01-22-2008, 04:16 AM
There is some interesting information in this story.
(It was submitted but rejected by DU-Watch by the way.)
http://tinyurl.com/2u2ots
'Pac-Man' molecule chews up uranium contamination
* 17 January 2008
* From New Scientist Print Edition. Subscribe and get 4 free issues
* Paul Marks
A MOLECULE that can bite a uranium-containing ion between its "jaws", not unlike the munching blob in the arcade game Pac-Man, could one day lead to a way to clean up groundwater contaminated with the toxic metal.
Uranium leaches into groundwater from natural deposits of its ore, depleted uranium munitions, nuclear facilities and the detritus of uranium mining. It occurs most commonly in the form of the water-soluble uranyl ion, (UO2)2+, in which the uranium atom is linked to two oxygen atoms by double bonds.
Allowing uranyl to react with other substances might change it into a different, insoluble ion, which can be filtered out. But uranium binds very strongly to oxygen - the bonds it forms are 25 per cent stronger than typical double bonds - making the uranyl ion very stable. Combined with its solubility, this makes dissolved uranium virtually impossible to remove. "It's a very problematic, persistent groundwater contaminant," says Polly Arnold, a chemist at the University of Edinburgh in the UK.
Enter Pac-Man. Arnold's colleague Jason Love had been working on improving catalysts for fuel cells using a large organic molecule known as a macrocycle, that can fold in half to form a structure like a pair of jaws. Love was using the gap between the jaws to capture a pair of cobalt ions, but Arnold realised that it was just the right size and shape to clamp onto a uranyl ion.
When she added the macrocycle molecule to uranyl ions dissolved in an organic solvent, she found that it did indeed capture them in its jaws, leaving one oxygen atom protruding (Nature, DOI: 10.1038/nature06467). What's more, a silicon-containing compound present in the mixture was able to bind to the protruding oxygen atom, a sign that the uranyl's stubborn bonds with oxygen had been weakened.
Because the macrocycle is destroyed by water, it cannot be used to remove uranium from contaminated water. But Arnold's team believe their demonstration that the uranyl ion's bonds can be loosened is a first step towards finding substances that can transform dissolved uranyl into an insoluble compound. "No one has been able to do this before," says Arnold. "We might now be able to develop and suggest new pathways for uranium removal from solution."
Robin Taylor, a chemist with Nexia Solutions, the research arm of British Nuclear Fuels in Sellafield in the UK, says the findings will help develop better processes for uranium sequestration and boost confidence in dealing with nuclear materials and waste.
The Edinburgh team will also investigate how some bacteria and iron-rich minerals reduce uranium concentrations naturally in contaminated water, and whether the macrocycle is able to loosen bonds in ions containing plutonium.
The Nuclear Age - Learn more about all things nuclear in our explosive special report.
From issue 2639 of New Scientist magazine, 17 January 2008, page 24
(It was submitted but rejected by DU-Watch by the way.)
http://tinyurl.com/2u2ots
'Pac-Man' molecule chews up uranium contamination
* 17 January 2008
* From New Scientist Print Edition. Subscribe and get 4 free issues
* Paul Marks
A MOLECULE that can bite a uranium-containing ion between its "jaws", not unlike the munching blob in the arcade game Pac-Man, could one day lead to a way to clean up groundwater contaminated with the toxic metal.
Uranium leaches into groundwater from natural deposits of its ore, depleted uranium munitions, nuclear facilities and the detritus of uranium mining. It occurs most commonly in the form of the water-soluble uranyl ion, (UO2)2+, in which the uranium atom is linked to two oxygen atoms by double bonds.
Allowing uranyl to react with other substances might change it into a different, insoluble ion, which can be filtered out. But uranium binds very strongly to oxygen - the bonds it forms are 25 per cent stronger than typical double bonds - making the uranyl ion very stable. Combined with its solubility, this makes dissolved uranium virtually impossible to remove. "It's a very problematic, persistent groundwater contaminant," says Polly Arnold, a chemist at the University of Edinburgh in the UK.
Enter Pac-Man. Arnold's colleague Jason Love had been working on improving catalysts for fuel cells using a large organic molecule known as a macrocycle, that can fold in half to form a structure like a pair of jaws. Love was using the gap between the jaws to capture a pair of cobalt ions, but Arnold realised that it was just the right size and shape to clamp onto a uranyl ion.
When she added the macrocycle molecule to uranyl ions dissolved in an organic solvent, she found that it did indeed capture them in its jaws, leaving one oxygen atom protruding (Nature, DOI: 10.1038/nature06467). What's more, a silicon-containing compound present in the mixture was able to bind to the protruding oxygen atom, a sign that the uranyl's stubborn bonds with oxygen had been weakened.
Because the macrocycle is destroyed by water, it cannot be used to remove uranium from contaminated water. But Arnold's team believe their demonstration that the uranyl ion's bonds can be loosened is a first step towards finding substances that can transform dissolved uranyl into an insoluble compound. "No one has been able to do this before," says Arnold. "We might now be able to develop and suggest new pathways for uranium removal from solution."
Robin Taylor, a chemist with Nexia Solutions, the research arm of British Nuclear Fuels in Sellafield in the UK, says the findings will help develop better processes for uranium sequestration and boost confidence in dealing with nuclear materials and waste.
The Edinburgh team will also investigate how some bacteria and iron-rich minerals reduce uranium concentrations naturally in contaminated water, and whether the macrocycle is able to loosen bonds in ions containing plutonium.
The Nuclear Age - Learn more about all things nuclear in our explosive special report.
From issue 2639 of New Scientist magazine, 17 January 2008, page 24