| Haze is a mixture of water and particles.The main hazard is PM2.5(aerodynamic diameter less than or equal to 2.5 microns particles),which has a very high penetration can directly enter the human bodies through the respiratory tract and cause serious harm.As an individual protective material,air filtration material can effectively help people avoid the damage of PM2.5.However,conventional melt-blown and spun-bond fibers,are subjected to low PM2.5 removal efficiency because of their large fiber diameter(1-50 ?m).Electrospinning,as a versatile technology to fabricate nanoscale fibers,can endow fibrous materials with large surface area to adsorb PM2.5 and adjustable tortuous interconnected pores to transport air flow.Thus,electrospun nanofibrous materials were proved to have the potential of achieving high filtration efficiency and low air resistance simultaneously.But,the existing electrospun nanofibrous air filtration materials in the haze environment(80-90% humidity),generally faced with undesirable sharp increase of pressure drop when humidity increase,therefore,it is urgent to prepare a kind of high efficiency air filter material which can maintain the constant of low pressure drop under high humidity.Considering the available air filtration materials that can not remove particles efficiently and especially allow air flowing easily under the high relative humidity of haze environment,here,we designed an air filter exhibiting low and stable resistance towards moisture,through endowed polyacrylonitrile(PAN)fibers with high far infrared ray(FIR)emissivity during electrospinning,and based on the resonance effect between FIR and water molecules to improve water freedom,which would contribute to destroying the continuous water films.Firstly,a high efficiency low resistance PAN air filter fiber membrane was constructed,the result suggested that the fiber diameter,together with the corresponding pore structure(pore size and porosity)had a negligible effect on the FIR emissivity,and PAN-15 fibrous membrane displayed a higher QF compared with other membranes.Second,the introduction of FIPs with optimized content brought about an elevated FIR emissivity,when the content of FIPs was 6 wt% the filtration performance and FIR emissivity were the best.Thirdly,the balance relationship between the far-infrared emissivity and the stability of pressure resistance was established.Also,the emission mechanism of FIR aroused from FIPs and rough structure was revealed clearly,the enhancement effect of FIR emissivity resulted from surface roughness was quantified(up to 16.4%).More importantly,we proved that the stability of pressure drop could be enhanced by FIR via measuring the existing form and content of water within PAN/FIPs membranes,it was also worthy to note that the RRPD decreased substantially from 20% to 8.9% with the inclusion of FIPs from 0 to 6 wt%.In addition,based on the optimization of PAN concentration and the amount of FIPs,the balanced between pore size and FIR emissivity was determined through elevating of basis weight,when the pore size was 2.1 ?m,the FIR emissivity was highest(90.8%).Finally,the resultant membranes exhibited a high filtration efficiency of 99.998%,whereas a low pressure drop of 79.5 Pa,the RRPD was decreased to 6%.The stability of pressure resistance had a significant increase than that of ordinary melt-blown material(the RRPD was 28.6%).Comparing with other fibrous membranes it displayed high PM2.5 removal efficiency,durable low pressure drop under high humidity.The fabrication of such an promising material may provide a new insight to design of air filtration materials with durable high performance. |
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