Nano-filter could cut cost of clean drinking water

Posted by Emma Woollacott

A Stanford University team has developed a new water purifier based on nanomaterials that could cut costs for clean drinking water dramatically.

The new filtering technology kills up to 98 percent of disease-causing bacteria in water in seconds. It does this without clogging, says the team, reducing the need for maintenance.

Most water purifiers work by trapping bacteria in tiny pores of filter material - but pushing water through those filters requires electric pumps and consumes a lot of energy. In addition, the filters can get clogged and must be changed regularly.

The new material, in contrast, has far larger pores, allowing water to flow through easily. It is also claimed to kill bacteria outright, rather than just trapping them.

The scientists knew that contact with both silver and electricity can destroy bacteria, and decided to combine the two in one system. They spread sub-microscopic silver nanowires onto cotton, and then added a coating of carbon nanotubes to increase the filter's electrical conductivity.

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

"Such technology could dramatically lower the cost of a wide array of filtration technologies for water as well as food, air, and pharmaceuticals where the need to frequently replace filters is a large cost and difficult challenge," says the report, which appears in Nanoletters.