Study On Preparation Of Graphene Oxide Composite Membrane With Tuning Inter-layer Spacing And Its Nanofiltration Performance

With the development of economy,the membrane separation technology is becoming more and more important in environmental protection,chemical industry,energy and other fields.Developing separation membrane with high performance is the main challenge.For the membrane separation technology,the key point is the property of membrane materials.Therefore,the development of new membrane materials is the one of the problems to be solved.Graphene oxide（GO）is 2D crystals carbon materials in the thickness of one single atom.The excellent mechanical property,extremely large surface area and ultra-thin molecular thickness of the GO sheets make it as an outstanding material in the field of membrane separation.In addition,it is easily designed and modified duo to the oxygen-rich functional groups.GO has the unique nanochannel,which is potential for application in pervaporation,desalination and water treatment.In this study,the inter-layer spacing between GO layers were tuned with solvent green（SG）,and then the GO composite membranes were prepared successfully in dye remove from the water or organic solvent.The results indicated that the GO composite membranes have potential application in industry.Firstly,GO nanosheets were modified by SG through the strongπ-πstacking interactions.The inter-layer spacing between GO layers were tuned with SG.The SG@GO nanocomposites were then assembled onto the surface of tubular ceramic substrate through immersion method.The morphologies and structures of the resulting SG@GO composite membranes were characterized by scanning electron microscope（SEM）,energy dispersive X-ray spectrometer（EDX）,X-ray diffraction（XRD）,and Fourier transform infrared（FTIR）and so on.XRD was used to determine the d-spacing of the GO laminates by employing the Bragg law.The composite membrane was used for removing dye molecules（Eriochrome black T）from water.It was found from the results that when the SG concentration was 1.2 g/L,the GO concentration was 0.2 g/L,the immersing time was 30 min,the SG@GO composite membranes showed a flux of330 Lm^-2h^-1MPa^-1,which was nearly 6-fold enhancement compared with that of the pristine GO membrane(56 Lm^-2h^-1MPa^-1),without sacrificing the dye rejection.Therefore,this strategy may provide a facile approach to tune the inter-layer spacing of GO laminates for efficient molecular separation.In addition,（SG@GO/PDDA）_n composite membranes were prepared onto surface of tubular ceramic substrate though layer-by-layer method with SG@GO nanocomposites and PDDA.The（SG@GO/PDDA）_n composite membranes were used for removing dye molecules from organic solvent.The presence of tubular ceramic substrate and polymer make the composite membranes more stable in the organic solvent.The morphologies and structures of the（SG@GO/PDDA）_n composite membranes were characterized by SEM,XRD.An electrokinetic analyzer was used to track the variations of the surface zeta potentials of the（SG@GO/PDDA）_n composite membranes with different layers.In the end,the effect of SG concentration,assembly layer number,different dye types on membrane performances were studied.When the SG concentration was 1.5g/L,assembly layer number was 3.5,the（SG@GO/PDDA）_n composite membranes were used for removing methyl blue molecules from methanol solution,the composite membranes showed the flux and dye rejection were 50 Lm^-2h^-1MPa^-1and 90.1%respectively.