The manufacture of modern electronics, wind energy components and other products is dependent on a secure supply of rare earth elements. Currently, the U.S. is dependent on China for imports of neodymium and dysprosium, putting a stable national energy supply at risk.

The U.S. can source crucial rare earth elements domestically by exploiting waste generated by phosphoric acid production. Researchers tested different mineral and organic acids, instead of the toxic pollutant-generating Rare earth oxides of gadolinium, praseodymium, cerium, samarium, lanthanum and neodymium. Source: U.S. Department of Agriculture Agricultural Research Servicechemicals commonly used, to extract six rare earth elements from a synthetic phosphogypsum.

A biolixiviant composed of spent medium containing organic acids from the growth of the bacterium Gluconobacter oxydans on glucose proved more efficient at metal extraction relative to pure gluconic acid at the same pH level. The mineral acids (sulfuric and phosphoric) failed to extract any rare earth elements in that scenario. Sulfuric acid was shown to be the most effective leaching agent while the mineral acids failed to extract any rare earth elements.

The leaching process could lead to the recovery of about 100,000 tons of rare earth elements from phosphogypsum waste, which approaches the 126,000 tons of rare earth oxides produced annually worldwide.

Researchers from Rutgers University, OLI Systems, Idaho National Laboratory, University of California Davis and Lawrence Livermore National Laboratory contributed to this development.