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Graphene used to filter sea water into drinking water

RATE THIS! +26
Posted in Science on 29th Mar, 2014 12:03 AM by AlexMuller

Graphene has proven itself as a wonder material with a vast range of unique properties. Graphene is hydrophobic; it repels water, but narrow capillaries made from graphene vigorously suck in water allowing its rapid permeation, if the water layer is only one atom thick, that is, as thin as graphene itself.

 
This bizarre property has attracted intense academic and industrial interest with intent to develop new water filtration and desalination technologies.
 
One-atom-wide graphene capillaries can now be made easily and cheaply by piling layers of graphene oxide, a derivative of graphene, on top of each other. The resulting multilayer stacks (laminates) have a structure similar to nacre (mother of pearl), which makes them also mechanically strong.
 
Two years ago, University of Manchester researchers discovered that thin membranes made from such laminates were impermeable to all gases and vapours, except for water. This means that even helium, the hardest gas to block off, cannot pass through the membranes whereas water vapour went through with no resistance.
 
Now the same team led by Dr Rahul Nair and Prof Andre Geim has tested how good the graphene membranes are as filters for liquid water. The results appear in the latest issue (Feb 14, 2014) of Science.
 
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 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.

Tags: graphenewaterdesalinationnanotechnology

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Comments

Author: Guest
Posted: 2014-03-29
+3
Access to clean drinking water is essential and is lacking in some parts of the world and in any case new methods in this area would benefit all. The task here is to see how to make methods using graphene affordable
4 Replies
Author: Guest
Posted: 2014-03-29
+0
For this method, both the required membrane size and costs for the application of producing pure water may be a limitation at present. Reply
Author: Guest
Posted: 2014-03-29
+0
Yes, and scaling up the process to produce useful sheets of the permeable graphene, while maintaining control over the pore sizes, will require further research - however, this may be quite soon! Reply
Reply
Author: Guest
Posted: 2014-03-29
+0
It is interesting that researchers are thinking about exploring biological applications of improved graphene, such as sensors for disease agents in the bloodstream, or delivery systems for targeting insoluble drugs to specific areas of the body. This could be very exciting and useful Reply


 

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