Bacterial cellulose-based aerogel for filtration and dust removal and preparation method of bacterial cellulose-based aerogel

Abstract

The preparation method comprises bacterial cellulose preparation, bacterial cellulose purification, gel preparation, solvent replacement and freeze drying and is characterized in that the bacterial cellulose is synthesized through fermentation of acetobacter xylinum, impurities are removed through high-temperature boiling, and the bacterial cellulose-based aerogel is prepared through freeze drying. Sodium alginate and KH590 are adopted to strengthen the mechanical property of bacterial cellulose, hydrophobic modification is carried out, and finally the bacterial cellulose-based aerogel which is partitioned according to pore diameters is prepared through a layered directional freezing method. The bacterial cellulose-based aerogel has no extreme condition tolerance requirement on a synthesis device, the preparation method of the aerogel is simple, and the prepared bacterial cellulose-based aerogel has excellent PM2.5 filtering efficiency, has the characteristics of high hydrophobicity and environmental friendliness, and has wide applicability in the field of productive dust treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of dust control, in particular to bacterial cellulose-based aerogel for filtering and dust removal and a preparation method thereof. Background Art

[0002] With the rapid development of industrialization, air pollution is becoming increasingly serious, with industrial dust emissions being one of the main causes of air pollution. The key to the dust removal performance of dry-type dust collectors lies in the dust removal filter material. Traditional dust removal filter materials mostly use fiber filter media, such as glass fiber and polyester fiber. However, these materials have disadvantages such as high filtration resistance, low biodegradability, poor environmental adaptability, and low energy efficiency, making them difficult to meet the requirements of green and efficient filtration.

[0003] Aerogel is a lightweight material with a porous structure that offers advantages such as high porosity and a high specific surface area, making it an ideal filter material. Bacterial cellulose is a natural polymer material synthesized by microorganisms that possesses excellent mechanical properties and biocompatibility. Combining bacterial cellulose with aerogel and improving its mechanical and hydrophobic properties is expected to develop a new type of dust removal and filtration material that is highly efficient, low-resistance, and environmentally friendly, which is of great significance for the efficient prevention and control of dust. Therefore, the present invention proposes a bacterial cellulose-based aerogel for efficient dust filtration in dry-type filter dust collectors and a preparation method thereof, in order to overcome the technical bottlenecks of traditional dust removal and filtration materials and improve the air quality in production sites. Summary of the Invention

[0004] In response to the above problems, bacterial cellulose-based aerogel for filtration and dust removal and its preparation method are provided, which solves the shortcomings of existing filter materials such as low filtration efficiency, high resistance, and poor biodegradability, and can provide strong support and innovative materials for efficient dust prevention and control.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] Bacterial cellulose-based aerogel for filtration and dust removal is characterized by using bacterial cellulose as the skeleton structure, using sodium alginate and silane coupling agent KH590 to strengthen the skeleton and cross-linking units. Its physical structure consists of honeycomb pores arranged in a directional and regular manner and stacked in layers. The gaps between adjacent pores and stacked layers form a multi-channel structure with continuous guidance. The preparation method of the bacterial cellulose-based aerogel for high-efficiency dust separation in dry-type filter dust collectors includes:

[0007] S1. Preparation of bacterial cellulose: (a) Bacterial activation: inoculate Acetobacter xylinum or other bacteria into HS culture medium and culture in a constant temperature incubator at 30°C for 3-4 days to restore the activity of the strain; (b) Expansion culture: collect the Acetobacter xylinum colonies and transfer them to new HS culture medium in a certain proportion. Place the large-capacity beaker of HS culture medium containing the colonies in a constant temperature incubator for static culture until the OD value of the culture reaches 0.6; (c) Fermentation of bacterial cellulose: transfer the Acetobacter xylinum culture liquid after the expansion culture to a fermenter and add the prepared fermentation medium. Connect the fermenter to a continuous fermentation system, control the temperature at 28-32°C, the pH at 6, the rotation speed at 100-200 r / min, and ensure the oxygen concentration in the tank. Fermentation is carried out with continuous stirring for 1 day. After the fermentation is completed, a gel-like bacterial cellulose film is formed on the wall of the fermenter. The film is removed after standing for 2 hours;

