WO2023082498A1 - 一种纳米纤维素气凝胶及其制备方法与应用 - Google Patents

一种纳米纤维素气凝胶及其制备方法与应用 Download PDF

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WO2023082498A1
WO2023082498A1 PCT/CN2022/078328 CN2022078328W WO2023082498A1 WO 2023082498 A1 WO2023082498 A1 WO 2023082498A1 CN 2022078328 W CN2022078328 W CN 2022078328W WO 2023082498 A1 WO2023082498 A1 WO 2023082498A1
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nanocellulose
preparation
cellulose
nano
airgel
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PCT/CN2022/078328
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English (en)
French (fr)
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马晓阳
陈怡安
陈之善
黄中原
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清远高新华园科技协同创新研究院有限公司
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Publication of WO2023082498A1 publication Critical patent/WO2023082498A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/0091—Preparation of aerogels, e.g. xerogels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/02—Loose filtering material, e.g. loose fibres
    • B01D39/04—Organic material, e.g. cellulose, cotton

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  • the invention belongs to the technical field of material synthesis, and in particular relates to a nano-cellulose airgel and a preparation method and application thereof.
  • HEPA High-Efficiency Particulate Air
  • the commonly used air filter materials are mostly fiber materials, such as polytetrafluoroethylene films, non-woven materials of polymer fibers and glass fiber materials. Although these materials have good filtration efficiency, they have defects such as not being environmentally friendly, having low functionality, and large resistance pressure drop.
  • the purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a nanocellulose airgel which can not only meet the filtration of particles and viruses in the air but also meet the requirements of environmental protection, and its preparation method and application.
  • the technical solution adopted by the present invention is: a nanocellulose airgel, the interior of the nanocellulose airgel is a porous network structure, its average pore diameter is 100-240nm, and the porosity is 69%. -88%; the nanocellulose airgel is prepared from nanocellulose, the length of the nanocellulose is 200-800nm, the diameter is 5-80nm, and the content of carboxyl functional groups on the surface is 0.3-1.0mmol/g .
  • the nanocellulose airgel provided by the technical solution of the present invention has a porous network structure inside, has properties such as high porosity and high mechanical strength, and can be effectively applied to the field of air filtration.
  • the particle removal efficiency of 0.01-2um is over 99.9%.
  • the nanocellulose used to prepare nanocellulose airgel also has a pore structure, which also has a certain interception effect on particles, and the nanocellulose is used as a raw material, which is simple Easy to get, and the way to get it is green and environment-friendly.
  • the present invention also provides a preparation method of nanocellulose airgel, comprising the following steps:
  • the cellulose includes bacterial cellulose or natural plant cellulose.
  • Bacterial cellulose and natural plant cellulose come from a wide range of sources, easy to obtain, and environmentally friendly.
  • the mass percent concentration of nanocellulose in the nanocellulose aqueous solution is 0.2-1.0%.
  • the average pore size of the nanocellulose airgel prepared is suitable, and the porosity is moderate.
  • the filtration efficiency of 0.01-2um particles is as high as 99.9%.
  • the solution containing chloride ions includes zinc chloride solution, calcium chloride solution or sodium chloride solution.
  • the concentration of chloride ions in the solution containing chloride ions is 0.8-1.6 mol/L.
  • the volume ratio of the solution containing chloride ions to the aqueous nanocellulose solution is 1: (1-5).
  • the replacement solvent includes tert-butanol or ethanol.
  • the specific process of continuous replacement is as follows: the nanocellulose hydrogel is successively soaked in 25%, 50%, 75% , 100% replacement solvent for 12-24 hours.
  • the freeze-drying time is 12-24 hours, and the freeze-drying temperature is (-24)-(-20)°C.
  • the invention also provides the application of the nano-cellulose airgel in the field of air filtration.
  • a kind of nano-cellulose airgel provided by the technical scheme of the present invention has a porous network structure inside, has properties such as high porosity and high mechanical strength, and can be effectively applied to the field of air filtration.
  • the removal efficiency of particles with a medium particle size of 0.01-2um is over 99.9%.
  • due to the high specific surface area and porosity of nanocellulose aerogels, in addition to effectively intercepting particles in the air, its filtration resistance is also small. That is, the product provided by the technical solution of the present invention can take into account both resistance pressure drop and filtration efficiency;
