Sunday, May 26, 2024

Promethium bound: Rare earth element's secrets exposed

May 22, 2024
DOE/Oak Ridge National Laboratory

Summary:
Scientists have uncovered the properties of a rare earth element that was first discovered 80 years ago at the very same laboratory, opening a new pathway for the exploration of elements critical in modern technology, from medicine to space travel.

FULL STORY


Scientists have uncovered the properties of a rare earth element that was first discovered 80 years ago at the very same laboratory, opening a new pathway for the exploration of elements critical in modern technology, from medicine to space travel.

Promethium was discovered in 1945 at Clinton Laboratories, now the Department of Energy's Oak Ridge National Laboratory, and continues to be produced at ORNL in minute quantities. Some of its properties have remained elusive despite the rare earth element's use in medical studies and long-lived nuclear batteries. It is named after the mythological Titan who delivered fire to humans and whose name symbolizes human striving.

"The whole idea was to explore this very rare element to gain new knowledge," said Alex Ivanov, an ORNL scientist who co-led the research. "Once we realized it was discovered at this national lab and the place where we work, we felt an obligation to conduct this research to uphold the ORNL legacy."

The ORNL-led team of scientists prepared a chemical complex of promethium, which enabled its characterization in solution for the first time. Thus, they exposed the secrets of this extremely rare lanthanide, whose atomic number is 61, in a series of meticulous experiments.

Their landmark study, published in the journal Nature, marks a significant advance in rare earth research and might rewrite chemistry textbooks.

"Because it has no stable isotopes, promethium was the last lanthanide to be discovered and has been the most difficult to study," said ORNL's Ilja Popovs, who co-led the research. Most rare earth elements are lanthanides, elements from 57 -- lanthanum -- to 71 -- lutetium -- on the periodic table. They have similar chemical properties but differ in size.

The other 14 lanthanides are well understood. They are metals with useful properties that make them indispensable in many modern technologies. They are workhorses of applications such as lasers, permanent magnets in wind turbines and electric vehicles, X-ray screens and even cancer-fighting medicines.

"There are thousands of publications on lanthanides' chemistry without promethium. That was a glaring gap for all of science," said ORNL's Santa Jansone-Popova, who co-led the study. "Scientists have to assume most of its properties. Now we can actually measure some of them."

The research relied on unique resources and expertise available at DOE national laboratories. Using a research reactor, hot cells and supercomputers, as well as the accumulated knowledge and skills of 18 scientists in different fields, the authors detailed the first observation of a promethium complex in solution.

The ORNL scientists bound, or chelated, radioactive promethium with special organic molecules called diglycolamide ligands. Then, using X-ray spectroscopy, they determined the properties of the complex, including the length of the promethium chemical bond with neighboring atoms -- a first for science and a longstanding missing piece to the periodic table of elements.

Promethium is very rare; only about a pound occurs naturally in the Earth's crust at any given time. Unlike other rare earth elements, only minute quantities of synthetic promethium are available because it has no stable isotopes.

For this study, the ORNL team produced the isotope promethium-147, with a half-life of 2.62 years, in sufficient quantities and at a high enough purity to study its chemical properties. ORNL is the United States' only producer of promethium-147.

Notably, the team provided the first demonstration of a feature of lanthanide contraction in solution for the whole lanthanide series, including promethium, atomic number 61. Lanthanide contraction is a phenomenon in which elements with atomic numbers between 57 and 71 are smaller than expected. As the atomic numbers of these lanthanides increase, the radii of their ions decrease. This contraction creates distinctive chemical and electronic properties because the same charge is limited to a shrinking space. The ORNL scientists got a clear promethium signal, which enabled them to better define the shape of the trend -- across the series.

"It's really astonishing from a scientific viewpoint. I was struck once we had all the data," said Ivanov. "The contraction of this chemical bond accelerates along this atomic series, but after promethium, it considerably slows down. This is an important landmark in understanding the chemical bonding properties of these elements and their structural changes along the periodic table."

Many of these elements, such as those in the lanthanide and actinide series, have applications ranging from cancer diagnostics and treatment to renewable energy technologies and long-lived nuclear batteries for deep space exploration.