[0008] S2. Bacterial cellulose purification: The removed bacterial cellulose membrane is repeatedly washed with deionized water to remove the culture medium and bacteria; the bacterial cellulose membrane is then placed in a 1% NaOH solution and heated to 80°C to repeatedly wash away residual proteins and other impurities on the surface; the washed bacterial cellulose membrane is then immersed in a prepared hydrogen peroxide solution, heated to 90°C, and slowly stirred for 1 hour before removal to remove organic impurities from the bacterial cellulose; finally, the bacterial cellulose membrane is rinsed with deionized water until neutral; the purified bacterial cellulose is crushed by a high-speed homogenizer to obtain bacterial cellulose suspensions of varying concentrations;

[0009] S3. Preparation of bacterial cellulose-based gel: Deionized water was heated to 60°C in a water bath. Sodium alginate powder, bacterial cellulose suspension, and KH590 were then added in the appropriate proportions. Stirring was continued for 4 hours at a speed of 1000-1400 rpm to form a viscous gel. Ultrasonic dispersion was then performed for 15 minutes. The gel was then aged in a refrigerator at 4°C for 2 hours to enhance mechanical properties and crosslinking strength.

[0010] S4. Solvent replacement: Immerse the aged wet gel in anhydrous ethanol solution. After 4 hours, remove the supernatant and pour it into anhydrous ethanol again. Repeat 3-5 times.

[0011] S5. Freeze-drying: Pour the wet gel after solution replacement into a customized mold and perform temperature-layered direction freezing. The aerogel is directionally frozen in three different layers to control the regional distribution of pore size. After the wet gel is directionally frozen for a certain period of time according to the prepared thickness, usually 10 minutes, it is taken out and placed in a refrigerator for further freezing. After 4 hours, it is taken out and placed in a freeze dryer and dried at -60°C and 1 Pa for 48 hours to obtain bacterial cellulose-based aerogel with directionally distributed pore size.

[0012] Furthermore, in step S3, the bacterial cellulose-based aerogel uses bacterial cellulose as a structural base, strengthens the skeleton by adding sodium alginate, strengthens the cross-linking effect by adding a silane coupling agent, and undergoes hydrophobic modification, with a dynamic contact angle of 100°; KH590 is only cross-linked on the surface of the bacterial cellulose and sodium alginate complex. After the addition of sodium alginate and KH590, the aerogel crystal structure presents a more amorphous distribution, but the overall cellulose I-type crystal structure is still maintained;

[0013] Furthermore, in step S3, the continuous stirred fermentation system includes a fermentation tank, a stirring paddle, a pH sensor, a temperature sensor, an air inlet pipe, a liquid inlet pipe, an oxygen concentration sensor, etc., and the relevant sensors are used to monitor various fermentation parameters in the tank in real time to keep the fermentation parameters within the set range; the stirring paddle adopts a three-layer inclined paddle design, which can form an effective disturbance area to ensure sufficient contact between the bacterial liquid and oxygen;

[0014] Furthermore, in step S2, the concentration of the hydrogen peroxide solution used for bacterial cellulose membrane purification is generally 2-4 g / L; sodium silicate is added as a stabilizer to prevent the hydrogen peroxide from decomposing too quickly; and the pH value is adjusted to 10-11 to obtain the best bleaching effect and reduce fiber damage;

[0015] Furthermore, in step S3, the skeleton strengthening component includes but is not limited to plant polysaccharides such as sodium alginate and konjac glucomannan, wherein the higher the polarity of the plant polysaccharide, the better the binding effect with the bacterial cellulose; the cross-linking unit strengthening component includes but is not limited to silane coupling agent KH590, methyltrimethoxysilane, etc., wherein the higher the polarity of the silane, the better the surface cross-linking effect and the higher the filtration efficiency;

[0016] Furthermore, in step S5, the layered directional freezing method divides the freezing area into three layers through a baffle, the central area is frozen with liquid nitrogen, the middle area is frozen with ethanol, and the outermost layer is frozen with ice water, and each layer uses a partition made of polytetrafluoroethylene material; the lower the freezing temperature, the faster the ice crystals form and the smaller the pore size in the wet gel; the customized mold can be designed according to demand to include but not limited to a cylinder, the bottom of which is brass or other high thermal conductivity metal, and the surrounding is polytetrafluoroethylene with high stability and high thermal insulation. The height usually determines the thickness of the aerogel. The smaller the thickness, the lower the pressure drop but the poorer the filtration efficiency, which is usually set to 1-3mm; during directional freezing, it is placed on a layered circular freezing table, and the other side of the freezing table contacts the low-temperature freezing liquid to achieve simultaneous layered freezing; bacterial cellulose-based aerogel can be prepared not only by pore size zoning, but also by fixed pore size preparation at a fixed freezing temperature. At this time, only liquid nitrogen is used as the freezing liquid, which can achieve rapid freezing, and it is taken out after 10 minutes and directly dried;

