Pervaporative concentration of ethanol-water mixtures using heterogeneous polydimethylsiloxane (PDMS) mixed matrix membranes

The PDMS mixed matrix membranes containing 10-μm sized zeolite were prepared, characterized, and tested on the pervaporation (PV) performance for ethanol-water solutions. We found that the membrane with the zeolite mixed after the PDMS cross-linker addition (" post-addition") was more effective at removing ethanol from the aqueous mixtures than the pristine PDMS and the PDMS-zeolite membrane made with the zeolite addition prior to the PDMS cross-linker addition. The ethanol solubility and diffusivity increased as the zeolite loading increased, and this increase contributed to a greater ethanol flux for the 30% zeolite-containing PDMS than the pristine PDMS for the same ethanol solution. The conventional flux and separation factor data were converted to permeability and selectivity values for a comparison with the data in the literature on the PV for a 10% ethanol solution. The post-addition PDMS-zeolite membrane that was prepared in the present work exhibited the highest ethanol permeability and the third greatest selectivity among the PDMS membranes, the PDMS copolymer membranes, and the PDMS-based mixed matrix membranes reported in the literature.