Water, Research - Graphene Sieve Turns Seawater Into Drinking Water

Researchers have created a new type of sieve to filter out common salts in seawater to make it safe to drink.  The filter is made from graphene, a sort of miracle material known for its strength and conductivity that has scientists racing to find new applications.

A research team at the University of Manchester had to overcome various obstacles, as they state in their results in the journal Nature Nanotechnology.  Such as, producing graphene in large quantities for a seawater filter is difficult and expensive.  They solved this by using graphene oxide which "can be produced by simple oxidation in the lab," according to lead researcher Dr. Rahil Nair.

"As an ink or solution, we can compose it on a substrate or porous material.  Then we can use it as a membrane," said Dr. Nair, "In terms of scalability and the cost of the material, graphene oxide has a potential advantage over single-layered graphene."

After that, the trick is to drill holes in the membrane to allow water to flow through.  "But if the hole size is larger than one nanometre, the salts go through that hole.  You have to make a membrane with a very uniform less-than-one-nanometre hole size to make it useful for desalination," Nair told BBC.  "It is a really challenging job," he added.

Scientists have already used graphene oxide to filter out small nanoparticles, organic molecules, and even large salts.  But then arises the third challenge.  Graphene Oxide swells ever so slightly when immersed in water.  That allows the smaller salts of seawater to flow through the pores along with water molecules.  Dr. Nair and colleagues got around that by bolstering each side of the graphene oxide with walls made of epoxy resin to lock it into place.

The next step will be to test the new technology against the best of what's already out there.

The need for better desalination filters is very real.  Because of climate change and pollution, the United Nations forecasts that 14 percent of the world's population will encounter water scarcity.