CN113368710B - Preparation method of hydrophobic bacterial cellulose aerogel-based air filtering membrane - Google Patents
Preparation method of hydrophobic bacterial cellulose aerogel-based air filtering membrane Download PDFInfo
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- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/08—Polysaccharides
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
- B01D46/54—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms
- B01D46/543—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms using membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
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- B01D2325/00—Details relating to properties of membranes
- B01D2325/38—Hydrophobic membranes
Abstract
The invention discloses a preparation method of a hydrophobic bacterial cellulose aerogel-based air filtering membrane, belonging to the field of air filtering materials; the preparation method comprises the steps of treating bacterial cellulose in the modes of water washing, alkali boiling, hydrothermal treatment and the like, modifying the bacterial cellulose with trimethylchlorosilane, dispersing the modified bacterial cellulose to obtain cellulose dispersion liquid with different concentrations, uniformly dispersing the cellulose dispersion liquid on cotton gauze in a vacuum filtration mode for forming, and performing supercritical drying to obtain hydrophobic bacterial cellulose aerogel based air filtration membranes with different thicknesses; the microstructure of the air filtering membrane is a three-dimensional nano network with smaller pores formed by hydrophobic bacterial cellulose nano fiber yarns between the rugged cotton fiber surface and the gaps, the macroscopic form of the air filtering membrane is a film, the air filtering membrane with the thickness of 0.1-1mm is prepared by the method, and PM is removed under the condition of high air flow velocity0.3The highest filtering efficiency of the filter can reach more than 99.9 percent (the air flow rate is 32.0L/min), the air resistance is less than 150Pa, and the contact angle of the membrane material is between 150 and 158 degrees.
Description
Technical Field
The invention relates to the field of air filtering materials, in particular to a preparation method of a hydrophobic bacterial cellulose aerogel-based air filtering membrane.
Background
In recent years, with the continuous development of modern industry in China and the rapid increase of automobile possession, the air quality is increasingly deteriorated, and the daily work and life of people are seriously influenced. According to the world health organization data, over 400 million people per year die prematurely from prolonged exposure to contaminated air containing fine particulate matter, wherein PM is present0.3Maximum Penetrating Particle Size (MPPS) of about 300nm, extremely harmful, and difficult to capture. Therefore, the development and preparation of high efficiency filter materials is a major issue concerning human health and economic development. The aerogel is a novel material which takes gas as a dispersion medium and has a continuous three-dimensional nano porous network structure, and is widely applied to the fields of filtering devices and the like due to the excellent characteristics of low density, high porosity, large specific surface area and the like.
At present, most of traditional air filtration membrane separation materials are synthetic high polymer materials, mainly plastic products synthesized by petrochemical raw materials such as polypropylene, polyethylene terephthalate and the like. The preparation process is limited by the conditions of the melt-blown process, the fiber diameter is often in a micron scale, the pores are large, the filtering effect on micro particles is limited, and the cost is high. Therefore, researchers are dedicated to exploring a hydrophobic air filtration membrane separation material which is light, thin, environment-friendly, renewable and low in cost.
Disclosure of Invention
The invention aims to provide a preparation method of a hydrophobic bacterial cellulose aerogel-based air filtering membrane, and a novel hydrophobic air filtering membrane is prepared by a simpler process method.
The technical scheme adopted by the invention is as follows: a preparation method of a hydrophobic bacterial cellulose aerogel-based air filtration membrane comprises the following steps:
step one, pretreatment of bacterial cellulose hydrogel: washing bacterial cellulose hydrogel (specifically massive food-grade coconut), boiling with alkali, and washing with water to obtain pure bacterial cellulose hydrogel; specifically, firstly, washing the bacterial cellulose hydrogel with deionized water for 5-7 h to wash off polysaccharides, proteins and bacterial thalli; then, soaking the mixture into 4-7% sodium hydroxide solution to react for 5-8 h at 60-90 ℃; then, the mixture is taken out and washed to be neutral by deionized water.