[0017] Preferably, in the aforementioned preparation method, the bacterial cellulose producing strains include but are not limited to Acetobacter xylinum and Gluconoacetobacter; the bacterial cellulose is fermented by stirring, and its diameter is 50-70 nm.

[0018] Preferably, in the aforementioned preparation method, the oxygen concentration monitoring value of the continuous fermentation device is set to 15% saturation; the Acetobacter xylinum or other bacterial species used to produce bacterial cellulose can be reused by collecting the residual liquid at the bottom of the fermentation tank after fermentation is completed, continuing to inoculate the strain into it and replenishing the culture medium, which will help reduce costs.

[0019] Preferably, in the aforementioned preparation method, the bacterial cellulose membrane is slightly transparent white, and its transparency is further increased after purification;

[0020] Preferably, in the aforementioned preparation method, the composition ratio of bacterial cellulose, sodium alginate, and KH590 is generally 1:1.5:1. By changing the composition ratio, the pore size can also be controlled. The general trend is that the higher the sodium alginate concentration, the smaller the pore size. The pore size can generally be between 1 μm and 30 μm.

[0021] Preferably, in the aforementioned preparation method, the bacterial cellulose-based aerogel can rebound to its original shape after being compressed to 20-80% of its volume multiple times;

[0022] Preferably, in the aforementioned preparation method, the bacterial cellulose-based aerogel can remain stable at a high temperature of 200°C, with a decomposition mass of less than 10%; and maintain internal channel flow when the humidity is less than 80% RH;

[0023] Preferably, in the aforementioned preparation method, the bacterial cellulose-based aerogel has an initial filtration efficiency of more than 99% for PM10 and more than 98% for PM2.5 in a high-concentration dust environment, and the filtration efficiency only decreases by 1% after being cleaned and reused five times;

[0024] Preferably, in the aforementioned preparation method, the bacterial cellulose-based aerogel has an area of degradation exceeding 40% after being embedded in soil for ten days, and has excellent biodegradability.

[0025] The present invention has the following technical effects:

[0026] The present invention provides a green and simple synthesis method of bacterial cellulose-based aerogels as claimed in the claims, which is the first application of bacterial cellulose-based aerogels in the field of industrial dust filtration. The invention makes full use of the ability of Acetobacter xylinum to synthesize bacterial cellulose, so that it can use HS culture medium as a nutrient substance to achieve continuous and efficient synthesis of bacterial cellulose under stirring culture conditions. Through the method of layered directional freezing, the oriented control of the pore size of different partitions of the aerogel is achieved to meet the requirement of reducing the filtration pressure drop. At the same time, sodium alginate and KH590 are used to strengthen the bacterial cellulose skeleton structure and make the aerogel have high hydrophobic properties, so that the bacterial cellulose-based aerogel has biodegradability, application stability and adaptability to high temperature and high humidity environments, and finally meets the technical requirements of the field of industrial dust prevention and control. In particular, the present invention only needs to be carried out under mild conditions, the technical steps are simple, and there are no strict conditions required. No toxic or harmful waste is generated during the synthesis process, which is green and environmentally friendly.

