Highlights

• Chinese researchers develop multi-step process to extract rare earth elements from hazardous mine waste, turning environmental liability into strategic mineral supply.
• Innovative extraction method achieves 94.4% rare earth leaching efficiency with potential to reduce mining dependency and support circular economy.
• Study demonstrates how environmental cleanup can simultaneously generate critical minerals for high-tech industries like electric vehicles and wind turbines.

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A new study led by Pan Yushi, Wu Pan, and Li Xuexian from China’s Nonferrous Metals Research Institute (opens in a new tab), published in Nonferrous Metals (Extractive Metallurgy) presents a landmark process for extracting rare earth elements (REEs) from acid mine drainage (AMD) sludge—one of the mining industry’s most persistent environmental hazards. The researchers developed a hierarchical extraction method combining chemical leaching, selective precipitation, and solvent extraction to turn toxic AMD waste into a potential new source of critical minerals.

Study Summary

The team’s process begins with iron and calcium removal using oxalic and hydrochloric acids, followed by acid redissolution and two-stage solvent extraction using the industrial reagent DEHPA (di-2-ethylhexyl phosphoric acid). Finally, the researchers use oxalic acid precipitation and high-temperature calcination (800°C) to yield a high-purity mixed rare earth oxide containing 81.3% REEs. Laboratory results showed:

• Iron removal efficiency: 96.6% using 1 mol/L oxalic acid at a 10:1 liquid-to-solid ratio.
• Calcium removal efficiency: 65.5% using 0.05 mol/L HCl, without major REE loss.
• Rare earth leaching efficiency: 94.4% under optimized HCl conditions.

This multi-step method not only recovers REEs efficiently but also neutralizes hazardous mine sludge, providing both environmental remediation and resource recovery.

Implications

This research shows how a pollutant long considered a waste liability—acidic sludge from metal mining—can become a secondary resource for high-value elements essential to electric vehicles, wind turbines, and advanced electronics. If scaled, the approach could reduce China’s dependence on new mining, lower environmental cleanup costs, and support circular economy goals by transforming existing waste streams into strategic material supplies. For global policymakers, it illustrates how green hydrometallurgy can align environmental and industrial interests.

Limitations

While laboratory performance is impressive, the study stops short of pilot-scale validation. Large-scale application faces hurdles: chemical consumption, wastewater management, energy demand for calcination, and process economics remain uncertain. Further, variations in AMD composition across sites may affect recovery efficiency, meaning the method may require local adaptation.

Conclusion

Pan and colleagues have demonstrated that acid mine drainage sludge—once an environmental burden—can be reimagined as a rare earth resource. Their hierarchical extraction method offers a model for sustainable resource recovery, advancing both environmental protection and critical mineral independence. The study underscores a broader truth: the next frontier of rare earth production may lie not in new mines, but in the cleanup of the old ones.

Citation: Pan, Y., Wu, P., & Li, X. (2025). 酸性__矿山废水沉淀污泥中稀土元素的分级提取工艺研究 (Study on Hierarchical Extraction of Rare Earth Elements from Acid Mine Drainage Sludge). Nonferrous Metals (Extractive Metallurgy), Issue 10, 209–218. DOI: 10.20237/j.issn.1007-7545.2025.10.020 (opens in a new tab).

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