Graphene Oxide Membrane

Graphene Oxide (GO) is a derivative of graphene, a 2-d material. This material is available in flakes that has a lot of potential applications including desalination of water. The flakes are stacked by vacuum filtration to form a membrane. The membrane consists of carboxylic acid (CA) and hydroxide (H) functional groups on the edges of the flakes and epoxide (E) and H functional groups on the plane side. The functional groups are distributed randomly and at an equal probability.
The functional groups usually tend to be saturated at a certain are on the flakes generating two regions of the flakes

1. Oxidised Region
2. Pristine Graphene Region

The pristine region of the membrane allows water to flow at a high flux, higher than conventional membrane used in reverse osmosis (RO).

The oxidised region have a low water flux since the flow of water are obstructed by the functional groups. The functional groups have strong interaction with water molecules. Interaction exhibits between water molecules with functional groups;

1. Van Der Waals
2. Formation of Hydrogen bond
3. Coulombic

Water tend to be adsorbed at the functional group region of the membrane. The adsorption of water causes the membrane to swells to accommodate more water molecules at a high pressure. The most favourable sites for water molecules to be adsorbed inside the membrane;

1. Edges of membrane (CA, E)
2. Plane of membrane (H, E)

Stacked GO flakes form a membrane which have interlayer distance in between flakes. Typical ....