The raw material 'bacterial cellulose hydrogel' is an existing product, specifically edible coconut, and is a metabolite formed by growth of wood acetic acid bacteria in a liquid culture dish. In the above process steps, the bacteria cellulose hydrogel is washed away with the residual of the acetobacter xylinum in an alkali cooking manner to obtain a pure bacteria cellulose hydrogel, and an acidic solution cannot be used in the process, and can destroy the microstructure of the bacteria cellulose hydrogel.
Adding water into the bacterial cellulose hydrogel to prepare slurry, and performing hydrothermal treatment to obtain a bacterial cellulose hydrothermal product with the mass fraction of 1.5-3.0%; specifically, adding water into the bacterial cellulose hydrogel prepared in the step one, pulping the bacterial cellulose hydrogel into a pulp by using a pulping machine, and then, carrying out centrifugal treatment to ensure that the concentration of the bacterial cellulose pulp is 1.5-3.0%; and then pouring the bacterial cellulose pulp into a hydrothermal reaction kettle, and treating for 1-3 h at the temperature of 120-140 ℃ to obtain a bacterial cellulose hydrothermal product with the mass fraction of 1.5-3.0%.
In the step, the bacterial cellulose slurry which is not hydrothermal is agglomerated in water, and the nano-fiber filaments are obviously agglomerated and cannot be uniformly dispersed in water; the bacterial cellulose pulp is put into a hydrothermal reaction kettle for hydrothermal treatment, and the dispersion effect of the cellulose nano-fibrils can be realized by adjusting the temperature and time of the hydrothermal treatment; the hydrothermal treatment mainly occurs on the surface of the cellulose nano-fiber, and in the hydrothermal process, water molecules move violently, so that hydrogen bonds among hydroxyl groups on the surface of the nano-fiber are damaged, the fiber aggregation degree is changed, the nano-fiber can be separated from each other and well dispersed, the serious agglomeration phenomenon is avoided, the nano-fiber is ensured to be dispersed uniformly, and the effective guarantee is provided for the high efficiency of the finally prepared separation membrane.
Completely replacing water in the bacterial cellulose hydrothermal product with dichloromethane, and performing ultrasonic dispersion treatment to obtain an aprotic bacterial cellulose dispersion liquid; specifically, 1.5-3.0% of the bacterial cellulose hydrothermal product prepared in the step two is placed in a centrifuge tube, and absolute ethyl alcohol is used for centrifugal replacement, so that water is completely replaced by the absolute ethyl alcohol; then, using dichloromethane for centrifugal replacement, and completely replacing absolute ethyl alcohol with dichloromethane; then ultrasonic dispersion treatment is carried out, so that the nano fiber filaments are dispersed more uniformly; the dispersing agent adopted by the dispersion liquid is aprotic dichloromethane; the protic dispersion not treated with methylene chloride easily reacts with the reaction agent, and the reaction agent is excessively consumed.
Adding a modifier into the aprotic bacterial cellulose dispersion liquid for hydrophobic modification, wherein the modifier is trimethylchlorosilane, and triethylamine is added to serve as an acid-binding agent, so that the cellulose is prevented from being corroded by acid; then, carrying out centrifugal displacement washing by adopting absolute ethyl alcohol, and then carrying out dispersion treatment to obtain a hydrophobic bacterial cellulose nanofiber dispersion liquid with the mass fraction of 0.003-0.05%;
specifically, adding trimethylchlorosilane and triethylamine into the aprotic bacterial cellulose dispersion liquid prepared in the third step, and heating and refluxing for 1-2 h; after the reaction is finished, centrifugal displacement washing is carried out by using absolute ethyl alcohol, and redundant trimethylchlorosilane and triethylamine are completely displaced; after centrifugal displacement, cellulose is gathered at the bottom and the tube wall of the centrifugal tube and stirred to be dispersed again; then further carrying out ultrasonic dispersion to prepare hydrophobic bacterial cellulose nanofiber dispersion liquid with the mass fraction of 0.003-0.05%; the mass ratio of the trimethylchlorosilane to the triethylamine to the aprotic bacterial cellulose dispersion is that the aprotic bacterial cellulose dispersion is trimethylchlorosilane to the triethylamine =1:1: 1-1.2.
