Fabrication And Numerical Optimization Of Electrospun Micro-nano Composite Electret Filter

Airborne particulate matter(PM)pollution poses a serious threat to human health.Air filtration technology is one of the most efficient solutions to PM purification and human health protection.As the core of the air filtration equipment,the development of high-efficiency and low-resistance filter membranes is of great significance for energy-saving and environmental protection.Compared with mechanical filter membranes,the filtration efficiency of electret membrane can be improved significantly without increasing resistance because of its additional electrostatic effect.However,most of researchers were focused on the initial filtration performance of electret membrane,and few efforts have been paid on its electrostatic attenuation and dust loading performance.Herein,a micro-nano composite electret membrane with robust charge storage stability was successfully designed and fabricated via electrospinning.Besides,the dust loading performance of electret membranes was investigated by experiments and simulations.It aims to provide theoretical guidance for the preparation and optimization of electret membranes.Firstly,a fluffy micro-nano composite electret membrane,composed of PS/PAN/PS was controllably fabricated via electrospinning.The composite membrane showed multi-scale filtration characteristics because of its combination of micro-nanopore structure and the hybrid of polar and non-polar materials.Due to the advantages of both nanofibers and electret materials,the composite filter exhibited a high filtration efficiency(?99.5%)and a low pressure drop(37 Pa)to aerosol particles(?0.3 ?m)under an airflow velocity of 5.3 cm/s.Then,the dust loading performance of electret membrane was experimentally evaluated.The results found that the filtration efficiency of PS membrane was greatly attenuated because of the strong electrostatic shielding effect.In comparison,the PAN nanofiber membrane exhibited a stable filtration efficiency,but it was easily blocked by particles and the dust loading capacity was much smaller than PS membrane.The composite membrane having fluffy threedimensional pore structure showed a large particle loading capacity.Moreover,with the nanofibers laminated between the two PS membranes,its filtration efficiency attenuation was slowed.A multi-needle corona charging device was built to recharge the composite electret membrane.It was found that the filtration efficiency of filter after recharging can be restored to more than 99.0%.Next,take the charge shielding and charge decay into account of,a numerical model was established to simulate the dust loading performance of electret membranes,and it was verified by experiments.The results showed that the dust loading process could be divided into three stages: electrostatic shielding,particle accumulation and surface filtration.During the electrostatic shielding,the particles were deposited on the fiber surface,resulting in the attenuation of filtration efficiency.As the particles continuously accumulated on fiber surface,the filtration efficiency rose and the pressure drop also increased exponentially.During the surface filtration,particles were deposited on the surface of membrane,leading to the formation of particle layer and the pressure drop linearly increased.The parameter analysis showed that the uniform deposition of particles was beneficial to improve the dust loading performance of electret membranes.Finally,combined with the mathematical model of dust loading and the genetic algorithm,the structural parameters of the composite membrane were optimized.After optimization,the service life of the composite membrane was increased by 2.3 times,saving 34.11% of equipment energy consumption while ensuring the filtration efficiency.In addition,it was found that increasing the fiber packing density according to the logistic model along the thickness allowed the particles to be deposited more uniformly among the fiber layers.