Researchers at the National Graphene Institute and School of Chemical Engineering and Analytical Science at The University of Manchester have developed an ultra-thin membrane using graphene-oxide sheets, that were assembled in a way that they were able to completely remove various organic dyes, dissolved in methanol, which were as small as a nanometre. This is exciting as GO membranes were once thought to be permeable only to aqueous solutions, but the researchers developed a new form of graphene oxide membrane that can filter organic solvents.
In the newly developed ultrathin membranes, graphene-oxide sheets are assembled in such a way that pinholes formed during the assembly are interconnected by graphene nanochannels, which produces an atomic-scale sieve allowing the large flow of solvents through the membrane. When used to filter Cognac and whisky, the membrane permitted alcohol to pass through but trapped the larger molecules that gives the whisky its color. Professor Nair, which led the group, said that "the clear whisky smells similar to the original whisky but we are not allowed to drink it in the lab, however it was a funny Friday night experiment!”
The newly developed membranes not only filter out small molecules but it boosts the filtration efficiency by increasing the solvent flow rate. The scientists added: “the developed membranes are not only useful for filtering alcohol, but the precise sieve size and high flux open new opportunity to separate molecules from different organic solvents for chemical and pharmaceutical industries. This development is particularly important because most of the existing polymer-based membranes are unstable in organic solvents whereas the developed graphene-oxide membrane is highly stable”.