SYNOPSISA wide range of homogeneous elastomeric membranes has been prepared using dicumylperoxide as a general cross-linking agent. The membranes have been used for both equilibrium sorption measurements and steady-state pervaporation experiments to study solution-diffusion phenomena in the removal of volatile organic components from aqueous solutions. Pervaporation experiments have been performed under identical hydrodynamic conditions in order to fix the boundary layer mass transfer coefficient a t a constant and known value. For comparison of the permeabilities of different pervaporation membrane materials, this is of utmost importance. A wide range of selectivity factors up to a value of 100,000 are obtained, whereas usually the permeabilities for the organic component are in the range of 10-'0-10-9 m'/s and 10-'4-10-'2 m 2 / s for water. The permeation and sorption data obtained for the various elastomers have been related to the chemical and physical nature of the elastomers through the solubility parameter and the glass transition temperature, respectively. Both diffusional and sorption effects seem to be important, determining the water-transport behavior in the elastomeric membranes. The solubility of the organic component appears to be independent of this combined solubility parameter. Differences in the permeabilities of the organic component can primarily be ascribed to structural parameters in the membrane material, like degree of unsaturation and presence of steric side groups. 0 1993 John Wiley & Sons, Inc.

A resistance-in-series model is used to describe the pervaporation performance of elastomeric membranes in the removal of volatile organic components from water. Equations have been derived to describe the organic component flux as a function of feed concentration, permeability of the organic component in the membrane, membrane thickness and liquid boundary layer mass transfer coefficient. The model has been verified using both homogeneous and composite membranes of polydimethylsiloxane, ethylene propylene rubber and polyoctenamer.Membranes with a wide range of thicknesses have been prepared and the pervaporation behaviour for the removal of toluene and trichloroethylene from aqueous solutions has been studied. The experiments show that the hydrodynamic boundary layer resistance is of great importance. For highly permeable polymers such as polydimethylsiloxane mass transfer in the boundary layer is rate determining and should be considered carefully in further development of the process. For less permeable polymers such as ethylene propylene rubber this effect becomes more dominant with decreasing membrane thickness. The water fluxes are inversely proportional to the thickness of the actual separating layer and they depend strongly on the type of elastomer used. A proper choice of the elastomeric material and the thickness of the separating layer will determine the selectivity of the process.

A technical and economic analysisPROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit Twente, op gezag van de rector magnificus, prof. dr. ir. J.H.A. de Smit, volgens het besluit van het College van Dekanen in het openbaar te verdedigen op vrijdag 26 oktober 1990 te 14.00 uur. e door HERMAN HENK NIJWUIS geboren op 7 september 1959 te Hengelo (Q) Dit grm€schrift is goedgekeurd door de promotor: prof. dr. C.A. Smolders Assistent promotor: dr. ing. M.H.V. Mulder Re€erent: d r . h4.C.H-van Drernen Removal of trace organics kom water by pervaporation; a technical and economic analysis ISBN 90 -9003759 -4