed.
While direct lithium extraction from brines has reached commercial deployment, rare earth recovery remains largely at the research and pilot stage projects currently conducted in the USA, Germany, Iceland and more. The technologies tested here consider the removal of REE as a secondary byproduct either through Electromigration and Electrohydrodynamic Separation, or Advanced Ion-Imprinted Resins (MRT). The former applies a perpendicular electric field to a flowing brine stream to force REE ions to migrate laterally based on their charge-to-mass ratio. The advantage of this technique allows for a complete bypass of physical filtration thus eliminating parasitic pumping loss and preventing silica scale clogging. MRT technology in comparison, employs macrocyclic ligands anchored to silica supports (adsorbent resin) that mimic the exact hydration shell and ionic radius of specific lanthanides thus selectively binding REE and excluding background salts.
The economic case is still being proven due to unresolved concerns about binding competition in salt-rich brines prematurely saturating adsorbents, post-Lithium-extraction silica scaling, and reinjection constraint due to the fouling of wells with additives that can lead to deep aquifers contamination.
Nevertheless, geothermal systems and large geothermal fields such as the Salton Sea may represent an intriguing future convergence of clean energy production and critical mineral supply. As geothermal exploration expands, the same subsurface understanding used to map heat-bearing fluid systems could also help evaluate their potential as secondary sources of critical minerals.