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Diverse morphologies of PVDF hollow fiber membranes and their performance analysis as gas/liquid contactors

Authors

  • Chunsheng Feng,

    1. School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798
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  • Rong Wang,

    Corresponding author
    1. School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798
    2. Singapore Membrane Technology Centre, Nanyang Technological University, Singapore 639798
    3. Institute of Environmental Science and Engineering, Nanyang Technological University, Singapore 639798
    • School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798
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  • Hongyan Zhang,

    1. School of Civil and Environmental Engineering, Nanyang Technological University, Singapore 639798
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  • Lei Shi

    1. Singapore Membrane Technology Centre, Nanyang Technological University, Singapore 639798
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Abstract

A systematic investigation on the morphology development of polyvinylidene fluoride hollow fiber membrane made using various N-methyl-2-pyrrolidone (NMP) aqueous solutions as an inner coagulant was carried out. The cross-sectional and inner surface morphology were analyzed with scanning electronic microscopy (SEM). It is found that with increase on NMP concentration, the morphology of the resultant membranes gradually shifted from a double-skin to a single-skin structure. When 40.0 ∼ 55.0 wt.% NMP solution was used, some unexpected macrovoids near the inner region were observed. This special morphology feature was attributed to the reduced solidification rate of the inner surface as a result of increase on NMP concentration, which sharply weakened the inner skin strength. While the existence of centralized stress formed in the phase inversion process, such as shrinkage stress from syneresis, resulted in fractured points in the nascent skin surface that finally made it difficult to maintain a uniform structure. Investigations on effects of the dope flow rate and the bore fluid velocity on the morphology of PVDF fiber membranes experimentally confirmed the suggestion. Three model membranes with double skins, single skin and single skin with macrovoids structures, respectively, were used to test their permeation performance in a CO2 membrane contactor system. The experimental results show the membranes without an inner skin present higher permeability and lower mass transfer resistance than the membrane with a double skin structure. © 2010 Wiley Periodicals, Inc. Journal of Applied Polymer Science, 2010

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