A team of researchers led by the Department of Energy (DOE) has discovered that rare earth elements (REEs) can be removed from two US coal byproduct materials through an ion-exchange process. This discovery has the potential to expand the US domestic resource base of these critical elements.

The findings were published in a peer-reviewed paper entitled A Study on Removal of Rare Earth Elements from US Coal Byproducts by Ion Exchange. The research indicated that removal of REEs through an ion-exchange process could offer significant cost and environmental advantages compared with extraction from conventional ores.

REEs have a number of important applications in the energy and technology sectors.

Producing REEs can be extremely challenging, as they are commonly produced from ores that are difficult to break down in order to extract the elements. This extraction can be energy intensive, requiring temperatures of over 500°F and exposure to concentrated acids. There are also emissions concerns.

A smaller portion of REE production, largely in China, involves a process known as “ion-exchange,” which rinses the ore at ambient temperature with a solution. The REEs in this type of ore are adsorbed onto a clay surface, and are removed into the solution. For two coal byproducts associated with a coal bed in Pennsylvania, REEs can be removed with an ammonium sulfate solution that is used commercially for REE recovery outside the US, according to this research.

These findings will appear in Metallurgical and Materials Transactions E, published by ASM International and The Minerals, Metals and Materials Society.

Edited from press release by Angharad Lock