Preparation And Research Of Zein Nonwovens With 3D Structure For Multi-efficiency Air Purification

With the rapid growth of global industry,air pollution has already become one of the most serious threats to public health and environment.In addition to particle matters(PMs),a wide range of chemical gases and harmful microorganisms are also included in air pollutants.One of the important means to reduce air pollution is to use effective air filters in specific applications,which requires that the filters could efficiently capture various types of pollutants in the air under low filtration resistance.Traditional air filters are difficult to degrade after use and likely to came as secondary pollution to the natural environment.Recently,zein has been found to react with the chemical gases including formaldehyde and carbon monoxide effectively by their rich functional groups,such as amino and hydroxyl.But the fibers in the membrane were easy to be stacked closely,causing high filtration resistance.Therefore,it is crucial to develop a green and multifunctional air filter with property of high filtration efficiency at low air resistance.Zeolite imidazole framework-8(ZIF-8),as an important porous material,shows great potential in air filtration because of its large specific surface area and rich functional groups.Zein,as a by-product after oil extraction,is a type of green,low-cost and high cross-linked macromolecular materials with rich sources,high molecular weight,reclaimed water stability and temperature resistance.The three dimensional fluffy structure can achieve low air resistance and high dust volume when it is applied to air filtration because of its large porosity.Herein,we are inspired by special shape of natural spiral grass and have fabricated a green and robust 3D nonwoven filter with controllable hierarchical structure from self-curved zein nanofibers modified by ZIF-8 via bi-solvent electrospinning and fumigation welding method.And its application prospects in the fields of PM filtration,formaldehyde removal and antibacterial were discussed.The specific contents of the research are as follows.(1)Study on the regulation of fiber morphology by different solvent ratio in spinning solution:Zein was spun in the mixed solvent of ethanol and water.The effects of solvent ratios of spinning solutions on the fiber morphology were studied to prepare fluffy nonwovens.Then the effects of morphology and structure on hydrophobic and mechanical properties were further analyzed.(2)Spinning parameters and process optimization: The orthogonal test(three-factor three-level)was selected to adjust the three parameters of voltage,propulsion speed of spinning fluid and receiving distance.The minimum average pore size of nonwovens is taken as the reference index.(3)Study on blended loading ZIF-8: The prepared ZIF-8 particles were mixed with zein spinning solution to study the effects of adding ZIF-8 on the morphology,structure and properties of electrospun fibers.The results showed that the fibers have the smallest average width when ZIF-8 is 10% of the solute mass,at this time,the porosity of the nonwovens is 85.73%.The addition of ZIF-8 has no significant effect on the thermal decomposition kinetics of zein nonwovens,which would increase the tensile strength,hydrophobic properties and adsorption capacity.(4)Solvent fumigation treatment of zein nonwovens loaded with ZIF-8: Solvent fumigation treatment was carried out on the blended nonwovens to study the effect of solvent fumigation on the morphology of nonwovens.When fumigating for 2 h,the exposure of ZIF-8 particles and the point bonding between fibers could be realized.After fumigation,the breaking strength and elongation at break of the nonwovens increased,showing the mechanical properties improved.The adsorption capacity of the nonwovens was enhanced,with the specific surface area and pore volume further enlarged.(5)Application research of ZIF-8 exposed zein nonwoven materials in the field of air purification: Through the two-step process of bi-solvent electrospinning and fumigation welding method,the functional groups and ZIF-8 particles could be exposed as much as possible,and the synergistic effect of the two could be played.The obtained filter materials realized "high efficiency and low resistance",having excellent formaldehyde removal ability and photocatalytic sterilization performance,providing novel insights for the sustainability of the air filtration industry.