Fluoride-mediated hydrophobic zeolite incorporated PDMS membrane for highly selective separating ethanol from aqueous solution

Membrane technology can reduce the energy consumption of alcohol/water separation process, while the membrane performance still needs to be improved. This study reports a fluoride-mediated hydrophobic zeolite incorporated polydimethylsiloxane (PDMS) membrane for highly selective separating ethanol from aqueous solution. A fluoride-assisted synthesis strategy was proposed to achieve synergistic control over the morphology and surface chemical properties of siliceous zeolites. Comprehensive characterizations revealed that fluoride-mediated MFI zeolite (F-MFI) possessed significantly lower silanol density and superior hydrophobicity compared to conventional hydroxide-synthesized MFI zeolite (Si-MFI), thereby improving the selective permeation of ethanol over water. The optimal F-MFI nanoplates (∼150 nm thickness) with high crystallinity were uniformly incorporated into the PDMS membrane, achieving outstanding performance for separating 5 wt% ethanol/water mixture at 40 °C (total flux of 1409 g m −2  h −1 and a separation factor of 19.7—approximately twice that of the pure PDMS membrane). This work provides a high-performance ethanol-selective membrane, and also demonstrates the importance of synthesis condition on the morphology and functionality of filler and the performance of resulting mixed-matrix membrane.