[0027] Compared with traditional dust removal filter materials (such as non-woven fiber filter materials), the technical advantages of the present invention are outstanding: the bacterial cellulose-based aerogel has a controllable directional pore structure, extremely high porosity and specific surface area, does not require stacking fiber density to achieve a balance between pressure drop and filtration efficiency, and is inherently environmentally friendly, making it an ideal alternative material for dust removal filter materials. Scanning electron microscopy, CT scanning, infrared spectroscopy, contact angle, and thermogravimetric testing of bacterial cellulose-based aerogel samples prepared by the method of the present invention show that the bacterial cellulose-based aerogel synthesized by the present invention has a layered directional pore structure, thereby forming a rich three-dimensional fiber network. At the same time, KH590 successfully cross-links the bacterial cellulose surface to form a siloxane network and a thiol-crosslinked aerogel surface, giving the aerogel high hydrophobicity, with a contact angle of 106°. In addition, it has higher thermodynamic stability, and its mass only decreases by 5% at 200°C, thereby achieving low resistance and high efficiency dust filtration in high temperature and high humidity environments. In addition, the bacterial cellulose-based aerogel synthesized by the present invention uses bacterial cellulose as a base material, which is inherently non-toxic and harmless and has excellent biodegradability.

[0028] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the present invention will be described in more detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The following is a flow chart of the preparation process of the present invention. In it, (1)-(18) indicate the instruments and components required for the synthesis, and (19)-(33) indicate the biochemical materials involved in the synthesis process.

[0030] Figure 2 The three-dimensional structure of bacterial cellulose-based aerogel.

[0031] Figure 3 This is the experimental diagram of the contact angle of bacterial cellulose-based aerogel.

[0032] Figure 4 This is the infrared spectrum of bacterial cellulose-based aerogel.

[0033] Figure 5 Scanning electron microscopy image of bacterial cellulose-based aerogel.

[0034] Figure 6 Thermogravimetric analysis diagram of bacterial cellulose-based aerogel. DETAILED DESCRIPTION

[0035] The container equipment designed by the present invention includes:

[0036] 5ml antifreeze ampoule (1), 316 stainless steel flat-head tweezers (2), 2ml disposable syringe (3), glass culture dish (4), glass applicator (5), constant temperature incubator (6), sterile plastic inoculating loop (7), 250ml triangular flask (8), continuous stirring culture tank and its control panel (9), oxygen concentration and temperature sensor (10), hose (11), 1000ml beaker (12), constant temperature water bath (13), high pressure homogenizer (14), mechanical stirrer (15), freezing liquid storage tank (16), partitioned directional freezing mold (17), freeze dryer (18).

[0037] The biochemical materials involved in the present invention mainly include:

[0038] Acetobacter xylinum freeze-dried product (19) stored in ampoules, standard HS culture medium (20) pH=7, HS bacterial suspension (21), bacterial cellulose film (22), NaOH solution (23), hydrogen peroxide solution (24), sodium silicate (25), deionized water (26), anhydrous ethanol (27), liquid nitrogen (28), ice water (29), sodium alginate (30), KH590 (31), bacterial cellulose-based aerogel (32), bacterial cellulose suspension (33), bacterial cellulose-based gel (34), brass (35), polytetrafluoroethylene (36).

[0039] Among them, Acetobacter xylinum is a standard strain of Acetobacter xylinum;

[0040] Standard HS culture medium, homemade, formula ( / L): glucose 20 g, peptone 5 g, yeast extract 5 g, anhydrous Na2HPO4 2.7 g, citric acid 1.5 g, pH = 7.

[0041] To facilitate understanding of the present invention, the present invention will be described more fully below through examples, with preferred embodiments of the present invention provided below. However, the present invention can be implemented in a variety of different forms and is not limited to the embodiments described herein. Any other embodiments obtained by modifying or equivalently replacing the technical solution of the present invention without inventive conception are within the scope of protection of the present invention.

[0042] The numerical values disclosed in the embodiments of the present invention are approximate values, not definite values. Where errors or experimental conditions permit, all values within the error range may be included without being limited to the specific numerical values disclosed in the embodiments of the present invention.

[0043] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0044] The bacterial cellulose-based aerogel for filtering and dust removal of the present invention and its preparation method are completed by the following steps:

[0045] Lightly burn the joint of ampoule 1 with an alcohol burner until it turns red. Drip sterile water to rupture the joint. Use 316 stainless steel flat-tipped tweezers 2 to pry the tube joint. Use a 2ml disposable syringe 3 to deliver liquid to the lyophilized Acetobacter xylinum 19. Take the bacterial suspension 21 and inoculate it into an activated culture dish 4. Spread it evenly with a glass applicator 5. Place the suspension in a constant-temperature incubator 6, adjust the temperature to 30°C, turn on the heating switch, and incubate at 30°C for 3-4 days. Use a sterile plastic inoculating loop 7 to scrape Acetobacter xylinum hyphae from the HS culture medium and transfer them to new HS culture medium 20 in a specific ratio. Place a large 1000ml beaker 12 of HS culture medium containing the colony in a constant-temperature incubator, adjust the temperature to 30°C, and wait until the OD value of the culture reaches 0.6.

