Nature: Microbial miners take on rare-earth metals

Nature story describes using microbes for rare earth separations, including CMI research with Team members Idaho National Laboratory, Lawrence Livermore National Laboratory and Penn State. 

These are some of the small but growing cadre of researchers are investigating a possible alternative: biomining. Many microorganisms naturally concentrate metals, and some are already used to mine copper and gold. The discovery about a decade ago of microbes that use lanthanides for their metabolism allowed researchers to explore the feasibility of adapting the microorganisms or their components to isolate rare earth elements.

REEs are metals that have valuable conductive, magnetic and fluorescent properties and that are used in everything from mobile phones to wind turbines. The metals impart strength and hardness to alloys, for example, and are found in superconductors and catalytic converters. 

In experiments at Idaho National Laboratory, G. oxydans secreted a gluconic acid mixture that was better at leaching rare metals from industrial waste than was a comparable concentration of commercial, pure gluconic acid. “We think there are other things being produced besides the gluconic acid,” says Vicki Thompson, a chemical engineer at INL.

Another tool that has become key to the burgeoning field of rare-earth biomining is lanmodulin, a lanthanide-binding molecule discovered in 2018. Co-discoverer Joseph Cotruvo Jr is a biochemist at CMI Team member Pennsylvania State University. 

Lanmodulin has provided researchers with a mechanism for isolating REEs, at least at the benchtop scale. A collaborator of Cotruvo’s at Lawrence Livermore National Laboratory, Dan McFarland Park, immobilized lanmodulin on agarose microbeads to create a column that could capture lanthanides. Starting with coal-mine ash from the northwestern United States, which contained less than 1% lanthanides overall, the team obtained a solution of 88.2% pure lanthanide. “It was so selective that we could take really dilute, poor sources of rare earths, and selectively capture using lanmodulin,” says Park.

Another key question is how long purification columns will last before they have to be replaced. So far in the lab, scientists have run their columns only dozens of times at most, but mining companies could require tens of thousands of runs. “Any time we talk to somebody in industry, that’s the first question they’ll ask,” says Park. “It’s still a pretty open question.”

Park advises scientists interested in studying this kind of process to talk to people in the mining industry to understand their needs. He’s also found “a wealth of expertise” in advice from peers at the Critical Materials Innovation Hub, a collaboration between labs in academia, industry and the US Department of Energy, led by Ames National Laboratory in Iowa. Its goal is to accelerate work on rare-earth and other materials that are key to clean energy. Conferences and journals from the American Chemical Society are also great resources for those interested in REE purification, Park says.

Link to the full story: Microbial miners take on rare-earth metals