Polydimethylsiloxane (PDMS)/ceramic composite membrane with high flux for pervaporation of ethanol-water mixtures

The separation of ethanol - water could be cost-competitive using pervaporation in the production of renewable biomass ethanol, but the performance of the modified or unmodified polymeric membranes still is not satisfactory. For the purpose of improving the pervaporation performance of polymeric membranes, especially for flux, polydimethylsiloxane (PDMS) was deposited uniformly on the surface of tubular nonsymmetric ZrO ₂/Al₂O₃ porous ceramic supports. The as-prepared composite membranes were characterized by scanning electron microscopy (SEM), Fourier transform infrared-attentuated total reflectance (FTIR-ATR), and pervaporation experiments. The thickness of the PDMS layer formed atop the ZrO₂ layer was on the order of 5-10 μm. In the ethanol-water pervaporation experiment, as the ethanol concentration increased, the total flux increased but the selectivity decreased. At the same time, with increasing operating temperature, the total flux of the composite membranes increased whereas the selectivity decreased. It was observed that the PDMS/ceramic composite membrane showed a great total flux of 19.5 kg m ^-2 h^-1 and selectivity of 5.7 for ethanol to water at a feed temperature of 343 K under a pressure of 460 Pa in an ethanol concentration of 4.3 wt %. The total fluxes of the PDMS/ceramic composite membranes were superior to other reported PDMS membranes.