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By looking at a problem at a nanoscale level, Pacific Northwest National Laboratory researchers are developing an economic way to extract valuable rare earth elements from geothermal fluids. This novel approach may help meet the high demand for rare earth elements that are used in many clean energy technologies.

Pacific Northwest National Labo­ratory (PNNL) researchers are among a handful of teams explor­ing new methods to recover strate­gic, critical, and high-value metals (SCVM) vital to a host of clean energy technologies, such as solar panels, wind turbines, electric vehicles, and energy-saving lighting.

PNNL began developing and testing a magnetic partitioning method dur­ing the first phase of the Geothermal Technologies Office’s (GTO’s) Mineral Recovery initiative in 2014, and the lab will continue to advance the tech­nology with the help of an additional $1.65 million recently awarded by the Energy Department for Phase II of the initiative.

The Energy Department is pursuing a range of research and development efforts to secure and diversify the supply of SCVM, including rare Earth elements; identify substitute materi­als; and develop better ways to recycle these materials. One exciting area of this research is the recovery of materi­als from fluids or “brine” produced from the Earth’s subsurface by geo­thermal and other energy or mining projects.

GTO is exploring unique ways to extract valuable resources that are sometimes dissolved in the large fluid volumes brought to the surface by geothermal plants. Brine pumped from underground naturally contains miner­als and other metals, such as rare earth elements, that are found within the hot rock below the Earth’s surface. Ex­tracting these valuable elements could provide geothermal energy produc­ers with another revenue source—the sale of rare earth elements. However, because the concentration of these elements is often very small, conven­tional extraction methods are simply too large and too expensive, and they would degrade the efficiency of geo­thermal energy plants.

Enter PNNL Fellow, Pete McGrail; he and his team developed a new process to extract rare earth elements from geothermal brine by incorpo­rating magnetic properties into a unique nanomaterial then using simple magnets to collect the material. The new method introduces magnetic nanoparticles consisting of a shell or framework that combines metal and an organic structure, or MOF, into the geothermal brine. The MOF outer layer carries molecules that are attrac­tive to rare earth elements, causing the elements to stick to the nanoparticle.

Using this method, the brine is then passed through a magnetic separator to remove the nanoparticles contain­ing rare earth elements. The now nanoparticle-free brine is recirculated to recover more rare earths from the geothermal fluids. What’s more, PNNL test results showed a nearly perfect rare earth element extraction rate of 99.99%.

 

Amped Up! Magazine is the Office of Energy Efficiency and Renewable Energy’s publication that highlights breaking technologies and achievements in renewable power, energy efficiency and sustainable transportation that influence global change toward a clean energy economy.