In the third and fourth steps, the process steps of the centrifugal displacement washing are basically the same, and the displacement of water in the slurry into absolute ethyl alcohol is taken as an example: pouring the bacterial cellulose hydrothermal product into a 50mL centrifuge tube, placing the centrifuge tube into a centrifuge, centrifuging the centrifuge tube for 10min at the rotating speed of 10000r/min, taking out the centrifuge tube, pouring out supernatant liquid, adding ethanol, stirring the mixture on a magnetic stirrer for 5min at the rotating speed of 5000rpm, then carrying out ultrasonic treatment for 10min at the power of 80% -90% to uniformly disperse the mixture, placing the centrifuge tube into the centrifuge for centrifuging, and repeating the step for 3-5 times to ensure complete replacement. The number of centrifugal displacement washes is 3-5, depending on the amount of solvent added, to ensure adequate displacement.
Step five, uniformly dispersing the hydrophobic bacterial cellulose nanofiber dispersion liquid on gauze in a vacuum filtration modeSpraying a small amount of absolute ethyl alcohol to keep the absolute ethyl alcohol moist, and performing supercritical drying to obtain a hydrophobic air filtering membrane; preferably, the dispersion liquid is uniformly dispersed on sterilized cotton gauze, the yarn count of the yarn in the cotton gauze is 15-60, and the yarn count density is 30-90 multiplied by 30-90; wherein the amount of the absolute ethyl alcohol sprayed is 1-3 mL; supercritical fluid adopts CO2The pressure of the fluid is 10-15MPa, and the supercritical circulation lasts for 1h-3 h.
The invention has the beneficial effects that: the invention provides a preparation method of a hydrophobic bacterial cellulose aerogel-based air filtering membrane, and a novel hydrophobic air filtering membrane is prepared by a simpler process method. The microstructure of the air filtering membrane is as follows: the thick and strong cotton fiber surface and the gaps are three-dimensional nano-network with smaller pores formed by hydrophobic bacterial cellulose nano-fiber filaments, the macroscopic form is a film, the thickness of the film prepared by the method is 0.1-1mm, and the PM is subjected to filtration efficiency and resistance test at high air flow rate0.3The filtration efficiency of the filter reaches more than 99.9 percent (the air flow rate is 32.0L/min), the pressure drop is only 30-150Pa, and the contact angle of the membrane material is between 150-158 degrees. The hydrophobic air filtering membrane prepared by the invention has the advantages of thinness, small air resistance, stable filtering performance, abundant and easily obtained raw material sources and environmental protection, and has important application value in the field of air filtering due to the renewable property of the cellulose raw material.
Drawings
FIG. 1 is a scanning electron microscope image of a finished air filtration membrane prepared in example 1 of the present invention; in the figure, A is a thick cotton fiber, and B is a three-dimensional nano network with smaller pores formed by hydrophobic bacterial cellulose nano fiber filaments.
FIG. 2 is a scanning electron microscope image of bacterial cellulose in voids of cotton fibers in the finished air filtration membrane prepared in example 1 of the present invention.
FIG. 3 is a scanning electron microscope image of bacterial cellulose in the voids of cotton fibers in a finished product of the filtration membrane prepared in comparative example 1 without hydrothermal treatment.
FIG. 4 is a diagram of a bacterial cellulose hydrogel raw material according to the present invention.
FIG. 5 is a diagram of a finished hydrophobic bacterial cellulose aerogel-based air filtration membrane prepared in example 1.
FIG. 6 is a diagram showing a vacuum filtration process.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the present invention will be further described in detail with reference to the following embodiments. The described embodiments are only some, but not all embodiments of the invention; the experimental methods used in the examples are all conventional methods unless otherwise specified; the materials, reagents and the like used are commercially available unless otherwise specified.
