| In recent years,with the rapid development of science and technology and the accelerated industrialization,the situation of water resources abuse and pollution has been gradually severe.The treatment technology of low surface energy and high adhesion wastewater,represented by oil-containing wastewater,is gaining more and more attention.Membrane technology has become the representative of advanced separation and purification technology since the new century,and it has been widely studied by virtue of its high efficiency,energy saving and low cost.The essence of membrane separation of oily wastewater is to build an anti-pollution membrane surface by super-impregnation on the membrane surface,and to separate oil-water mixed emulsions by using a pollution resistance mechanism and a pollution repulsion mechanism.Among them,submerged superhydrophilic and superoleophobic membranes,which adopt pollution resistance mechanism and isolate oil components underwater,have become the key research direction for separation of oily wastewater by membrane method due to its easy preparation and flux advantages.In this dissertation,graphene oxide（GO）,which is rich in oxygen-containing groups and has a flexible two-dimensional surface,was selected as the membrane forming material,and concave-tufted clay（ATP）nanorods and ultrafine activated carbon（UAC）particles were used as the co-blended intercalation materials.GOAC)membranes and S-GOAC membranes using small-sized GO nanosheets were prepared on ceramic substrates pretreated with3-aminopropyltriethoxysilane（APTES）,and the construction mechanism of micro-nano composite surfaces of GO-based blended membranes and the separation mechanism of oil-water emulsions were proposed by analyzing their anti-pollution performance,separation performance,stability and the composition of surface rough structure.（1）GOAP composite membranes were prepared by vacuum filtration method,and their morphology,anti-pollution performance,separation performance and stability were investigated.The distribution forms of ATP nanorods inside and on the membrane surface were determined,as well as the construction forms of hierarchical nano-rough structures on the GOAP membrane surface.The effect of PVA on membrane structure and stability,and the effect of ceramic substrate pretreated by APTES on the bonding strength of GOAP membrane body to ceramic substrate were explored.The underwater superhydrophilicity and superoleophobicity of GOAP membranes were achieved,and their water flux was elevated 12.4 times to 16.16 L·m-2·h-1 compared to pure GO membranes（GOM）,and the filtration rate was maintained above 99%with a flux recovery rate of up to 83.31%.However,due to the poor size compatibility of ATP and GO sheet layers,ATP,while constituting a nanoscale rough structure,also agglomerates and masks the native folds of GO nanosheets,hindering the formation of the micro-nano composite structure,resulting in the poor anti-pollution performance of GOAP membranes in the actual separation of emulsions.（2）In order to construct a micro-nano composite structure on the membrane surface and achieve good anti-pollution performance of the membrane in separating emulsions.Block UAC particles were selected instead of one-dimensional ATP nanorods,and GOAC membranes were prepared by vacuum filtration method.A lotus leaf-like micro-nano composite rough structure was successfully constructed on the membrane surface,which consists of micron-scale bumps generated by the GO nanosheets wrapped with UAC particles and nanoscale secondary folds formed by the bending of the GO nanosheets during wrapping.With the intercalation effect of UAC co-blending and the micro-nano composite structure on the surface,the water flux of the membrane reached94.38 L·m-2·h-1,which is 72.6 times that of GOM.The underwater oil droplet contact angle reached 163°,realizing the underwater super-oil sparing performance of the membrane,and it has more than 99%filtration rate,95.72%flux recovery rate and 14.55%flux decrease rate in actual separation of emulsions.（3）In order to verify the theory of the construction of lotus-like micro-nano composite structure of GOAC membrane,the effect of size matching of membrane composites on the membrane structure and performance was investigated in this paper.S-GOAC membrane was prepared by selecting small size GO nanosheets（500 nm-5μm）,and the corresponding characterization and performance comparison were performed with GOAC membrane using homemade GO nanosheets（10-15μm）.The results showed that the membrane surface of S-GOAC was not only distributed with a large amount of broken and exposed activated carbon,but also had a low number of secondary folds and uneven distribution.Its pure water flux and flux recovery rate were 76.10 L·m-2·h-1 and 72.23%,with a 19.37%decrease in flux compared to GOAC.After the comprehensive analysis of surface microstructure and anti-pollution performance,the construction mechanism of the micro-nano composite rough structure on the membrane surface and the separation emulsion mechanism of the membrane were further proposed. |
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