COUPLING PHENOMENA IN THE REMOVAL OF CHLORINATED HYDROCARBONS BY MEANS OF PERVAPORATION

In some pervaporation systems, coupling effects may play an important role. This occurs e.g. in the pervaporation of a multicomponent mixture of chlorinated hydrocarbons (Cl-HCs) in water through organophilic membranes. Several mixtures of Cl-HCs were pervaporated through organophilic PDMS membranes. The membranes were composite membranes: a dense top layer consisting of PDMS (polydimethylsiloxane), filled with hydrophobic zeolite on a layer consisting of porous PAN (polyacrylonitrile) on polyester fabric. The pervaporation experiments were carried out with ternary mixtures of water, chloroform and a second Cl-HC, as well as with acetone and isopropanol. The concentration of chloroform was kept constant during all experiments. The concentration of the other organic component was varied. In all experiments a decrease of the flux of the organic components was noticed for the ternary mixtures with respect to the binary mixtures. To investigate whether the coupling occured due to the zeolite, additional pervaporation experiments were performed with PDMS membranes without zeolite, with binary mixtures as well as with ternary mixtures of all components. With these membranes, almost no coupling phenomena could be observed.