Water molecules flow through carbon nanotubes.

Researchers at the Lawrence Livermore National Laboratory announced last week a breakthrough use of carbon nanotubes that could the energy-efficiency of desalination processes.

Molecules move rapidly through naturally occurring biological membranes, the pores of which regulate cellular traffic, allowing very small molecules to pass through rapidly while larger molecules are held up. Led by Olgica Bakajin, the in Livermore, Calif.-based research team mimicked the natural process using carbon nanotubes and discovered that narrow diameter carbon nanotubes could provide a simplified model of membrane channels by, as Bakajin explains it "reproducing these critical features in a simpler and more robust platform."

The team discovered in 2006 that water would flow quickly through carbon nanotubes, but its most recent discovery has to do more with what carbon nanotube membranes can keep out than what they allow to flow through. When researchers flowed salt water through the carbon nanotube membranes, pores in the tubes rejected the ions that made up the salt, allowing the water to pass through quickly, without additional force.

The  technology could greatly improve the energy efficiency of the desalination process, which currently requires power to push salt water through membranes at high speeds. By using carbon nanotube membranes instead of mesh membranes, desalination plants could let water flow naturally through their systems.

“While carbon nanotube membranes can achieve similar rejection as membranes with similarly sized pores, they will provide considerably higher permeability, which makes them potentially much more efficient than the current generation of membranes,” Aleksandr Noy, a senior member of the LLNL team, said in an announcement about the discovery.

Meanwhile, in a feature entitled "Carbon nanotubes: the new asbestos?" in the May 2008 issue of Nature Magazine, the results of a study conducted by researchers at the University of Edinburgh in Scotland linked linear, multi-walled carbon nanotubes to precancerous growths in lab mice similar to those caused by asbestos. The potential health risks associated with the material could be a serious obstacle to its use in industrial applications such as desalination.