  • the nanocellulose airgel provided by the technical solution of the present invention uses nanocellulose as a raw material, wherein the nanocellulose itself also has a pore structure, and has a certain interception effect on particulate matter, and the nanocellulose is used as a material.
  • Raw materials are simple and easy to obtain, and the way to obtain them is green and environmentally friendly.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 5 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 13nm, a length of about 320nm, and a surface carboxyl functional group content of 0.5mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of 0.4mol/L CaCl in the solution to obtain nanocellulose hydrogel , and use Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of 0.8mol/L ZnCl in the solution to obtain nanocellulose hydrogel , and use Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 1000 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 0.6mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 5 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 45nm, a length of about 560nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 80nm, a length of about 740nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • Step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) is crushed with a homogenizer for 1 minute, then the crushed material is passed through a 100-mesh sieve, and the filtered product is added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 160nm, a length of about 940nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise into the ZnCl solution of 200mL of 2.0mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 1500g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 0.9mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 0.2mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • step (2) Preparation of nanocellulose aqueous solution: the cellulose slurry prepared in step (1) was crushed with a homogenizer for 10 minutes, then the crushed material was passed through a 100-mesh sieve, and the filtered product was added to 400 g of water to obtain nanofibers plain aqueous solution; the obtained nanocellulose has a diameter of about 6nm, a length of about 420nm, and a surface carboxyl functional group content of 1.5mmol/g;
  • step (3) Preparation of nanocellulose hydrogel: the nanocellulose aqueous solution described in step (2) is rotationally added dropwise to a concentration of 200mL of ZnCl2 of 0.4mol/L to obtain nanocellulose hydrogel. Washing with deionized water;
  • nano-cellulose alcohol gel the nano-cellulose hydrogel described in step (3) is once soaked in 25%, 50%, 75%, 100% tert-butanol aqueous solution for 20 hours by mass percentage , to obtain nano-cellulose alcohol gel;
  • nano-cellulose airgel pour the nano-cellulose alcohol gel described in step (4) into a glass bottle, unscrew the bottle cap, put it into liquid nitrogen to freeze for 5 minutes, and then place it in a cold Freeze-drying is carried out in a drying machine for 24 hours, and the temperature is set at (-20)° C. After freeze-drying, nanocellulose airgel is obtained.
  • the nanocellulose aerogels prepared in Examples 1-8 and Comparative Examples 1-5 are measured for average pore size and porosity, and the average filtration efficiency when the nanocellulose aerogels prepared for air filtration are detected and applied And the resistance pressure drop, wherein, when applied to air filtration, the statistics are the filtration efficiency of particles with a particle size of 0.01-2um, and the results are shown in Table 1;
  • Example 1 150 80 99.948 60
  • Example 2 180 73 99.935 56
  • Example 3 155 81 99.954 62
  • Example 4 100 84 99.984 81
  • Example 5 240 69 99.908 46
  • Example 6 120 80 99.979 79
  • Example 7 123 86 99.921 53
  • Example 8 107 88 99.905 50
  • Comparative example 1 350 57 94.456 35 Comparative example 2 87 89 99.987 125 Comparative example 3 324 61 95.432 40 Comparative example 4 160 84 99.436 103 Comparative example 5 165 88 99.897 113
  • the average filtration efficiency of the prepared nanocellulose airgel is above 99.9%, and the average resistance pressure drop is small, below 81%;
  • Example 1 and Comparative Example 2 when the mass percentage of chloride ions in the solution containing chloride ions was too high, the obtained nanocellulose gas The gel pore size is too small, although better filtration efficiency can be guaranteed, but the resistance pressure drop is too high, as can be seen from Example 1 and Comparative Example 3, when the mass percentage of nanocellulose in the nanocellulose aqueous solution is too high When low, nanocellulose pore size is too low, thereby filter efficiency can significantly reduce, as can be seen from embodiment 1 and comparative example 4, when the mass percent of nanocellulose in the nanocellulose aqueous solution is too high, caused resistance pressure It can be seen from Example 1 and Comparative Example 5 that when the surface carboxyl content in the nanocellulose aqueous solution is too high, the resistance pressure drop is too high.

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Abstract

一种纳米纤维素气凝胶及其制备方法与应用。纳米纤维素气凝胶的内部呈多孔网状结构，其平均孔径为100-240nm，孔隙率为69％-88％；纳米纤维素气凝胶由纳米纤维素制备而成，纳米纤维素的长度为200-800nm，直径为5-80nm，表面羧基官能团的含量为0.3-1.0mmol/g。纳米纤维素气凝胶具有高比表面积和孔隙率，能兼顾阻力压降和过滤效率；并且纳米纤维素本身也具备孔隙结构，对颗粒物也有一定的拦截效果。

