Construction Of Multi-structured Blow-spun Polyacrylonitrile Nanofiber Membranes And The Application In Complex Oily Wastewater Treatment

With the rapid development of industrialization and urbanization,the global clean water supply is facing increasing pressure.Due to the lack of advanced technology and lax supervision and other reasons,a large number of pollutants are directly discharged into the water and cause pollution.The composition of these wastewater is very complex,especially the insoluble oil and organic dyes,which pose a fatal and long-term threat to the water system and the ecological environment.Constructing special wettability fibrous membrane materials is an effective strategy to treat oily wastewater.However,most of the membrane materials with special wettability are still unable to effectively separate the emulsion system stabilized by surfactants and treat various water-soluble pollutants（such as dyes and surfactants）in water.In this paper,a series of multi-structured fibrous membranes were constructed by combining blow-spinning technology with various chemical synthesis and material preparation methods to remove typical pollutants from water.The specific research contents are as follows:（1）Preparation and the oil/water separation performance of superhydrophilic/underwater superoleophobic nanofibrous membrane based on polyacrylonitrile system with high durability and versatility.A multifunctional superhydrophilic/underwater superhydrophobic titanium dioxide/silver/polyacrylonitrile（Ti O₂/Ag/PAN）nanofiber membrane was prepared by blow spinning technology.PAN fibers and Ag/Ti O₂ nano-protrusions on the surface together endowed the fibrous membranes with superhydrophilic and underwater superoleophobic properties（the underwater oil contact angle is greater than 150^o）.Based on this,the nanofiber membrane showed high separation flux(1829.37±83.51 L m^-2 h^-1)and separation efficiency（>99%）.In addition,Ti O₂/Ag nano-protrusions were constructed on the surface of porous PAN nanofibers by photoreduction and hydrolysis,which made the fibrous membranes have good photocatalytic degradation ability.At the same time,it also has antibacterial activity and biosafety.In addition,nanofibrous membranes remain stable under various corrosive solution treatments（including acid,alkali,high concentration salt and organic solvent）,high temperature treatment,ultraviolet irradiation and ultrasonic treatment.（2）Multifunctional surface structure construction and synergistic enhancement of oily wastewater treatment performance of blow-spun nanofibers.Adsorption-photocatalytic co-treatment technology is an efficient and environmentally friendly method to degrade organic pollutants.ZIF-8 metal-organic skeleton and graphene oxide（ZIF-8/GO）hierarchical structure was constructed on the surface of blow-spun polyacrylonitrile nanofibers to enhance the multifunctional treatment ability of complex wastewater.According to the“Wenzel”model,the surface interface hydrophilicity was enhanced by constructing a hierarchical structure with rough surface to promote the solid-liquid contact area.The superhydrophilic and underwater superoleophobic surface enables the composite fibrous membrane to have good emulsion separation performance(The maximum flux of separating surfactant-free emulsions（SFEs）is up to 6779.66 L m^-2 h^-1,separating surfactant-stabilized emulsions（SSEs）is up to 3402.25 L m^-2 h^-1).The composite fibrous membrane also showed excellent organic dye adsorption capacity（75%dye adsorption during 2 hours dark treatment）,photocatalytic degradation performance under visible light（The degradation rate reached 96.5%in 90 min）and antibacterial performance.In addition,the fiber membrane has good biosafety and will not cause toxic effects on aquatic organisms.These excellent properties make the membrane have great potential in complex wastewater purification.（3）Inspired by the hierarchical structure of Setaria viridis,the superwettability nanofibrous membrane with hierarchical surface structure and its treatment performance of complex oily wastewater were designed and studied.Multifunctional zinc oxide/polyaniline/polyacrylonitrile（Zn O/PANI/PAN）nanofibrous membranes with needle-like Zn O nanorods were prepared by blow-spinning,in-situ synthesis and hydrothermal synthesis.The surface wettability of composite membrane was enhanced by constructing hierarchical hydrophilic surface structure.Due to the rich N-and O-groups and the synergistic effect with"Setaria viridis"structure,the composite fibrous membranes have high separation flux of SFEs(up to 8597.40 L m^-2 h^-1),high separation flux of SSEs(up to 2253.50 L m^-2 h^-1),excellent separation efficiency（>99.9%）.In addition,due to the electronic synergy of Zn O and PANI,the fibrous membrane has good photocatalytic degradation ability.The composite membrane can remain stable under harsh conditions and has good biological safety,and will not cause burden to the water environment.These excellent properties make Zn O/PANI/PAN nanofiber membranes have great potential in the treatment of oily wastewater.By constructing hydrophilic hierarchical structure,the treatment capacity of complex oily wastewater can be strengthened.High-performance nanofiber membrane in wastewater treatment will provide a new strategy for the next generation of multifunctional membrane separation process.