In the middle of the 20th century, the United States became a leading global supplier of rare earth elements (REEs). These valuable materials were used extensively in the manufacture of innovative technologies like color televisions and other high-tech devices of the time. However, U.S. dominance in the rare earth market began to slip near the turn of the 21st century, and now China exports almost all the world’s rare earth elements.
Modern technologies, like those used in energy and defense systems, still rely heavily on rare earths for their manufacture, so the U.S. Department of Energy (DOE) is working diligently to secure a domestic supply. To meet this goal, researchers at DOE’s National Energy Technology Laboratory (NETL) are researching better ways to characterize a variety of REE sources. Among the many ways in which NETL is approaching this challenge, is a new miniaturized laser technology that shows promise for quantifying the concentrations of rare earths in sources like coal and coal-related byproducts.
“We can use this sensor to detect REE concentrations in situ,” Dustin McIntyre, inventor of the technology, explained. “To determine what elements are present, the device creates a pulse of light that is amplified and focused to make a spark. The spark emits light in all directions, creating characteristic atomic emissions. This light is then back-transmitted through the device, traveling up the optical fiber, up to a spectrometer that analyzes the light for elemental composition.”
The sensor technology is based on laser-induced breakdown spectroscopy (LIBS), but NETL has miniaturized a traditional LIBS system so that it can be placed in situ and determine rare earth concentrations without the need to remove a sample and bring it back to the lab. Source characterization is a crucial step for assessing the commercial viability of a potential extraction site. The system has successfully demonstrated rapid measurement of REEs in both solid and liquid samples at ppm level concentrations.
“You could even use this sensor to monitor the extraction process,” McIntyre said. “The technology could assure that you are consistently achieving a high enough concentration to meet commercial needs.”
The LIBS sensor is showing great potential for enabling successful REE extraction operations using sources like coal ash and acid mine drainage, which may help to invigorate coal country and attract advanced manufacturing facilities and jobs to those areas. Innovating powerful monitoring systems that yield quick and effective information in-the-field, is one way NETL researchers are building upon the Laboratory’s mission to discover and mature technology solutions that enhance the nation’s energy foundation and protect the environment for future generations.