Highlights

• Researchers at Curtin University demonstrated that acid crack leach residue—currently discarded waste—can recover approximately 65% of remaining rare earths using recyclable organic acids instead of harsh chemicals.
• The study reveals that processing waste contains rare earth concentrations comparable to fresh ore, exposing inefficiencies in conventional extraction and offering a path to improve supply security.
• By reprocessing tailings rather than mining new ore, Western producers can reduce environmental impact and challenge China's rare earth processing monopoly through smarter flowsheets.

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A new open-access study led by K. Yamini of Curtin University’s Western Australian School of Mines (opens in a new tab), working with Laurence Dyer, Jonah Gamutan, and Bogale Tadesse, tackles one of the rare earth industry’s quiet inefficiencies: the loss of valuable rare earth elements (REEs) in processing waste.

Published in Resources, Conservation and Recycling (February 2026), the paper (opens in a new tab) demonstrates that acid crack leach (ACL) residue—a byproduct of conventional rare earth extraction—can be reprocessed to recover roughly 65% of remaining rare earths, using recyclable organic acids rather than harsh mineral reagents.

Curtin University’s Western Australian School of Mines

For readers unfamiliar with rare earth processing, the significance is simple: material that is currently discarded as waste often contains rare earth concentrations comparable to fresh ore. Recovering it improves supply security, lowers environmental impact, and slightly loosens the global chokehold created by China’s dominance in rare earth processing.

How the Study Works

Conventional rare earth extraction uses sulfuric acid roasting and leaching to dissolve rare earths from ores such as monazite. What’s left behind—ACL residue—is rich in iron phosphate and sulphates and still contains meaningful rare earth content (about 2.8% total REE in this study).

Instead of sending this residue to tailings, the researchers applied a two-stage “technospheric mining” process:

1. Oxalic acid leaching is used to break down the residue and mobilize rare earths.
2. EDTA leaching to selectively complex and recover rare earths that reprecipitate or remain trapped.

By carefully controlling acid concentration and dosing—sometimes adding oxalic acid gradually rather than all at once—the team reduced contamination from iron and phosphorus and improved selectivity. The result: overall rare earth recovery of ~65%, the highest reported for this specific waste stream.

Key Findings That Matter

• Waste is not waste: ACL residue contains rare earth grades comparable to some mined ores, revealing systemic inefficiencies in today’s flowsheets.
• Organic acids can work at scale—on paper: Oxalic acid and EDTA are recyclable, offering a lower-toxicity alternative to traditional reagents.
• Process behavior is kinetic, not simple chemistry: Recovery depends heavily on dosing strategy and timing, not just equilibrium chemistry.
• Flexibility beats bespoke designs: The flowsheet proved adaptable across different residues, suggesting broader applicability beyond a single mine.

Why This Matters in a China-Dominated Supply Chain

China still controls the overwhelming majority of global rare earth processing capacity, not because it mines the most ore, but because it extracts and separates material more completely. This study underscores a critical point: processing efficiency is power.

If Western producers can recover more rare earths from existing waste streams, they will reduce reliance on new mining, cut costs, and marginally weaken China’s processing monopoly. Tailings reprocessing won’t replace primary supply—but it can meaningfully stretch each ton of ore further.

Limitations and Open Questions

This is not a silver bullet.

• Recovery is not 100%: About one-third of rare earths remain unrecovered.
• Reagent intensity remains high: Although recyclable, oxalic acid consumption is substantial and must be optimized for commercial scale.
• Pilot-scale economics are untested: Laboratory success does not guarantee industrial viability without cost and throughput validation.
• Industry funding disclosed: The research received support from Lynas Rare Earths and Western Australian institutions—transparent, but worth noting.

The Bottom Line

This study shows that closing the loop in rare earth processing is technically feasible today, not decades away. By mining the waste of yesterday’s extraction plants, producers can improve sustainability, economics, and supply resilience—critical goals in a world racing toward electrification and clean energy.

China’s advantage in rare earths has always been about processing discipline. This paper is a reminder that smarter flowsheets—not just new mines—are where the next gains will be found.

Citation: Yamini, K., Dyer, L., Gamutan, J., & Tadesse, B. (2026). Closing the loop in conventional rare Earth extraction: Treatment of acid crack leach residue using organic acids. Resources, Conservation and Recycling, 226, 108678. https://doi.org/10.1016/j.resconrec.2025.108678 (opens in a new tab)

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