The achievement will, among other things, ease the difficult job of separating these valuable elements, according to Jansone-Popova. The team has long worked on separations for the whole series of lanthanides, "but promethium was the last puzzle piece. It was quite challenging," she said. "You cannot utilize all these lanthanides as a mixture in modern advanced technologies, because first you need to separate them. This is where the contraction becomes very important; it basically allows us to separate them, which is still quite a difficult task."

The research team used several premier DOE facilities in the project. At ORNL, promethium was synthesized at the High Flux Isotope Reactor, a DOE Office of Science user facility, and purified at the Radiochemical Engineering Development Center, a multipurpose radiochemical processing and research facility. Then, the team performed X-ray absorption spectroscopy at the National Synchrotron Light Source II, a DOE Office of Science user facility at DOE's Brookhaven National Laboratory, specifically working at the Beamline for Materials Measurement, which is funded and operated by the National Institute of Standards and Technology.

The team also performed quantum chemical calculations and molecular dynamics simulations at the Oak Ridge Leadership Computing Facility, a DOE Office of Science user facility at ORNL, using the lab's Summit supercomputer, the only computational resource capable of providing the necessary calculations at the time. In addition, the researchers used resources of the Compute and Data Environment for Science at ORNL. They expect future calculations to be performed on ORNL's Frontier, the world's most powerful supercomputer and the first exascale system, which is able to perform more than a quintillion calculations each second.

Popovs emphasized that the ORNL-led accomplishments can be attributed to teamwork. Each of the Nature paper's 18 authors was critical to the project, he said.

The achievement sets the stage for a new era of research, the scientists said. "Anything that we would call a modern marvel of technology would include, in one shape or another, these rare earth elements," Popovs said. "We are adding the missing link."

Besides Popovs, Ivanov and Jansone-Popova from ORNL's Chemical Sciences Division, the paper's co-authors include Darren Driscoll, Subhamay Pramanik, Jeffrey Einkauf, Santanu Roy and Thomas Dyke, also of ORNL's Chemical Sciences Division; Frankie White, Richard Mayes, Laetitia Delmau, Samantha Cary, April Miller and Sandra Davern of ORNL's Radioisotope Science and Technology Division; Matt Silveira and Shelley VanCleve of ORNL's Isotope Processing and Manufacturing Division; Dmytro Bykov of the National Center for Computational Sciences at ORNL; and Bruce Ravel of the National Institute of Standards and Technology.

This work was primarily co-sponsored by DOE's Office of Science for ligand synthesis, lanthanide complexation studies, crystallization processes, spectroscopic analyses and simulation efforts. The production, purification and preparation of the promethium sample were supported by the DOE Isotope Program, managed by the Office of Science for Isotope R&D and Production. The single-crystal X-ray diffraction data collection and refinement were supported by the DOE Office of Science.

Story Source:

Materials provided by DOE/Oak Ridge National Laboratory. Original written by Lawrence Bernard and Leo Williams. Note: Content may be edited for style and length.

Journal Reference:Darren M. Driscoll, Frankie D. White, Subhamay Pramanik, Jeffrey D. Einkauf, Bruce Ravel, Dmytro Bykov, Santanu Roy, Richard T. Mayes, Lætitia H. Delmau, Samantha K. Cary, Thomas Dyke, April Miller, Matt Silveira, Shelley M. VanCleve, Sandra M. Davern, Santa Jansone-Popova, Ilja Popovs, Alexander S. Ivanov. Observation of a promethium complex in solution. Nature, 2024; 629 (8013): 819 DOI: 10.1038/s41586-024-07267-6

Extreme complexity in formation of rare earth mineral vital for tech industry

Date:May 20, 2024
Source: Trinity College Dublin

Summary:
Researchers have unveiled that myriad, intricate factors influence the genesis and chemistry of bastnasite and rare earth carbonates, which are critically needed for today's tech industry and its hardware outputs. Their work unveils a newly acquired depth of understanding that had previously been unexplored in this field. In combination, the findings mark a significant advancement and promise to reshape our understanding of rare earth mineral formation.


