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In this paper, isocyanate-treated graphene oxide (iGO), which can be well dispersed in organic solvent, was prepared in a simple manner and showed excellent compatibility with polysulfone (PSF). iGO-PSF ultrafiltration membranes were prepared by the classical phase inversion method. The separation performance and the antifouling property of the prepared membranes were investigated in detail. The antifouling property of the prepared membranes was found to be greatly enhanced by the addition of iGO, and we attributed the enhanced antifouling property to the improved hydrophilicity, the more negative zeta potential and the improved smoothness of the membrane surface.

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This study was designed to prepare functionalized multiwalled carbon nanotubes (MWNTs-COOH) incorporated chitosan membrane for separation of ethanol/water mixtures by pervaporation. The pristine MWNTs were treated by mixed acid and then functionalized by diisobutyryl peroxide. The structure and property of the functionalized MWNTs were characterized by Fourier transform infrared and Raman spectroscopies and transmission electron microscopy. A series of functionalized MWNTs incorporated chitosan membranes were prepared by solution blending method. The swelling degree of the resulting membranes in ethanol/water mixtures was 6 times that of the pristine chitosan membrane. The permeation flux of the membranes increased significantly with increasing functionalized MWNTs content in blend membrane matrix in pervaporation. On the basis of the experiments of sorption equilibrium, the solubility and the diffusion coefficient of membranes in water, ethanol, and 90% ethanol/water mixtures were obtained. Compared with the calculated diffusion coefficient (D 90 ), the measured diffusion coefficient (D 90 T ) in 90% ethanol/water mixtures was higher, taking M(2) for an example, D 90 was 0.193 × 10 -6 m 2 /s, and D 90 T was 0.41 × 10 -6 m 2 /s, which indicated the functionalized MWNTs were more prone to increased water permeation when ethanol and water penetrated into the membrane simultaneously. In addition, effects of MWNTs content in the membrane matrix and operating temperature on pervaporation performances were investigated. After introducing functionalized MWNTs, the Arrhenius activation parameters for the total permeation decreased from 28.15 to 12.91 kJ/mol, which indicated that the carbon nanotubes filled membranes were easier to penetrate and exhibited higher flux performance than a pristine membrane.

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Polyurethane hybrid membranes containing graphene oxide (GO) with different morphologies were prepared by in situ polymerization. The separation of CO2/N2 gas mixtures was studied using these novel membranes. The results from the morphology characterization of GO samples indicated that the oxidation process in the improved Hummers method introduced oxygenated functional groups into graphite, making graphite powder exfoliate into GO nanosheets. The surface defects on the GO sheets increased when oxidation increased due to the introduction of more oxygenated functional groups. Both the increase in oxygenated functional groups on the GO surface and the decrease in the number of GO layers leads to a better distribution of GO in the polymer matrix, increasing thermal stability and gas separation performance of membranes. The addition of excess oxidant destroyed the structure of GO sheets and forms structural defects, which depressed the separation performance of membranes. The hybrid membranes containing well-distributed GO showed higher permeability and permeability selectivity for the CO2. The formation of GO aggregates in the hybrid membranes depressed the membrane performance at a high content of GO.