A research team in the UK has come up with a graphene-based sieve which can remove salt from seawater. This breakthrough could be the solution millions of people need in order to get access to clean drinking water. It’s currently being compared to existing desalination membranes, but appears to be very promising.
The results were reported in the Nature Nanotechnology journal, and showed how the University of Manchester team, led by Dr Rahul Nair, solved some of the complex challenges that arise from using graphene oxide.
Interestingly, it was another team from the same university that had first isolated graphene back in 2004. In case you don’t know, graphene is a single layer of carbon atoms arranged in a hexagonal lattice, where the atoms are at the vertices of the hexagons. It has a host of unusual properties such as electrical superconductivity when coated with lithium, and also shows very high tensile strength.
Now, what’s problematic with graphene is that it’s extremely hard to make, which makes it very expensive, whereas “graphene oxide can be produced by simple oxidation in the lab”, says Dr Nair to BBC News.
There are other challenges, and Dr Nair continues, “To make single layered graphene permeable, you’d need to drill small holes in the membrane. If the hole size is larger than one nanometre, the salts go right through the hole. So you’d have to make a membrane with a very uniform hole size for it to be useful for desalination. Which is really challenging.”
Graphene oxide membranes, however, can keep out nanoparticles much larger than water molecules, such as large salts and organic molecules, but they weren’t able to filter out sodium chloride (NaCl), until now. The team used an epoxy resin to coat the graphene oxide membranes, and voila, NaCl begone!
We hope the breakthrough means that we will see simple portable (and affordable) machines that can input sea water and output pure drinking water soon. With UN projections claiming that by 2025 14 per cent of the world’s population will face water shortages, this might go a long way in preemptively solving that problem.