The Fabrication Of The Nanofiber Composite Membrane And Its Applications In The Field Of Air Filtration

Nanofiber material presents high surface area and high porosity and is considered as a good candidate as air filter.The electrospinning methods are often used to prepared nanofibrous filtration media but it is high cost and low efficiency.Additionally,How to make a good balance between filtration efficiency andpressure drop remains a challenge.Herein,it is significant to develop nanofiber-based air filter through a technique with high throughput and low cost.In this work,PVA-co-PE/CAB composite nanofiberswere fabricated by a melt phase separation method followed by the solvent-removal of CAB substrate,suspension of nanofibers,layer-by-layered coating.Furthermore,by using this method,PVA-co-PE NF/CaCO₃ composite membranes were prepared with introducing CaCO₃ microparticles into nanofiber suspension dispersion.PVA-co-PE/TiO₂ nanofibrous membranes werefabricated with the incorporation of TiO₂ nanoparticles into nanofiber.The morphology and microstructure was analyzed by field emission scanning electron microscope（FSEM）,X-ray diffraction（XRD）and so on.The other physico-chemical properties are detected by Single fiber contact angle tester,pore size analyzer,electrostatic potentiometer and so on.The filtration properties were investigated by using automatic filtering tester.The effect of nanofiber coverage density,content of inorganic particles on the physico-chemical structure and properties are studied as well as the relationship between filtration performance and structure.The results show that with increasing coverage density of nanofiber from 1.06g/m² to 1.59g/m²,air filter exhibits a significant increase in filtration efficiency from 65.7% to 92.5%（0.3μm Na Cl particles）,drop resistance rises sharply from 18 mm H₂O to 89 mm H₂O trend.This is mainly derivedfrom the reduced nanofibrous membrane pore size caused by the increased coverage density of nanofibers.Compared to air filter withpristine nanofibers,with the content of CaCO₃ microparticles from 10% to 30%)in nanofiber coatingincreasing,the filter with a same fiber coverage density presents filtration efficiency increased from 70% to 90%（0.3μm Na Cl particles）,while the pressure drop shows a decreasing trend（45mm H₂O to 20 mm H₂O）.The main reason is: the introduction of CaCO₃ microparticles into the coating enlarges the distance between nanofibers and makes the structure of nanofiber coating loose,which further afford wider channelfor air penetration.On the other way,it is originated from the rugged surface of CaCO₃ microparticles which provides more chances for the adsorption of contaminant particles.Additionally,with the content of TiO₂ in nanofibers increasing from 1% to 7%,the filter with a same fiber coverage density presents filtration efficiency increased from 90% to 98%（0.3μm Na Cl particles）,while the pressure drop shows a decreasing trend（93mm H₂O to 70 mm H₂O）.The main reason is: the TiO₂ nanoparticles increases the density of the fibers themselves.When the weight is constant,the pore size of nanofiber coating increases which results in the easy penetration of air flow.On the other hand,TiO₂ leads to the electrostatic charge generating electrostatic field.It increases the chance to adsorb the contaminant particles especially the fine particles.In summary,the incorporation of functional particles in to the nanofiber or nanofiber coating can improve the electrostatic property and the 3D structure,which further enhances the air filtration performance.It provides an approach to develop the nanofiber based air filter media with low energy consume and high filtration efficiency.