The new technique, developed by a team of scientists from the Universities of Bath, Swansea and Edinburgh in the UK, doesn’t use any external pressure but instead uses a small amount of electrical energy to pull chloride ions through a membrane towards a positively charged electrode.
This causes water molecules to be pushed through at the same time as the chloride, a bit like a piston.
Meanwhile, sodium ions remain on the other side of the membrane, attracted to the negatively charged electrode.
The chloride ions are then recycled back into the chamber containing the salt water and the process is repeated, gradually drawing more and more water molecules through.
Professor Frank Marken, from the University of Bath’s Water Innovation Research Centre and Institute for Sustainability, who led the study, predicts this could be used on a small scale where drinking water is needed but there is not the infrastructure available, such as in remote areas or disaster zones.
“Currently reverse osmosis uses so much electricity, it requires a dedicated power plant to desalinate water, meaning it is difficult to achieve on a smaller scale,” said Professor Marken. “Our method could provide an alternative solution on a smaller scale, and because water can be extracted without any side products, this will save energy and won’t involve an industrial scale processing plant. It could also potentially be miniaturised to use in medical applications such as dosing systems for drugs like insulin.”
"Zhongkai Li and Frank Marken have developed polymeric materials that can act as a new type of molecular electrical pump for water,” said Professor Jan Hoffman, Co-Director of the Water Innovation Research Centre (WIRC) at Bath.
“I think the discovery can potentially have a revolutionary impact on desalination of seawater and also processes for drying materials and recovering water. Of course, there is still a long way to go to create full scale technology based on the recent discovery, but it definitely looks promising and very innovative compared to existing pumping and desalination technologies."
Dr Mariolino Carta from Swansea University, said: "Microporous materials have enormous potential especially in separation and water purification, but also in catalysis. In the future even better materials and processes will be available."
The technology is currently at the proof-of-concept stage, converting only a few millilitres. The team is now looking for partners for potential collaboration and investment to scale up the process to a litre which will enable them to calculate energy consumption more accurately.
The team would also like to explore other potential applications such as drying processes or recovering water from different sources.
Individuals or organisations wishing to find out more or collaborate should contact Dr Frank Marken.
Tuning and Coupling Irreversible Electroosmotic Water Flow in Ionic Diodes: Methylation of an Intrinsically Microporous Polyamine (PIM-EA-TB), is published in the journal ACS Applied Materials & Interfaces. DOI: 10.1021/acsami.3c10220
The research was funded by the Engineering and Physical Sciences Research Council.
