With the rapid development of industry,people consume a lot of energy such as petroleum,which makes the problem of environmental pollution increasingly serious.Among them,the water pollution caused by oily wastewater is particularly dangerous,which not only ruins the ecosystem,but also threatens the life safety of human beings and other organisms.Therefore,it is urgent to develop an efficient method for treating oily wastewater.Carbon membranes have attracted much attention due to their flexible operation,excellent thermal stability,environmental adaptability,and adjustable porous structure.However,before large-scale application,the anti-pollution properties and separation properties of carbon membranes need to be greatly improved,thereby improving operational stability,cost performance and market competitiveness.Therefore,this paper proposes to regulate the hierarchical porous structure and surface properties of microfiltration carbon membranes based on composite methods,in order to improve the separation performance and antifouling properties of carbon membranes,and lay a foundation for rich membrane material preparation technology and application.First,the hierarchical pore structure and surface properties of microfiltration carbon membranes were regulated by two composite techniques,blending method and in-situ synthesis method,respectively.The first is to the hybrid carbon membrane were fabricated from phenolic resin as the precursor,activated alumina(γ-Al2O3),activated carbon(AC)and activated alumina and activated carbon blend(γ-Al2O3/AC)as dopants,by blending and carbonization.The second is to use dopamine hydrochloride(DA)as a modifier to synthesize polydopamine(PDA)in situ on the surface and in the pores of the carbon membrane.Regulating the hierarchical porous structure and surface properties of carbon membranes by introducing dopants.Secondly,the thermal stability,functional group,microcrystalline structure,microscopic morphology,pore structure and hydrophilicity of the membranes were characterized by thermogravimetric analyzer,fourier transform infrared spectrometer,X-ray diffractometer,scanning electron microscope,N2 adsorption method,bubble pressure method and water contact angle meter,respectively.Finally,the effects of factors such as the type and amount of blending agent,PDA synthesis time,oily wastewater concentration,trans-membrane pressure and feed flux on the performance of carbon membranes separation oily emulsified wastewater were explored,and the anti-pollution property was investigated.The results show that the prepared carbon membranes matrix comprises both macropores and mesopores and microporous and other hierarchical pore structures.Both modification methods can effectively regulatethe hierarchical porous structure and surface properties of the microfiltration carbon membrane,and with a view to optimizing the microfiltration carbon membrane separation performance for oily wastewater.Specifically:(1)Forγ-Al2O3 hybrid carbon membranes,the introduction ofγ-Al2O3 improves the thermal stability of the precursor membrane and the surface wettability of the carbon membrane.When the content ofγ-Al2O3 is15wt.%,the obtained carbon membrane has the smallest average pore size of macropores and the highest porosity is 0.35μm and 42.19%,respectively,and the average pore size of mesopores is 3.87nm,and the oil rejection reaches to 98.72%,and the permeation flux of 10960.13 kg/m2·h·MPa.(2)For AC hybrid carbon membranes,the introduction of the dopant both enhanced the thermal stability of the precursor membrane and the hydrophilicity of the carbon membrane,and also narrowed the pore size distribution.When the AC content is 10wt.%,the prepared carbon membrane has the smallest average pore size of macropores is 0.21μm,and the average pore size of mesopores is 4.22nm,and the oil rejection reaches to 97.47%,along with the permeation flux of 3853.96 kg/m2·h·MPa.When the dual dopantγ-Al2O3/AC was introduced,the prepared carbon membrane has the lowest average pore size of macropores is 0.18μm,and the average pore size of mesopores is 4.84nm,and the oil rejection reaches to 99.67%,along with the permeation flux of 9461.93 kg/m2·h·MPa;In addition,the presence ofγ-Al2O3/AC significantly enhanced the fouling resistance of the carbon membrane.(3)When the carbon membrane was modified by in situ synthesis of PDA,the hydrophilicity and separation were significantly improved,and the permeation flux of distilled water reaches to 68535.56kg/m2·h·MPa,which increases by 65.4%than the pure carbon membrane.At the same time,the highest permeation flux to oily wastewater reaches 13330.83 kg/m2·h·MPa,which increases by132.8%,along with the oil rejection reaches to 93.36%.Compared with the pure carbon membrane,the total pollution ratio is reduced by 7.7%. |