An asymmetric silica membrane supported on a porous alumina tube substrate was prepared by dip-coating and then surface modification multistage assembly synthesis. The mesoporous silica membrane was repeatedly modified with hexamethyldisilazane after dip-coating in silica sol solution. The separation layer of the silica membrane had an average thickness of 2 pm, mean pore radius of 1.16 nm, and BET surface area of 225 m(2).g(-1). In the presence of 1 wt.% acetic acid, the membrane effectively removed ethanol and acetone from 5 wt.% organic/water binary system, or 5.0 wt.% organic-94.0 wt.% water ternary feeds by pervaporation (PV) over a temperature range of 303-323 K. The separation factor (alpha) of ethanol at 303 K was about 8.7, while that of acetone was 28.4. The total permeate fluxes at 303 K were 0.92 and 1.15 kg.m(-2).h(-1) for ethanol/water and acetone/water feed solution, respectively. Furthermore, the separation mechanism is discussed on the basis of the relationship between the electronegativity of the feed solution composition and electronic structure of silane coupling modifier. (C) 2011 Elsevier B.V. All rights reserved.