Description

一种纳米纤维素气凝胶及其制备方法与应用 技术领域
本发明属于材料合成技术领域，尤其涉及一种纳米纤维素气凝胶及其制备方法与应用。
背景技术
目前雾霾问题已经成为人们面临的非常严重的环境问题，制备有效地过滤空气中小颗粒物的材料已经成为亟待解决的问题。但是目前的空气过滤材料普遍还存在着过滤效率低和阻力压降大等缺陷。HEPA(High-Efficiency Particulate Air)过滤材料目前是非常高效的空气过滤材料，通常的HEPA材料的过滤效率可以达到99.99％，但是这种技术在中国还是处于探索阶段。目前常用的空气过滤材料多为纤维材料，比如聚四氟乙烯薄膜、聚合物纤维的无纺布材料和玻璃纤维材料。这些材料虽然有较好的过滤效率，但是存在不绿色环保，功能性低，阻力压降大等缺陷。
发明内容
本发明的目的在于克服上述现有技术的不足之处而提供一种既能满足对空气中的颗粒物、病毒等的过滤又符合绿色环保要求的纳米纤维素气凝胶及其制备方法与应用。
为实现上述目的，本发明采取的技术方案为：一种纳米纤维素气凝胶，所述纳米纤维素气凝胶内部呈多孔网状结构，其平均孔径为100-240nm，孔隙率为69％-88％；所述纳米纤维素气凝胶由纳米纤维素制备而成，所述纳米纤维素的长度为200-800nm，直径为5-80nm，表面羧基官能团的含量为0.3-1.0mmol/g。
本发明的技术方案提供的一种纳米纤维素气凝胶，其内部呈现多孔网状结构，具有高孔隙率、高机械强度等性质，能够有效的应用于空气过滤领域，其 对空气中粒径为0.01-2um的颗粒物去除效率达99.9％以上；同时，制备纳米纤维素气凝胶的纳米纤维素本身也具备孔隙结构，对颗粒物也有一定的拦截效果，且以纳米纤维素为原料，其简单易得，获取途径绿色环保。
另外，本发明还提供了纳米纤维素气凝胶的制备方法，包括以下步骤：
(1)纳米纤维素水溶液的配制：利用TEMPO氧化体系处理纤维素得纤维素浆料，接着将纤维素浆料破碎、过筛、加水，得纳米纤维素水溶液；
(2)纳米纤维素水凝胶的制备：将步骤(1)所述纳米纤维素水溶液旋转滴加至含有氯离子的溶液中，得纳米纤维素水凝胶；
(3)纳米纤维素醇凝胶的制备：将步骤(2)所述纳米纤维素水凝胶与置换溶剂进行连续置换，得纳米纤维素醇凝胶；
(4)纳米纤维素气凝胶的制备：将步骤(3)所述纳米纤维素醇凝胶冷冻干燥，得纳米纤维素气凝胶。
作为本发明所述制备方法的优选实施方式，所述步骤(1)中，纤维素包括细菌纤维素或天然植物纤维素。
细菌纤维素和天然植物纤维素来源广泛，获取途径简单、绿色环保。
作为本发明所述制备方法的优选实施方式，所述步骤(1)中，纳米纤维素水溶液中纳米纤维素的质量百分比浓度为0.2-1.0％。
当纳米纤维素水溶液中纳米纤维素的质量百分比浓度在上述范围时，制备得到纳米纤维素气凝胶的平均孔径合适，且孔隙率适中，在应用于空气过滤时，其对空气中粒径为0.01-2um的颗粒物的过滤效率高达99.9％以上。
作为本发明所述制备方法的优选实施方式，所述步骤(2)中，含有氯离子的溶液包括氯化锌溶液、氯化钙溶液或氯化钠溶液。
作为本发明所述制备方法的优选实施方式，所述步骤(2)中，含有氯离子的溶液中氯离子的浓度为0.8-1.6mol/L。
作为本发明所述制备方法的优选实施方式，所述步骤(2)中，含有氯离子的溶液与纳米纤维素水溶液的体积比为1：(1-5)。
作为本发明所述制备方法的优选实施方式，所述步骤(3)中，置换溶剂包括叔丁醇或乙醇。
作为本发明所述制备方法的优选实施方式，所述步骤(3)中，连续置换的具体过程如下：将纳米纤维素水凝胶分别依次持续浸泡在质量百分数为25％、50％、75％、100％的置换溶剂中12-24小时。
作为本发明所述制备方法的优选实施方式，所述步骤(4)中，冷冻干燥的时间为12-24小时，冷冻干燥的温度为(-24)-(-20)℃。
另外，本发明还提供了纳米纤维素气凝胶在空气过滤领域的应用。
与现有技术相比，本发明的有益效果为：
第一：本发明的技术方案提供的一种纳米纤维素气凝胶，其内部呈现多孔网状结构，具有高孔隙率、高机械强度等性质，能够有效的应用于空气过滤领域，其对空气中粒径为0.01-2um的颗粒物去除效率达99.9％以上；同时，由于纳米纤维素气凝胶具有高比表面积和孔隙率，在有效的拦截空气中的颗粒物外，其过滤阻力也较小，即本发明技术方案提供的产品能兼顾阻力压降和过滤效率；
第二：本发明的技术方案提供的一种纳米纤维素气凝胶以纳米纤维素为原料，其中，纳米纤维素本身也具备孔隙结构，对颗粒物也有一定的拦截效果，且以纳米纤维素为原料，简单易得，获取途径绿色环保。
具体实施方式
为更好的说明本发明的目的、技术方案和优点，下面将结合具体实施例对本发明作进一步说明。
实施例1
本实施例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的 NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
实施例2
本实施例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.016g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入1.6g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎5分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为13nm，长度约为320nm，表面羧基官能团的含量为0.5mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳 米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
实施例3
本实施例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的CaCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
实施例4
本实施例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的 NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.8mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
实施例5
本实施例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入1000g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳 米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
实施例6
