Stanford Develops New Device To Purify Water Using Sunlight

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It might look like a piece of bark floating in your water bottle, but it is a solar-powered water purifier.

The tiny tablet device is the result of research by scientists at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University‘s Institute for Materials and Energy Science. At 1cm by 2cm, it is only half the size of a postage stamp. The findings were published in the journal Nature Nanotechnology.

Device uses broad spectrum of light

Despite its small size, the device can decontaminate water using light from the sun. The technology could be a boon for hikers, and potentially help improve hygiene in developing countries. It is quicker and easier to use than boiling water or using an ultraviolet wand, which must be charged.

There are existing devices which use UV light to decontaminate water, and they can take anywhere from a few hours to two days to work, says the Swiss Federal Institute of Aquatic Sciences and Technology’s Solar Water Disinfection initiative. The major advantage of the Stanford tablet is that it only takes a few minutes to decontaminate the water, due to the fact that it uses a broad spectrum of light rather than just UV.

“UV light only counts for 4 percent of the total solar energy,” Chong Liu, a Stanford postdoctoral researcher and author of a report on the device, said. “If you can also use visible light, that’s 50 percent of solar energy, so you just use it for free, why not just use most of the solar to do water disinfection and to harness more light and to use it more efficiently?”

How does water purifier work?

The device is made up of a glass tablet with copper and “nanoflakes” of molybdenum disulfide, an industrial lubricant. If the conditions are right, the nanoflakes provoke a chemical reaction that decontaminates the water by killing microbes.

In a controlled experiment the tablet was found to kill 99.999% of bacteria in 25 milliliters of water within 20 minutes. Different amounts of water can be treated using larger tablets, and the device is not meant to cost more than a few dollars, according to Liu.

It is hoped that the device could be commercialized within three to five years, following a series of real-world tests. However there is one drawback; as it stands the device only kills E.coli and lactic acid bacteria. It does not decontaminate water of viruses or chemicals such as lead, but the scientists are working to add more cleansing capabilities.

Potential applications in developing countries

“The easiest water we can treat [right now] is in outside activities, when you scoop water from the river and that water is not really cloudy or heavily polluted, but might contain microorganisms,” Liu said. “You can dump in the device and it can kill the bacteria.”

According to the United Nations around 663 million people do not have access to clean drinking water, while nearly 1,000 children die every day from preventable diseases caused by poor water and sanitation.

While it is possible to imagine the device being popular with backpackers, Liu has loftier aims to help those in developing countries. If the device can be proven to eliminate viruses and other harmful chemicals, it could offer a great way of reducing deaths from preventable diseases.

“As a researcher it’s really exciting for us to see that by developing technologies you have the potential to help a lot of people,” said Liu.

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