Winter/Spring 2007

LABORATORY EXPERIMENTS with a type of nanomaterial that has great promise for industrial use show significant potential for dispersal in aquatic environments – especially when natural organic materials are present.

photo by Gary Meek When mixed with natural organic matter in water from the Suwannee River – a relatively unpolluted waterway that originates in southern Georgia – multiwalled carbon nanotubes (MWNTs) remain suspended for more than a month, making them more likely to be transported in the environment, according to Georgia Tech researcher Jaehong Kim.

When mixed with natural organic matter in water from the Suwannee River – a relatively unpolluted waterway that originates in southern Georgia – multi-walled carbon nanotubes (MWNTs) remain suspended for more than a month, making them more likely to be transported in the environment, according to research led by the Georgia Institute of Technology.

Carbon nanotubes, which can be single- or multi-walled, are cylindrical carbon structures with novel properties that make them potentially useful in a wide variety of applications including electronics, composites, optics and pharmaceuticals.

“We found that natural organic matter, or NOM as we call it, was efficient at suspending the nanotubes in water,” says Jaehong Kim, an assistant professor in the Georgia Tech School of Civil and Environmental Engineering.

The research was published in the January 2007 issue of the American Chemical Society journal Environmental Science & Technology. Kim is the corresponding author and conducted the research with Professor Joseph Hughes, graduate student Hoon Hyung, and postdoctoral researcher John Fortner, all at Georgia Tech. The U.S. Environmental Protection Agency funded the research.

“We don't know for certain why NOM is so efficient at suspending these nanotubes in the laboratory,” Kim says. “We think NOM has some chemical characteristics that promote adhesion to the nanotubes more than to some surfactants. We are now studying this further.”

In the lab, Kim and his colleagues compared the interactions of various concentrations of nanotubes with different aqueous environments – organic-free water, water containing a 1 percent solution of the surfactant sodium dodecyl sulfate (SDS), water containing a commercially available sample of Suwannee River NOM and an actual sample of Suwannee River water from the same location as the commercially available preparation. They agitated each sample for one hour and then let it sit for up to one month.

The researchers then used transmission electron microscopy (TEM), measurements of opacity and turbidity, and other analyses to determine the behavior of nanotubes in these environments.

The researchers found:

photo by Gary Meek These beakers contain samples of carbon nanotubes or the nanomaterial C60, also known as "buckyballs," mixed in water stabilized either by surfactants or natural organic matter.