From: Allison Winter, ENN
Published June 28, 2013 08:45 AM

Chemists Introduce New Energy Efficient Seawater Desalination Method

Having access to fresh water is a human necessity. We rely on fresh water not only for drinking, but also for crop irrigation and food production. And in an ever-changing world, with ever-changing landscapes, many communities are often faced with access limitations to fresh water due to both natural and man-made causes. This is what turns communities to the sea- an abundant, yet salty water source.

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Seawater desalination is one way to address water needs, but many methods rely on large, expensive equipment which is not always efficient. So with this problem comes a solution from chemists at The University of Texas at Austin and the University of Marburg in Germany, as this team has introduced a new method that creates a small electrical field that removes salts from the water. In addition, researchers say this new process consumes less energy and is dramatically simpler than conventional techniques. In fact, the process can run on a store-bought battery.

The technique, called electrochemically mediated seawater desalination, was described last week in the journal Angewandte Chemie. 

To achieve desalination, the researchers apply a small voltage (3.0 volts) to a plastic chip filled with seawater. The chip contains a microchannel with two branches. At the junction of the channel an embedded electrode neutralizes some of the chloride ions in seawater to create an "ion depletion zone" that increases the local electric field compared with the rest of the channel. This change in the electric field is sufficient to redirect salts into one branch, allowing desalinated water to pass through the other branch.

"The neutralization reaction occurring at the electrode is key to removing the salts in seawater," said Kyle Knust, a graduate student at the University of Texas, and first author on the paper.

The ion depletion zone prevents salt from passing through, resulting in the production of freshwater.

So far researchers have achieved 25 percent desalination. Although drinking water requires 99 percent desalination, they are confident that goal can be achieved.

"This was a proof of principle," said Knust. "We've made comparable performance improvements while developing other applications based on the formation of an ion depletion zone. That suggests that 99 percent desalination is not beyond our reach."

This new method holds particular promise for the water-stressed areas in which about a third of the planet's inhabitants live.

Read more at the University of Texas.

Water image via Shutterstock.

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