Study On The Effective Regulation Of Oil-water Separation Performance Based On The Pore Structure And Hydrophilicity Of Carbon Membranes

With the improvement of society deveopment and people’s living standard,human confront more serious problems on recourses,energy and environment.Among them,the treatment of oily wastewater,one of the typical polluted water,has become one of the most urgent problems.Among the various types of oily wastewater,the most difficult one is emulsified oil with an average particle size of 0.1～10μm.Conventional separation techniques are sujected to the drawbacks of high cost and energy consumption and ineffective separation efficiency.On the contrary,membrane separation has been attracted much attention for oily wastewater treatment due to their advantages of small footprint,high separation performance,low consumption of resources and energies,simple operation,etc.However,it needs to greatly improve the anti-fouling ability and separation efficiency before large-scale industrial application due to its late emergence.Therefore,this work proposes to conduct a study on the effective control of oil-water separation performance based on pore structure and surface hydrophilicity according to the characteristics and separation mechanism of carbon membranes.Firstly,microfiltration carbon membranes were prepared by using phenolic resin as precursor material,hexamethylenetetramine as curing agent,carboxymethyl cellulose as binder,and magnetic silica（Fe₃O₄@Si O₂）,or structure of the hollow silica（CSS-Si O₂）or hollow mesoporous silica（HM-Si O₂）as additives,through the preocessces of grinding,molding and carbonization.The thermal stability of modified materials,functional group,pore structure,crystallite structure,microstructure and surface wettability of carbon memrbanes were characterized by Thermogravimetric Analyzer（TGA）and Fourier Infrared Spectrometer（FT-IR）,X-Ray Diffraction（XRD）,Scanning Electron Microscope（SEM）,Transmission Electron Microscopy（TEM）,Contact Angle Tester,respectively.The effects of modification methods（i.e.,doping and impregnation）,and dopant amount,dopant types,solution concentration,impregnation time of modified materials,and different test conditions on the oil-water separation performance were investigated.In addition,the anti-fouling performance of the composite carbon membranes after backwashing and regeneration was also investigated.The results showed that:（1）Fe₃O₄@Si O₂ composite carbon membrane.The thermal stability of the precursor membrane and the surface wettability of the carbon membrane were significantly improved after the addition of Fe₃O₄@Si O₂.The optimal average pore sizes and the minimum porosities of the composite carbon membranes containing 20wt.%doping amount were 0.2514μm and 45.550%,respectively.The optimum rejection rate and permeation flux could reach 93.29%and 7396.95 Kg/m²·h·MPa,respectively.（2）CSS-Si O₂composite carbon membrane and HM-Si O₂ composite carbon membrane.The incoporation of silicon with two different morphologies significantly improved the thermal stability of precursor membrane and the surface wettability of carbon membranes.When the doping content was 20 wt.%,both CSS-Si O₂ composite carbon membranes and HM-Si O₂ composite carbon membranes exhibited the lowest average pore size and the largest porosity.They were correspondingly 0.191μm and 0.1432μm,and 50.30%and 52.81%.When the doping content was 20wt.%,the best separation performance of CSS-Si O₂ composite carbon membrane for oily wastewater was:rejection rate 99.67%,and permeation flux 4309.12 Kg/m²·h·MPa.The best separation performance of HM-Si O₂ composite carbon membrane:rejection rate 99.12%.and permeation flux 2401.96 Kg/m²·h·MPa.（3）Impregnated composite carbon membrane.After impregnation modification,both the average pore size and porosity of the carbon membrane decreased.When the impregnation solution concentration was 3%and the impregnation duration was 60s,the minimum average pore size and porosity of the composite carbon membrane could reach 0.1288μm and 31.9620%.When the impregnation time was 40s,the best separation effect was obtained as the rejection rate was 99.85%,along with the permeation flux of 392.16 Kg/m²·h·MPa.The anti-fouling analysis found that the rejection rate was basically unchanged,but the permeation flux had a slight loss for the impregnated carbon composite membrane.