Example 1
Preparing a hydrophobic bacterial cellulose aerogel-based air filtering membrane with the mass fraction of 0.015%.
Firstly, 50g of edible coconut is washed for 6 hours by using excessive deionized water; then, the mixture is immersed into 300mL of 5% sodium hydroxide solution and is reacted for 8 hours at 70 ℃; then, the mixture is taken out and washed to be neutral by deionized water.
Step two, adding water into the bacterial cellulose hydrogel prepared in the step one, pulping the bacterial cellulose hydrogel into slurry by using a pulping machine, and then carrying out centrifugal treatment to enable the concentration of the bacterial cellulose slurry to be 2.0%; and then, pouring the bacterial cellulose pulp into a hydrothermal reaction kettle, and treating for 2 hours at the temperature of 120 ℃ to obtain a bacterial cellulose hydrothermal product with the mass fraction of 2.0%.
Step three, placing 30mL of the bacterial cellulose hydrothermal product with the concentration of 2.0% prepared in the step two in a centrifuge tube, performing centrifugal replacement by using absolute ethyl alcohol, and completely replacing water by the absolute ethyl alcohol; then, using dichloromethane for centrifugal replacement, and completely replacing absolute ethyl alcohol with dichloromethane; and then the ultrasonic dispersion treatment enables the dispersion of the nano-fiber filaments to be more uniform.
Pouring the non-protonic bacterial cellulose dispersion liquid into a flask, adding trimethylchlorosilane and triethylamine, and heating and refluxing for 1.5 h; after the reaction is finished, centrifugal displacement washing is carried out by using absolute ethyl alcohol, and redundant trimethylchlorosilane and triethylamine are completely displaced; after centrifugal displacement, cellulose is gathered at the bottom and the tube wall of the centrifugal tube and stirred to be dispersed again; then further carrying out ultrasonic dispersion to prepare a hydrophobic bacterial cellulose nano-fiber dispersion liquid with the mass fraction of 0.015%; the mass ratio of the trimethylchlorosilane to the triethylamine to the aprotic bacterial cellulose dispersion is that the aprotic bacterial cellulose dispersion is trimethylchlorosilane to the triethylamine =1:1: 1.1.
In the third and fourth steps, the process steps of the centrifugal displacement washing are basically the same, and the following example is that water in the slurry is replaced by absolute ethyl alcohol: pouring the bacterial cellulose hydrothermal product into a 50mL centrifuge tube, placing the centrifuge tube into a centrifuge, centrifuging the centrifuge tube for 10min at the rotating speed of 10000r/min, taking out the centrifuge tube, pouring out supernatant liquid, adding ethanol, stirring the mixture on a magnetic stirrer for 5min at the rotating speed of 5000rpm, then carrying out ultrasonic treatment for 10min at the power of 80% -90% to uniformly disperse the mixture, placing the centrifuge tube into the centrifuge for centrifuging, and repeating the step for 3-5 times to ensure complete replacement. The number of centrifugal displacement washes is 3-5, depending on the amount of solvent added, to ensure adequate displacement.
Step five, uniformly dispersing the hydrophobic bacterial cellulose nanofiber dispersion liquid on gauze in a vacuum filtration mode, then spraying a small amount of absolute ethyl alcohol to keep the hydrophobic bacterial cellulose nanofiber dispersion liquid moist, and performing supercritical drying to obtain a hydrophobic air filtering membrane; the yarn count of the yarn in the cotton gauze is 60, and the yarn count density is 65 multiplied by 78; wherein the amount of the absolute ethyl alcohol sprayed is 2 mL; supercritical fluid adopts CO2The pressure of the fluid is 13MPa, and the supercritical circulation is carried out for 2 h. This example produced a hydrophobic bacterial cellulose aerogel-based air filtration membrane having a thickness of 0.7 mm.
