303507 Exploration of N-Doped Graphene Incorporated Polyethersulfone (PES) Hollow Fiber Membranes
Polyethersulfone (PES) is widely used as a material for ultrafiltration (UF) and microfiltration (MF) membranes and as a substrate material for forward osmosis/pressure retarded osmosis membranes because of its excellent properties for hollow fiber spinning [1-4]. The physical and chemical properties of PES membranes can be altered by the incorporation of various nanomaterials. Graphene is an exciting new material which has attracted attention in many fields due to its distinctive mechanical and electrical properties in recent years. The use of graphene oxide-derived graphene materials as filler has been proved to be able to significantly improve the mechanical properties (elastic modulus, tensile strength) and thermal stability of polymer nanocomposites .
However, graphene oxide was found to produce unstable dispersions in the N-methyl pyrrolidone (NMP) solvent used in fabrication of polymeric membranes. In contrast, N-doped graphene dispersions can be formed easily and have high stability in NMP. Therefore, this study explored the effect of N-doped graphene on the property of PES membranes when it is incorporated. Comprehensive experiments were designed and conducted utilizing the nonsolvent-induced phase-inversion method to fabricate PES hollow fiber membranes with and without N-doped graphene. Various graphene loadings and spinning parameters were used to make N-doped graphene/PES composite membranes in order to identify the membrane with improved performances in terms of mechanical strength, and/or separation.
Preliminary experimental results reveal that the addition of N-doped graphene into the PES solution increased the elongation of the membranes from 105% to 175% at similar tensile strength. However, with an increase in the loading amount of N-doped graphene, defects occur on the resultant membrane, which leads to a higher molecular weight cut-off (MWCO). As the internal coagulant becomes softer, the occurrence of apparent defect is reduced in N-doped graphene/PES composite membrane, resulting in lower pure water permeability and lower molecular weight cut-off (MWCO) as compared to the plain PES membrane. Clearly, the incorporation of N-doped graphene into the PES membrane to achieve desirable performance is not a trivial task and worth to conduct systematic investigation.
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