A team of international researchers has found a new way to purify water using a filter made of plasma-charged carbon nano-tubes that can easily remove harmful contaminants and even salt from otherwise undrinkable water.

The new filters are small and easy to integrate into a teapot-sized portable water purifier. For poor or remote villages, these devices would be much more practical than building a large-scale purification plant, which would require a large amount of energy and high labour costs to keep running.

The project was a collaboration between Singapore University of Technology and Design, led by Associate Professor Hui Ying Yang, CSIRO, Massachusetts Institute of Technology (MIT), the University of Sydney, and Hong Kong Polytechnic University.

“Small portable purification devices are increasingly recognised as the best way to meet the needs of clean water and sanitation in developing countries and in remote locations, minimising the risk of many serious diseases,” said Dr Zhaojun Han, of CSIRO’s world-leading Plasma Nanoscience Laboratories.

“The large industrialised purification plants we see in other parts of the world are just not practical – they consume a large amount of energy and have high labour costs, making them very expensive to run.”

Although some smaller portable devices do already exist, because they rely on reverse osmosis and thermal processes, they are able to remove salt ions but are unable to filter out organic contaminants from the briny water found in some river and lake systems.

“For people in remote locations, briny water can sometimes be the only available water source,” Han says. “That’s why it’s important to not only be able to remove salts from water, but to also be able to put it through a process of purification.”

“Our study showed that carbon nanotube membranes were able to filter out ions of vastly different sizes – meaning they were able to remove salt, along with other impurities.”

The other downside of existing portable devices is that they require a continuous power supply to operate their thermal processes. The new membranes can be operated as a rechargeable device, making them perfect for locations without access to electricity.

Now that the effectiveness of the method has been proven, the research team plans to extend the project to investigate the filtration properties of other nanomaterials. They will begin by looking at graphene, which has similar properties to carbon nanotubes, but could be made considerably denser and stronger.