Is Graphene the Perfect Water Filter of the Future?

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Graphene: The Super-Material of the 21st Century

Graphene - a thin sheet of carbon atoms - along with its cousin, the carbon nanotube, is one of the most promising materials discovered in a long time. It has superlative properties when it comes to strength, thinness, conductivity, optics, etc. We know a lot about, but scientists and engineers are still finding new ways to use it. The latest discovery has to do with a property of graphene that makes it superpermeable with respect to water.

When a metal container was sealed with such a film, even the most sensitive equipment was unable to detect air or any other gas, including helium, to leak through.

It came as a complete surprise that, when the researchers tried the same with ordinary water, they found that it evaporates without noticing the graphene seal. Water molecules diffused through the graphene-oxide membranes with such a great speed that the evaporation rate was the same independently whether the container was sealed or completely open.

Dr Rahul Nair, who was leading the experimental work, offers the following explanation: “Graphene oxide sheets arrange in such a way that between them there is room for exactly one layer of water molecules. They arrange themselves in one molecule thick sheets of ice which slide along the graphene surface with practically no friction.

“If another atom or molecule tries the same trick, it finds that graphene capillaries either shrink in low humidity or get clogged with water molecules.” (source)

This should allow graphene to be used to purify water, removing everything else from it and thus making it drinkable.

There might be other technical or economic reasons why graphene won't be used in water filtration any time soon, but economies of scale should make it cheaper to produce every year, and this superpermeability could make it useful for at least some water filtration tasks (ie. when you need to remove extremely toxic molecules from water and you need to be sure that you caught every last one of them).

Via Manchester U.

Tags: Water Crisis

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