GoKawiilFormer University of Chicago Pritzker School of Molecular Engineering PhD student Siqi Zou (left) and Assoc. Prof. Chong Liu led a team of reseachers from UChicago PME and Northwestern University that developed a cleaner method to separate rare earth elements from each other, which could affect technology manufacturing. (Photo by John Zich)
Rare earth elements like lanthanum, neodymium, and dysprosium are used to build the electric motor in your car, the LED lights in your house, and the MRI machine at your doctor’s office. But first, they have to be mined and separated from each other. Historically, that purification has been a difficult, costly, process, relying on huge amounts of toxic chemicals.
Now, researchers in the lab of Assoc. Prof. Chong Liu at the University of Chicago Pritzker School of Molecular Engineering (UChicago PME), working with colleagues at Northwestern University and Argonne National Lab, have discovered a cleaner method to separate rare earth elements from each other.
The new approach relies on a layered form of manganese oxide—a mineral material with the right size layers to allow ions to slip in and out and to differentiate rare earth elements.
“This is the first time that people have used electrochemical intercalation and harnessed the structural characteristics to separate similar lanthanides, which are intrinsically very hard to separate,” said Liu, senior author of the new study, which published in Nature Chemical Engineering. “What’s also valuable is that we provided a lot of new understanding of how rare earth ions are interacting with this material and how we can manipulate it to better selectivity.”
“This kind of separation is competitive with other rare earth separation methods, but it’s done in water, without organic solvents,” said George Schatz, professor of chemistry at Northwestern University and a co-author of the study. “That’s a difference that could actually matter at manufacturing scale.”
This is the first time that people have used electrochemical intercalation and harnessed the structural characteristics to separate similar lanthanides, which are intrinsically very hard to separate. Assoc. Prof. Chong Liu, senior author of the study
Squeezing elements through channels
The 17 rare earth elements—including the 15 lanthanides, plus scandium and yttrium—rarely occur alone. They’re almost always mined together and chemically they’re nearly identical, with only tiny differences in ion size and acidity differentiating each one. Pulling them apart typically requires custom-built molecules and large amounts of acid, which is used to strip each element off those molecules.
“Rare earths always come mixed together, whether they’re in an ore or in a waste stream, and separating them from each other is a second, very challenging step even after you’ve pulled them away from everything else,” said UChicago PME graduate student Jiadong Liu, a co-first author of the new paper.
... continue reading