by Jane Bird
New approaches to filtration and extracting moisture from air promise to alleviate the world’s looming water scarcity crisis.
Filtration is being transformed by thin sheets of graphene, a carbon-based material invented in 2004 at Manchester University. Rahul Raveendran Nair, the university’s professor of materials physics, says graphene has the potential to deliver large quantities of clean water via desalination and the removal of pollutants.
Meanwhile, improved technology for capturing water vapour from the air holds out hope for arid regions.
In April 2017, Prof Nair demonstrated that a multi-layer membrane made from graphene oxide can filter out the sodium chloride in seawater much more quickly and cleanly than existing techniques.
“The graphene filter is like a mesh or sieve with holes so small that salt molecules cannot pass through,” Prof Nair says. The filters were recently shown to be able to filter even the dye molecules of whisky, turning the liquid colourless. The university is in talks with potential manufacturers with a view to enlarging the membranes — currently A4-sized — and demonstrating that the technology can be used in practical applications.
“We have shown it works in the laboratory, now we want to demonstrate it in realistic conditions,” says Prof Nair. He hopes full-sized desalination plants with graphene membranes will be possible within five years.
Commitments to existing desalination technology may hold back large-scale commercial development of graphene systems in the short term, Prof Nair says. However, he thinks that a small scale version of the graphene filter can be developed for bottles and household units within two years.
To explore the possibilities, the university is collaborating with Icon Lifesaver, a company based in the east of England. The business currently makes filters that can remove microbes, bacteria and viruses. Joe Lovegrove, technical manager of Icon Lifesaver, says: “Graphene has the potential to create the ultimate filter that can also take out chemicals, solutes, salts and compounds such as pesticides.
“Its scope is absolutely massive. It would give us effectively the ultimate water filter that you could use to convert water at any source from being dangerous to safe as quickly as you can drink it.” Icon Lifesaver hopes to demonstrate that 400ml and 750ml bottles with easy-to-clean filters are viable for mass production. “People don’t want to spend time and effort cleaning,” says Mr Lovegrove.