Research On The Preparation Of Superwetting Materials And Their Application In The Field Of Water Treatment

The water crisis has become the second biggest environmental problem in the world after global warming.It is reported that around 40%of the world’s population lives in areas where fresh water resources are scarce.At the same time,increasing industrialization and human activities have further led to a serious deterioration in water quality.Freshwater shortages and water pollution are exacerbating the global water crisis,and research into sustainable,green and efficient methods for recovering dilute water from the air and for separating and purifying contaminated oil-water mixtures has become an urgent priority for researchers.On this basis,this thesis focuses on two main aspects of research work on water recovery from air and separation and purification of oil-water mixtures:（i）a hair-like microneedle array structure was prepared by using magnetic field lines to induce directional growth of magnetic particles,and the energy barrier difference formed by the gap of the array structure can effectively capture small mist-like droplets in air;（ii）an asymmetric wetting nanofiber membrane was prepared by spraying method using vinyl alcohol/ethylene copolymer（PVA-co-PE）nano fibers as raw material,asymmetric wettable nanofiber membranes were prepared by spraying method for the selective separation of oil-water mixtures.The carbon nanotube-doped nanofiber aerogel was then prepared by mixing the PVA-co-PE nanofiber suspension with carbon nanotubes and then freeze-setting.The filtration throughput was substantially increased without affecting the filtration efficiency,and various oil-water mixtures could be effectively separated under pressure,improving the service life of the separation material under complex environments.Details of the research are as follows.（1）A mixed solution of magnetic Fe₃O₄ particles,resin and solvent was uniformly sprayed onto the glass substrate,and the magnetic Fe₃O₄ particles drove the PDMS to grow directionally in the direction of the magnetic field lines under the induction of the external magnetic field to obtain the hair-like microneedle array structure.The hair-like composite coating with water collection and super double sparse properties was obtained by dipping in 1H,1H,2H,2H-Perfluorooctyltriethoxysilane（PFOTS）solution to reduce the surface free energy of the material.In addition,the hair-like composite coating showed good stability at high and low temperatures,in acid and alkaline environments and after sandpaper friction treatment.（2）Asymmetric wettability nanofiber antimicrobial films were prepared by uniformly spraying hydrophilic PVA-co-PE nanofibers on both sides of a commercial polypropylene（PP）substrate and loading Ag nanoparticles onto the fiber film using the reduction reaction of silver nitrate,followed by one-sided hydrophobic modification of one side of the nanofiber film.The asymmetric wettability of the nanofiber membranes allows for the selective separation of oil-in-water and oil-in-water emulsions with an efficiency of up to 99%.In addition,with the synergistic effect of the bactericidal effect of Ag nanoparticles on the hydrophilic side and the drainage of liquid on the hydrophobic side,the nanofiber membranes have high antibacterial and bactericidal properties against Staphylococcus aureus and Escherichia coli,improving the cycle life of the nanofiber membranes when separating oil-water mixtures in a practical environment.（3）To solve the problem of low flux of nanofiber membranes,the above PVA-co-PE nanofibers were cross-linked with glutaraldehyde and carbon nanotubes,and the carbon nanotube-doped nanofiber aerogel material was obtained after freeze-drying.The addition of carbon nanotubes improved the hydrophilic and mechanical properties of the aerogel,and the flux was as high as 12000 L m^-2 h^-1 when separating oil-in-water emulsions at one atmosphere pressure while maintaining high filtration efficiency,which has great prospects for application in the treatment of oily wastewater.