Adsorption equilibrium of organic vapors on single-walled carbon nanotubes

Gravimetric techniques were employed to determine the adsorption capacities of commercially available purified electric arc and HiPco single-walled carbon nanotubes (SWNTs) for organic compounds (toluene, methyl ethyl ketone (MEK), hexane and cyclohexane) at relative pressures, p/p0, ranging from 1 × 10−4 to 0.95 and at isothermal conditions of 25, 37 and 50 °C. The isotherms displayed both type I and type II characteristics. Adsorption isotherm modeling showed that SWNTs are heterogeneous adsorbents, and the Freundlich equation best describes the interaction between organic molecules and SWNTs. The heats of adsorption were 1–4 times the heats of vaporization, which is typical for physical adsorption of organic vapors on porous carbons.