Electrically-Controlled Permeation of Vapors Through Carbon Nanotube Network-Based Membranes

Abstract

DC voltage was used to control and increase the permeation rate of typical carbohydrate and alcohol vapors through a conductive membrane composed either of a layer of entangled multiwalled carbon nanotubes or of a nanotube layer strengthened by a porous polyurethane nonwoven mat. The permeation rate rise was partly due to the Joule effect increasing the membrane temperature and the vapor pressure in the vicinity of the inlet side of the membrane. However, the effects of vapor polarity and the interaction of vapor and charged nanotubes were also involved. When the nanotube membrane was uncharged, the permeation rate was higher for nonpolar hydrocarbon and nonpolar tetrachlormethane vapors than for polar methanol vapors. The opposite effect was observed for an electrically charged membrane. Whereas the increasing voltage and, consequently, the membrane temperature increased the relative permeation rates of both vapor types, the relative permeation rate of alcohol vapors was up to twofold higher than the corresponding rates for carbohydrate vapors at the similar membrane temperature.