Improving the performance of nanocomposite membranes by incorporating inorganic fillers for gas separation

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Copyright: Sutrisna, Putu Doddy
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Abstract
Polymeric membrane-based gas separation process provides an environmentally attractive alternative to gas absorption and adsorption. However, the permeability/selectivity trade-off, the operational stability under aggressive feed gas, and carbon dioxide (CO2)-induced plasticisation behaviour remain key challenges for its application in flue gas and natural gas treatment. Combining polymer and particles inside mixed matrix membranes (MMMs) has a good potential to address these challenges. The first part of this research studied the CO2 permeation behaviour in dense film MMMs and composite hollow fibre membranes incorporating block co-polymer (Pebax-1657) with Metal Organic Frameworks (MOFs) particles, namely Zeolitic Imidazolate Framework (ZIF-7 and -8) and University of Oslo-66 (UiO-66). The presence of MOFs reduced the polymer flexibility, thus inhibited the increase in CO2 permeability. Membrane plasticisation was not observed in Pebax-based membranes while the selectivity was relatively unchanged. In addition, the hydrogen bonding between MOFs and Pebax improved the membrane’s operational stability under high pressure. Another major challenge in MMMs is to control the microvoids at the interfacial region and improve MOFs loading. In the second section of this study, flexible ZIF and rigid UiO-66 were incorporated in nanocomposite hollow fibre membranes, and (–COOH) and (–NH) modified UiO-66s were applied to investigate the effect of surface functionalization. Up to 80 wt% UiO-66 can be incorporated, and improvements in CO2 permeance and selectivity were obtained with (-NH) functionalized UiO-66. In general, more rigid MOFs are preferred to mitigate defects and improve gas selectivity. In addition, pure ZIF membranes emerge as an attractive material for molecular sieving membrane. ZIF-8 is one of the most studied ZIFs due to its simple fabrication process and use of environmentally friendly solvent. Fabrication of ZIF-8 membrane on inert polymeric surface is still challenging. This research functionalised PVDF hollow fibre support with TiO2-APTES and polydopamine-polyethylenimine to induce ZIF-8’s growth. Both methods could form ZIF-8 membranes with thickness below 1 µm that yielded one of the highest hydrogen permeances achieved by ZIF-8 membranes (> 105 x 10-7 mol m-2 s-1 Pa-1) and H2/CO2 selectivity of 7.5. This accomplishment opens up the pathway to use ZIF-8 as gutter layer in composite membranes.
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Author(s)
Sutrisna, Putu Doddy
Supervisor(s)
Chen, Vicki
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Publication Year
2017
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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