[0046] The culture of Acetobacter xylinum was transferred to a continuous stirring fermenter 9, and 1000 ml of deionized water 24 was added to the fermenter. An oxygen hose 11 and an oxygen concentration and temperature sensor 10 were connected to the fermenter, and the power was turned on. The continuous fermentation system 9 controlled the temperature in the fermenter to 28-32°C, the pH to 6, the rotation speed to 100-200 rpm, and the oxygen saturation in the tank to 15%. Continuous stirring fermentation was performed for two days. After fermentation, a gelatinous bacterial cellulose film 22 formed on the upper layer of the Acetobacter xylinum culture. After standing for two hours, the gelatinous bacterial cellulose film 22 was removed.

[0047] The removed gelatinous bacterial cellulose membrane 22 is repeatedly washed with deionized water 26 in a beaker 12 to remove the culture medium and bacteria. After cleaning, the gelatinous bacterial cellulose membrane is placed in a beaker containing a 1% NaOH solution 23 and placed in a constant temperature water bath 13 and heated to 80°C. In the constant temperature solution, the bacterial cellulose membrane 22 is clamped with tweezers and repeatedly washed to remove proteins and other impurities remaining on its surface. The washed bacterial cellulose membrane 22 is immersed in a 3g / L hydrogen peroxide solution 24 with sodium silicate 25 added. The beaker containing the solution and the bacterial cellulose membrane is placed in a constant temperature water bath 13 and heated to 90°C. The mechanical stirrer 15 is connected to the beaker and the speed knob is adjusted to 180r / min and stirred slowly for 1 hour. After completion, the bacterial cellulose membrane 22 is removed with tweezers and placed in a clean beaker and washed with deionized water 24 until the bacterial cellulose membrane is neutral. At this point, the bacterial cellulose membrane purification is completed. The purified bacterial cellulose is placed in a high-speed homogenizer 14 and crushed to prepare a bacterial cellulose suspension 33 with a concentration of 1%.

[0048] Take 500ml of deionized water 26 and add it to beaker 12. Place it in a constant temperature water bath and adjust the temperature to 60°C. Weigh a certain amount of sodium alginate 30, KH59031, and 500ml of bacterial cellulose suspension 33. Add sodium alginate powder, bacterial cellulose suspension, and KH590 in a ratio of 1.5:1:1. Place a mechanical stirrer near the constant temperature water bath, fix the beaker with a clamp, place the stirring paddle in the middle of the solution, turn on the rotary switch, turn the speed knob to 1200r / min, and stir for 4 hours to form a viscous gel 34. Then, place the beaker 12 containing the gel 34 in an ultrasonic disperser for ultrasonic dispersion for 30 minutes to remove bubbles. Then, remove the beaker 12 and place it in a constant temperature incubator 6 at a constant temperature of 4°C for aging for 2 hours.

[0049] The beaker containing the aged wet gel 34 was taken out, and the aged wet gel 34 was immersed in the absolute ethanol solution 27. After 4 hours, the supernatant of the solution was taken and poured into the absolute ethanol solution again, and repeated 5 times.

[0050] The wet gel after the replacement solution is poured into a directional freezing mold 17 with a bottom of brass 35 and a height of 3mm surrounded by polytetrafluoroethylene 36. The brass 35 at the bottom of the mold is connected to a brass bracket, and the brass bracket is immersed in a freezing liquid placement tank (16) filled with layered freezing liquid, which is respectively liquid nitrogen 28, ice anhydrous ethanol 27, and ice water 29 from the inner layer to the outer layer. The bottom of the central area of the directional freezing mold 17 is circular, and the brass bracket connected thereto is immersed in the area filled with liquid nitrogen in the freezing tank. The bottom of the middle area of the directional freezing mold 17 is annular and separated from the central area, and the brass bracket connected thereto is immersed in the area filled with liquid nitrogen and ice anhydrous ethanol in the freezing tank. The bottom of the outermost area of the directional freezing mold is annular and separated from the middle area. The temperature is low, and its brass bracket is immersed in the area filled with liquid nitrogen and ice water in the freezing tank. The gel was directionally frozen for 10 minutes in three different regions. After direction freezing, it was taken out and placed in a refrigerator for further freezing. After 8 hours, it was taken out and placed in a freeze dryer 18. The power and vacuum pump were turned on to maintain the drying environment at -60°C and 1 Pa. After drying for 48 hours, bacterial cellulose-based aerogel 32 with a directional pore size distribution was obtained.

