Eric Schelter gripped a pair of heavy metal rotor plates from an old wind turbine, one in each hand, and moved them closer together until suddenly — thunk!
The plates were jammed together so tightly that they could not be pried apart by hand. That’s because they were lined with industrial-strength magnets — metallic wafers of the kind that enable wind turbines to supply 6 percent of the electricity generated in the United States.
The scientific principle behind it is straightforward, with one important hitch: Where to get the magnets?
Schelter, an associate professor of chemistry at the University of Pennsylvania, thinks a big part of the answer should be recycling.
He won a “Green Chemistry” award from the U.S. Environmental Protection Agency this year after his lab devised a method to separate the materials in these magnets, called rare earths. And if the team can perfect the process, it will have implications for the environment, national security, and the high-tech economy.
Despite the name, the metals are not especially rare — but currently most of the world’s production comes from mines in China, which long ago beat U.S. mining operations on costs. In addition to powering wind turbines — because spinning magnets induce the flow of electrons — these materials serve as the hidden workhorses behind too many technologies to mention. Among them: smartphones, TVs, computer hard drives, fluorescent lightbulbs, advanced weapons systems, and electric cars. Rare earths even play a role in oil refining.
And when Chinese supplies are tight, as they were five years ago, the concern ripples from manufacturers to the White House.
In September, with rare-earth prices climbing once again, President Trump was joined by Afghan president Ashraf Ghani in supporting U.S. companies that seek to mine the materials in Afghanistan. The materials are plentiful there, though there is little of the necessary infrastructure in place. What’s more, refining the metals consumes vast amounts of energy and yields toxic byproducts that have contaminated sites across Asia.
Schelter, who has a poster in his office with the motto “Get Excited and Make Things,” has a greener approach.
The method his lab developed is aimed at separating two rare earth metals, in particular, a pair of tongue-twisters called neodymium and dysprosium. These metals are combined in varying amounts, depending on the type of high-tech product they are used to make. The recycling process requires separating the metals again so manufacturers can make something new.
It all started when one of Schelter’s graduate students, Justin A. Bogart, was studying some of the fundamental chemistry of rare earths, and he developed a claw-shaped molecule called a ligand.
The team discovered that this “claw” bonded in different ways with neodymium and dysprosium ions. With dysprosium, the claw closes tightly, resulting in a small molecular complex. With neodymium, the claw is open a bit wider, resulting in a larger molecule.
The larger one is easily dissolved in benzene, a common industrial solvent, whereas the smaller one is not. So to separate the two, the Penn chemists just add benzene and pour the result through a very fine filter. The neodymium solution is captured in a small vial, while the dysprosium is caught in the filter.
“Like spaghetti in a colander,” Schelter joked.
So far, the separated metals resulting from this process are 95 percent pure, which Schelter would like to improve. Another hitch: The process does not work well in the presence of moisture. If it were to be commercialized, the need to ensure a moisture-free environment would add to costs.
Still, Schelter is hopeful the process can be optimized to the point that it is competitive with the output of Chinese mines.
Elsewhere, the U.S. Department of Energy is funding research into extracting rare-earth metals from the byproducts of mining and burning coal — including one project at Pennsylvania State University. And researchers have even explored mining rare earths and other metals from the ocean floor.
As with any alternatives to traditional methods of extracting natural resources, the interest in them will come down to price.
Schelter is well-aware of the economic and strategic connotations of his work. But as his EPA green chemistry award suggests, he comes at the problem from an earth-friendly view.
“For me, it’s a passion project,” Schelter said. “How can we turn waste into resources?”