Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Physical Sciences, Technology, Biochemistry & Molecular Biology, Chemistry, Physical, Engineering, Chemical, Materials Science, Multidisciplinary, Polymer Science, Chemistry, Engineering, Materials Science, pervaporation, bio-ethanol, metal-organic framework, stability, PDMS, MMM, MIXED MATRIX MEMBRANES, SEPARATION, MIXTURES, BUTANOL, BIOBUTANOL, COMPONENTS, DESIGN, DEHYDRATION, PERFORMANCE, PERMEATION, metal–organic framework, C16/23/006#57594018, C3/23/017#57618914, 12ZQ420N#55267580, 0904 Chemical Engineering, 0905 Civil Engineering, 0907 Environmental Engineering, 4004 Chemical engineering, 4011 Environmental engineering

Abstract:

Mixed matrix membranes (MMMs) have shown great potential in pervaporation (PV). As for many novel membrane materials however, lab-scale testing often involves synthetic feed solutions composed of mixed pure components, overlooking the possibly complex interactions and effects caused by the numerous other components in a real PV feed. This work studies the performance of MMMs with two different types of fillers, a core-shell material consisting of ZIF-8 coated on mesoporous silica and a hollow sphere of silicalite-1, in the PV of a real fermented wheat/hay straw hydrolysate broth for the production of bio-ethanol. All membranes, including a reference unfilled PDMS, show a declining permeability over time. Interestingly, the unfilled PDMS membrane maintains a stable separation factor, whereas the filled PDMS membranes rapidly lose selectivity to levels below that of the reference PDMS membrane. A membrane autopsy using XRD and SEM-EDX revealed an almost complete degradation of the crystalline ZIF-8 in the MMMs. Reference experiments with ZIF-8 nanoparticles in the fermentation broth demonstrated the influence of the broth on the ZIF-8 particles. However, the observed effects from the membrane autopsy could not exactly be replicated, likely due to distinct differences in conditions between the in-situ pervaporation process and the ex-situ reference experiments. These findings raise significant questions regarding the potential applicability of MOF-filled MMMs in real-feed pervaporation processes and, potentially, in harsh condition membrane separations in general. This study clearly confirms the importance of testing membranes in realistic conditions.