New low-power desalination method could be used in disaster zones

New method for purifying drinking water could be used in disaster-hit areas with limited electrical power.

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Researchers from the UK’s Universities of Bath, Swansea, and Edinburgh have developed a new desalination method that converts seawater into drinking water that could be useful in disaster zones where there is limited electrical power.

Reverse osmosis is the most popular method for removing salt (sodium chloride) from seawater. This process uses a porous membrane to filter out the salt and other impurities, leaving behind fresh water.

Reverse osmosis has become increasingly popular in recent years due to its effectiveness and efficiency in producing clean water from seawater. However, the method also requires a substantial amount of electricity in order to generate the necessary water-pushing pressure. Also, the membrane often clogs up with captured salt, reducing the efficiency of the process.

The new technique doesn’t utilize any external pressure but instead uses a small amount of electrical energy to pull chloride ions through the porous membrane toward a positively charged electrode.

As a result, water molecules get pushed through the membrane along with the chloride ions, just like a piston. Meanwhile, sodium ions remain on the other side of the membrane and are attracted towards the negatively charged electrode.

The chloride ions are then recycled back into the chamber holding the saltwater, and the process is repeated, drawing more and more water molecules through gradually. Eventually, most of the water will accumulate on the positive-electrode side of the membrane, completely free of salt.

Researchers predict that 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,” Professor Frank Marken, who led the study, said in an official statement. “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.”

The new desalination technology is currently at the proof-of-concept stage and can only convert a few milliliters of water at a time. The team is actively seeking partners for potential collaboration and investment to help develop the technology up to the point that it can process one liter of water, which will provide more accurate calculations of energy consumption.

Moreover, the team is keen to explore other potential applications of this technology, such as drying processes and water recovery from different sources.

Journal reference:

  1. Zhongkai Li, John P. Lowe, Philip J. Fletcher, Mariolino Carta, Neil B. McKeown, and Frank Marken. Tuning and Coupling Irreversible Electroosmotic Water Flow in Ionic Diodes: Methylation of an Intrinsically Microporous Polyamine (PIM-EA-TB). ACS Applied Materials and Interfaces, 2023; DOI: 10.1021/acsami.3c10220

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