Desorption and pervaporation properties of zeolite-filled Poly(dimethylsiloxane) membranes

The role played by zeolite fillers in PDMS membranes was studied by desorpt ion and pervaporation. The data on the desorption of different solvents fro m the membranes made of poly(dimethylsiloxane) (PDMS) filled with silica an d different zeolites show that the solvent molecules are extracted in two s tages. The first stage, which occurs at a low temperature (ca.50 degreesC), would correspond to the extraction of the solvent molecules in the 'bulk-l ike state' in PDMS, while the last stage, at high temperature, would corres pond to the extraction of the solvent molecules in the 'bound state'. There is a clear contribution of the zeolites to the membrane performances in pe rvaporation, even at a low zeolite content in PDMS (ca. 20 wt. %). The hydr ophobic zeolites enhance significantly the organic flux, leading to an impr ovement of both the flux and the selectivity of PDMS. The ZSM-5 zeolite imp arts to PDMS a higher selectivity but lower flux compared with SY-2 zeolite . The silica filler exhibits a crosslinking effect on PDMS, i.e. a slightly higher selectivity and lower flux than the pure PDMS membrane.