Tunable Fabrication And PM2.5 Filtration Performance Of High-efficiency And Low-resistance Nanofiber Membranes Made By Electrospinning

The pollution of PM2.5 is becoming more and more serious all over the world,and people pay more and more attention to it.Although the content of these particles in the atmosphere is very small,they have a great impact on the visibility of the air,and have an unprecedented adverse impact on atmospheric physical chemistry,biosphere and climate.Moreover,these suspended particles,as well as the pollen,bacteria,fungi and viruses adsorbed on their surfaces,are easy to be inhaled into the human body,resulting in or aggravating diseases such as respiratory,cardiovascular,infectious and allergic diseases.At present,most of the air filter materials are made of melt blown nonwovens,which not only has low efficiency and high resistance,but also can not meet the needs of different occasions in the actual application process.Therefore,in this paper,a series of high-efficiency and low resistance nanofiber filter materials were prepared by electrospinning.According to the requirements of different occasions,the fiber filter materials with antibacterial,high humidity resistance,high temperature resistance and reusability were also prepared.The specific research contents are as follows:（1）Bacteria and viruses suspended in the air of hospitals and other public places usually adhere to the surface of PM2.5,which is one of the key factors in the outbreak of infectious diseases.And bacteria and viruses will cause greater harm to human body once they are enriched in protective articles such as masks.Therefore,if the medical mask filter material can filter the particles and kill the bacteria and viruses,it will greatly improve its protective effect on human body.Herein,two-dimensional titanium carbide Ti₃C₂T_x MXene nanosheets with active surface-terminating groups（O,OH and F）were used to modify the polyacrylonitrile（PAN）nanofiber filters to strengthen their interaction force with PM2.5.These forces were measured quantitatively through the force-distance curve-based AFM showing that the MXene modification of the PAN fiber induces three times larger interaction forces than before.The obtained filters show high PM2.5 removal efficiency of～99.7%with a low pressure drop of～42 Pa.Moreover,the presence of MXene nanosheets strongly inhibits the propagation of bacteria（e.g.E.coli and S.aureus）in the filters.Such filters can significantly improve air quality,especially in public places such as hospitals.（2）The occurrence of haze is usually accompanied by the increase of environmental humidity,which will not only increase the concentration of PM2.5,but also cause a lot of difficulties in particle filtration.The pressure drop of above PAN filter increased from 77 Pa to 368 Pa under high humidity of 90–95%after 45 min,due to its hydrophilicity.This is because the hydrophilic membrane will absorb the water vapor in the air,causing the pore to be blocked.In order to solve this problem,hydrophobic polyvinyl chloride（PVC）nanofiber filters with bead-on-string structure are designed to steadily remove particle matter under high relative humidity of 90-95%.The developed hydrophobic filters possessed comparable separation performance with the hydrophilic one,but greatly enhanced stability.After the introduction of bead-on-string structure,the filtration performance can be furtherly improved due to the formed large cavities and hydrophobicity.Such hydrophobic PVC filters can be promising candidates for air purification in practical applications especially in wet seasons.（3）Although the above-mentioned electrospun organic polymer PAN and PVC nanofiber membranes have excellent air filtration performance,they do not have high temperature resistance characteristics and cannot meet the treatment requirements of factory flue gas and automobile exhaust gas.And its single fiber is flexible,after water treatment,the structure of the fiber membrane will change greatly,resulting in the reduction of its filtration performance by about 40%,without the potential of reuse.Therefore,an inorganic Si O₂ nanofiber membrane was prepared by sol-gel electrospinning and high temperature calcination.The fiber membrane can withstand 800 ^oC high temperature,fully meet the requirements of factory exhaust gas and automobile exhaust gas treatment.After water treatment,the fiber membrane still retains its original porous three-dimensional structure.Compared with PAN and PVC nanofiber membrane,the membrane has the best filtration performance with a quality factor of 0.036 Pa^-1.This kind of material is expected to be reused in the use process,greatly reducing the cost of filter material replacement,and to a large extent,alleviating the shortage of medical resources such as masks and the difficult treatment of medical waste during the epidemic.