Fabrication Of ZIF/PEBAX Mixed Matrix Membranes And Its Application For Ethanol Recovery By Pervaporation

As a subclass of MOFs,ZIFs(zeolitic imidazolate frameworks)are built of metal ions and imidazolate ligands.ZIFs not only show high porosity,strong adsorption capacity,relatively high thermal and chemical stability,but also possess tunable structure,which make them attractive materials for many applications,such as catalysis,energy storage and separation.Incorporation of ZIFs into polymer for separation has drawn more and more attention and the key factors for fully utilizing the functionality of ZIFs is futher modification and the good dispersibility in polymer matrix.In this work,the performance of ZIF-8-90/polyether-block-amide(PEBAX)mixed matrix membranes(MMMs)are promoted by chemical modification and process optimization respectively.Firstly,hybrid ZIF-8-90 nanoparticles are modified by pentafluoropropylamine(F-ZIF-8-90),and incorporated into PEBAX matrix to fabricate MMMs.F-ZIF-8-90/PEBAX MMM presents better separation performance than ZIF-8-90/PEBAX MMM,which is probably because that F-ZIF-8-90 exhibits higher hydrophobicity and better compatibility with PEBAX as compared to the unmodified one.The effect of F-ZIF-8-90 loading on the physicochemical properties and separation performance is studied,where the MMM with 5wt%F-ZIF-8-90 loading shows the best performance.The effects of feed temperature and feed ethanol concentration on the pervaporation performance of F-ZIF-8-90/PEBAX MMM are also investigated.The results show that the increase in feed temperature can promote the flux and separation factor of the F-ZIF-8-90/PEBAX MMM at the same time,and the increase in the feed concentration can promote the flux too,but lead to a lower separation factor.In addition,an in-situ strategy is also developed to fabricate ZIF-8-90/PEBAX MMM.The effects of ZIF-8-90 loading,feed temperature and concentration on the separation performance are also investigated systematically.The obtained MMM by in-situ method shows an optimized separation performance,with a separation factor of 6.78 and a corresponding flux of 140.7 g/m~2h(5 wt%ethanol solution,70°C).Compared to the conventional direct doping method,the in-situ process is much simpler and endows the ZIF-8-90/PEBAX MMM with significantly improved separation performance.