In Appalachian coal country, researchers plan to turn toxic waste into treasure. Pollution left behind by abandoned mines is an untapped source of rare earth elements.
Rare earth metals are a valuable set of 17 items , needed to make everything from smartphones and electric cars to fluorescent lights and lasers. In connection with the rapid growth of world demand and China’s almost monopoly on the production of rare earth metals (in the United States there is only one operating mine ) there is great interest in finding alternative sources, e.g. increased processing .
Extracting rare earth elements from coal waste offers a two-for-one deal: by extracting the metals, you’re also helping to clean up pollution.
Long after a coal mine closes, it can leave a dirty legacy. When some of the rock left over after mining is exposed to air and water, sulfuric acid is formed, which extracts heavy metals from the rock. This sour soup can pollute waterways and harm wildlife.
Recovery of rare earth elements from the so-called acid mine drainage will not be able to meet the growing demand for metals on its own, admits Paul Zemkiewicz, director of the West Virginia Water Research Institute in Morgantown. But he points to several advantages.
Unlike the ore mined in typical rare earth mines, the drainage is rich in essential rare earth elements. In addition, mining from acid mine drainage also does not create radioactive waste, which is usually a byproduct of rare earth mines, which often contain uranium and thorium along with rare earth elements. And from a practical point of view, existing acid mine drainage treatment facilities can be used to collect rare earth elements for recycling. “Theoretically, you could start production tomorrow,” says Zemkiewicz.
Zemkevych and his colleagues estimate that nearly 600 metric tons of rare-earth elements and cobalt, another sought-after metal, can be produced annually from the several hundred sites that are already treating acid mine drainage.
Currently, a pilot project in West Virginia takes material extracted from an acid mine drainage site and extracts and concentrates rare earth elements.
If such a scheme turns out to be feasible, Zemkiewicz envisions a future in which treatment facilities send their rare-earth residues to a central facility for processing and element separation. Economic analysis shows that this is not an enrichment scheme. But, he says, that could be enough to cover the cost of cleaning up the mine’s acid drainage.
