Highlights

• Researchers review emerging rare earth element separation technologies that could reduce environmental impact and processing complexity.
• New approaches like aqueous two-phase systems, solvometallurgy, and magnetophoretic separation offer potential alternatives to traditional liquid-liquid extraction.
• The goal is to develop more sustainable and economically viable methods for extracting critical minerals, particularly for Western supply chains.

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Bailey Lake ( (opens in a new tab)FAMU-FSU College of Engineering; National High Magnetic Field Laboratory) with Theo Siegrist, (opens in a new tab) Thomas E. Albrecht (Colorado School of Mines), Hadi Mohammadigoushki (opens in a new tab), Munir Humayun (opens in a new tab), and corresponding author Jamel Ali (opens in a new tab) review the state of rare-earth element (REE) separations in Industrial & Engineering Chemistry Research (ACS).

In A Nutshell

Today’s dominant refinery method—traditional liquid–liquid extraction (T-LLE)—works, but at a cost: tons of kerosene and acids, high energy use, and hazardous waste. This review explains how emerging approaches could shrink the footprint and boost selectivity when peeling apart REEs that behave almost identically in solution.

What the paper finds.

Method	Summary	Risks
Aqueous two-phase systems (ATPS)	Water-heavy, often using ionic liquids to avoid flammable organics; promising control over selectivity	Risks more contaminated wastewater and viscosity/throughput hurdles
Nonaqueous systems (NAS)/solvometallurgy	Swaps water for green polar solvents (e.g., ethylene glycol), deep eutectic solvents (DES), or ionic-liquid pairs	Some have run in mixer–settlers (TRL —5) and can reduce steps, energy, and water
Synergistic chemistry	combining extractants (e.g., TODGA + TBP) or adding auxiliary agents (e.g., lactic/acetic/citric acids) can lift distribution ratios and separation factors, especially for heavy REEs—without redesigning entire plants.	The main risks of this synergistic chemistry approach are process instability and scalability. Combining multiple extractants or auxiliary agents can produce unpredictable chemical interactions, leading to phase separation issues, unwanted precipitates, or reduced selectivity under industrial conditions. It may also complicate waste treatment and increase solvent degradation or corrosion.
Magnetophoretic separation	exploits differences in magnetic susceptibility (not just ionic size). Early studies show paramagnetic ions migrating in magnetic fields, hinting at a chemistry-plus-magnets route—but it’s early (TRL 1–2).	Low technological maturity and uncertain scalability. At this early stage (TRL 1–2), results are mostly laboratory curiosities—magnetic fields strong enough to separate ions may be energy-intensive and hard to scale, and the behavior of ion clusters in real process fluids is still poorly understood.

Why it matters.

If scalable, these routes could cut solvents and waste, lower costs, and de-risk Western supply chains for EV motors, wind turbines, and defense electronics—areas currently constrained by China-centric midstream capacity. The near-term wins are likely incremental (synergistic additives in existing circuits; selected solvometallurgical lines for high-value streams). The long-term prize is a hybrid toolkit: greener solvents where they pencil, plus magnet-assisted steps to shorten flowsheets and improve yields.

Limitations

• TRL reality check: most concepts are ≤5—validated in labs or pilots, not at full industrial cadence.
• Process economics: viscosity, phase separation, kinetics, solvent make-up losses, and wastewater treatment can erase lab gains.
• Health & safety: some ionic liquids/solvents raise toxicity or persistence concerns; green labels require cradle-to-grave validation.
• Selectivity context: performance varies by feed chemistry (e.g., magnet scrap vs. ore leachates); no one-size-fits-all recipe.

Bottom line for REEx readers.

Think evolution, not revolution: start by tuning today’s circuits (synergists/auxiliaries), pilot solvometallurgical lines where water and waste dominate OPEX, and fund magnetophoretic R&D as an option-value bet. The path to cleaner, domestic REE refining is a portfolio—targeted upgrades now, platform shifts as TRLs rise.

Citation: Lake, B., Siegrist, T., Albrecht, T. E., Mohammadigoushki, H., Humayun, M., & Ali, J. (2025). Recent Advances in Rare Earth Element Recovery: Liquid–Liquid Extraction and Magnetophoretic Separation. Industrial & Engineering Chemistry Research. https://doi.org/10.1021/acs.iecr.5c02137 (opens in a new tab)

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