Filtration efficiency and resistance test
The filtering efficiency and resistance test is carried out by an SX-L1056E1 type automatic filtering tester which accords with the national GB2626-2006 standard, and the test method comprises the following steps: the dust concentration is 30-200mg/m3The median diameter CMD0.075 ± 0.02 μm was counted, the dust source used was sodium chloride aerosol having a particle diameter of about 300nm, the air flow rate was 32.0L/min, and the filtration efficiency was the ratio of the weight or number of particles trapped by the filter to the weight or number of particles contained in the air before filtration, expressed as a percentage. The pressure drop is the pressure difference of the air before and after the filter.
Through the test, the air filtration membrane pair PM prepared in the example 10.3The filtration efficiency of (1) is 99.976%, and the pressure drop is 100 Pa; furthermore the contact angle of the film material was 153 °; fig. 1 and 2 are scanning electron microscope images of the hydrophobic bacterial cellulose aerogel-based air filtration membrane according to the embodiment.
Example 2
Preparing a hydrophobic bacterial cellulose aerogel-based air filtration membrane with the mass fraction of 0.005%.
Firstly, 50g of edible coconut is washed for 5 hours by using excessive deionized water; then, the mixture is immersed into 300mL of 4% sodium hydroxide solution and is reacted for 8 hours at 80 ℃; then, the mixture is taken out and washed to be neutral by deionized water.
Step two, adding water into the bacterial cellulose hydrogel prepared in the step one, pulping the bacterial cellulose hydrogel into a pulp by using a pulping machine, and then, carrying out centrifugal treatment to ensure that the concentration of the bacterial cellulose pulp is 1.5%; and then, pouring the bacterial cellulose pulp into a hydrothermal reaction kettle, and treating for 3 hours at the temperature of 120 ℃ to obtain a bacterial cellulose hydrothermal product with the mass fraction of 1.5%.
Step three, placing 30mL of the bacterial cellulose hydrothermal product with the concentration of 1.5% prepared in the step two in a centrifuge tube, performing centrifugal replacement by using absolute ethyl alcohol, and completely replacing water by the absolute ethyl alcohol; then, using dichloromethane for centrifugal replacement, and completely replacing absolute ethyl alcohol with dichloromethane; and then the ultrasonic dispersion treatment enables the dispersion of the nano-fiber filaments to be more uniform.
Pouring the non-protonic bacterial cellulose dispersion liquid into a flask, adding trimethylchlorosilane and triethylamine, and heating and refluxing for 1 h; after the reaction is finished, centrifugal displacement washing is carried out by using absolute ethyl alcohol, and redundant trimethylchlorosilane and triethylamine are completely displaced; after centrifugal displacement, cellulose is gathered at the bottom and the tube wall of the centrifugal tube and stirred to be dispersed again; then further carrying out ultrasonic dispersion to prepare hydrophobic bacterial cellulose nanofiber dispersion liquid with the mass fraction of 0.005%; the mass ratio of the trimethylchlorosilane to the triethylamine to the aprotic bacterial cellulose dispersion is that the ratio of the aprotic bacterial cellulose dispersion to the trimethylchlorosilane to the triethylamine is =1:1:1.
Step five, uniformly dispersing the hydrophobic bacterial cellulose nanofiber dispersion liquid on gauze in a vacuum filtration mode, then spraying a small amount of absolute ethyl alcohol to keep the hydrophobic bacterial cellulose nanofiber dispersion liquid moist, and performing supercritical drying to obtain a hydrophobic air filtering membrane; the yarn count of the yarn in the cotton gauze is 60, and the yarn count density is 65 multiplied by 78; wherein the amount of the absolute ethyl alcohol sprayed is 1 mL; supercritical fluid adopts CO2The pressure of the fluid is 10MPa, and the supercritical circulation lasts for 3 h. This example produced a hydrophobic bacterial cellulose aerogel-based air filtration membrane having a thickness of 0.3 mm.
Using the same test method and test conditions as in example 1, the air filtration membrane removed PM0.3The filtration efficiency of (2) was 99.942%, the pressure drop was 50Pa, and the contact angle of the membrane material was 150 °.
Example 3
Preparing a hydrophobic bacterial cellulose aerogel-based air filtration membrane with the mass fraction of 0.03%.
