Preparation And Application Of Polyacrylonitrile-based Composite Nanofiber Filter Media For Air Purification

With the increasing attention to air quality,the research on the filtration of solid particles in the air and the corresponding filter media has become more and more mature.The nanofiber membrane prepared by electrospinning has been widely studied and applied to air filter materials because of its high specific surface area and high rejection rate.With the further research,the experimental conditions of polymer electrospinning and other factors have basically matured.Polyacrylonitrile(PAN),polyvinyl alcohol(PVA),polyether sulfone(PES),and polyamide 66(PA-66)are common polymers used in electrospinning.Among them,PA-66 can produce spider silk fibers with a diameter of less than 100 nm,by controlling the spinning conditions.This paper aims to prepare anti-delayed PVA / PAN nanofiber filter and hydrophobic anti-delayed PA-66 / PAN / PES nanofiber filter by fiber cross-linked composite spinning and polymer co-dissolving composite spinning,respectively.In this paper,firstly,three-dimensional nanofiber filter media was prepared by using PAN as the base material.PVA and PAN are used as reinforcing structure fibers and integral filling fibers,respectively,in the overall fiber filter.In order to improve the filtration efficiency and mechanical properties of the membrane,the membrane was cross-linked with a certain concentration of a mixed solution of glutaraldehyde(GA),acetone zand acetic acid.By reducing the content of hydroxyl groups in the PVA nanofibers,the hydrophobicity of the fiber filter was enhanced,thereby improving the stability of the membrane,preventing the delamination phenomenon of the fiber membrane and increasing the compactness between the fibers in the membrane.The stainless steel mesh(SSM)impregnated with a dilute solution of PVA was used as the receiving substrate for fiber deposition which facilitates fiber applications in high-strength environments such as high pressure.The mechanical properties of the fibrous filter were determined by using a tensile tester and the results showed that the maximum strain and toughness reached 144.58% and 5.33 J/g,respectively.In addition,the fiber membrane was used as an air purification material to filter particles in the air.The density of the particles before and after filtration was measured and the mechanism of the interception of the particles by the fibers was discussed.Under the same test conditions,the PVA / PAN fiber filter has a lower pressure drop(418 ± 23 Pa).Comparing with the filtering efficiency of the commercial mask materials,the particles have excellent retention efficiency in the air.The filtration efficiency was 99% for particles with a size of 0.3-5 ?m.In addition,the application of polymer co-dissolved and layered composite fiber membrane structures in filter media was explored.The PA-66 was used to prepare dendritic nanofibers and the hydrophobic PES was used as the surface layer membrane to prepare a simple and effective PA-66 / PAN / PES composite nanofiber filter.The middle layer of the material was electrospun from PAN / PES blend polymer solution using N,Ndimethylformamide(DMF)as solvent.The substrate that receives the nanofiber filter was the SSM which has been water spray treated.The scanning electron microscopy characterization and specific surface area test results showed that increasing the amount of PES under the same spinning conditions was beneficial for reducing the fiber diameter and increasing the porosity of the membrane.At the same time,the mechanical properties of the membrane without SSM(5.857 MPa)were measured by tensile tests.The high hydrophobicity of the PES fiber resulted in a good hydrophobicity of the contact angle of about 130.58 ° on the surface of the PA-66 / PAN / PES filter membrane.When the sample thickness was as equal as possible,the PAN / PES-3 filtration efficiency was greater than 99% by performing a retention test of 0.3-5 ?m particles in the actual air environment.In addition,the regeneration performance of the filter membrane was explored through mechanical vibration and air backflushing.