Graphene membrane enables single-step water purification

Monday, 19 February, 2018

Graphene membrane enables single-step water purification

CSIRO scientists have used their own specially designed form of graphene to make water purification simpler, more effective and quicker. Published in the journal Nature Communications, their breakthrough potentially solves one of the great problems with current water filtering methods: fouling.

Over time, chemical- and oil-based pollutants coat and impede water filters, meaning contaminants have to be removed before filtering can begin. As the world’s strongest material, graphene is an ideal candidate for filtering applications — or would be, if it wasn’t typically water repellent.

Last year, the CSIRO team succeeded in creating a graphene film with microscopic nanochannels that let water pass through, but stop pollutants. According to lead author Dr Dong Han Seo, their ‘Graphair’ membrane can “replace the complex, time-consuming and multistage processes currently needed with a single step”.

As an added advantage, Graphair is said to be simpler, cheaper, faster and more environmentally friendly than graphene to make. It consists of renewable soybean oil, more commonly found in vegetable oil.

A Graphair sample.

Looking to prove their technology in a real-world setting, Dr Seo and his colleagues took water samples from Sydney Harbour and ran it through a commercially available water filter that had been coated with Graphair. Researchers from QUT, the University of Sydney, UTS and Victoria University then tested and analysed its water purification qualities.

Without Graphair, the membrane’s filtration rate halved in 72 hours. When the Graphair was added, the membrane filtered even more contaminants (99% removal) faster. Even when coated with pollutants, the membrane continued to work.

“Our graphene membrane enables 100% salt rejection as well as 100% rejection of household contaminants such as detergents and oil without fouling, which was tested over many days,” Dr Seo said.

Dr Seo described Graphair as “a perfect filter for water purification” with an enormous potential impact, noting that “what we are talking about is eliminating all the expensive complex pre-treatment water treatment process”.

“This technology can create clean drinking water, regardless of how dirty it is, in a single step,” Dr Seo said. “All that’s needed is heat, our graphene, a membrane filter and a small water pump.”

CSIRO is currently looking for industry partners to scale up the technology so it can be used to filter a home or even town’s water supply. It is also investigating other applications, such as the treatment of sea water and industrial effluents.

“We’re hoping to commence field trials in a developing-world community next year,” Dr Seo said.

Top image caption: Dr Dong Han Seo.

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