Study On The Structure And Applications Of Biomimetic High-performance Fiber-based Composites

In recent years,with the development of industry and the continuous improvement of people's living standards,the problem of water pollution in China is getting worse.On the one hand,daily life,industrial production and frequent offshore oil spills produce a large amount of oily sewage;On the other hand,a large number of dyes and heavy metal ions are directly discharged into the water environment due to technical defects of use and post-treatment in the manufacturing and production of many industries,which poses a serious threat to human health and the ecological environment.By constructing special wettability materials and applying them to oil/water separation,it has solved many shortcomings in traditional separation technologies,and has become an effective separation technology for the treatment of oily wastewater.However,most of these materials still face the disadvantages of only being able to separate the free or immiscible oil/water mixture.They could not treat the emulsion system stabilized by surfactants and various water-soluble pollutants in the water phase(such as heavy metal ions,dyes,surfactants,etc.).Therefore,it is urgent to develop new and efficient sewage treatment materials.Nanofibers possess several advantages with large aspect ratio,high porosity,large specific surface area,etc.,thus,the corresponding membranes exhibit high porosity,coherent pore structure,good permeability and retention and adsorption performance for the target.In addition,the surface wettability of membrane materials could be effectively regulated by modifying their surface,which ensure fiber membranes can be precisely designed to treat mixtures of different properties.Therefore,nanofiber membrane has broad application prospects in the field of wastewater purification.In view of the limitations in the application of existing sewage treatment materials,in this article,we developed a variety of material preparation and surface/interface modification methods to cooperatively regulate the structures and surface wettability of the polymer fibrous membranes.Thus,the separation efficiency for various oil/water mixtures and anti-fouling property of the membranes were drastically improved.The structure-activity relationship between material structure and performance was clarified,and its mechanism was analyzed.The multifunctional application of fiber membrane is explored.It lays the foundation for the research and development of a new type of nanofiber separation membrane material for wastewater purification with multiple components.The specific research work is summarized as follows:(1)A facile method to fabricate superhydrophobic/superoleophilic membranes based on a fluorine-free system by the combination of electrospun polyimide(PI)nanofibers and a novel in-situ polymerized polybenzoxazine(PBZ)functional containing silica nanoparticles(SNP)is proposed.The resultant PI-based membrane has outstanding superhydrophobicity and superoleophilicity with water and oil contact angles above 154°and approaches 0°,respectively.Simultaneously,the membrane possesses extraordinary chemical and thermal stability and high salt tolerance.Furthermore,the membrane presents high separation efficiency(above 99%)and high-flux(4798Lm^-2h^-1)as well as good reusability and oil content in the filtrate below 5 ppm for separation of various oil/water mixture.Significantly,these studies offer a simple yet cost-effective technique to fabricate superhydrophobic/superoleophilic membranes and have potential use for oily wastewater treatment and oil spill clean-up.(2)A flexible,durable and magnetic pH-responsive F₃O₄/MA–TiO₂/PI electrospun nanofibrous membrane(ENM)was fabricated via an electrospinning and green dip-coating route.Combining the rough hierarchical structure and pH-responsive wettability,the as-prepared hybrid membrane can controllably separate a range of not only heavy oil/water but also light oil/water mixtures by only adjusting the pH of the aqueous medium.Both separations exhibit a large flux and outstanding efficiency for the tested oil/water mixtures even after 20 reuse cycles due to the hierarchical structure and flexibility of the membrane.In addition,the flexibility and magnetism of the membrane make it easily removed with a magnet after the separation of the oil/water mixtures.More importantly,the as-prepared membrane not only has excellent stability towards high temperature,corrosive organic solvent/salt solution immersion,and UV irradiation but also shows great resistance to mechanical abrasion and ultrasonic treatment,and the preparation method is facile,environmentally friendly,and cost-effective.Thus,such a membrane may offer exciting opportunities in the application of oily wastewater treatment and on-demand oil/water separation.(3)We describe the preparation of multifunctional superhydrophobic nanofibrous membrane by using a facile and novel nature-inspired method,i.e.,plant polyphenol(tannic acid)metal complex is introduced to generate rough hierarchical structures on the surface of an electrospun polyimide(PI)nanofibrous membrane,followed by modification of poly(dimethylsiloxane)(PDMS).Taking an as-prepared tannic acid?-Al³⁺-based superhydrophobic membrane as an example,it not only exhibits anti-impact,low-adhesive and self-cleaning functions,but also presents excellent performance in the separation of various oil-water mixtures.A high flux up to 6935Lm^-2h^-1with a separation efficiency of over 99% and the oil contents in water below 5ppm is obtained even after repeating use for twenty separation cycles.Additionally,the membrane exhibits excellent UV-shielding property,attributing to the inherent UV-absorbing ability of tannic acid.Furthermore,the membrane also possesses additional properties including antibacterial activity,good biocompatibility,robust mechanical strength,and excellent resistance to various harsh conditions.These attractive properties of the as-prepared membrane make it a promising candidate for potential applications in industrial oil-contaminated water treatments and oil-water separation.(4)A novel zeolitic imidazolate framework-8@thiolated graphene(ZIF-8@GSH)composites-based polyimide(PI)nanofibrous membrane was developed via a facile electrospinning and in situ hydrothermal synthesis approaches for effective purification of oily wastewater.The membrane showed superhydrophobicity/superoleophilicity and high separation efficiency(>99.9%)for a wide range of oil/water mixtures and water-in-oil emulsions.Besides,the membrane demonstrated excellent photocatalytic dye degradation,antibacterial,self-cleaning,and mechanochemical durable abilities,showing high potential in oily wastewater treatment and water remediation.(5)A multifunctional branched poly(ethylenimine)(b PEI)and poly(acrylic acid)(PAA)/tungsten oxide/polyacrylonitrile(PP/WO₃/PAN)composite membrane was fabricated by the combination of blow spinning and layer-by-layer methods.The incorporated WO₃ in generated in hydrophilic PAN fibers by spinning the precursor method,which simultaneously reveals remarkable photodegradation performance towards mimetic organic pollutions and excellent antibacterial activity due to their electron synergetic effect.In addition,the micro/nanoporous structure of the PP/WO₃/PAN composite membrane also ensures its good oil-water separation performance.Moreover,the reduction reaction of W atoms in the WO₃ network upon solar irradiation endows the membrane with superior heavy metal ion removal capability.Significantly,the membrane exhibits water-enabled self-healing performance due to the coated polyelectrolyte layer.More importantly,the membrane could be easily scaled-up;was free-standing,durable,and biocompatible;and exhibited no additional toxic effect on the surrounding environments.These outstanding properties make the membrane to have significant potential applications in wastewater treatment.