本实施例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入4g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为0.6mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
实施例7
本实施例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的 NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎5分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为45nm，长度约为560nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
实施例8
本实施例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为80nm，长度约为740nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳 米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
对比例1
本对比例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎1分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为160nm，长度约为940nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
对比例2
本对比例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的 NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为2.0mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
对比例3
本对比例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入1500g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为0.9mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳 米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
对比例4
本对比例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.032g TEMPO和0.2gNaBr加入到200mL水中，再加入10g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为0.2mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
对比例5
本对比例提供的纳米纤维素气凝胶的具体合成步骤如下：
(1)纳米纤维素浆料的制备：将0.096g TEMPO和0.6gNaBr加入到200mL水中，再加入2g纤维素，接着加入3.2g质量百分数为12％的次氯酸钠溶液，室温下搅拌10分钟，然后在搅拌的情况下往反应体系中滴加质量百分数为1％的 NaOH水溶液，直至体系的pH值为10，停止反应，得纤维素浆料；
(2)纳米纤维素水溶液的配制：将步骤(1)制备得到的纤维素浆料用均质机破碎10分钟，接着将破碎后的物质过100目筛，将过滤产物加入400g水中得纳米纤维素水溶液；得到的纳米纤维素直径约为6nm，长度约为420nm，表面羧基官能团的含量为1.5mmol/g；
(3)纳米纤维素水凝胶的制备：将步骤(2)所述纳米纤维素水溶液旋转滴加至浓度为0.4mol/L的200mL的ZnCl 2溶液中，得纳米纤维素水凝胶，用去离子水洗涤；
(4)纳米纤维素醇凝胶的制备：将步骤(3)所述纳米纤维素水凝胶一次浸泡在质量百分数为25％、50％、75％、100％的叔丁醇水溶液中20小时，得纳米纤维素醇凝胶；
(5)纳米纤维素气凝胶的制备：将步骤(4)所述纳米纤维素醇凝胶倒入玻璃瓶中，瓶盖拧松，先放入液氮中5分钟冷冻，再放置在冷干机中24小时进行冷冻干燥，温度设定为(-20)℃，冻干后，得纳米纤维素气凝胶。
效果例
将实施例1-8和对比例1-5制备得到的纳米纤维素气凝胶进行平均孔径、孔隙率的测量，同时检测应用制备得到的纳米纤维素气凝胶进行空气过滤时的平均过滤效率以及阻力压降，其中，应用于空气过滤时统计的为对粒径在0.01-2um的颗粒物的过滤效率，结果如表1所示；
表1：纳米纤维素气凝胶的表征与应用数据
  平均孔径(nm) 孔隙率(％) 过滤效率(％) 平均阻力压降(Pa)
实施例1 150 80 99.948 60
实施例2 180 73 99.935 56
实施例3 155 81 99.954 62
实施例4 100 84 99.984 81
实施例5 240 69 99.908 46
实施例6 120 80 99.979 79
实施例7 123 86 99.921 53
实施例8 107 88 99.905 50
对比例1 350 57 94.456 35
对比例2 87 89 99.987 125
对比例3 324 61 95.432 40
对比例4 160 84 99.436 103
对比例5 165 88 99.897 113
从表1中可以看出，当采用本发明提供的技术方案时，制备得到的纳米纤维素气凝胶的平均过滤效率都在99.9％以上，并且平均阻力压降较小，在81％以下；从实施例1-8可以看出，孔隙率越大，过滤效率越高，但同时阻力压降也会升高，并且在制备过程中，纳米纤维素水溶液中纳米纤维素的质量百分数、纳米纤维素与含氯离子溶液的体积比、含氯离子溶液中氯离子的质量百分数等参数都会对产品的平均孔径、孔隙率带来影响；从实施例1和对比例1可以看出，当制备得到的纳米纤维素的直径过大时，过滤效率会显著降低，从实施例1和对比例2中可以看出，当含氯离子溶液中氯离子的质量百分数过高时，得到的纳米纤维素气凝胶孔径过小，虽然可以保证较好的过滤效率，但是引起了阻力压降过高，从实施例1和对比例3中可以看出，当纳米纤维素水溶液中纳米纤维素的质量百分数过低时，纳米纤维素孔径过低，从而过滤效率会显著降低，从实施例1和对比例4中可以看出，当纳米纤维素水溶液中纳米纤维素的质量百分数过高时，引起了阻力压降过高，从实施例1和对比例5中可以看出，当纳米纤维素水溶液中表面羧基含量过高时，引起了阻力压降过高。
最后应当说明的是，以上实施例以说明本发明的技术方案而非对本发明保护范围的限制，尽管参照较佳实施例对本发明作了详细说明，本领域的普通技术人员应当理解，可以对本发明的技术方案进行修改或者等同替换，而不脱离本发明技术方案的实质和范围。

