Preparation And Filtration Performance Of Cellulose Nanofibrils-based Composite Aerogel Sheet

With the rapid development of modern industry,air pollutants produced by industrial activities,construction projects,garbage incineration and automobile exhaust are becoming more and more serious in some areas,posing a serious threat to human health.Among these air pollutants,PM2.5pollution is the most frequent and recognized as one of the most serious pollution problems.Before eliminating the source of PM2.5,developing green and efficient air filtration materials is one of the effective ways to protect people’s health.Therefore,this paper aims to study a kind of air filtration material with high filtration efficiency,low pressure drop and green environmental protection,which can be used to protect against PM2.5 pollution.Nano-cellulose（CNF）aerogel has the characteristics of high surface area and porosity,and can be used as an excellent air filtration material.In this paper,the effects of different adhesives on the filtration performance of CNF aerogel and the construction of CNF,CaCO₃or bamboo activated carbon（BAC）nanoparticles composite air filtration sheets were studied.In addition,this paper explored the filtration mechanism of CNF composite aerogel sheet,promoted the development of PM2.5 filter materials,and provided theoretical and technical basis for the development of green air filter materials.The main results are as follows:（1）In order to explore the feasibility of constructing composite aerogel sheets based on CNF,CNF was compounded with polyvinyl alcohol（PVA）,polyethylene glycol（PEG）and polyethylene imine（PEI）,respectively.CNF/PVA,CNF/PEG,CNF/PEI aerogel sheets were prepared by freeze drying to explore its forming mechanism and filtration performance.The optimum ratio of CNF/PVA aerogel sheet with mass ratio of 1:0.5 was determined by comparing the filtration performance of different components.Its tensile strength was～150 k Pa and PM2.5 filtration efficiency was～90%（the pressure drop was only 18 Pa）.This study provides strong support for the preparation and molding of CNF composite aerogel sheet for air filtration.（2）In order to improve the porosity and specific surface area of CNF based aerogel sheet and prepare an air filtration with environmental protection,simple preparation and high filtration efficiency,a high efficiency air filtration sheet was prepared by adding CaCO₃nanoparticles on the basis of CNF/PVA through freeze drying.The prepared CNF/PVA/CaCO₃composite aerogel sheet had good thermal stability and environmental friendliness.Due to its regular cage structure,CNF/PVA/CaCO₃（CNF:PVA:CaCO3 mass ratio is 1:0.5:0.36）composite aerogel sheet co improve the ability to capture PM2.5,and the filtration efficiency reached 97.94%.In this study,inorganic nanoparticles were added to construct the pore structure,which provided technical reference for the preparation of composite aerogel sheet with larger specific surface area.（3）In order to further improve the filtration performance of CNF based aerogel sheet,bamboo activated carbon（BAC）nanoparticles with negatively charged surface were introduced.Using CNF,PVA and BAC as raw materials,a high efficiency air filtration sheet with good thermal stability and environmental friendliness was prepared by freeze-drying.The CNF/PVA/BAC（CNF:PVA:BAC mass ratio is 1:0.5:1.5）aerogel sheet had an excellent ability to capture PM2.5 due to the double filtration formed by its network structure and the electrostatic adsorption on the surface of BAC.The filtration efficiency was up to 99.69%and the pressure drop ws very low（12 Pa）.In this paper,the double filtration mechanism of aerogels was investigated to provide theoretical and technical guidance for the construction of composite aerogel sheet with high filtration performance.