A Molecular Dance in Rare Earth Element Chemistry: Argonne Scientists Reveal the Choreography Behind Lanthanide Separation

LEMONT, Ill.--(BUSINESS WIRE)--What do magnets, smartphones and medical imaging devices have in common? They all depend on rare earth elements called lanthanides, which are vital for modern technology. Yet, separating these chemically similar elements from one another has long been one of chemistry’s toughest puzzles.

Now, scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have cracked open the mystery, revealing the molecular choreography that governs lanthanide separation — a breakthrough that could transform how we process these critical materials.

Lanthanides are a group of 15 metallic elements found near the very bottom of the periodic table. However, they are chemically very similar and are often found together in ores, making them notoriously difficult to separate.

Traditionally, lanthanides are separated using a method called solvent extraction. In this process, the lanthanides are dissolved in an acidic solution and then selectively separated into an oil phase. Special molecules in the oil, called extractant molecules, bind to the lanthanides and help separate them.

Imagine a crowded dance floor where each dancer represents a molecule. The researchers found that the way these molecules “dance” around the lanthanide ion determines which element gets separated during extraction.

Using a simulation-based technique called metadynamics, the team created a map of the "energy landscape" of this molecular dance. This map shows the energy costs and benefits of different molecular arrangements.

Michael Servis, an Argonne chemist, explained, “Metadynamics helps us see all the possible ways molecules can arrange themselves around the lanthanide. This technique gives us clues about why some lanthanides are easier to separate than others.”

The study found that lighter lanthanides form stronger bonds with the extractant molecules. Heavier lanthanides struggle due to crowding on the dance floor.

“The extractant molecule, ions and water must fit around the lanthanide, creating a crowded environment, which can affect extraction efficiency,” Servis said.

Many conventional separation systems typically extract heavier lanthanides more easily, but this study observed the opposite.

The research also highlighted the role of water molecules in the dance. Some water molecules bind directly to the lanthanide ion and help stabilize interactions, forming hydrogen bonds that expand the possible dance moves.

This discovery not only advances understanding of lanthanide chemistry but also paves the way for more efficient and affordable ways to separate rare earth elements. Looking ahead, the team is exploring other solvents and extractant molecules that could improve selectivity even further.

Servis noted, “Our approach bridges fundamental coordination chemistry with real-world solution conditions, giving us insights that can make separation processes better.”