Liquid membranes are porous membranes with the pores filled with a liquid solvent. Permeabilities of volatile organic compound (VOC) vapor through triethylene glycol (TEG) derivative liquid membrane are calculated by solution-diffusion theory with activity coefficient model from quantum calculation. Methanol, acetone, benzene, toluene and acetaldehyde are focused as volatile organic compounds. The TEGs are triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, and triethylene glycol monobutyl ether. The solubilities of VOC vapor in TEG derivatives were obtained from two type activity coefficient models, COSMO-SAC based on quantum calculation and modified UNIFAC. The diffusion coefficients of VOC vapor were calculated by Wilke-Chang equation. The logarithmic absolute deviations of the permeability in cm(3) (STP) cm cm(-2) cm Hg(-1) between the experimental data and the predicted results are 0.44 and 0.47 in the case of COSMO-SAC and UNIFAC. The separations of benzene, toluene and acetone vapor from air through TEG liquid membrane were also simulated using the experimental and calculated permeabilities using COSMO-SAC and modified UNIFAC. (C) 2010 Elsevier B.V. All rights reserved.