[Show abstract][Hide abstract] ABSTRACT: We have synthesized nano-sized zeolitic imidazolate frameworks (ZIF-8) and prepared polybenzimidazole (PBI)/ZIF-8 mixed matrix membranes (MMMs) with uniform morphology comprising ZIF as high as 58 wt% by directly mixing the as-synthesized ZIF-8 suspension into the polymer dope for pervaporation dehydration of ethanol, isopropanol (IPA) and butanol. Pervaporation test data show that the water permeability of PBI/ZIF-8 (1:1) MMMs is about one order higher than the original PBI membrane (14,000–22,000 vs. 1200–2300 Barrer). The apparent activation energy calculated from the Arrhenius equation indicates that there is a 29.2% reduction of energy barrier for penetrant transports for PBI membranes consisting of 33.7 wt% ZIF-8 nano-particles. As a result, the 33.7 wt% ZIF-8 in PBI membrane increases water permeability four times without much decrease in selectivity for water. The 58.7 wt% ZIF-8 in PBI membrane has a very high water permeability but a relatively low selectivity. Furthermore, the MMMs also show effectiveness in suppressing ethanol-induced swelling on the polymeric matrix owing to its inorganic properties. Vapor sorption studies confirm that the enhancement of pervaporation performance is primarily attributed to the significant improvement in diffusivity selectivity. With high thermal stability, chemical resistance and excellent compatibility with PBI, ZIF-8 nano-particles are promising fillers for enhancing the overall separation performance of low permeability but high performance materials like PBI.
Journal of Membrane Science s 415–416:577–586. · 4.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: By modifying the synthesis route, we have synthesized ZIF-90 nanoparticles with an average particle size of 55 nm and embedded them into P84 polymeric membranes with excellent dispersion for the dehydration of isopropanol (IPA)/water mixture via pervaporation. The effects of ZIF-90 loading as well as feed temperature on pervaporation performance of the mixed matrix membranes (MMMs) were systematically investigated. The flux of MMMs increases with increasing ZIF-90 loading due to the enhanced fractional free volume, while the separation factor of water/IPA can be maintained at 5432 when the ZIF-90 loading is less than 20 wt%, but reduced to 385 when the ZIF-90 loading is 30 wt%. Interestingly, the application of sulfonated polyethersulfone (SPES) as a primer to ZIF-90 nanoparticles before fabricating MMMs consisting of 30 wt% ZIF-90 recovers the separation factor without sacrificing the flux. The best MMM showed the separation performance with a flux of 109 g m−2 h−1 and a separation factor of 5668 at 60 °C. This encouraging performance suggests a promising future of ZIF-90/P84 composite membranes for the dehydration of IPA via pervaporation process.
Journal of Membrane Science 01/2014; 453:155–167. · 4.09 Impact Factor
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