Preparation And Properties Of Electrospun PAN Membranes For Oil-water Separation Based On Click Chemistry

In recent years,with the discharge of production and living wastewater into rivers and lakes,and the leakage of oil pollutants caused by crude oil extraction and marine transportation,serious water pollution has been caused,which poses a serious danger to human physical and mental health.Therefore,the treatment of oily wastewater,especially surfactant-stabilized emulsions,is of great significance to human beings.Traditional technologies for treating oily wastewater have many disadvantages such as high cost and low separation efficiency,so it is important to explore membrane separation technologies with high separation efficiency,low cost,simple operation and no secondary pollution.However,there are also some problems in the use of separation membranes.The most common problem is that there is membrane fouling on the surface of hydrophobic and oleophilic membranes.Membrane fouling will increase the mass transfer resistance and seriously shorten the service life and reusability of the membrane.Constructing a hydrophilic and oleophobic functional layer on the membrane surface can solve this problem and endow the separation membrane with hydrophilic and underwater oleophobic properties.This is mainly because when the membrane is separating emulsions,the membrane surface first attracts water molecules to form a hydration layer,the existence of the hydration layer will prevent oily contaminants from touching the membrane surface and thus contaminate the membrane,while the water phase will pass through the membrane surface through the hydration layer,so the purpose of anti-fouling can be achieved while separating emulsions.Traditional surface modification techniques for separation membranes often require complex reaction conditions and processes.This topic proposes the use of click chemistry for the functional surface modification of electrostatically spun polyacrylonitrile（PAN）membranes.The membranes containing sulfhydryl groups on the surface were firstly prepared by electrostatic spinning blending method,and then the functional treatment of the membranes was carried out by thiol-ene click chemistry in order to improve their hydrophilic properties and underwater oleophobic properties with excellent antifouling properties.First,MPAN membranes with sulfhydryl-rich surface were obtained by blendingγ-mercaptopropyltriethoxysilane（MPTES）with polyacrylonitrile（PAN）,and then 3-[N,N-dimethyl-[2-（2-methylprop-2-enoyloxy）[ethyl]ammonium]propane-1-sulfonate inner salt（SPE）was grafted onto the surface of MPAN membranes by thiol-ene click chemistry,and the reaction was initiated by heat.Raman spectroscopy and Elman reagent were used to confirm the feasibility of blending,and the microstructure and chemical composition of the modified membranes were observed and analyzed by scanning electron microscopy（SEM）,energy spectroscopy（EDS）analysis,and X-ray electron spectroscopy（XPS）.The grafting treatment of SPE improved the hydrophilicity of the PAN membrane and exhibited oleophobicity under water.When the separation experiments of different emulsions were carried out under the action of gravity,the membrane showed excellent separation efficiency,and at the same time had good antifouling performance,the flux recovery rate was as high as 94%,and the pure water flux of the membrane reached 787 L/（m~2·h）.In order to further optimize the oil-water separation performance of the separation membrane,on the basis of electrostatically blending PAN and MPTES,dimethyl diallyl ammonium chloride（DMDAAC）was grafted by photo-initiated thiol-ene click chemistry to obtain the oil-water separation performance and DPAN modified membrane with excellent stability.The chemical composition of the modified DPAN membranes was analyzed by infrared spectroscopy,and multiple tests and characterizations were performed on the modified membranes.The experimental results show that the modified membranes have excellent hydrophilic and underwater lipophobic properties,exhibit excellent stability in different acid-base solutions and organic solutions,and maintain stable wetting properties even under prolonged UV light irradiation.At the same time,it showed high separation efficiency in separating surfactant-stabilized emulsions,and more importantly,the flux return rate was still as high as 99.8%after the emulsion separation test,and there was no significant staining on its fiber surface.The optimal experimental protocol was obtained by optimizing the amount of finishing agent,with the optimized mass concentration of SPE at 10 wt%and DMDAAC at 15 wt%.Taken together,the results show that the subject provides new insights into the research of membrane separation technology application in the field of oil-water separation and the application of click chemistry on separation membranes.