Firstly, washing 50g of edible coconut by using excessive deionized water for 7 hours; then, the mixture is immersed into 300mL of 6% sodium hydroxide solution and is reacted for 6 hours at 80 ℃; then, the sample was taken out and washed with deionized water to be neutral.
Step two, adding water into the bacterial cellulose hydrogel prepared in the step one, pulping the bacterial cellulose hydrogel into a pulp by using a pulping machine, and then, carrying out centrifugal treatment to ensure that the concentration of the bacterial cellulose pulp is 3.0%; and then, pouring the bacterial cellulose pulp into a hydrothermal reaction kettle, and treating for 1h at the temperature of 140 ℃ to obtain a bacterial cellulose hydrothermal product with the mass fraction of 3.0%.
Step three, placing 30mL of the bacterial cellulose hydrothermal product with the concentration of 3.0% prepared in the step two in a centrifuge tube, performing centrifugal replacement by using absolute ethyl alcohol, and completely replacing water by the absolute ethyl alcohol; then, using dichloromethane for centrifugal replacement, and completely replacing absolute ethyl alcohol with dichloromethane; and then the ultrasonic dispersion treatment enables the dispersion of the nano-fiber filaments to be more uniform.
Pouring the non-protonic bacterial cellulose dispersion liquid into a flask, adding trimethylchlorosilane and triethylamine, and heating and refluxing for 2 hours; after the reaction is finished, centrifugal displacement washing is carried out by absolute ethyl alcohol, and redundant trimethylchlorosilane and triethylamine are completely displaced; after centrifugal displacement, cellulose is gathered at the bottom and the tube wall of the centrifugal tube and stirred to be dispersed again; then further carrying out ultrasonic dispersion to prepare hydrophobic bacterial cellulose nanofiber dispersion liquid with the mass fraction of 0.03%; the mass ratio of the trimethylchlorosilane to the triethylamine to the aprotic bacterial cellulose dispersion is that the aprotic bacterial cellulose dispersion is trimethylchlorosilane to the triethylamine =1:1: 1.2.
Step five, uniformly dispersing the hydrophobic bacterial cellulose nanofiber dispersion liquid on gauze in a vacuum filtration mode, then spraying a small amount of absolute ethyl alcohol to keep the hydrophobic bacterial cellulose nanofiber dispersion liquid moist, and performing supercritical drying to obtain a hydrophobic air filtering membrane; the yarn count of the yarn in the cotton gauze is 60, and the yarn count density is 65 multiplied by 78; wherein the amount of the sprayed absolute ethyl alcohol is 3 mL; supercritical fluid adopts CO2The pressure of the fluid is 15MPa, and the supercritical circulation is 1.5 h. This example produced a hydrophobic bacterial cellulose aerogel-based air filtration membrane having a thickness of 1 mm.
Using the same test method and test conditions as in example 1, the air filtration membrane removed PM0.3The filtration efficiency of (2) is 99.991%, the pressure drop is 130Pa, and the contact angle of the membrane material is 155 deg.
According to the invention, the bacterial cellulose hydrogel is added with water to prepare slurry, and then the hydrothermal treatment is adopted, so that the hydrothermal treatment process has important significance for the material disclosed by the invention. Comparative example 1 is provided below to illustrate by comparison with example 1.
Comparative example 1
The same procedure as in example 1 was repeated except that no hydrothermal treatment was carried out. FIG. 3 is a scanning electron microscope image of bacterial cellulose in the voids of cotton fibers in the finished product of the filtration membrane prepared in comparative example 1 without hydrothermal treatment. Compared with the figure 2, the bacterial cellulose in the cotton fiber gaps has obvious adhesion and agglomeration phenomena without hydrothermal treatment, and the gaps are few.
Comparative example 1 to PM Using the same test methods and test conditions as example 10.3The filtration efficiency of (1) is 95.276%, the pressure drop is 120Pa, and the membrane materials are contactedAngle is 152 °; the effect is lower than in example 1.
