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CNT membrane has the potential to clean up
Olgica Bakajin and her team from Lawrence Livermore National Laboratory, US, have been putting CNTs to use as a high-performance membrane that could dramatically reduce the amount of energy required to purify water.
The researchers coat their CNT array with Si3N4 to fill in the gaps between the tubes and make sure that liquid flows only through the narrow pores. To complete the membrane chip, the scientists shave off the top and the bottom of the coated array and then open up the closed CNT “caps” by adding carboxylic acid groups.
Simulations reveal that the success of the membrane is due to both the hydrophobicity and the atomic smoothness of CNTs. Surprised by just how good the membrane appears to be, the group is now putting its chip though a more rigorous testing program.
When the chair turned to the audience for questions, Bakajin was immediately quizzed about the cost of the device.
“CNTs are expensive, but when you look at how much material is actually used then the membrane’s material costs turn out to be low even at today’s CNT prices,” she explained. “The problem is fabricating the membrane, because at the moment it takes a graduate student three days to make one of these.”
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