When
Monday, April 27, 2026, at 10:00 a.m.
Heileen (Helen) Hsu-Kim
Professor
Civil & Environmental Engineering
Duke University
"Resourcing Critical Metals from Waste Streams: Learned from Extracting Rare Earth Elements from Acid Mine Drainage and Cole Combustion Residuals"
Harshbarger 118A-A1
ABSTRACT: Waste streams such as mine drainage, coal ash and other combustion residuals have been proposed as a low grade resource of critical minerals such as rare earth elements (REE). These feedstocks are an attractive source of REE because of environmental benefits gained in converting wastes into valuable materials. However, major challenges exist in valorizing such wastes, including that waste disposal sites tend to be geographically dispersed and that such wastes comprise variable chemical composition that require customized and modular REE recovery approaches at each waste site. This presentation will discuss the challenges in the extraction and refining of REE from wastes such as acid mine drainage and coal fly ash. Lessons learned from the biogeochemistry field, including fundamental principles of metal-ligand competition and metal ion interactions at interfaces, are applicable in understanding how to overcome the challenges of REE recovery from low grade feedstocks. Examples include the application of supported liquid membranes (SLM) for REE extraction and the potential to use historical energy supply datasets to predict the chemical quality of coal combustion residuals that could be available for waste reuse and mineral recovery.
BIOSKETCH: Heileen (Helen) Hsu-Kim is a professor of civil and environmental engineering at Duke University, where she has been a member of the faculty since 2005. Prior to joining Duke, Hsu-Kim completed her BS degree in environmental engineering at MIT, and MS/PhD degrees in environmental engineering at UC-Berkeley. Hsu-Kim’s expertise area is aquatic geochemistry, trace element biogeochemistry and nanogeoscience. In addition to her work on critical metals in coal mine wastes, her research group is exploring valorization opportunities for legacy solid wastes stored at coal fired power plants. Her team also investigates the environmental distribution and exposure risks of trace element contaminants such as mercury in the Amazon and lead in urban soils. Hsu-Kim is also the director of graduate studies for Duke’s Civil and Environmental Engineering Department and is an associate editor for Environmental Science & Technology.