DARPA Bets on New Chemistry to Challenge China's Rare Earth Separation Advantage

Highlights

• DARPA funded University of Utah researchers developing metal-organic framework sorbents to selectively separate chemically similar rare earth elements.
• Adding EDTA improved the dysprosium-to-lanthanum separation factor from approximately 2 to 11.5, with sodium acetate pushing it further to roughly 13.
• The technology targets rare earth separation—not mining—the true strategic bottleneck where China holds decades of industrial expertise.
• Research remains at laboratory scale using synthetic solutions and has not yet demonstrated commercial throughput, reagent economics, or sorbent longevity.
• The investment signals a U.S. strategy shift toward leapfrogging conventional solvent extraction rather than replicating China's existing separation infrastructure.

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Separating rare earth elements is often called the industry's "million-stage marathon." A new study (opens in a new tab) published in Hydrometallurgy suggests there may eventually be a shorter route. PhD candidate Easton Sadler (opens in a new tab), Professor Michael L. Free, (opens in a new tab) and Dr. Prashant K. Sarswat (opens in a new tab) of the University of Utah and Purdue University report a laboratory-scale rare earth separation technology that combines engineered metal-organic framework (MOF) sorbents with carefully controlled aqueous chemistry to selectively separate chemically similar rare earth elements. The research was supported by the U.S. Defense Advanced Research Projects Agency (DARPA (opens in a new tab)), underscoring growing U.S. government interest in next-generation rare earth refining technologies. While the work remains at the laboratory stage, it represents another example of Washington investing beyond mining and into the far more strategically important midstream—the chemical separation technologies that China has spent decades perfecting.

Who Conducted the Research?

The study was led by Easton Sadler with senior investigators Professor Michael L. Free and Dr. Prashant K. Sarswat, researchers at the University of Utah, one of the United States' leading academic centers for extractive metallurgy and critical materials research. Funding was provided by DARPA under contract HR0011-24-3-0333, illustrating the Department of Defense's growing interest in rebuilding domestic capabilities for critical mineral processing rather than relying exclusively on foreign technology.

Study Methods

The team designed several families of engineered zinc-based tetrapod materials that were converted into metal-organic framework (MOF) sorbents and functionalized with trimesic acid. They then systematically varied solution chemistry—including pH, ionic strength, competing salts, EDTA, and sodium acetate—to determine whether the surrounding chemical environment could improve separation selectivity among individual rare earth ions. Rather than relying solely on new materials, the researchers tested whether the chemistry surrounding the materials could become another tool for selectively capturing specific rare earth elements.

Key Findings

The engineered sorbents demonstrated adsorption capacities approaching 260 mg/g under optimized conditions. More importantly, the researchers substantially improved selectivity between light and heavy rare earths. Adding EDTA increased the dysprosium-to-lanthanum separation factor from approximately 2 to 11.5, while sodium acetate further increased the ratio to roughly 13.

The work demonstrates that manipulating aqueous coordination chemistry may dramatically improve adsorption selectivity without relying entirely on traditional solvent extraction.

Why This Matters

Rare earth mining is not the principal bottleneck in today's supply chain.

Separation is. China dominates commercial rare earth refining largely because it possesses decades of expertise operating massive solvent extraction facilities containing hundreds—sometimes thousands—of mixer-settler stages. If adsorption-based technologies eventually prove scalable, they could reduce chemical consumption, lower environmental impacts, simplify plant design, and shorten processing flowsheets.

That remains a significant "if."

What the Study Does Not Demonstrate

Investors should avoid confusing an encouraging laboratory result with a commercial process.

The experiments were conducted under carefully controlled laboratory conditions using synthetic solutions rather than complex industrial feedstocks. The paper does not demonstrate continuous operation, industrial throughput, reagent economics, impurity tolerance, sorbent lifetime, regeneration costs, or commercial-scale manufacturing. No comparison was made against complete commercial solvent extraction circuits under production conditions.

These remain substantial engineering hurdles.

Rare Earth Exchanges Assessment

This study represents exactly the type of research Western governments should be funding. Rather than attempting to replicate China's existing separation infrastructure molecule-for-molecule, DARPA is supporting efforts to leapfrog conventional solvent extraction through fundamentally different chemistry.

Whether this specific platform ultimately succeeds commercially remains uncertain.

What is increasingly clear, however, is that America's rare earth strategy is expanding beyond mining. The next strategic battlefield is the midstream—where chemistry, materials science, and process engineering will determine whether the United States can build competitive refining capacity capable of challenging China's decades-long lead.

Citation: Sadler, E., Free, M.L., & Sarswat, P.K. (2026). Separation and purification of rare earth elements via selective adsorption by Trimesic acid and enhanced by aqueous complexing agents. Hydrometallurgy, Article 106827.

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