Rare earths extracted from US coal mine wastewater

Rare earth elements are being extracted from wastewater flowing out of retired coal mines in West Virginia, in a pilot project that researchers say could help clean polluted mine drainage while adding to the United States' supply of critical minerals.

West Virginia University researchers developed the project with public financing after finding about 10 years ago that acid mine drainage from shuttered mines contained rare earths. At a retired coal mine in Mount Storm, the reddish water is collected, treated and used to recover rare earths in concentrated form before being discharged back into the environment.

Lance Lin, director of the WVU Rare Earth Elements Initiative, said the process removes pollutants and recovers rare earths as a valuable byproduct. He said the drainage is rich in heavy rare earths, which are already naturally dissolved and do not require a new mine to extract them.

The Mount Storm facility remains small. Lin said it can produce about four tons of rare earth oxides a year, with heavy rare earths making up about 45 percent of the total. WVU engineer David Hoffman said a broader rollout producing 300 metric tons a year could meet seven to eight percent of global demand for rare earths such as terbium and dysprosium.

Rare earths are used in powerful magnets for electric vehicles, wind turbines, drones and fighter jets. The United States has one rare earths mine, at Mountain Pass in California, and China dominates production and refining.

Tommee Larochelle, an engineer who specialises in rare earth extraction and refining processes, questioned the commercial viability of the WVU project but said it could help ensure a minimum supply for the defence industry if political support and financing align.

The rare earth concentrate still needs to be separated into individual elements and processed. A startup involved in the WVU project has reached a preliminary agreement with REalloys to treat rare earths extracted from acid mine drainage.