Preparation of Zeolitic Imidazolate Framework-91 and its modeling for pervaporation separation of water/ethanol mixtures

Abstract

Zeolitic Imidazolate Framework (ZIFs) have received much attention in recent years because of their good compatibility with polymer, and their ultramicroporosities that are in the range of the kinetic diameter of several important gas and liquid molecules. In this study, three different ZIF particles, i.e., ZIF-90 and its derivatives (ZIF-91 and ZIF-92) were synthesized and incorporated into polydimethylsiloxane (PDMS) matrix to fabricate ZIF/PDMS nanocomposite membrane for pervaporation recovery of ethanol. The morphologies and structures of ZIF particles and their nanocomposite membrane were characterized by various techniques. The results show that ZIF-91 particles with hydroxyl functional groups have good compatibility with PDMS and are dispersed well in PDMS matrix. Meanwhile, ZIF-91/PDMS nanocomposite membrane have higher pervaporation performance compared to ZIF-90/PDMS and ZIF-92/PDMS nanocomposite membrane with the same loading of 20 wt%. The effects of particle loading, feed concentration and temperature on the separation performance of ZIF-91/PDMS membranes were also investigated. The results indicate that ZIF-91/PDMS-20 wt% membrane showed a prominent separation factor of 15.8 at 55 °C with a comparable total flux of 846 g/(m2 h), which were higher than that of pure PDMS (4.1, 496 g/(m2 h)). In addition, the pervaporation modeling for the flux and separation factor of ZIF-91/PDMS membrane were established with quadratic equations of temperature and feed concentration, which can be used to predict separation performance according to the experiment conditions.