Researchers from Penn State and the US Department of Energy (DOE) have found an economical method to extract rare-earth elements (REEs) from coal byproducts through a chemical process called ion-exchange.
The rare-earth elements widely used in many industries are a set of 17 metals such as scandium, yttrium, lanthanum and cerium.
The American Chemistry Council said that these elements support more than $329bn of economic output in North America.
Penn State professor of energy and mineral engineering Sarma Pisupati said: "We have known for many decades that rare-earth elements are found in coal seams and near other mineral veins.
"However, it was costly to extract the materials and there was relatively low demand until recently."
The researchers used by-products of coal production from the Northern Appalachian region of the US and investigated whether REEs can be safely extracted through the ion-exchange process.
The eco-friendly process requires less energy and involves rinsing the coal with a solution that releases the REEs that are bound it.
In order to carry out the study, researchers used coal byproducts, with some not considered or marked as refuse during mining operations as they were of poor quality.
The study also involved locations within the coal seam that contained the highest amounts of the elements and the highest concentration was often found in the poorest quality coal.
Several coal-mining companies in Pennsylvania are set to partner with the team to explore the possibility of a commercial REE-extraction operation.
Image: Rare-earth oxides, clockwise from top centre: praseodymium, cerium, lanthanum, neodymium, samarium, and gadolinium. Photo: courtesy of Peggy Greb / USDA.