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Multipurpose device shows desalination potential

With an added potential capability of desalination, innovative chemists at the University of California, Irvine (UCI), have developed a new solar powered generator.

The innovators are calling their prototype the ‘synthetic, light-driven proton pump’ because of its potable water potential.

The device is similar to silicon photovoltaic cells but differs in that instead of being produced via electrons, its electricity comes from the motion of ions.

“The materials used to make such a device can be dirt-cheap,” said Shane Ardo, UCI assistant professor of chemistry. “We’re talking about common polyethylene plastic, light-absorbing dye molecules and water.”

How does the desalination work?

In Ardo’s laboratory, researchers devised a system based on dual layers of dye-coated, ion-transporting membranes. When struck with light from a laser pointer – a laboratory simulation of sunlight – the dye releases ions.

Positively charged protons, also known as cations, pass through one sheet, while negatively charged hydroxides, also known as anions, pass through the other. These photoactive membranes generate 60 millivolts, on average, occasionally climbing to more than 100 millivolts, as measured by Ardo’s team. Read more on Indian Space research…

“Our results represent considerable progress toward a device that directly converts sunlight into ionic electricity, which has implications for direct desalination of seawater,” Ardo said.

When speaking in public about this research, he often holds up an ordinary plastic water bottle and asks, “What if it were possible to dip this container in the ocean, let it sit in full sun for about an hour and then be able to drink the water? The prospect of that is revolutionary.”

The elusive ion-exchange

According to lead author William White, a graduate student in Ardo’s lab, scientists have been trying to develop an ion-exchange power generator for decades with limited success.

“There had been other experiments dating back to the 1980s that photo-excited materials so as to pass an ionic current through them,” he said.

“Theoretical studies said that those currents should be able to reach the same levels as their electronic analogs, but none of them worked all that well.”

The researchers see other possible applications for the technology, including as part of a brain-computer interface system. Silicon-based devices and aqueous environments don’t mix, but the flexible, fluid-permeable structures being developed in the Ardo lab may one day offer a way of integrating living tissue and artificial circuitry.

The research work was supported by UCI’s School of Physical Sciences and the Gordon and Betty Moore Foundation.


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