Scientists have invented a novel way of converting seawater into drinking water, which might be beneficial in disaster zones where electricity is scarce.
The most common technique for removing salt (sodium chloride) from seawater is reverse osmosis, which employs a permeable membrane that permits water molecules but not salt molecules to pass through.
However, this process needs tremendous pressure and significant quantities of power. The membrane frequently clogs, lowering the process’s efficiency.
The novel technology, created by a team of scientists from the Universities of Bath, Swansea, and Edinburgh, employs a modest amount of electrical energy to draw chloride ions through the membrane and toward a positively charged electrode.
This enables water molecules to be pushed through at the same time as chloride molecules, similar to a piston.
Meanwhile, sodium ions are drawn to the negatively charged electrode on the other side of the membrane.
The chloride ions are subsequently recycled back into the saltwater chamber, and the process is repeated, pulling more and more water molecules through.
The study was led by Professor Frank Marken of the University of Bath’s Water Innovation Research Centre (WIRC) and Institute for Sustainability, who suggested that it could be used on a small scale where drinking water is needed but infrastructure is unavailable, 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. 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 miniaturized to use in medical applications such as dosing systems for drugs like insulin.
Frank Marken, Professor, Water Innovation Research Centre, University of Bath
The system is now at the proof-of-concept stage, converting only a few milliliters, but the team is now searching for partners for future collaboration and funding to scale up the process to a liter, allowing them to calculate energy use more precisely.
The researchers would also like to investigate other possible uses, such as drying procedures or water recovery from other sources.
Zhongkai Li and Frank Marken have developed polymeric materials that can act as a new type of molecular electrical pump for water. 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.
Jan Hoffman, Professor and Co-Director, Water Innovation Research Centre, University of Bath
Dr. Mariolino Carta from Swansea University commented, “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.”
Li, Z., et al. (2023) Tuning and Coupling Irreversible Electroosmotic Water Flow in Ionic Diodes: Methylation of an Intrinsically Microporous Polyamine (PIM-EA-TB). ACS Applied Materials & Interfaces. doi:10.1021/acsami.3c10220