At-Source Recovery of Rare Earth Elements from Coal Mine Drainage

Technology Partner: West Virginia University Research CorporationAward Number: FE0031524
Project Duration: 11/16/2017 – 5/15/2019
Total Project Value: $864,258

Key Technology Area: Separation Technologies
Project Partners: Virginia Polytechnic Institute and State University

The project objective is to develop a process to extract an enriched, mixed rare earth element (REE) product from acid mine drainage (AMD) at the site of production, upstream of conventional AMD treatment. Two AMD cases— net acid and net alkaline (Cases A and B, respectively)—will be explored. The products will be processed through an acid leaching/solvent extraction (ALSX) plant to compare performance with ongoing ALSX trials using conventional AMD sludge feedstock. The project team will evaluate the benefits of separating REEs from the AMD stream under reducing conditions such that iron and manganese will remain in their reduced (Fe2+, Mn2+) states. As reduced species, they will bypass the REE extraction process, improving overall process economics. In Case A, the pH is raised to just pH 4, which will precipitate REEs but not Al, Fe2+, or

Mn2+, metals that would otherwise need to be separated to achieve high REE purities. In Case B, the team will explore the application of an electrochemically stimulated supported liquid membrane strategy to separate REEs from ferrous ion. The project will demonstrate that significant improvements in REE extraction efficiency can be obtained through separation of REEs from aqueous phase AMD, upstream of conventional AMD treatment, by (1) creating an enriched REE feedstock, (2) producing a more consistent feedstock, (3) reducing transportation costs to an REE refinery, (4) reducing acid consumption in the acid leaching step, and (5) reducing the volume of waste produced at the ALSX plant.

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Typical AMD treatment facility showing the lime treatment unit, reduced Fe(OH)2 sludge (blue), the mechanical aerator, and resulting Fe(OH)3 oxidized sludge.

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