Nav: Home

Old molecule, new tricks

January 22, 2020

Fifty years ago, scientists hit upon what they thought could be the next rocket fuel. Carboranes -- molecules composed of boron, carbon and hydrogen atoms clustered together in three-dimensional shapes -- were seen as the possible basis for next-generation propellants due to their ability to release massive amounts of energy when burned.

It was technology that at the time had the potential to augment or even surpass traditional hydrocarbon rocket fuel, and was the subject of heavy investment in the 1950s and 60s.

But things didn't pan out as expected.

"It turns out that when you burn these things you actually form a lot of sediment," said Gabriel Ménard, an assistant professor in UC Santa Barbara's Department of Chemistry and Biochemistry. In addition to other problems found when burning this so-called "zip fuel," its residue also gummed up the works in rocket engines, and so the project was scrapped.

"So they made these huge stockpiles of these compounds, but they actually never used them," Ménard said.

Fast forward to today, and these compounds have come back into vogue with a wide range of applications, from medicine to nanoscale engineering. For Ménard and fellow UCSB chemistry professor Trevor Hayton, as well as Tel Aviv University chemistry professor Roman Dobrovetsky, carboranes could hold the key to more efficient uranium ion extraction. And that, in turn, could enable things like better nuclear waste reprocessing and uranium (and other metal) recovery from seawater.

Their research -- the first example of applying electrochemical carborane processes to uranium extraction -- is published in a paper (link) that appears in the journal Nature.

Key to this technology is the versatility of the cluster molecule. Depending on their compositions these structures can resemble closed cages, or more open nests, due to control of the compound's redox activity -- its readiness to donate or gain electrons. This allows for the controlled capture and release of metal ions, which in this study was applied to uranium ions.

"The big advancement here is this 'catch and release' strategy where you can switch between two states, where one state binds the metal and another state releases the metal," Hayton said.

Conventional processes, such as the popular PUREX process that extracts plutonium and uranium, rely heavily on solvents, extractants and extensive processing.

"Basically, you could say it's wasteful," Ménard said. "In our case, we can do this electrochemically -- we can capture and release the uranium with the flip of a switch.

"What actually happens," added Ménard, "is that the cage opens up." Specifically, the formerly closed ortho-carborane becomes an opened nido- ("nest") carborane capable of capturing the positively-charged uranium ion.

Conventionally, the controlled release of extracted uranium ions, however, is not as straightforward and can be somewhat messy. According to the researchers, such methods are "less established and can be difficult, expensive and or destructive to the initial material."

But here, the researchers have devised a way to reliably and efficiently flip back and forth between open and closed carboranes, using electricity. By applying an electrical potential using an electrode dipped in the organic portion of a biphasic system, the carboranes can receive and donate the electrons needed to open and close and capture and release uranium, respectively.

"Basically you can open it up, capture uranium, close it back up and then release uranium," Ménard said. The molecules can be used multiple times, he added.

This technology could be used for several applications that require the extraction of uranium and by extension, other metal ions. One area is nuclear reprocessing, in which uranium and other radioactive "trans-uranium" elements are extracted from spent nuclear material for storage and reuse (the PUREX process).

"The problem is that these trans-uranium elements are very radioactive and we need to be able to store these for a very long time because they're basically very dangerous," Ménard said. This electrochemical method could allow for the separation of uranium from plutonium, similar to the PUREX process, he explained. The extracted uranium could then be enriched and put back into the reactor; the other high-level waste can be transmuted to reduce their radioactivity.

Additionally, the electrochemical process could also be applied to uranium extraction from seawater, which would ease pressure on the terrestrial mines where all uranium is currently sourced.

"There's about a thousand times more dissolved uranium in the oceans than there are in all the land mines," Ménard said. Similarly, lithium -- another valuable metal that exists in large reserves in seawater -- could be extracted this way, and the researchers plan to take this research direction in the near future.

"This gives us another tool in the toolbox for manipulating metal ions and processing nuclear waste or doing metal capture out of oceans," Hayton said. "It's a new strategy and new method to achieve these types of transformations."

Research in this study was conducted also by Megan Keener (lead author), Camden Hunt and Timothy G. Carroll at UCSB; and by Vladimir Kampel at Tel Aviv University.
-end-


University of California - Santa Barbara

Related Uranium Articles:

Not everything is ferromagnetic in high magnetic fields
High magnetic fields have a potential to modify the microscopic arrangement of magnetic moments because they overcome interactions existing in zero field.
Old molecule, new tricks
Fifty years ago, scientists hit upon what they thought could be the next rocket fuel.
Unused stockpiles of nuclear waste could be more useful than we might think
Chemists have found a new use for the waste product of nuclear power -- transforming an unused stockpile into a versatile compound which could be used to create valuable commodity chemicals as well as new energy sources.
Uranium chemistry and geological disposal of radioactive waste
A new paper to be published on Dec. 16 provides a significant new insight into our understanding of uranium biogeochemistry and could help with the UK's nuclear legacy.
Laser-produced uranium plasma evolves into more complex species
When energy is added to uranium under pressure, it creates a shock wave, and even a tiny sample will be vaporized like a small explosion.
Using building materials to monitor for high enriched uranium
A new paper details how small samples of ubiquitous building materials, such as tile or brick, can be used to test whether a facility has ever stored high enriched uranium, which can be used to create nuclear weapons.
Uranium toxicity may be causing high rates of obesity and diabetes in Kuwait
Kuwait has some of the highest rates of obesity and diabetes in the world, and scientists don't know why.
Bio-inspired material targets oceans' uranium stores for sustainable nuclear energy
Scientists have demonstrated a new bio-inspired material for an eco-friendly and cost-effective approach to recovering uranium from seawater.
Searching for lost WWII-era uranium cubes from Germany
In 2013, Timothy Koeth received an extraordinary gift: a heavy metal cube and a crumpled message that read, 'Taken from Germany, from the nuclear reactor Hitler tried to build.
ORNL investigates complex uranium oxides with help from CADES resources
To accelerate the process of identifying novel uranium oxide phases, an ORNL team studied 4,600 different potential crystal structures of uranium oxide compositions on Metis, a CADES high-performance computing cluster.
More Uranium News and Uranium Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Uncharted
There's so much we've yet to explore–from outer space to the deep ocean to our own brains. This hour, Manoush goes on a journey through those uncharted places, led by TED Science Curator David Biello.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Dispatch 1: Numbers
In a recent Radiolab group huddle, with coronavirus unraveling around us, the team found themselves grappling with all the numbers connected to COVID-19. Our new found 6 foot bubbles of personal space. Three percent mortality rate (or 1, or 2, or 4). 7,000 cases (now, much much more). So in the wake of that meeting, we reflect on the onslaught of numbers - what they reveal, and what they hide.  Support Radiolab today at Radiolab.org/donate.