Phosphate Wastes are Viable Sources of Rare Earth Elements, Say University Researchers and Scientists

A recent study conducted by researchers at Rutgers University revealed that phosphogypsum wastes produced in the process of extracting phosphoric acid from phosphate rock, is a potential source of Rare Earth Elements or REEs. In a separate collaborative research conducted with the Idaho National Laboratories (INL) and the Critical Materials Institute, a team of university researchers and scientists, also found an environmentally method by which REEs can be extracted from the phosphogypsum wastes.

Understanding the Importance of Rare Earth Elements

The collaborative research is a U.S. Department of Energy initiative aimed at boosting the supply of important rare earth elements essential for the production of clean energy. That is because currently, there is a shortage of supply; except in China, which accounts for about 90% of REEs produced worldwide. That being the case, China controls much of the REEs being supplied globally.

REEs neodymium and dysprosium are essential for technologies that produce solar energy, wind energy, high-tech vehicles,and modern electronic communication devices like smartphones. Since the U.S. produces only about 9 percent (9%) of REEs available across the globe, a shortage of rare earth element puts the energy security of the United States at risk.

Rutgers University and Idaho National Lab Researches Yield Positive Results

Rutgers University researchers together with research scientists of the Idaho National Laboratories, have found a potential solution in solving the scarce supply of rare earth elements or REEs.

The solution mainly involves the use of phosphogypsum, a waste material produced by the phosphoric acid production process, which contains rare earth elements. Every year, it is estimated that 250 million tons of phosphate rocks are mined to produce phosphoric acid for fertilizers.

In every phosphate rock that is mined, about less than 0.1 percent of REE exists. The amount becomes significant, when quantifying the millions of tons of phosphate rocks mined every year throughout the country.

In 2017 alone, the U.S. mined approximately 28 million metric tons of phosphate rocks. On a global scale, it is estimated that about 100,000 tons of REEs generally end up as mining wastes, which is almost as much as the 126,000 tons of REEs commercially produced on a global scale.

The next problem pondered was an environment friendly method by which REEs can be extracted from the phosphogypsum wastes. The current methods in place, make use of harsh chemicals. Increased amounts of harmful substances, to be used in extracting REE from tons of phosphogypsum wastes, will all the more increase the acidic and toxic pollutants contaminating the geographical environment.

The INL Arrives at an Eco-Friendly Solution for Extracting REEs from Industrial Wastes

During the course of their experiments. the INL team of scientists led by Dr. David Reed of the Biological and Chemical Processing Department at the INL, found a sustainable, eco-friendly solution.

The INL scientists used bio-acid mixtures, primarily made from gluconic acid produced by Gluconobacter, a type of bacteria that produces bio-acids in fruits. Experiments revealed that the Gluconobacter bio-acid solution outperformed other mineral acids. In comparing REE extraction results using pure gluconic acid at the same level of acidity of pH2.1, the Gluconobacter bio-acid did a better job of extracting REEs from mining wastes.

Other extraction methods tested mineral acids, such as sulfuric and phosphoric acids, using the same level of pH as the bio-acid. The mineral acids manifested inability to extract REEs. In a comparative test using the four different acids at the same level of concentration, only sulfuric acid gave better results than the bio-acid, as far as REE extraction was concerned.

The good news is that the Idaho National Laboratory has already tested the Gluconobacter bio-acid in extracting REEs from the phosphogypsum wastes, and the results still showed the same efficiency.