Summary: RAE Questions
Department of Chemical and Biomolecular Engineering, Spring 2006
Question 1. Since the discovery of carbon nanotubes many advances have been made in the
synthesis and purification of Single Walled Nanotubes (SWNT), bringing the concept of a "space
elevator", a cable up to 100,000 km long, tethered to the Earth and made of nanotubes, closer to
reality. Separation of SWNT aggregates according to size, metallic/semiconducting properties
and chirality has been attempted using a range of organic molecules ranging from small
molecular weight species to biologically active DNA. Discuss SWNT synthesis methods. What
properties are important? How could the best nanotubes for "space elevators" be produced?
Discuss separation methods using organics and biomolecules such as DNA. What would be the
main process concerns associated with SWNT separation for this futuristic application? Propose
a synthesis and separation process for SWNT that would overcome some of the challenges
associated with manufacturing a space elevator out of nanotubes.
Question 2. Contaminated soil and groundwater is often remediated through use of microbes.
One of the limiting factors in bioremediation is transport of the bacteria to the location of the
contaminants. Many bacteria that can degrade soil are both motile and chemotactic; they can
sense concentration gradients and move preferentially in the direction of higher concentrations of
degradable contaminants. In the absence of any concentration gradients, their mobility is similar
to Brownian motion of suspended particles. Because of the transport considerations, it is
important to understand the behavior of bacteria in porous media. Propose a research plan that