2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Ion exclusion in the surface-modified carbon nanotube membranes.

H.G. Park, J.K. Holt, G. Klunder, C.P. Grigoropoulos, A. Noy and O. Bakajin
Lawrence Livermore National Laboratory, US

ion exclusion, carbon nanotube, functionalization, desalination

We report on the ion filtration capabilities of a membrane made of carbon nanotubes with openings modified with chemical functionalities. Carbon nanotube membranes show several orders of magnitude higher water permeability relative to conventional membranes [1]. Coupling the enhancement of the water flux with the selective transport of different ions through such membrane could have far-reaching implications for drastic reduction of the cost of the future seawater desalination applications [2]. We report on the measurements of ion permeability through the sub-2 nanometer carbon nanotube membranes functionalized with different chemical functionalities at the opening. Capillary electrophoresis measurements show that these membranes functionalized with the negatively charged groups exclude a significant portion of anions (over 50%) while passing the cations through. We discuss the potential mechanism for the membrane selectivity and the implications of these results to the current and future reverse osmosis desalination applications. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. This work was supported from the Defense Advanced Research Projects Agency and the Lawrence Livermore National Laboratory Student Employee Graduate Research Fellowship. [1] Holt, J., H.G. Park, Y. Wang, M. Stadermann, A.B. Artyukhin, C.P. Grigoropoulos, A. Noy and O. Bakajin, Fast Mass Transport Through Sub-2-Nanometer Carbon Nanotubes, Science, 312, 1034 (2006) [2] R.F. Service, Desalination Freshens Up, Science, 313, 1088 (2006)

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