How coal mine drainage can become a source of rare earths

Coal mining. (Reference image by Arianselmani, Wikimedia Commons.)

A recent study published in the journal Environmental Engineering Science presents a novel process for extracting rare-earth elements from coal mine drainage.

The experimental process has been patented by a team at Ohio State University and it was shown to successfully clean coal mine drainage while producing rare-earth elements in samples from various rivers across Ohio, Pennsylvania, and West Virginia.

“One thing that surprised me was just how well our process cleans up the water,” Jeff Bielicki, co-author of the paper, said in a media statement. “From an environmental standpoint, the major benefit of this work is that we’re successfully trapping and neutralizing so much pollution.”

According to Bielicki, currently, coal mine drainage is treated using active treatment systems that employ chemicals to clean the water, or passive treatment systems, which often depend on bacterial activity or geochemical methods.

The study shows that passive approaches tend to require fewer resources and have fewer environmental impacts. Thus, the Ohio State team used a passive system employing a combination of alkaline industrial by-products, including materials like water treatment plant sludge, to neutralize the coal drainage and capture the rare-earth elements.

“It’s designed to let the natural seepage of coal mine drainage percolate through the material to trap and extract it,” the researcher said. 

He also explained that the average time it takes to rid water of waste often varies because the process largely depends on how quickly water flows out from the mine.

The new method, however, was able to capture a variety of metals such as terbium, neodymium and europium, which play critical roles in phone displays, batteries, microphones, speakers and other parts.

The process is currently more costly than the current market price of rare metals, but further advances are expected to bring the price down.

Bielicki said he hopes their research will inform future policy surrounding coal waste disposal and help the public to examine the environmental repercussions of mining outside of typical costs, like its impact on human health and the ecosystem at large.

“Nothing we do to our environment is benign, so while shifting away from coal and other fossil fuels is beneficial in several different dimensions, we need to effect these transitions in ways that address a larger sphere of issues than just cost,” he said. “Our research is a vital step in addressing the legacies of those environmental and social consequences.”

3 0