Three diamine monomers (ethylenediamine, butylenediamine, and p-phenylenediamine) were selected for cross-linking graphene oxide (GO) to prepare composite graphene oxide-framework (GOF) membranes through filtration using a pressure-assisted self-assembly technique. The membranes were applied to separate an ethanol−water mixture by pervaporation. Unmodified GO comprised only hydrogen bonds and π−π interactions, but after cross-linking it with a diamine, attenuated total reflectance−Fourier transform infrared and X-ray photoelectron spectroscopy demonstrated that the diamine was chemically bonded both to GO and the membrane support. Moreover, GO hydrophilicity was substantially altered; water contact angle increased from 24.4°to 80.6°(from cross-linking with an aliphatic structure of diamine to cross-linking with an aromatic structure). Results of X-ray diffraction showed that d-spacing in GOF layers varied from 10.4 to 8.7 Å. For GOFs presoaked in 90 wt % ethanol−water, covalent bonds between the layer and diamine could effectively suppress stretching of d-spacing. Cross-linking with ethylenediamine produced a composite membrane that exhibited a short interlayer dspacing and delivered an excellent pervaporation performance at 80 °C: permeation flux = 2297 g/(m 2 h); water concentration in permeate = 99.8 wt %. The membrane showed stability during a long-term operation at 30 °C for 120 h.

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The free volume sizes and distributions and multilayer structures in asymmetric thin layer polyamide membranes in the wet state have been first time measured using the variable monoenergy slow positron beam (VMSPB). This paper presents a newly developed method which combines the technique of plasma-enhanced chemical vapor deposition to form a barrier layer for high-vacuum condition to seal the composite polyamide and of interfacial polymerization between 2-aminoethanethiol (AETH) and trimesoyl chloride (TMC) on the surface of modified asymmetric polyacrylonitrile (mPAN) membrane (AETH-TMC/ mPAN), under the wet condition encountered during the pervaporation process in which they are in direct contact with the liquid environment provided by the feed solution. During the VMSPB experiments under a high vacuum, our new method maintained the thin-film composite (TFC) membrane in the wet conditions typically experienced in VMSPB experiments wherein it directly contacts the liquid feed environment, which is essential in the course of real measurements as there is a high interaction between the feed solution and the membrane. The results of free volumes and layer structures in the wet state are compared with the dry sate and are supported by the results using SEM and FTIT-ATR measurements.