CMI Rare-Earth Elements Separation Technology Licensed to Marshallton

A rare-earth elements separation technology for separation has been licensed to Marshallton Research Laboratories, a North Carolina-based manufacturer of organic chemicals serving a range of industries.

The technology, developed by scientists at the Department of Energy's Critical Materials Institute (CMI) Oak Ridge National Laboratory and Idaho National Laboratory, provides insight into how to cost effectively separate in-demand rare earth elements, which could transform the industry to the benefit of U.S. producers.

Rare Earth Elements (REEs) - A group of 17 metallic elements, including 15 lanthanides plus yttrium and scandium whose unique electronic properties make them essential for the production of electronics, optical technology, alloys and high-performance magnets. These powerful permanent magnets are essential for clean energy technologies and defense applications.

Individual rare earth elements do not exist in mineable concentrations in the earth's crust, but are naturally mineralized together and must be chemically separated to be used in technological applications. Their physical and chemical similarities make them extremely difficult to separate and costly, while generating large amounts of waste. Extraction and separation of rare metals for technical applications is mainly overseas, mainly in China.

To meet the growing demand for these materials and to limit the nation's dependence on foreign sources, ORNL and INL scientists working under the banner of CMI, the Department of Energy's Center for Energy Innovation led by Ames Laboratory, applied their expertise in chemical synthesis, separations, and engineering to design and produce new extractants based on diglycolamide (DGA) ligands and corresponding processes for separating lanthanides that go beyond current technology.

REEs are commercially separated using liquid-liquid extraction, which uses ligands, organic molecules composed of carbon, hydrogen, oxygen, and nitrogen atoms, as extractants to selectively bind REE ions. An oily solvent containing the extractant is vigorously mixed with an aqueous solution rich in REEs and then allowed to separate in the same manner as the oil and vinegar in salad dressing.

ORNL's Chemical Sciences Division has been experimenting with an alternative DGA called TOGDA, which has a separation factor of 2.5 and is already a significant improvement over phosphorus-based extractants. However, a key variable in the economics of the process is the loading capacity, how many grams per liter of extractant can be held in the organic solvent without adverse reactions.

The ORNL team gave the test ligand to Lyons to be tested under industrial operating conditions using a counter-current solvent extraction system. The system consists of a series of vessels that mix and precipitate material through a series of liquid-liquid extraction stages to isolate rare metal compounds.

During the mixing, the ligands use electron-rich donor groups to attract metal ions and bind them in a coordinated manner. The extraction of some lanthanides but not others depend on the availability of the appropriate number and arrangement of functional groups in the ligand, the atoms in the molecule that can maintain their function independently of other atoms, and the size of the ligands and their ability to mix with oily organic solvents.

The ORNL team, in collaboration with Lyon, has designed, synthesized, and tested a library of chemically modified ligands that narrow the range of novel agents for industrial applications that have the potential to outperform state-of-the-art technology in terms of REE selectivity. Each agent behaves differently based on its physical arrangement and the electronic activity it suggests.

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