Fabricating a ZIF-8@Polydimethylsiloxane(PDMS)/PVDF mixed matrix composite membrane for separation of ethanol from aqueous solution via vapor permeation

To date, vapor permeation (VP) technology has been attracted increasing attentions in ethanol fermentation process, in which the improvement of membrane performance is critical. In this study, zeolitic imidazolate frameworks (ZIF-8) was successfully synthesized and chosen as incorporating nanofillers for fabrication of mixed matrix membrane (MMMs) using polydimethylsiloxane (PDMS) as the matrix. A simple modified "prime" method with higher viscosity of coating solution was implemented for preventing agglomeration of ZIF-8 during membrane preparation process. A thin ZIF-8@PDMS layer of 5.4 mu m was obtained and firmly coated on a PVDF porous substrate to form the robust composite membrane structure. The chemical structure, morphologies, surface properties, and solvent uptakes of the resultant membrane were investigated compared with pristine PDMS/PVDF membrane. The VP performance for separation of ethanol/water binary solution in the concentration range of fermentation broth (1 similar to 7 wt %) were tested and discussed by comparison of the ZIF-8@PDMS/PVDF MMM and pristine PDMS/PVDF membrane. The trans-membrane flux, separation factor, ethanol permeability, and membrane selectivity were all promoted by the embedded ZIF-8 nanofillers.