Preparation And Characterization Of Composite Porous Nanofibrous Membranes For Air Filtration

With the rapid development of China’s industrialization, more and more dust particulate were discharged into the atmosphere. The air pollution caused serious damages on human and the earth. Particularly, fine particles(< 2.5μm), as one of the most serious sources of air pollution, turned out to be a major cause of adverse health effects ranging from human respiratory tract to extrapulmonary organs. Therefore, it is of great importance to design and prepare an effective filter to solve the ultrafine dust pollution in the air, which was a major issue for healthy livelihood. Nowadays, the nonwoven filter based on conventional fibers usually suffer from many performance disadvantages, such as relatively low filtration efficiency and high energy consumption, as well as unsuitable for the capture of fine particles due to the micro-sized fiber diameter. Nanofibrous membranes of hybrid structure and boost air filtration performance were prepared by electrospinning technique in this work. Furthermore, the membrane structure and its performance under relevant experimental conditions were investigated in detail.Hierarchically structured ultrafine fiber membranes exhibiting boost air filtration performance were prepared by electrospinning polystyrene(PS) /multiwalled carbon nanotubes(MWCNTs) solution. The fiber diameter, morphology and filtration performance of pristine PS membranes could be finely controlled by the concentration of PS solution. By employing the MWCNTs incorporation, the obtained PS/MWCNTs hybrid ultrafine fibers exhibited nano-wrinkle and nano-mountain structure on their surface. By using N2 adsorption method and measuring the water contact angle, the major contribution of MWCNTs on enhancing the surface roughness of hybrid fibers has been confirmed. Filtration performance studies revealed that the filtration efficiency and pressure drop of resultant hybrid membranes could be improved by introducing hierarchical structures. Furthermore, compared with pristine PS membrane, the asprepared PS/MWCNTs membrane exhibited improved filtration efficiency(99.95%) and pressure drop(374.6Pa) under the face velocity of 85 L/min. By electrospinning PS-33(with coarse fibers) and PS/MWCNTs(PS-23-15 with fine fibers) with muti-jets simultaneously and adjusting the jet ratios, the optimized porous membrane mixed with coarse and fine fibers had a decreased pressure drop(235.4Pa) and high filtration efficiency(99.68%).A novel airborne particulate filtration medium, consisting of a hybrid structure, i.e. a nanofiber/nano-net, was prepared by electrospinning polyvinylidene fluoride(PVDF) solution. The morphology of nano-net architecture can be finely controlled by regulating the additives in solution, the relative humidity(RH) and type of substances in electrospinning process. By using the sodiumdodecylbenzenesulfonate(SDBS) as additive, applying 25% RH and iron wire mesh as substance, nano-nets of several fascinating features, such as extremely small diameter(~20nm), high coverage rate(~97%) and suitable pore diameter(~246nm), can be fabricated easy. The nanofibers/nano-net structure bring to the filtration medium several excellent filtration features such as high filtration efficiency(99.5%), low pressure drop(66.9Pa), facile filters cleaning, and more lightweight. By adjusting the thickness of the PVDF/SDBS nanofibers/nano-net membrane, the optimized porous membrane had a appropriate transmittance(>40%) and high filtration efficiency(>95%), which can be applied as windows filtration.