Construction And Application Of Silicon Dioxide Nanofibers Reinforced By Cellulose Aerogel

In recent years,indoor air pollution has become a hot topic in the field of environmental governance.Indoor air pollution is composed of small particulate pollutants and harmful gaseous substances,which can enter the bloodstream and respiratory system of the human body and seriously endanger human health.Aerogel is widely used in air filtration because of its large specific surface area,high porosity and high dust capacity.Among the materials forming aerogel,cellulose has a wide range of sources and distribution,which is non-toxic,renewable,biocompatible,biodegradable and other characteristics.In addition,there are a large number of hydroxyl groups in its molecule,and the hydrogen bond formed will break and reorganize,which is conducive to the formation of gel.Therefore,in this work,silica nanofibers reinforced cellulose aerogel was constructed with cellulose as raw material,combined with electrospinning,sol gel and freeze drying technology,and its structure and performance were systematically characterized.The results show that the aerogel material has excellent mechanical properties,and has broad application potential in the field of air filtration and adsorption separation.The specific research content is as follows:Cellulose aerogels were prepared with NaOH/urea/water as solvent system,combined with sol gel and freeze drying method.During the preparation process,the crystal form was transformed from cellulose type I to cellulose type II,which verified the successful preparation of cellulose aerogel.The concentration range of gel was determined by measuring the viscosity of cellulose solution.The results showed that the cellulose with 4-6 wt%concentration had a perfect gel system.Cellulose aerogels were prepared in this concentration range.Cellulose aerogel at 6 wt%concentration had good morphology,uniform pore size distribution,and porosity of more than 85%.At the same time,it also had excellent mechanical properties,with a compressive strength of up to 0.64 MPa.In order to solve the problems of cellulose aerogel with low strength,small elasticity and large pore size,cellulose aerogels reinforced with silica nanofibers（C-SNFs composite aerogels）were prepared by combining electrospinning and sol-gel technology and applied in the field of air filtration.The results showed that the C-SNFs composite aerogels formed a three-dimensional spatial network structure with nanofiber penetration.The pore size distribution of 0.75%C-SNFs composite aerogel was narrow,and the average pore size was low（1.27μm±0.15μm）,with a high porosity（90.55%）.It also had excellent mechanical properties,with a compressive strength of 8.7 MPa.After 100 cycles of compression,the maximum stress compression modulus of aerogel can be maintained at more than 80%of the original value,and it had stable viscoelastic mechanical properties.In addition,the filtration efficiency of 0.75%-C-SNFs aerogel can reach 99.91%,and the air resistance was only 78.21Pa（32 L min-1）.After 10 cycle tests,the aerogel still maintained a stable removal efficiency of 99.92%for PM_2.5 particles.Compared with other air filters,the 0.75%-C-SNFs composite aerogel filter material basically realized the improvement of PM_2.5 removal rate,and showed excellent cycle filtration performance.To further expand the application field of cellulose aerogel,this paper used the solution immersion method to load ZIF-67 on aerogel to obtain composite aerogels（ZIF-67@C-SNFs composite aerogels）.The results showed that after soaking for 24 hours ZIF-67@C-SNFs composite aerogel had good microstructure,uniform pore size distribution and porosity of92.3%.The mechanical properties had also been improved,and the compression strength can reach 10.1 MPa.In 100 cycles of compression tests,the maximum stress compression modulus of aerogel can maintain more than 85%of the original value,and the viscoelastic mechanical properties were very stable.In addition,it had excellent formaldehyde adsorption performance,with an adsorption efficiency of 93.75%.It can be seen that the preparation process of this topic is pollution-free and the method is simple,laying the foundation for future air filtration and adsorption fields.