Synthesis of ZIF-7/chitosan mixed-matrix membranes with improved separation performance of water/ethanol mixtures

In this study, microporous ZIF-7 crystal particles were successfully incorporated into chitosan (CS) membranes to form ZIF-7/CS mixed-matrix membranes (MMMs). The as-prepared ZIF-7/CS MMMs were used to separate mixtures of water/ethanol at 25 °C in the pervaporation process. The different ZIF-7 loadings in CS polymer with 0.25 g GA, such as 2.5, 4, 5, 6 and 7.5 wt%, have been tried and ZIF-7 with 5 wt% loading is the best loading condition. The separation efficiency of MMMs with 5 wt% ZIF-7 incorporation showed 19 times higher than that of the pristine CS membranes because of the rigidified polymer chain of the MMMs. The separation factor and the flux of the ZIF-7/CS membranes clearly exceed the upper limit of the previously reported CS based membranes and MMMs. The present work demonstrates better pervaporation performance of the ZIF-7 incorporated CS MMMs for the separation of water and ethanol and the feasibility of using this system for pervaporation.