Nanomaterials Vulnerable To Dispersal In Natural Environment

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 research led by the Georgia Institute of Technology.

Carbon nanotubes, which can be single- or multiwalled, 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," said Jaehong Kim, an assistant professor in the Georgia Tech School of Civil and Environmental Engineering.

The research will be published in the January issue of the American Chemical Society journal Environmental Science & Technology. Kim is the senior author and conducted the research with Professor Joseph Hughes, graduate student Hoon Hyung, both at Georgia Tech, and postdoctoral researcher John Fortner from Georgia Tech and Rice University. 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 said. "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 MWNTs 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.