Graphene-Oxide Filter Can Turn Your Whiskey, Cognac Colorless

Graphene-oxide membranes are known to be great filters. They have been modified in the past to be impermeable to all solvents except water. The International Business Times had reported in April that a team of researchers from the University of Manchester has made a breakthrough that could potentially change the way we drink water. They used a grapheme-oxide membrane that can be used as a sieve to remove salt from seawater. Now, the same team has tweaked the filter around a bit to remove the amber pigment from whiskey, making it clear.

A study published by a team of researchers from the University of Manchester in journal Nature Materials shows that tailor-made grapheme-oxide layers can let only certain molecules pass through them by manipulating the size.

The study was led by Professor Rahul Nair at the National Graphene Institute and School of Chemical Engineering and Analytical Science at The University of Manchester. The team used ultra-thin membranes of graphene-oxide sheets which were manipulated and arranged on a molecular level so that they let only organic dyes dissolved in methanol pass through. These pores on the surface of the membrane were nearly a few nanometers wide.

The pinhole structure of the pores were formed by interconnecting graphene nanochannels, which produces an ‘atomic-scale sieve allowing the large flow of solvents through the membrane,’ said a press release by the University of Manchester.

This method which is being dubbed as organic solvent nanofiltration (OSN) differs from the other study published by the team where grapheme based microfilters were used to desalinate salt water. Here, OSN technology separates charged or uncharged organic compounds from an organic solvent.

The team demonstrated the new improvement on the filter by using it to completely remove various organic dyes as small as a nanometre dissolved in methanol.

"Just for a fun, we even filtered whiskey and cognac through the graphene-oxide membrane. The membrane allowed the alcohol to pass through but removed the larger molecules which give the amber color. The clear whiskey smells similar to the original whiskey but we are not allowed to drink it in the lab, however, it was a funny Friday night experiment!" Nair said in the release.

The OSN method proved an improvement on the desalination filters by boasting of an increased flow rate of the solvent which helped speed up up the filtration process.

"Chemical separation is all about energy, various chemical separation processes consume about half of industrial energy usage. Any new efficient separation process will minimize the consumption of energy, which is in high demand now. By 2030, the world is projected to consume 60% more energy than today," Prof. Nair added.

Dr. Su, who led the experiment, added that the function of the filter is not restricted to alcohol. The developed membranes have a very precise sieve size which can be manipulated in very miniscule proportions. The high flux that the OSN method displays opens up 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," she added.

By using ultra-thin membranes, this is the first clear-cut experiment to show how other solvents can be filtered out, proving that there is potential for organic solvent nanofiltration.

Graphene- the world's first two-dimensional material is known for its versatile superlatives, it can be both hydrophobic and hydrophilic, stronger than steel, flexible, bendable and one million times thinner than a human hair.