Preparation Of Polyvinylidene Fluoride-based Electrospun Nanofiber Membrane With Micro-nano Surface Morphology And Its Application In Oil-water Separation

With the advancement of science and technology and the rapid development of society,the separation of oily wastewater has become an urgent problem to be solved.In this project,the poly(vinylidene fluoride-co-tetrafluoroethylene)(PVDF-TFE)micro-nano membrane,poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)double-layer micro-nano membrane and poly(vinylidene fluoride-co-tetrafluoroethylene)/ polyvinylidene fluoride(PVDF-TFE/PVDF)composite membrane were prepared by electrospinning technology.The surface micrographs of the membranes were characterized by Scanning Electron Microscope(SEM),the tensile strength of the membrane was studied by tensile testing,and the hydrophobicity of the membrane was also studied by Contact Angle Measurement.The oil-water separation performance and recycling performance of the membrane for different oil-water mixtures and oil-water emulsions were tested.The specific research results as follows:(1)PVDF-TFE membranes were prepared by electrospinning under different concentrations,solvents and voltages conditions.When the spinning solution concentration was 20%,the solvent was N,N-dimethylformamide(DMF)and the voltage was 17 k V,it could be constructed as a combination of micro beads and nano fibers.The composite structure was similar to the surface morphology of the Lotus Effect.The membrane has a contact angle of up to 154°for water and close to 0° for oil.The tensile strength reached 9.591 MPa.When the heat pressing temperature was 120 ℃,the adhesion between the membrane and the substrate was enhanced,and the membrane still maintained a good hydrophobic property.In the separation test of oil-water mixtures and water-in-oil emulsions composed of four different organic solvents and water,PVDF-TFE micro-nano membrane showed an excellent separation performance.The water content of the filtrated oil after separation of the n-hexane/water,toluene/water,petroleum ether/water and chloroform/water mixtures is lower than that of the original solvent.The water content of the filtrated oil after separation of the water-in-n-hexane,water-in-toluene and water-in-petroleum ether emulsions is lower than that of the original solvent.After 10 times oil-water separation experiments,the water content of the filtrated oil is still lower than that of the original solvent.The PVDF-TFE micro-nano membrane has a good recycling performance.(2)The PVDF-HFP double-layer membrane was prepared by electrospray/electrospinning technology.The nanofibers at the bottom layer and the micro beads at the top layer combined to form a rough composite structure.The contact angle of the PVDF-HFP double-layer membrane for water is up to 150 °,which is higher than the contact angle of the PVDF-HFP single-layer membrane to 141°.And the tensile strength have been increased to 1.2 MPa.In the separation test of oil-water mixtures and water-in-oil emulsions composed of four different organic solvents and water,PVDF-HFP double-layer micro-nano membrane showed an excellent separation performance.The water content of the filtrated oil after separation of the n-hexane/water,toluene/water and petroleum ether/water mixtures is lower than that of the original solvent.The water content of the filtrated oil after separation of the water-in-n-hexane and water-in-toluene emulsions is lower than that of the original solvent.After 10 times oil-water separation experiments,the water content of the filtrated oil is still lower than that of the original solvent.The PVDF-HFP double-layer micro-nano membrane has a good recycling performance.(3)The PVDF-TFE/PVDF composite membrane was prepared by electrospinning blending solution.Its surface fibers were in different diameters and the beads were linked by nanofibers.The micro beads and nanofibers form a rough composite structure,which lead the membrane to be hydrophobic.In addition,after heat treatment at 100 ℃,the PVDF-TFE/PVDF composite membrane enhanced its adhesion to substrate.While the membrane has a contact angle of up to 154°for water and close to 0° for oil.In the separation test of oil-water mixtures and water-in-oil emulsions composed of four different organic solvents and water,PVDF-TFE/PVDF composite membrane showed an excellent separation performance.The water content of the filtrated oil after separation of the n-hexane/water,toluene/water and petroleum ether/water mixtures is lower than that of the original solvent.The water content of the filtrated oil after separation of the water-in-n-hexane and water-in-toluene emulsions is lower than that of the original solvent.After 10 times oil-water separation experiments,the water content of the filtrated oil is still lower than that of the original solvent.The PVDF-TFE/PVDF composite membrane has a good recycling performance.