It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (9)
1. A preparation method of a hydrophobic bacterial cellulose aerogel-based air filtration membrane is characterized by comprising the following processes:
adding water into the bacterial cellulose hydrogel to prepare slurry, and performing hydrothermal treatment to obtain a bacterial cellulose hydrothermal product with the mass fraction of 1.5-3.0%; the reaction temperature of the hydrothermal treatment is 120-140 ℃, and the reaction time is 1-3 h;
completely replacing water in the bacterial cellulose hydrothermal product with dichloromethane, and performing ultrasonic dispersion treatment to obtain an aprotic bacterial cellulose dispersion liquid;
adding a modifier into the aprotic bacterial cellulose dispersion liquid for hydrophobic modification, wherein the modifier is trimethylchlorosilane, and triethylamine is added to serve as an acid-binding agent; then, carrying out centrifugal displacement washing by adopting absolute ethyl alcohol, and then carrying out dispersion treatment to obtain a hydrophobic bacterial cellulose nanofiber dispersion liquid with the mass fraction of 0.003-0.05%;
uniformly dispersing the hydrophobic bacterial cellulose nanofiber dispersion liquid on gauze in a vacuum filtration mode, spraying a small amount of absolute ethyl alcohol to keep the hydrophobic bacterial cellulose nanofiber dispersion liquid moist, and performing supercritical drying to obtain the hydrophobic air filtration membrane.
2. The method for preparing the hydrophobic bacterial cellulose aerogel-based air filtration membrane according to claim 1, wherein the method comprises the following steps: before the bacterial cellulose hydrogel is prepared into slurry, the pure neutral bacterial cellulose hydrogel is obtained by adopting water washing, alkali boiling and water washing.
3. The method for preparing the hydrophobic bacterial cellulose aerogel-based air filtration membrane according to claim 2, wherein the method comprises the following steps: the alkali cooking process is that the bacterial cellulose hydrogel is immersed into 4-7% sodium hydroxide solution to react for 5-8 h at 60-90 ℃.
4. The method for preparing the hydrophobic bacterial cellulose aerogel-based air filtration membrane according to claim 1, wherein the method comprises the following steps: the hydrothermal treatment is carried out in a hydrothermal reaction kettle.
5. The method for preparing the hydrophobic bacterial cellulose aerogel-based air filtration membrane according to claim 1, wherein the method comprises the following steps: the process of completely replacing water in the bacterial cellulose hydrothermal product with dichloromethane comprises the following steps: firstly, carrying out centrifugal replacement by using absolute ethyl alcohol, and completely replacing water by the absolute ethyl alcohol; subsequently, the mixture was centrifuged and replaced with dichloromethane, and the absolute ethanol was replaced again with dichloromethane.
6. The method for preparing the hydrophobic bacterial cellulose aerogel-based air filtration membrane according to claim 1, wherein the method comprises the following steps: the hydrophobic modification process is heating reflux for 1h-2 h; the mass ratio of the trimethylchlorosilane to the triethylamine to the aprotic bacterial cellulose dispersion is that the aprotic bacterial cellulose dispersion is trimethylchlorosilane to the triethylamine =1:1: 1-1.2.
7. The method for preparing the hydrophobic bacterial cellulose aerogel-based air filtration membrane according to claim 1, wherein the method comprises the following steps: the gauze is sterilized cotton gauze, the yarn count of the yarn in the cotton gauze is 15-60, and the yarn count density is 30-90 multiplied by 30-90.
8. The method for preparing the hydrophobic bacterial cellulose aerogel-based air filtration membrane according to claim 1, wherein the method comprises the following steps: supercritical fluidThe drying conditions are that CO is adopted2The pressure of the fluid is 10-15MPa, and the supercritical circulation lasts for 1h-3 h.
9. The method for preparing a hydrophobic bacterial cellulose aerogel-based air filtration membrane according to any one of claims 1 to 8, wherein: the bacterial cellulose hydrogel is an edible coconut and is a metabolite formed by growth of wood acetic acid bacteria in a liquid culture dish.
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