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.