How To Obtain Drinkable Water From Sea Water

Membranes made from graphene oxide could act as perfect molecular sieves when immersed in water, blocking all molecules or ions with a hydrated size larger than 9 Å. This new result, from researchers at the University of Manchester in the UK, means that the laminated nanostructures might be ideal for water filtration and desalination applications.
Graphene is a sheet of carbon just one atom thick in which the atoms are arranged in a honeycomb lattice. Graphene oxide is like ordinary graphene but is covered with molecules such as hydroxyl groups. Graphene-oxide sheets can easily be stacked on top of each other to form extremely thin but mechanically strong membranes. These membranes consist of millions of small flakes of graphene oxide with nanosized empty channels (or capillaries) between the flakes.

Water and small-sized ions and molecules permeate super fast in the graphene-oxide membrane, but larger species are blocked. The size of the membrane mesh can be tuned by adjusting the nanochannel size
According to the team, the membranes could be ideal for removing valuable salts and molecules from contaminated larger molecules – for example during oil spills. “More importantly, our work shows that if we were able to further control the capillary size below 9 Å, we should be able to use these membranes to filter and desalinate water,” says co-team-leader Rahul Nair.
Indeed, the team says that it is now busy looking at ways to control the mesh size of the graphene oxide and reduce it to about 6 Å so that the membranes can filter out even the smallest salts in sea water. “We might achieve this by preventing the graphene-oxide laminates from swelling when they are placed in water,” says Nair.
Our ultimate goal would be to make a filter device from the carbon-based material that allows you to obtain a glass of drinkable water from sea water using a hand-held mechanical pump,” adds team member Irina Grigorieva.