West Virginia University (WVU) is currently building a research facility intended to develop rare earth metal recovery processes for acid mine sludge. The $3.38 million-dollar project will test the technological scalability of these recovery processes and develop US supply chains from acid mine sources and treatment. WVU will partner with Rockwell Automation, a sensor and control specialist, to build the facility.
Current methods of rare earth metal production create large amounts of contaminated waste. The metals are mined from rock, crushed into dust, and then filtered after an intense chemical bath. This must be repeated several times, and then the rare earth metals must be further processed to separate heavy rare earths from light rare earths. Due to relaxed environmental regulations, China currently dominates production using this traditional method.
However, rare earth-enriched sludges are a byproduct of coal mining, and it’s estimated that America’s Appalachian mountains could produce up to 800 tons of rare earths a year. In the new process, the sludge would be dissolved in acid, then mixed and settled into an emulsion. Finally, extractant chemicals would separate rare earths from the water, and the remainder would be sent for further processing into rare earth oxides. Any waste created would be returned to the acid mine drainage plant’s disposal system. The researchers state that scandium produced by the facility will be worth $4,500 per kg and can be further refined into a form worth up to $15,000 per kg.
“Acid mine drainage from abandoned mines is the biggest industrial pollution source in Appalachian streams, and it turns out that these huge volumes of waste are essentially pre-processed and serve as good rare earth feedstock. Coal contains all of the rare earth elements, but it has a substantial amount of the heavy rare earths that are particularly valuable,” says WV Water Research Institute Director Paul Ziemkiewicz.
“Currently, acid mine drainage treatment is a liability, an environmental obligation. But it could turn into a revenue stream, incentivizing treatment and creating economic opportunity for the region. This process uses an existing waste product that is abundant in our region. It is also much easier to extract, requires much milder acids and has negligible waste materials when compared to conventional rare earth recovery methods.”