| Particulate pollutants in the air are the main cause of air pollution,threatening public health and the ecological environment.Air quality requirements are becoming more stringent around the world.However,traditional petroleum-based synthetic polymer fiber filter materials may cause secondary pollution to the environment due to their non-degradable properties.Therefore,it is of great significance to study biodegradable air filter materials.In this paper,a biodegradable zein air filter was prepared by loading zein fibers on cellulose paper towels by electrospinning technology.Firstly,the feasibility of cellulose paper towel as base material was studied,the influence of the mass ratio of mixed solvent ethanol/water(EtOH/DI)on the morphology,structure and performance of the filter was explored,and the formation mechanism of different zein fiber morphology was analyzed.In addition,in view of the poor mechanical properties of zein fiber,ethylene vinyl alcohol copolymer(EVOH)was introduced,and the effect of the distribution structure of EVOH and zein on the performance of the filter was studied.The main contents are as follows:(1)Electrospinning zein fibers have poor mechanical properties and are difficult to be used in air filtration alone,so a substrate material loaded with zein fibers is usually required.In this paper,the performance requirements of commercial cellulose paper towel as a substrate material are firstly studied,specifically in terms of morphology,porosity,pore size distribution and air filtration.As a biodegradable three-dimensional porous structure material,cellulose paper towel has a high porosity of 85.17%and an average pore size of 49.549 μm,and the air filtration efficiency and pressure drop are 5.3%and 6.1 Pa,respectively.In addition,zein interacts with cellulose paper towel,which will produce hydrogen bonds,making them more adhesive.Therefore,cellulose paper towel shows excellent mechanical support without affecting the overall filtration performance of the filter,and is a good choice as a filter substrate(2)By adjusting the mass ratio of mixed solvent ethanol/water(EtOH/DI),air filters with different zein fiber morphologies(round or flat ribbon)were successfully prepared.The difference in morphology may be attributed to the following two points.a:The high volatility of EtOH results in the difference in the volatilization rate of the solvent inside and outside the zein jet;b:The solubility difference of zein in different concentrations of ethanol.From the perspective of air filtration performance,the performance of the flat ribbon zein fiber air filter is much higher than that of the circular zein fiber filter,and its filtration efficiency for removing PM0.3.And it still maintains stable filtration performance under repeated filtration,different air flow rates or different ambient humidity.In addition,the filter was completely degraded after 42 h in cellulase solution,and significantly degraded after 14 days of natural soil burial,showing excellent biodegradation performance.Finally,the zein filter also shows some potential in oil-water separation applications.(3)In order to improve the mechanical properties of zein fibers,EVOH/zein composite air filter was prepared by blending EVOH and zein by electrospinning technology,and the effect of EVOH addition on filter performance was studied.The comparison found that the pure zein filter had ultra-low stress(0.16 MPa)and low strain(12%),while the mechanical properties of the EVOH/zein composite air filter were significantly improved,reaching 0.6 MPa stress and 55%strain.In addition,the addition of EVOH improves the hydrophobicity of the filter,which facilitates the use of the filter in humid environments.Finally,the effects of the distribution structure of EVOH and zein fibers on the filtration performance and mechanical properties of the filter were studied.In terms of filtration performance,the staggered distribution of EVOH fibers and zein fibers is more conducive to obtaining lower pressure drop;From the mechanical properties,the upper and lower distribution structures of EVOH fibers and zein fibers have greater advantages for the strain of the filter,while the staggered distribution structure is more favorable for the stress of the filter. |
