Highlights

• Innovative hydrometallurgical processes can recover 70-100% rare earth elements from coal ash through advanced leaching and extraction techniques.
• Technology currently at TRL 3-5, with potential commercial deployment in 2-4 years targeting mixed rare earth concentrates.
• Sustainable recovery offers a waste-to-value pathway for utilities and potential alternative to traditional rare earth mineral extraction.

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Lead author and PhD candidate (industrial chemist) Rabiatu Adamu Saleh (opens in a new tab), Nile University of Nigeria and colleagues review the state of hydrometallurgical recovery of rare earth elements (REEs) from coal ash in the International Journal of Coal Preparation and Utilization (online Sept. 3, 2025). The paper (opens in a new tab) synthesizes recent progress in acid/alkali leaching, ion exchange, solvent extraction, sequential extraction, and emerging bio/ionic-liquid routes, with attention to feedstock mineralogy, process conditions, cost, and environmental footprint.

What the authors actually show

• Coal ash is a real secondary REE reservoir; pretreatments (alkali/thermal) followed by mineral acids can push total REE recovery into the ~70–100% range in optimized lab settings.
• Downstream selectivity matters: ion exchange and solvent extraction can deliver high-purity fractions, but require multi-stage circuits and careful impurity control (Fe/Al/Ca).
• Sustainability knobs: closed-loop reagent management, LCA framing, and waste minimization are emphasized to move beyond bench chemistry toward credible flowsheets.

Why this matters for magnet supply chains

If scalable, coal-ash hydromet could diversify LREE/HREE feed (notably Dy/Tb from certain ashes) without opening new pits, dovetailing with U.S./EU policy to de-risk China-centric midstream. Utilities sitting on legacy ash ponds gain a potential “waste-to-value” pathway; magnet makers gain optionality on oxide supply.

How far to commercialization—reasonably?

• Today: Technology Readiness Level (TRL) ~3–5. Multiple pilots and semi-industrial trials exist, but feed variability (speciation across glassy/organic/discrete phases) still whipsaws recoveries and reagent bills.
• Near term (2–4 years): Expect municipal/utility-scale demos that integrate pretreatment + leach + SX/IX + precipitation with partial reagent recycle. Early commercial skids may target mixed REE concentrates rather than individual oxides.
• Scale (5–10 years): Broad deployment hinges on bankable TEAs/LCAs, consistent ash assays/offtakes, and permitting for acid handling and effluents. Without policy supports (tax credits, offtake guarantees), timelines skew to the long end.

Limitations to keep in frame

• Chemistry vs. reality: Many headline recoveries rely on aggressive acids (HCl/HNO₃/HF), rigorous pretreatment, and high reagent loads—cost and effluent risk rise fast outside the lab.
• Selectivity bottleneck: Separating neighboring lanthanides at scale still means multi-stage SX (energy/solvent intensive) or costly tailored resins.
• Feed heterogeneity: Ash chemistry varies by coal rank, boiler, and burn regime; flowsheets must be site-specific, complicating “copy-paste” rollouts.
• Outliers & speculation: The paper’s brief suggestion to conceptually lump cesium with REEs is non-standard and not relevant to REE commercialization.

Bottom line

This is a serious, well-sourced review that moves coal-ash REE recovery from “intriguing lab work” toward process integration. For investors and strategics: track pilot mass balances, closed-loop reagent recovery, independent product specs, and first offtakes. Commercial supply at a meaningful scale is plausible in the next cycle, but only with disciplined flowsheet design, policy nudges, and utility partners willing to be early movers.

Citation: Saleh RA, Gimba ASB, Adeleke AA, Olosho AI, Ikubanni PP, Adesina O, Aminu MD, Omotosho E. “Advancements in hydrometallurgical processes for rare earth elements recovery from coal ash.” International Journal of Coal Preparation and Utilization. Published online Sept 3, 2025. doi:10.1080/19392699.2025.2551654.

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