Graphene is a somewhat popular material in research labs because of its many wonderful properties, including high strength and conductivity. The atom-thick sheet of carbon also has some weird properties, such as being hydrophobic, except when used to create narrow capillaries. Two years ago researchers at the University of Manchester have tested how graphene dioxide is at filtering water vapor and now they have tested it for filtering liquid water.
In the previous experiment the researchers found that laminates of graphene dioxide were impermeable to all gases and vapors besides water vapor, which passed through as though nothing were there. Even helium, the smallest molecule could not escape. Graphene dioxide was used because it allowed for atom-wide capillaries to be formed by stacking layers on top of each other, forming the laminate. When immersed in water, the laminates did swell up as it absorbed water, but water was still able to flow through very quickly.
Some ions were also able to pass through the membrane, but only those smaller than nine angstroms, or 0.9 nanometers. However the researchers do believe that with more work they will be able to reduce that value, allowing for an ultrafast filtration system that could remove even some of the smallest ions found in seawater.
Source: University of Manchester