Preparation Of PMIA@PVDF Composite Electrospinning Fiber Membrane And Evaluation Theirs Oil-water Separation Application

Oily wastewater exists widely in every field of life.How to separate it effectively is an urgent problem to be solved.Membrane separation is a very effective method for oil and water separation due to its obvious advantages such as low energy consumption,high separation efficiency and simple operation.Due to its extremely high specific surface area and highly cross-linked internal porous structure,the nanofiber membrane prepared by electrospinning method has attracted extensive attention.Electrospinning nanofiber membrane is an ideal material for oil-water separation due to its high permeation flux and high efficiency in oil-water mixture separation.Polyvinylidene fluoride（PVDF）has been widely used in oil-water separation due to its own characteristics.Although it has good chemical stability and strong hydrophobicity,its further application in oil-water separation field is limited due to its poor mechanical properties.Polyisophthaloyl m-phenylenediamine（PMIA）,as a kind of high performance fiber,is known for its light weight,high strength and flame retardant properties.It can be used to enhance the mechanical properties of electrospinning fiber.In this paper,the spinning processes of PMIA and PVDF were firstly explored to determine the appropriate spinning conditions.Then,coaxial electrospinning fiber membrane was prepared with PMIA as the core and PVDF as the shell,and the influence of the ratio of the two spinning liquid flow rates on the surface morphology and performance of coaxial electrospinning fiber was investigated.Then,tetrmethoxy silane（TMOS）and perfluorodecyltriethoxysilane（PFOTS）were used to modify the prepared coaxial electrospinning fiber,and the PFOTS modified PMIA@PVDF（Si O₂）composite electrospinning fiber membrane with superhydrophobic properties was prepared.Subsequently,the coaxial electrospinning fiber membrane was modified by ZIF-8 particles and polybenzoxazine（PBZ）,and the hydrophobic PBZ modified PMIA@PVDF（ZIF-8）composite electrospinning fiber membrane with high surface roughness and low surface energy was prepared.In this paper,the spinning process of PMIA and PVDF was investigated by using the self-made electrospinning machine and the spinning liquid concentration and spinning voltage is variables.The surface morphology of different samples was observed by SEM,and the appropriate spinning process was determined.Then,PMIA@PVDF coaxial electrospinning fiber membrane with different coaxial shell ratio was prepared by using coaxial electrospinning needle（22-17G）.The coaxial structure of PMIA@PVDF coaxial electrospinning fiber membrane with different coaxial shell ratio was characterized by SEM and TEM.Ideal coaxial electrospinning fiber membrane could be obtained when the solution flow ratio of coaxial shells was 3:5.The mechanical properties test showed that the introduction of PMIA component played a good role in strengthening the composite fiber membrane.When the spinning liquid flow ratio of the core-shell solutions was 3:5,the contact Angle of the electrospinning fiber membrane was 145.7°at the maximum,and the separation flow rate of oil-water mixture was the highest.The separation flow rates of methylene chloride-water and trichloromethane-water were both above 1900L/m²h,and the separation efficiency reached more than 99%.Secondly,different contents of TMOS were introduced into the PVDF spinning solution of the shell layer,and different contents of TMOS electrospinning fiber films were obtained by coaxial electrospinning and subsequent heat treatment,After that,the coaxial electrospinning fiber films with 4.8 wt.%TMOS were fluorinated and modified by PFOTS at different temperatures to obtain PFOTS modified PMIA@PVDF（Si O₂）electrospinning fiber.When the fluorinated modification temperature is-10℃,the PFOTS modified PMIA@PVDF（Si O₂）electrospun fiber shows a more complex rough structure on the surface than the non-fluorinated electrospun fiber,and the water contact Angle can reach 154.8°at the maximum.The prepared electrospun fiber membrane sample has superhydrophobicity.At the same time,this electrospinning fiber membrane sample also showed a very high separation flow rate of oil-water mixture.The separation flow rate of methylene chloride-water was the highest,reaching 2722.8 L/m²h,and the separation efficiency could reach more than 99%.Thirdly,ZIF-8 particles were loaded on the surface of PMIA@PVDF coaxial electrospinning fiber,and then benzoxazine（BAF）was used to modify the surface of the electrospinning fiber.After heating and self-polymerization,polybenzoxazine（PBZ）modified PMIA@PVDF（ZIF-8）electrospinning fiber membrane with good hydrophobicity was prepared.When the response time is 1.5 h,and PBZ content is 1wt.%the samples of electrospinning fibers surface can be seen,there is a lot of ZIF-8 particles,and the existence of PBZ make ZIF-8 particles adhesion on the electrospinning fiber surface,the surface of electrospinning fiber still has great surface roughness.The maximum water contact Angle of this coaxial electrospinning fiber membrane sample can reach 152.5°,indicating that this electrospinning fiber membrane sample has a strong hydrophobicity.Meanwhile,the separation flow rate of methylene chloride-water is the highest,reaching 2495.4 L/m²h,and the separation efficiency can reach more than 99%.