Multilevel-layer-structured polyamide 6 (PA6) and poly(trimethylene terephthalate) (PTT) nanofibrous membranes were fabricated by an electrospinning method. The morphology of the multileveled layers membranes were characterized by scanning electron microscopy. The tensile strength of the PA6-PTT membranes were controlled by the regulation of the layer structure. Additionally, the surface area of the multilevel-layer-structured membranes was also investigated with the nitrogen physisorption isotherms. Furthermore, the multilevel-layered membranes, with a tensile strength of 9.8 MPa and a surface area of 5.1601 m 2 /g on 300-nm dioctylphthalate (DOP) aerosol particles, showed a higher efficiency (95.825%) and a lower pressure drop (55 Pa) than the pure PA6 membranes (with values of 94.634% and 467 Pa, respectively). This suggested a new method for high-efficiency and lowpressure-drop filtration applications. Correlations between the filtration pressure drop and filtration efficiency with the structure of the membranes, particle size, and surface velocity were proposed, and the advantage of the multilevel-layered structure is also discussed.
High quality heterogeneous polysulfone affinity flat filter membranes having chelating groups were prepared by phase separation by the use of blends of chelating resin and polysulfone as membrane materials, N,Ndimethylacetamide as the solvent, and water as the extraction solvent. The effects of blending ratio, chelating resin grain size, and temperature of casting solution on the structure of affinity membranes were investigated. The sorption process of an affinity filter membrane for Hg 2ϩ , adsorbed under various chelating conditions such as chelating resin grain size, pH value, and the concentration of the metallic ion solution, was also studied. The results revealed that the greatest chelating capacity of an affinity filter membrane for Hg 2ϩ was 1050 g/cm 2 per membrane under appropriate conditions, and the sorption isotherms of Hg 2ϩ could be expressed by the Freundlich sorption model. Dynamic chelating experiments indicated that the Hg 2ϩ could be extracted with the affinity filter membrane and reextracted under acidic conditions.
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