FULL STORY

In a ground-breaking study, researchers from Trinity College Dublin have unveiled that myriad, intricate factors influence the genesis and chemistry of bastnäsite and rare earth carbonates, which are critically needed for today's tech industry and its hardware outputs.

Their work, just published in international journal Global Challenges, unveils a newly acquired depth of understanding that had previously been unexplored in this field. In combination, the findings mark a significant advancement and promise to reshape our understanding of rare earth mineral formation.


Crucially, as global demand for rare earth elements continues to rise -- largely to satisfy the growing demand for the mobile phones, batteries and speakers in which they are put to work -- insights from this research could have far-reaching implications and various industrial and environmental applications.

What have the researchers found?

Contrary to prior assumptions, the new research reveals that the formation of bastnäsite -- the top rare earth mineral exploited by industry -- is not a straightforward process but instead one driven by a very complex interplay of multiple factors.

The experimental approach involved studying the interaction between solutions containing multiple rare earth elements and common calcium-magnesium carbonate minerals like calcite, aragonite and dolomite (which are ubiquitous in nature) under hydrothermal conditions ranging from 21 to 210 °C. The team tested two solution types: one with equal rare earths concentrations, and another one simulating concentrations more typical of the usual hydrothermal fluids found on Earth.

The findings show that when the common calcium-magnesium carbonate minerals react with rare earth-rich fluids, they change their structures and chemical compositions, forming a series of rare earth-bearing minerals with exotic names like lanthanite, kozoite, bastnasite and cerianite, with very complex chemistries, shapes and textures.


Particularly interesting is that different solution types lead to distinct outcomes: For example, equal-concentration solutions promote kozoite and bastnasite crystallisation, maintaining similar rare earths ratios in solids and solutions.


Conversely, hydrothermal fluids mimicking the ones found on Earth result in rare earth-bearing minerals with varied elemental distributions -- and some of these even go through decarbonation processes due to the formation of rare earth oxides.

Ultimately, the experiments showcase the extremely dynamic nature of rare earths mineral formation, with unstable minerals transforming into more stable ones over time, and sometimes developing textures impacted by adjacent mineral reactions that further underscore the complexity of the process.

What are the potential implications?

The implications of this research extend far beyond the laboratory. Understanding the complex processes involved in bastnäsite formation has profound implications for geologists and industry alike. The research demonstrates that the development of advanced simulation models is strongly needed, allowing scientists to replicate natural conditions and explore alternative methods for mineral extraction or synthesis.

While challenges remain, the insights from this study open the door for new experimental protocols to understand the fate of rare earth elements in complex geological ores where they concentrate.

Melanie Maddin, PhD researcher in Geology in Trinity's School of Natural Sciences, is the lead author of this study. She said: "These findings challenge the models previously applied to rare earth mineral formation. Our research highlights the dependence of crystallisation pathways, mineral formation kinetics, and chemical texture on a myriad of factors, including rare earth concentrations, ionic radii, temperature, time, and host grain solubility."


Juan Diego Rodriguez-Blanco, Principal Investigator of the research group and Professor in Trinity's School of Natural Sciences, emphasised the significance of these findings in understanding not only bastnäsite formation but also the broader field of rare earth mineralogy.

Dr Rodriguez-Blanco, a funded investigator in iCRAG (Science Foundation Ireland Research Centre in Applied Geosciences), said: "This study opens new avenues for research in geochemistry and mineralogy, paving the way for a more comprehensive understanding of mineral formation processes."

Story Source:

Materials provided by Trinity College Dublin. Note: Content may be edited for style and length.


Journal Reference:Melanie Maddin, Remi Rateau, Adrienn Maria Szucs, Luca Terribili, Brendan Hoare, Paul C. Guyett, Juan Diego Rodriguez‐Blanco. Chemical Textures on Rare Earth Carbonates: An Experimental Approach to Mimic the Formation of Bastnäsite. Global Challenges, 2024; DOI: 10.1002/gch2.202400074


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Trinity College Dublin. "Extreme complexity in formation of rare earth mineral vital for tech industry." ScienceDaily. ScienceDaily, 20 May 2024. <www.sciencedaily.com/releases/2024/05/240520122731.htm>.


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