Fluid filter composed of vertically aligned carbon nanotubes.

Researchers at Rensselaer and Banaras Hindu University (India) have devised a simple method to produce carbon nanotube filters that efficiently remove micro- to nanoscale contaminants from water and heavy hydrocarbons from petroleum. Made entirely of carbon nanotubes, the filters are easily manufactured using a novel method for controlling the cylindrical geometry of the structure.

“The research demonstrates how to spray well-ordered nanotube structures directly onto a substrate,” says Pulickel Ajayan, professor of materials engineering at Rensselaer and one of the authors of “Carbon Nanotube Filters.” The paper, published in the September issue of Nature Materials, describes the manufacture and application of the filters.

The filters are hollow carbon cylinders several centimeters long and one or two centimeters wide with walls one-third to one-half a millimeter thick. They are produced by spraying benzene into a tube-shaped quartz mold and heating the mold to 900 degrees Celsius. The nanotube composition makes the filters strong, reusable, and heat resistant, and they can be cleaned easily for reuse.

“In the future, we hope to be able to spray, or print, a great variety of nanotube structures directly onto substrates,” Ajayan says. “This method provides a better way of creating more interesting shapes and structures from nanotubes. By adjusting the size and flow of the nozzle, we can define the geometric structure of the nanotube form.”

The carbon nanotube filters offer a level of precision suitable for different applications. The experiments demonstrated that the filters may be useful in producing high-octane gasoline. They also can remove 25-nanometer-sized polio viruses from water, as well as larger pathogens, such as E. coli and Staphylococcus aureus bacteria.

The research is supported in part by the Center for the Directed Assembly of Nanostructures at Rensselaer and the Ministry of Education in India.


Originally published in Rensselaer Magazine, Fall 2004

Published October 1, 2004