Highlights

• Missouri researchers developed chitosan-based hydrogels that selectively extract dysprosium and terbium from mine waste with up to 162 mg/g capacity and 95% removal rates in field trials at Pea Ridge mine.
• The bio-based sorbents work across different pH conditions, show strong selectivity over other rare earths, and maintain 70% capacity after five regeneration cycles, avoiding solvent-intensive traditional methods.
• The technology could help reduce dependence on China's 80% processing monopoly of heavy rare earths critical for EV motors and wind turbines, though scaling from lab to industrial deployment remains unproven.

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Heavy rare earth elements like dysprosium (Dy) and terbium (Tb) are the“secret sauce” inside high-performance magnets—and China currently dominates their supply. In a new open-access study in Chemical Engineering Journal Advances, John Earwood, Luke Henke, and senior author Baolin Deng, based at the Missouri Water Center with USGS/EPA support, introduce a novel chitosan-based hydrogel that can selectively strip Dy and Tb out of mine waste.

Their experiments show very high capture capacity, strong selectivity, and promising performance on real waste streams from Missouri’s Pea Ridge mine, hinting at a cleaner pathway for recovering critical heavy rare earths from U.S. soil rather than relying on Chinese processing.

Study Methods: Turning Shrimp Shells into Heavy-REE Sponges

The team designed alkali/urea chitosan hydrogels (AUCH)—soft, water-rich materials made from chitosan, a biopolymer derived from crustacean shells. They “imprint” the gel with Dy or Tb ions during synthesis, so the final material contains binding sites shaped specifically for these metals.

Two crosslinkers create pH-tuned variants:

• AUCH-D (1,2,7,8-diepoxyoctane): optimized for acidic conditions
• AUCH-G (glutaraldehyde): optimized for alkaline conditions

The researchers then measured uptake kinetics and capacity across 25–65 °C, tested performance over a wide pH range, characterized structure with SEM/FTIR/thermal analysis, evaluated selectivity in mixed rare earth solutions, and ran field trials on actual mine drainage and tailings from the Pea Ridge iron–REE deposit in Missouri.

Key Findings: High Capacity, High Selectivity, Real Waste Validation

1. Exceptional loading of Dy and Tb

In controlled lab solutions, the imprinted hydrogels achieved very high sorption capacities: up to 162.53 mg/g for Tb(III) and 132.05 mg/g for Dy(III). The data fit Langmuir isotherms and pseudo-second-order kinetics, consistent with chemisorption—true chemical binding, not just weak sticking to the surface.

2. Tuned for different pH regimes

AUCH-D performed best around pH 4 (acidic), while AUCH-G peaked around pH 8 (mildly alkaline). Together, they cover a wide range of realistic mine conditions without heavy pH adjustment, a cost and environmental advantage.

3. Strong preference for Dy/Tb over other rare earths

In competitive tests with lanthanum, samarium, and europium, the Dy/Tb-imprinted gels grabbed Dy and Tb much more strongly, confirming genuine selectivity rather than indiscriminate metal uptake.

4. Real-world mine waste success

Using water from the Pea Ridge mine:

• In acidic drainage, AUCH-D removed 95.77% of Tb and ~73% of Dy.
• In alkaline tailings, AUCH-G removed 78.06% of Dy and ~67% of Tb.

The materials maintained selectivity even in complex, “dirty” solutions and kept >70% of their capacity after five regeneration cycles, supporting the idea of repeated use in a recycling plant. For a lay reader: these gels act like smart sponges that “prefer” Dy and Tb, pull them out of dirty water, and can be squeezed out and reused multiple times.

Why This Matters for China’s Processing Monopoly

Today, China not only mines a large share of rare earths; it processes over 80% and produces around 90% of high-performance REE magnets. Heavy rare earths Dy and Tb are the tightest chokepoints in that system, critical for EV motors, drones, wind turbines, and defense hardware.

This study does not replace Chinese separation plants—but it does point to three important strategic possibilities:

Secondary HREE supply from U.S. waste

Recovering Dy and Tb from mine tailings and acidic drainage turns legacy waste into a domestic resource, potentially easing Beijing’s leverage at the margin.

Cleaner, less solvent-intensive separation

The chitosan hydrogels avoid large volumes of organic solvents used in traditional solvent extraction, aligning with tightening environmental standards in the U.S. and Europe.

Design principles for future materials

The authors show how subtle differences in Dy vs Tb chemistry and crosslinker choice can be exploited to fine-tune selectivity—knowledge that can carry over into future membranes, sorbents, or hybrid processes.

Limitations and Questions Investors Should Keep in Mind

Lab-to-plant gap

Results are from batch tests and small-scale field trials. We do not yet know how AUCH materials perform in continuous industrial systems or at the thousands-of-tons scale.

Cost and durability

Five regeneration cycles with ~70% capacity retention is promising—but large plants need dozens to hundreds of cycles. Long-term degradation, fouling, and real-world maintenance costs remain unknown.

Selective extraction ≠ full supply chain

Even perfect Dy/Tb recovery from U.S. tailings does not solve the lack of domestic separation, metal, and magnet manufacturing at scale.

Commercial interest and IP

Co-author Baolin Deng holds a pending patent (“MINE TAILINGS RECOVERY,” USPTO #63/707,864), which signals commercialization potential but also highlights that the technology is in early, proprietary development, not a ready-to-deploy open standard.

REEx View

Earwood, Henke, andDeng’s work is a genuinely innovative step toward cleaner,more selective recovery of Dy and Tb from mine waste, and it fits squarely into a broader circular-economy push to chip away at China’s processing dominance.

But this is still technology development, not yet a bankable replacement for conventional separation plants. For investors and policymakers, the takeaway is clear: materials science can help unlock stranded HREE value in Western waste streams—but only coordinated investment along the whole chain (from waste recovery to magnets) will translate breakthroughs like this into real geopolitical leverage.

Citation: Earwood J., Henke L., Deng B. “Selective dysprosium/terbium recovery from mine waste using ion-specific alkali/urea chitosan hydrogels.” Chemical Engineering Journal Advances, Volume 24, November 2025, 100864. https://doi.org/10.1016/j.ceja.2025.100864 (opens in a new tab)

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