Magazine article Science News

Savvy Sieve: Carbon Nanotubes Filter Petroleum, Polluted Water

Magazine article Science News

Savvy Sieve: Carbon Nanotubes Filter Petroleum, Polluted Water

Article excerpt

Bridging the gap between the nanoworld and the macroworld, researchers have created a membrane out of carbon nanotubes and demonstrated its potential for filtering petroleum and treating contaminated drinking water.

Scientists have long valued carbon nanotubes for their high strength and thermal properties (SN: 6/5/04, p. 363), yet it's been a challenge to assemble nanotubes into useful materials large enough for people to hold in their hands.

Researchers at Rensselaer Polytechnic Institute in Troy, N.Y., and Banaras Hindu University in Varanasi, India, have now devised a method for making such large-scale structures and found an application for them.

The researchers injected a solution of benzene and ferrocene--the materials needed to assemble the carbon nanotubes--into a stream of argon gas and then sprayed the mixture into a quartz tube. The tube was located inside a furnace heated to 900[degrees]C.

A dense forest of carbon nanotubes formed on the inner walls of the quartz tube, yielding a hollow black cylinder. The researchers carefully removed the cylinder, which measured several centimeters long and up to a centimeter in diameter. It was composed of trillions of nanotubes. Each nanotube was only a few hundred microns long, essentially the thickness of the carbon cylinder's wall.

"It's a pretty amazing structure if you think about it," says lead investigator Pulickel Ajayan of Rensselaer.

To test their cylinder as a filter, the researchers capped one end and let petroleum flow into it. As the oil passed through the cylinder's wall, the membrane caught the large and complex hydrocarbons--a necessary step in making gasoline. …

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