Graphene sieves can turn seawater into drinking water by filtering common salts from water to make it safe to drink. Graphene-oxide membranes have attracted lots of attention for new filtration technologies. These findings came from a group of scientists at the University of Manchester that were published in the journal Nature Nanotechnology on the 4th of April 2017. Previously graphene-oxide membranes had shown potential for gas separation and water filtration.
Graphene-oxide membranes that were developed at the National Graphene Institute have already shown that they can be used to filter out small nanoparticles, organic molecules, and large salts. However, they couldn’t be used for sieving out common salts which would require smaller sieves. Previous research at the University of Manchester found that when in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger ions or molecules are blocked. The group from Manchester have developed these graphene membranes and found a strategy so the membranes wont swell when in water. They can precisely control the pore size in the membrane which can sieve common salts out of water making it safe to drink. They use realisation of scalable membranes with uniform pore size down to atomic size to do this. When common salts are dissolved in water a ‘shell’ of water molecules will form around the salts molecules.
The tiny capillaries of the graphene-oxide membranes can then block the salt from flowing along with water. Water molecules are able to pass through the membrane barrier and flow fast which is ideal for application of these membranes for desalination.