Description of dehydration performance of amorphous silica pervaporation membranes

The dehydration performance of a ceramic pervaporation membrane is studied for the separation of isopropanol/water mixtures. The membranes are provide d by ECN (The Netherlands) and consist of a water selective amorphous silic a top layer and four alumina supporting layers. For the system investigated , these membranes appear to combine high selectivities with high permeabili ties. This results in a very high pervaporation separation index (PSI up to 6000 kg/m(2) h at 80 degreesC). A generalized Maxwell-Stefan model has bee n set up to model the fluxes. From this analysis it follows, that the water flux is only proportional to its own driving force. It is experimentally d emonstrated that this holds for a wide range of operating conditions and fe ed compositions. From these data, values of various Maxwell-Stefan diffusiv ities are estimated. (C) 2001 Elsevier Science B.V. All rights reserved.