Fixed pore size in graphene-oxide membranes shows promise for drinking water

The findings from a group of scientists at Manchester University were published today in Nature Nanotechnology. 

Graphene-oxide membranes developed at the National Graphene Institute have already demonstrated the potential for filtering small nanoparticles, organic molecules, and large salts. They couldn’t, however, be used for sieving common salts used in desalination technologies, which require even smaller sieves.

Previous research at Manchester University found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger molecules are blocked.

The Manchester-based group has now further developed these graphene membranes and have found a strategy to avoid swelling when exposed to water. According to the University, the pore size in the membrane can be precisely controlled to sieve common salts out of salty water and make it safe to drink.

When the common salts are dissolved in water, they form a ‘shell’ of water molecules around the salt's molecules that allow the capillaries of the graphene-oxide membranes to block the salt from flowing along with the water. Water molecules are able to pass through the membrane barrier and flow quickly, which is ideal for application of these membranes for desalination.