Enhancement on the permeation performance of polyimide mixed matrix membranes by incorporation of graphene oxide with different oxidation degrees

Graphene oxide (GO) with different oxidation degrees were synthesized by harsh oxidation of graphite using the improved Hummers method. The GO/polyimide (PI) mixed matrix membrane was successfully fabricated by in situ polymerization of PI monomers (3,3,4,4-biphenyltetracarboxylic dianhydride and 4,4-diaminodiphenyl ether) with GO. The structure of GO was characterized by Fourier transform infrared, transmission electron microscopy, atomic force microscopy, X-ray diffraction, and thermal gravimetric analysis-differential thermal analysis. The performance of different GO/PI mixed matrix membranes was evaluated by permeation experiments of CO2/N-2 gas mixture (volume ratio, 1:9). Results showed that more polar functional groups were introduced to GO with the increase in oxidation degree of GO in the preparation process, producing fewer layers and more translucent structures. GO with higher oxidation degree has significant effect on its dispersion in the N,N-dimethylacetamide solvent and polymer matrix materials. The permeability of GO/PI hybrid membranes for CO2 and N-2 increased. The CO2/N-2 permeation selectivity of membranes exhibited a trend of initial increase, followed by a decrease, with the increase in oxidation degree, when the same amount of GO was added. For GO with the same oxidation degree, the permeability and permeation selectivity of hybrid membrane initially increased, and then decreased with the addition content of GO. In the case of hybrid membrane containing 1wt% monolayer GO, the maximum permeability and permeation selectivity of hybrid membranes for CO2 were 14.3 and 4.2 times more than that of PI membrane without GO, respectively. Copyright (c) 2015 John Wiley & Sons, Ltd.