The rare earth elements integral to producing modern technology — rechargeable batteries, electric cars, solar panels, refrigerators — aren’t actually all that rare. But they’re hard to get.
Though they are relatively common in the planet’s crust, they don’t often exist in concentrations high enough to mine efficiently. Large-scale rare earth mines are sparsely located, and more than 90% of the world’s rare earth processing goes through China, leaving American tech companies vulnerable to high tariffs and export limits.
But researchers at the University of Missouri are part of a growing movement to produce rare earth elements domestically, taking advantage of the minerals’ presence in Missouri’s former mines.
Traditional methods of rare earth mining are resource-intensive and pose significant environmental damage. Technology developed by the Missouri Water Center, according to researcher Pan Ni, aims to extract these elements at a lower cost and impact, using a resource that’s already there: waste.
“Not many research teams can approach the performance as we do,” Ni said. “We are like a pioneer in this field, trying to use this advanced technology to help the state or the country to produce this very valuable and emergent resource.”
The process begins with mine wastewater, contaminated and abandoned as mines close. The water often contains molecules of rare earth elements, but making use of them is complicated. Because the 17 elements typically considered “rare earth” have very similar physical and chemical properties, differentiating them to extract the desired material is difficult.
“It's like you have 17 twin brothers or sisters … so how you tell which one is which one, that's the most challenging part,” Ni said.
That’s where the researchers’ new technology comes in.
Using a technique called “ion imprinting,” Ni’s team creates small, spherical polymer beads capable of selectively extracting a desired element as water is filtered through them. The polymers themselves are made of a different kind of waste — byproducts from seafood processing — and can be reused at least ten times, driving down costs.
Ni compared ion imprinting to being fitted for a suit: tailoring each type of polymer to an element’s exact properties, allowing the molecules that “fit” to be picked up by the beads.
Then, a non-toxic solvent is used to dissolve the molecules out of the polymer. The pH of the mixture is then adjusted to convert the element into a solid form. After being heated, the material is usable in rare earth applications, like renewable energy technology.
The method, Ni said, has shown to be effective in laboratory settings. Now, the team is seeking to adapt their findings for use in the wider mining industry. Ongoing research at the center concerns the longevity of the beads — Ni said they’re hoping to find a material capable of being reused 50 to 100 times. Further research will also address the cost and practicality of the method.
To that end, the project recently received a $2.8 million grant from the Department of Energy to scale the technology and bolster America’s domestic supply of rare earth elements.
“We will try our best to use the DOE-funded money to show the public that, maybe, Missouri can be one of the centers to produce the rare earth elements in a considerable amount,” Ni said.
Ni said the wastewater used in the extraction process remains contaminated after the rare earth elements have been removed, largely due to the acidic nature of most mine waste. Still, he said the project presents an opportunity for Missouri to increase its supply of these critical materials without creating new waste.
“This wastewater is already there in the mining site. So whether we have this project or not, it's always there,” Ni said. “As long as there's some mining activity, as long as someone gets the permit to do the mining, that wastewater is there.”
In addition to partners inside Missouri, the team is currently working with the University of Colorado to explore applications in the Rocky Mountains’ mining regions.
