Researchers Say Low-Cost Way to Make Seawater Drinkable is Near

Sometime soon, making seawater drinkable may be as easy as picking up a battery at the nearest mini-mart.

Chemists at the University of Texas at Austin and the University of Marburg in Germany have announced a new way of separating salt from of seawater that is much simpler than previous methods and, according to a UT press release, "requires so little energy that it can run on a store-bought battery."

The technique, called electrochemically mediated seawater desalination, uses a small electrical field that removes salts from seawater, according to a recent study published in the journal Angewandte Chemie.

"The availability of water for drinking and crop irrigation is one of the most basic requirements for maintaining and improving human health," said research leader Richard Crooks, UTA's Robert A. Welch Chair in Chemistry in the College of Natural Sciences.

"Seawater desalination is one way to address this need, but most current methods for desalinating water rely on expensive and easily contaminated membranes," he said. "The membrane-free method we've developed still needs to be refined and scaled up, but if we can succeed at that, then one day it might be possible to provide fresh water on a massive scale using a simple, even portable, system."

To achieve desalination, researchers applied small electrical voltage (3.0 volts) to a plastic chip that was filled with seawater and also contained a small channel with two branches and an electrode positioned at their junction.

The electrode, the study explained, neutralized a portion of the chloride ions contained in the seawater to create a zone in which the ions were depleted and the localized electrical field was boosted, compared with the rest of the channel.

The change in the electric field was strong enough to redirect salts into one branch, allowing desalinated water to pass through the other branch.

The zone of depleted ions basically kept the salt from passing through, resulting in the production of fresh water.

The paper explained Crooks and his colleagues have so far achieved 25 percent desalination through their new technique, though drinking water requires 99 percent desalination.

Nonetheless, said Kyle Knust, a graduate student in Crooks' lab and first author on the paper, "This was a proof of principle. 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."

The new desalination method --- which was primarily funded by the United States Department of Energy, but supported in part by the startup Okeanos Technologies, which has a pending patent on the new technology --- is expected sometime in the future provide an inexpensive source of drinkable water in the regions of the world where salt water is abundant but fresh water is severely limited.

"People are dying because of a lack of fresh water," said Tony Frudakis, founder and CEO of Okeanos Technologies. "And they'll continue to do so until there is some kind of breakthrough, and that is what we are hoping our technology will represent."

Even though the new desalination system is now only able to create very small amounts of fresh water, he continued, approaches are already being drawn up to meet the needs of entire communities.

Okeanos, Frudakis said, "has even contemplated building a small system that would look like a Coke machine and would operate in a standalone fashion to produce enough water for a small village."