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Research Water easily evaporates through graphene oxide membranes but they represent an impermeable barrier for other molecules.
Image Credit: Dr Rahul R.Nair

Published on February 17th, 2014 | by James Ayre

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Graphene’s Great Water-Filtration Potential Unveiled By New Research

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February 17th, 2014 by
 
The great potential that graphene has shown with regard to electronics and energy technologies is well known, but there’s quite a bit more to graphene than ‘just’ that…. In particular, the material possesses a number of strange qualities with regard to its interactions with water — qualities that are now ripe for exploitation, according to new research from the University of Manchester.

Water easily evaporates through graphene oxide membranes but they represent an impermeable barrier for other molecules. Image Credit: Dr Rahul R.Nair

Water easily evaporates through graphene oxide membranes but they represent an impermeable barrier for other molecules.
Image Credit: Dr Rahul R.Nair

Previous work had shown that thin membranes made from graphene oxide laminates were impermeable to all gases and vapours, except for water. And now, new research has built on this discovery by testing the effectiveness of these membranes with regard to water filtration — producing findings that show that they have an astonishingly accurate mesh that allows “them to distinguish between atomic species that are only a few percent different in size,” and that they’re ultrafast, filtering with a speed similar to that of warm liquid passing through a coffee filter.

The press release from the University of Manchester explains the research:

The researchers report that, if immersed in water, the laminates become slightly swollen but still allow ultrafast flow of not one but two monolayers of water. Small salts with a size of less than nine Angstroms can flow along but larger ions or molecules are blocked. Ten Angstroms is equivalent to a billionth of a metre.

The graphene filters have an astonishingly accurate mesh that allows them to distinguish between atomic species that are only a few percent different in size. On top of this ultraprecise separation, it is also ultrafast. Those ions that can go through do so with such a speed that it’s as if the graphene membranes were an ordinary coffee filter.

The latter effect is due to a property that the Manchester scientists call “ion sponging.” Their graphene capillaries suck up small ions as powerful hoovers leading to internal concentrations that can be hundreds of times higher than in external salty solutions.

Researcher Dr Rahul Nair stated: “The water filtration is as fast and as precise as one could possibly hope for such narrow capillaries. Now we want to control the graphene mesh size and reduce it below nine Angstroms to filter out even the smallest salts like in seawater. Our work shows that it is possible.”

The co-author of the new study, Dr Irina Grigorieva, added: “Our ultimate goal is to make a filter device that allows a glass of drinkable water made from seawater after a few minutes of hand pumping. We are not there yet but this is no longer science fiction.”

The new research was just published in the journal Science.

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.



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