Rare earth elements are actually quite abundant in the earth’s crust. They are called rare because of how difficult they are to separate from ore in large amounts. Because rare earth elements are critical components of smartphones, solar panels, computer chips, and many other types of technology, demand for them has been steadily increasing – in turn, putting pressure on mining companies to find a way to make them less “rare.” Recently, scientists from Pennsylvania State University made some progress on this front by finding a way to extract rare earth elements from coal mining refuse.
The method the scientists developed uses a lixiviant – making it quite similar to processes used in precious metals mining and refining. A lixiviant is a liquid medium used to selectively extract certain metals from ore or mineral. Using nitric acid to leach base metals out precious metals, or using sodium cyanide to extract gold out of ore are examples of lixiviants at work.
Using poor-quality, refuse-grade coal, Penn State researchers found that ammonium sulfate was able to leach about 0.5% of the rare earth elements contained in the coal. Perhaps not a groundbreaking amount, but it’s a promising starting point for increasing the production of rare earth elements in an efficient and environmentally-friendly manner.