Claims (10)

  1. 一种纳米纤维素气凝胶，其特征在于，所述纳米纤维素气凝胶的内部呈多孔网状结构，其平均孔径为100-240nm，孔隙率为69％-88％；所述纳米纤维素气凝胶由纳米纤维素制备而成，所述纳米纤维素的长度为200-800nm，直径为5-80nm，表面羧基官能团的含量为0.3-1.0mmol/g。
  2. 如权利要求1所述纳米纤维素气凝胶的制备方法，其特征在于，包括以下步骤：
    (1)纳米纤维素水溶液的配制：利用TEMPO氧化体系处理纤维素得纤维素浆料，接着将纤维素浆料破碎、过筛、加水，得纳米纤维素水溶液；
    (2)纳米纤维素水凝胶的制备：将步骤(1)所述纳米纤维素水溶液旋转滴加至含有氯离子的溶液中，得纳米纤维素水凝胶；
    (3)纳米纤维素醇凝胶的制备：将步骤(2)所述纳米纤维素水凝胶与置换溶剂进行连续置换，得纳米纤维素醇凝胶；
    (4)纳米纤维素气凝胶的制备：将步骤(3)所述纳米纤维素醇凝胶冷冻干燥，得纳米纤维素气凝胶。
  3. 根据权利要求2所述的制备方法，其特征在于，所述步骤(1)中，纳米纤维素水溶液中纳米纤维素的质量百分比浓度为0.2-1.0％。
  4. 根据权利要求2所述的制备方法，其特征在于，所述步骤(2)中，含有氯离子的溶液包括氯化锌溶液、氯化钙溶液或氯化钠溶液。
  5. 根据权利要求2所述的制备方法，其特征在于，所述步骤(2)中，含有氯离子的溶液中氯离子的浓度为0.8-1.6mol/L。
  6. 根据权利要求2所述的制备方法，其特征在于，所述步骤(2)中，含有氯离子的溶液与纳米纤维素水溶液的体积比为1：(1-5)。
  7. 根据权利要求2所述的制备方法，其特征在于，所述步骤(3)中，置换溶剂包括叔丁醇或乙醇。
  8. 根据权利要求2所述的制备方法，其特征在于，所述步骤(3)中，连 续置换的具体过程如下：将纳米纤维素水凝胶分别依次持续浸泡在质量百分数为25％、50％、75％、100％的置换溶剂中12-24小时。
  9. 根据权利要求2所述的制备方法，其特征在于，所述步骤(4)中，冷冻干燥的时间为12-24小时，冷冻干燥的温度为(-24)-(-20)℃。
  10. 如权利要求1所述的纳米纤维素气凝胶在空气过滤领域的应用。
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CN110483830A (zh) * 2019-07-31 2019-11-22 武汉纺织大学 超轻高弹丝素微纳米纤维气凝胶及其制备方法与应用
CN114011345A (zh) * 2021-11-12 2022-02-08 清远高新华园科技协同创新研究院有限公司 一种纳米纤维素气凝胶及其制备方法与应用

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