Rare earths rise from coal fly ashes

Researchers at Detroit’s Wayne State University (WSU) have developed a method to extract rare earth elements (REEs) from domestic coal fly ash produced by a local power plant.
 Rare earths rise from coal fly ashes  Rare earths rise from coal fly ashes  Rare earths rise from coal fly ashes  Rare earths rise from coal fly ashes  Rare earths rise from coal fly ashes

The US has explored many ways to obtain REEs from coal-based resources

The National Energy Technology Laboratory project used custom-built reactors at Los Alamos National Laboratory (LANL) to process coal fly ash samples taken from a coal-fired power plant in Detroit.

The team has modified molecules that are used with magnetic resonance imaging (MRI) contrasting agents — chemicals used for MRI scan diagnostics— to separate rare earth elements.

The process, called hydrothermal leaching, used a novel sorbent medium, a material used to absorb or adsorb liquids or gases, developed at WSU in coordination with LANL and the University of California, Los Angeles.

The sorbent was used in a solid-liquid recovery process, which eliminated the use of potentially hazardous organic solvents.

Multiple techniques previously developed to process spent nuclear materials were also used to separate lanthanides from other elements occurring with them, resulting in the production of REEs.

The process produced a rare earth oxide powder that was more than 13% in weight.

With WSU's hydrothermal process, more than 76 percent of the REEs in the coal fly ash can be extracted; that represents a 20 percent increase over conventional acid-based methods," the researchers claim.

"For several years, we've explored many ways to obtain REEs from coal-based resources, ranging from acid mine drainage to the fly ash from power plants," said NETL Project Manager Maria Reidpath in an article published by the US Office of Fossil Energy. "With this project, we've demonstrated that technologies developed for different purposes can be used creatively to help the nation [the US] develop its own REE feedstock."

NETL now plans to work on commercialising the technology, with disclosure for the sorbent media filed with WSU and a patent application to be submitted soon. 

US power-sector coal consumption is projected to have reached 558.3 million short tons in 2019, while 1.5 billion st of fly ash is estimated to sit in the country's storage basins and landfills.