Global Challenges/Chemistry Solutions

Supplying Safe Drinking Water: Electrified nano filter promises to cut costs for clean drinking water

November 15, 2010



A new filter, the black object in the
neck of this funnel, is made from
nanoparticles and could cut the cost
of purifying water.
Credit: American Chemical Society

Summary

Scientists are reporting development and successful initial tests
of an inexpensive new filtering technology that kills up to 98
percent of disease-causing bacteria in water in just seconds
without clogging. The technology could aid many of the almost
one billion people lacking access to clean, safe drinking water.
A report on the work appears in the American Chemical
Society’s monthly journal Nano Letters.

Scientists are reporting development and successful initial tests of an inexpensive new filtering technology that kills up to 98 percent of disease-causing bacteria in water in just seconds without clogging. The technology could aid many of the almost one billion people lacking access to clean, safe drinking water. A report on the work appears in the American Chemical Society’s monthly journal Nano Letters.

Most water purifiers do their jobs by trapping bacteria in tiny pores of filter material. Pushing water through those filters, however, requires electric pumps and demands lots of energy. The filters also can get clogged, so they often have to be replaced. A new material developed by Yi Cui of Stanford University could avoid many deficiencies of traditional filters. For starters, it does not trap bacteria like most technologies. It kills them outright. The material also contains larger pores than conventional filters to allow for a better flow of water.

For more on the new technology, here is Dr. Cui:

“The removal of bacteria and other organisms from water is very important, not only for drinking and sanitation but also in industry as there’s a frequent need to replace filters due to clogging. The product we’ve developed could dramatically lower the cost of many filtration technologies for water as well as food, air, and pharmaceuticals, where the need to replace filters is common and very challenging.”

Dr. Cui’s research team knew that contact with silver and electricity can destroy bacteria. So they decided to combine the two approaches. To create the filter, they spread sub-microscopic silver nanowires onto cotton and then added a coating of carbon nanotubes to give the material extra electrical conductivity.

Tests of the filter on E. coli-tainted water showed that the silver/electrified cotton killed up to 98 percent of the bacteria. As a bonus, the material never clogged and water flowed through it quickly without any need for a pump.

“These water filters are very durable and we expect that they could operate for longer periods of time compared to what’s currently on the market, but the next step our team needs to take is to determine whether our filter can kill the wide range of dangerous bacteria found in polluted water. The ultimate impact of the technology could be used either as an integrated component into existing filtration systems to help with water flow or as a direct point-of-use filter for removing bacteria and other pathogens.”

Smart Chemists/Innovative Thinking

Smart chemists. Innovative thinking. That’s the key to solving global challenges of the 21st Century. Be sure to check our previous Global Challenges podcast episodes by visiting www.acs.org/globalchallenges. Today’s podcast was written by John Simpson. For the American Chemical Society, I’m Adam Dylewski in Washington.

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Yi Cui, Ph.D.
Stanford University