[ RadSafe ] Venus Flytrap Material Captures Radioactive Waste

[Cary Renquist]

>From the headline I thought that they were using some sort of Venus
Flytrap derived fibers (or something) to bind Cesium...  

    The new material is part of a class of materials made of spongelike
frameworks of inorganic elements. 
    Over the years, these materials have been used for everything from
catalyzing chemical reactions to 
    capturing carbon dioxide from the air.
    They found that when the cesium enters, it not only displaces DMA,
it also binds to a sulfur atom in 
    the lattice. This tugs on the framework and pulls the holes closed,
thereby trapping the cesium inside, 
    a bit like a molecular Venus flytrap. Further studies also showed
that the material preferentially bound 
    cesium ions even in the presence of chemically similar alkali
metals.

Cary
--
Cary.renquist at ezag.com

Venus Flytrap Material Captures Radioactive Waste -- ScienceNOW 
http://bit.ly/cVHYGN

Of all the radioactive isotopes left over from nuclear weapons testing
and nuclear power plants, cesium-137 is among the most dangerous. The
soft, silvery-white metal has a half-life of 30 years, enters the body
quickly, and can trigger cancer even decades after exposure. Removing
cesium-137 from the environment has proven difficult, but researchers
say they have a promising new way to clean it up: a flexible, porous
solid that grabs cesium ions much like a Venus flytrap ensnares its
prey.

The new material is part of a class of materials made of spongelike
frameworks of inorganic elements. Over the years, these materials have
been used for everything from catalyzing chemical reactions to capturing
carbon dioxide from the air. Mercouri Kanatzidis, a chemist at
Northwestern University in Evanston, Illinois, and his student Nan
Ding--now an assistant professor at Claflin University in Orangeburg,
South Carolina--were working to create one of these inorganic
frameworks, possibly one that could be used to capture environmental
contaminants.

The researchers made their framework from a mixture of gallium, tin, and
sulfur, which formed sheets with holes. They also added dimethylammonium
(DMA) ions. The sheets stacked atop one another with the holes running
up and down through the material and with the DMA ions sitting in
between the layers.

Judging from the size of the holes in the framework, Kanatzidis and Ding
suspected that cesium-137 ions might be able to wiggle through the holes
into the heart of the solid and trade places with the DMA, which, like
the cesium's ions, are positively charged. And that's what happened. But
then to the researchers' surprise, when they attempted to flush out the
cesiums with other charged ions, such as lithium and sodium, the cesium
didn't exchange places as expected and instead remained locked in the
solid.

To find out why, Kanatzidis and Ding took an x-ray snapshot of their
material. They found that when the cesium enters, it not only displaces
DMA, it also binds to a sulfur atom in the lattice. This tugs on the
framework and pulls the holes closed, thereby trapping the cesium
inside, a bit like a molecular Venus flytrap. Further studies also
showed that the material preferentially bound cesium ions even in the
presence of chemically similar alkali metals. That suggests that the
material might work in a chemically complex environment such as one
found at a nuclear cleanup site, the team reports online this week in
Nature Chemistry.

"Binding metal ions is not an easy task. And being able to do that
selectively is difficult," says Omar Yaghi, a chemist and open framework
materials designer at the University of California, Los Angeles.
Kanatzidis says the new material is not likely to head straight for
nuclear cleanup sites. That's because it uses gallium, an expensive
metal. So he and his colleagues are now looking to replace the gallium
with cheaper components for use in similar cesium trapping materials.