Fabrication And Pervaporation Performances Of Graphene Oxide-based Composite Membranes

Graphene oxide（GO）membrane have received extensive attention in the field of separation due to its unique interlayered structure and fast water transport channel.In this thesis,the manipulation of the GO sheets size,interlayered structure and surface property was investigated.GO-based membranes were prepared on polyacrylonitrile（PAN）substrates and then subjected to pervaporation dehydration to enhance separation performance.Large-sized GO sheets were prepared by changing the ultrasonic exfoliation and centrifugal separation processes.HLGO membranes were obtained by filtrating large-sized GO solution.GO sheet size had a great impact on the interlayer alignment process and HLGO membrane exhibited highly laminated interlayer structure.Defects in the prepared HLGO membrane were fewer and mass transfer paths for molecules within the interlayer channels were longer,which were conducive to the improvement of separation performance and could reduce the critical membrane thickness effectively.Consequently,under the thickness of 100 nm,HLGO membrane displayed excellent pervaporation performance at 25°C for 2.6 wt%water/dimethyl carbonate solution.The permeation flux was 1.57 kg m^-2 h^-1 with 98.03 wt%water content in permeate.When HLGO membrane was used for the dehydration of organic solvents with large molecular diameter and separation of methanol/methyl tert-butyl ether mixture,outstanding separation performance was also achieved.HLGO membrane has great application potential in the field of pervaporation.Novel GO composite membranes were fabricated on PAN substrates via inserting copper hydroxide nanostrands（CHNs）between GO sheets and coupling with an ultrathin hydrophilic sodium alginate（SA）top-layer.The homogeneous intercalation of CHNs could enlarge the permeation channels within base GO membrane without destroying its main interlayered structure,which effectively facilitates the transport of water molecules.The SA layer with superior hydration capacity was firmly adhered on base GO membrane via hydrogen bonding and electrostatic interaction,which could improve hydrophilicity of membrane surface and enrich more water molecules.Under optimal SA deposit and CHNs intercalation,the permeation flux through the prepared SA/GO-CHNs membrane could reach up to 3.65 kg m^-2 h^-1 with an excellent separation selectivity（99.70 wt%water content in permeate）at 70°C for 10 wt%water/ethanol solution.With elevated feed temperatures,more prominent separation performance was obtained.In addition,SA/GO-CHNs membrane possessed satisfactory long-term operation stability,enhanced mechanical strength and firm interfacial adhesion,indicating that it could have a promising development prospect in practical separation applications.