Separation of a Toluene/Ethanol Mixture by Pervaporation Using Active Carbon-Filled Polymeric Membranes

In order to improve the separation properties of dense polymeric membranes toward a toluene/ethanol mixture, various active carbons and two types of zeolites were introduced into a thin polymeric film in order to form a heterogeneous membrane composed of solid particles surrounded by a polymer phase. Active carbons show a high adsorption selectivity for an aromatic compound over ethanol in the low concentration range of the aromatic component. Sorption and pervaporation experiments were carried out with a toluene/ethanol mixture, and they showed no improvement in selectivity and a decrease in flux for membranes filled with active carbons. For zeolite-filled membranes, both selectivity and flux decreased. A permeability model derived for heterogeneous systems was used. It confirmed that the carbon particles have a closed porous structure, allowing no transport from one side to the other, and that the zeolites have an ethanol selective permeation behavior.