Air adsorption and separation on carbon nanotube bundles from molecular dynamics simulations

Using molecular dynamics (MDs) simulations, the adsorption of a nitrogen-oxygen mixture (representing air) on (8, 8), (10, 10), and (12, 12) single-walled carbon nanotube (SWCNT) bundles is investigated as a function of temperature, air loading and diameter of nanotubes at subcritical (T = 100 K) and supercritical (T = 200 and 300 K) temperatures of the air. In order to do this, heat of adsorption, diffusion coefficients, activation energy, and radial distribution functions (RDFs) were computed for further analysis of the adsorption process. The simulation of exposing air on nanotube bundles, show that the amount of adsorption, heat of adsorption, and diffusion coefficients are strongly influenced by the applied temperature, i.e., along with the temperature increase, the amount of adsorption would be reduced. Furthermore, the results show that oxygen is selectively adsorbed relative to nitrogen, so carbon nanotubes (CNTs) can be considered as promising gas-filtering systems in addition to their previous gas-storage capability. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.