Rare Earth Elements From Phosphate Waste

Rare earth elements have become one of the most strategically important materials on Earth. Many high-tech industries depend on rare earth elements like neodymium and dysprosium for solar and wind energy and electric vehicles, as well as modern electronics like smartphones and medical devices. Rare earth elements are especially rare, but do not often accumulate in sufficient concentrations to be financially viable for extraction. Currently China controls almost 90% of the supply of rare earth elements—a fact that has some national security experts nervous.

There are a variety of sources for rare earth elements, including hard rock mining and purification from sediments. The search is on world-wide for alternative sources and recent announcements of huge reserves in sea-bottom mud off the coast of Japan, and a source in a kaolin clay mine in the state of Georgia, south of Atlanta, show some promise. Now, researchers at Rutgers University have found a possible new source of rare earth elements— phosphate rock waste.

Each year, approximately 250 million tons of nsi-189 phosphate powder rock are mined to produce phosphoric acid for fertilizers. In the US approximately 28 million metric tons were mined in 2017. Rare earth elements typically are found in concentrations less than 0.1 percent in phosphate rock. That means about 100,000 tons of these elements per year end up in phosphogypsum waste—almost as much as the approximately 126,000 tons of rare earth oxides produced worldwide each year.
Recovering rare earth elements from phosphogypsum—the waste product from phosphoric acid production—has potential, but must be done in an environmentally sound manner. Conventional methods to extract the elements from ores generate millions of tons of toxic and acidic pollutants. But another method might use organic acids produced by bacteria, said Paul J. Antonick and Zhichao Hu, from the Department of Materials Science and Engineering in Rutgers’ School of Engineering. They described their work in a Rutgers University news release.