Fabrication Of Functional Electrospun Fibrous Composite Membranes And Evalution Theirs Oil-water Separation Application

Oil-water separation has become one of the most common pollutants in the world.Membrane separation has been proved to be an effective technique to separate oil–water mixtures.Electrospun fibrous membranes have unique and interesting features for oil-water separation such as high surface area to volume ratio,large porosity,interconnected pore structure and flexibility in surface functionalities.These properties result in high permeability in oil–water separation,which can not only improve the separation efficiency but also reduce the energy consumption of the process.However,most of the prepared fibrous membranes still have some drawbacks such as poor mechanical properties,poor separation performance,could not free-standing,the complex and costly fabrication process,the limited transition range of surface wettability,the inevitable oil fouling,and could not meet the requirement of remote operation of oil/water separation unit that they suffer from significant restriction in their practical industrial applications.The dissertation work is directly aimed to address these problems and further achieved the practical application of oil-water separation membranes.The properties of a series of high performance composite fibrous oil-water separation membrane are studied in details.Moreover,the potential application of fibrous oil-water separation membrane is evaluated.Preparation of high strength PBZ/SNPs/CA-PI composite fibrous membrane by co-axial electrospinning and subsequently imidizated and then modified biobased CA-PI fibers using fluoride benzoxazine in the presence of silica nanoparticles.Preparation of ‘flexible' PI/CA/F-PB/SNPs composite fibrous membrane by co-axial electrospinning and subsequently imidizated and then modified biobased PI/CA fibers using ‘heavily' fluoride benzoxazine in the presence of silica nanoparticles.The novel dual pH and ammonia-vapor responsive SNPs/DA-TiO₂/PI membrane was prepared dip-coating of electrospun PI with decanoic acid?DA?-TiO₂ and silica nanoparticles?SNPs?.Photothermal-responsive polyurethane?PU?/poly?methyl methacrylate?-block-poly?N-isopropylacrylamide??PMMA-bPNIPAAm?composite fibrous membranes are designed and fabricated by co-axial electrospinningThe main contents of this work are as follows:1.The high strength PBZ/SNPs/CA-PI composite fibrous membranes were prepared by coaxial electrospinning of biobased CA with polyamide acid was performed to fabricate core–sheath structured biobased CA–PAA fibers which were subsequently imidizated resulting in high strength CA–PI fibers.Then modified CA–PI fibers using fluoride benzoxazine in the presence of silica nanoparticles,we have study their oil-water separation performance.The high strength biobased CA–PI fibrous membranes were fabricated by coaxial electrospinning and subsequently imidizated,the effect of PI on the mechanical behavior of biobased CA was studied.Fluorinated benzoxazine?BAF-tfa?was then in situ polymerized in the presence of silica nanoparticles forming a hydrophobic polymeric layer on the surface of the CA–PI fibers and resulting the FPBZ/SNPs/CA-PI composite fibrous membrane.The optimized F-PBZ-1/SNP-4/CA–PI membranes show a fine hierarchical roughness,have a tensile stress is higher than 200 MPa,a high water contact angle of 160° and an extremely low oil contact angle of 0°.Importantly,the fibrous membrane seemed very stable under various harsh conditions,like Acid and alkali and high temperature with high flux?1136±50 L·m-2·h-1?and separation?>99%?even after re-use of the membranes,making it promising in practical application of oil-water separation.2.To fabricate high ‘flexible' PI/CA/F-PBZ/SNPs,biobased cellulose acetate?CA?and PAA were co-axially electrospun;the ‘flexible' PAA core was then imidizated at high temperature to obtain core/shell structured biobased CA/polyimide?PI?electrospun fibrous membranes;subsequently the surface of the fibers was modified with ‘heavily' fluorinated polybenzoxazine?FPB?in the presence silica nanoparticles?SNPs?.‘flexible' PAA fibrous membrane and ‘heavily' fluorinated polybenzoxazine?F-PB?were synthesized successfully.Then BAF-btfa and SNPs were subsequently introduced into the surface of PI/CA by in situ polymerized and resulting the high ‘flexible' PI/CA/F-PBZ/SNPs composite fibrous membrane.The membranes show a much higher critical tensile stress?130 MPa?and critical tensile strain?52%?using PI obtained by the polycondensation of 3,3,4,4-Biphenyl tetracarboxylic dianhydride?BPDA?with 4,4-diaminodiphenyl ether?ODA?.Due to the use of the ‘heavily' fluorinated polybenzoxazine,the membranes are superhydrophobic with a water contact angle of 162° and an oil contact angle which approaches 0° and thus possess great potential for oil–water separation.3.A novel dual pH-and ammonia-vapor-responsive SNPs/DA-TiO₂/PI composite fibrous membranes was developed,the pH-and ammonia-induced wettability transitions and selective oilwater permeation of the prepared membranes are evaluated in detail.As far as excellent mechanical strength,stability of PI-based fibrous membranes is concerned,decanoic acid?DA?-TiO₂ mixture and a silica nanoparticle pre-gel solution were introduced into the surface of PI by dip-coating.The novel SNP/DA-TiO₂/PI membrane exhibits superhydrophobicity in air and superoleophilicity in neutral aqueous environments?e.g.,at pH 6.5?.However,the membrane becomes hydrophilic and superoleophobic in basic aqueous environments?e.g.,at pH 12?.The membrane has extremely high flux?6500 ± 100 L·m-2·h-1?and separation efficiency?> 99%?,thermal stability and abrasion resistance.changes in the surface wettability can also be induced by exposure to ammonia vapor,which might facilitate remote-controlled oil-water separations.4.Photothermal-responsive polyurethane?PU?/poly?methyl methacrylate?-block-poly?Nisopropylacrylamide??PMMA-b-PNIPAAm?core-shell structured fibrous membranes are fabricated and the photothermal-responsive property of the membranes were investigated.Based on high tensile strain PU,temperature-responsive copolymer poly?methyl methacrylate?-blockpoly?N-isopropylacrylamide??PMMA-b-PNIPAAm?,Ag nanoparticles?Ag NPs?and singlewalled carbon nanotube?SWCNT?.Co-axial electrospinning of PMMA-b-PNIPAAM with PU was performed to fabricate high flexible,free-standing,easy bending,core-shell structured PU/PMMA-b-PNIPAAM nanofibers,being PMMA-b-PNIPAAM fibers with a PU core.Besieds,SCNTs,AgNPs were dispered in PMMA-b-PNIPAAM electrospun solution.The as-prepared membranes with photothermal-modulable oil/water wettability and are capable of separating oilin-water nanoemulsions with separation efficiency higher than 99% through regulating illumination time and power.The membrane provides great potential for the generation of remote operation point-of-use water treatment devices.In summary,a series of high performance composite fibrous membranes were fabricated.These composite fibrous membranes showed good oil-water performance.Actually,this strategy provided a facile and versatile method to prepare high performance composite fibrous membranes with various polymer and modified material.These functional composite fibrous membranes have a good application prospect in the field of wastewater treatment and oil-water separation.