Study On Structural-Performance Adjustment And Emulsified Oil-water Separation Performance Of Microfiltration Carbon Membranes

Since the beginning of the 21^st century,with the rapid development of the global economy and industrial technology,the problems of environmental damage and water pollution have become increasingly dangerous.Among them,oily wastewater has seriously threat humans,animals,plants,as well as the environment since the pollutant comes from a variety of sources.Especially for emulsified oil-water,traditional methods are less effective in treating emulsified oil-water mixtures,and usually involve energy consumption and secondary pollution.Membrane technology has attracted widespread attention in academia and industry for its advantages such as high separation efficiency,easy operation,excellent production flexibility,simple equipment,and environmental friendliness.However,before the large-scale application of membrane separation technology,it is necessary to further improve the separation and anti-pollution.Therefore,the development of high-performance membrane materials has become a key hot issue for this technology.Carbon membrane,as a new type of membrane material,has not only the advantages of high thermal stability and corrosion resistance,but also the characteristics of easy regulation and abundant pores.It is expected to become an ideal membrane material for emulsified oil-water mixture separation.In this paper,a series of microfiltration composite carbon membranes were prepared by phenolic resin as precursor,sodium carboxymethyl cellulose as binder,polyacrylonitrile fiber?PANF?,inorganic oxides?SiO₂,TiO₂ and Fe₂O₃?and sepiolite mineral soil?SEP?as dopants,via the processes of blending,forming,drying and carbonization.The functional groups,thermal stability,pore structure,microstructure,morphology and hydrophilicity of the membrane materials were analyzed by Fourier transform infrared spectrometer,thermogravimetric analyzer,bubble pressure gauge,X-ray diffraction,scanning electron microscope and contact Angle tester.The influences of the types and dosages of the three dopants,before and after the dopants modification,membranes morphology,permeation time,feed concentration,trans-membrane pressure,salt and acid interference in the feed and other preparation and operating conditions on the emulsified oil-water separation performance of the microfiltration composite carbon membrane were investigated.Finally,the influence of the anti-fouling performance of carbon membrane after backwash regeneration was investigated.Results have showed that:?1?Polyacrylonitrile fiber composite carbon membranes.The addition of PANF has a significant impact on the thermal stability of the precursor membranes;When the content was 5wt.%PANF,membrane has the maximum porosity of 56.72%.When the content was 3wt.%alkali modified PANF,membrane has the minimum mean pore size.When the content was 1wt.%PANF,membrane has the highest permeation flux of 69295 kg m^-2 h^-1 MPa^-1,When the content was 3wt.%alkali modified PANF,membrane has the highest oil rejection of 94.23%.Compared with the flat membrane,the tubular carbon membrane has the advantages of high permeability and strong processing capacity,but the oil rejection is slightly lower.?2?Inorganic oxide composite carbon membranes.The introduction of inorganic oxide enhanced the thermal stability of the precursor membranes;Fe₂O₃ composite membrane has the smallest average pore size,the strongest hydrophilicity;TiO₂ composite membrane has rich porosity;When the content was 8wt.%SiO₂,carbon membrane has the highest oil rejection of 99.99%.When the content was 25wt.%Fe₂O₃,carbon membrane has the optimal anti-pollution capacity.?3?Sepiolite composite carbon membranes.The addition of acid modified sepiolite?A-SEP?improves the thermal stability of the precursor membranes;A-SEP composite carbon membranes has the best separation effect on oil-water emulsion.When the content was 35wt.%A-SEP,the oil rejection was 97.6%and the permeation flux was8323.89kg m^-2 h^-1 MPa^-1 under the condition that the feed flowrate was 6mL min^-1,the feed concentration was 100mg L^-1 and the trans-membrane pressure was 0.06MPa.Membrane material has good applicability under high salinity,the separation efficiency has decreased by only 5.4%.But the oil rejection has dropped to 41.6%under strong acid,the separation ability has been greatly reduced.The amount is 35wt.%A-SEP carbon membrane,the flux recovery ratio is 2.5 times that of pristine membrane,which has excellent anti-pollution ability.