[0051] After the preparation is completed, 0.5mm*0.5mm aerogel is cut and CT three-dimensional scanning reconstruction is performed to observe the overall internal structure. From the figure, it can be seen that it has a layered oriented pore structure distribution, which provides a possibility for reducing the pressure drop during filtration.

[0052] The researchers further tested its hydrophobic properties by dropping a 2-microliter water droplet on the aerogel surface and recording its contact angle over a long period of time. The results showed that the aerogel had strong hydrophobicity, with a contact angle exceeding 100°, and the water droplet could still maintain its shape after ten minutes.

[0053] Figure 4 This is the infrared spectrum of bacterial cellulose, which reflects the chemical structure characteristics of the material.

[0054] In order to further observe the surface morphology of bacterial cellulose-based aerogel, SEM experiments were carried out. The observation results showed that it has a layered oriented honeycomb pore distribution and abundant three-dimensional fiber channels inside. Its fiber pores can increase the probability of contact with particles and thus improve the filtration efficiency.

[0055] Figure 6 This shows the decomposition of bacterial cellulose-based aerogel at high temperature. At 200°C, it still retains more than 95% of its mass, indicating its excellent thermal stability and can be used for dust filtration in high temperature and high humidity environments.

[0056] In addition, the present invention can achieve increased production of surfactant by only changing the external environment of fermentation, meeting the requirements of use in the field of dust removal and filtration, without the need to genetically enhance the fermentation strain, thereby maintaining the stability of the strain's ability to produce surfactant over generations.

[0057] Application Example 1

[0058] The main application steps of the bacterial cellulose-based aerogel for efficient dust separation in coal mine dust collectors of the present invention include:

[0059] a. Prepare bacterial cellulose-based aerogel into a full-section filter membrane and install it directly in the rear section of the dust collector through a fixture.

[0060] b. When the dust collector is in operation, aerogel is prepared by aperture partitioning according to the cyclonic flow field inside the dust collector.

[0061] c. Adjust the dust collector wind speed to ensure that the filtration wind speed near the aerogel is 4m / s.

[0062] d. After running to the limit pressure drop, open the reverse blowing cleaning device to clean the dust and reuse it.

[0063] While the present invention has been described in detail above using general explanations, specific embodiments, and experiments, it will be readily apparent to those skilled in the art that modifications and improvements may be made to the present invention. Therefore, any such modifications and improvements that do not depart from the spirit of the present invention are intended to fall within the scope of protection claimed herein.

Claims

1. Bacterial cellulose-based aerogel for filtration and dust removal, characterized in that: The bacterial cellulose-based aerogel uses bacterial cellulose as its skeleton structure, with sodium alginate and silane coupling agent KH590 used to strengthen the skeleton and cross-linking units. Its physical structure consists of honeycomb pores arranged in a directional and regular pattern and stacked in layers. The gaps between adjacent pores and stacked layers form a multi-channel structure with continuous guidance. The preparation method of the bacterial cellulose-based aerogel for high-efficiency dust separation in dry filter dust collectors includes: S1. Preparation of bacterial cellulose: (a) Bacterial activation: inoculate Acetobacter xylinum or other bacteria into HS culture medium and culture in a constant temperature incubator at 30°C for 3-4 days to restore the activity of the bacteria; (b) Expansion culture: collect the Acetobacter xylinum colonies and transfer them to new HS culture medium in a certain proportion. Place the large-capacity beaker of HS culture medium containing the colonies in a constant temperature incubator and culture them in a static culture until the OD value of the culture reaches 0.6; (c) Fermentation of bacterial cellulose: transfer the Acetobacter xylinum culture medium that has completed the expansion culture to a fermenter and add deionized water. Connect the fermenter to a continuous fermentation system, control the temperature at 28-32°C, the pH at 6, the rotation speed at 100-200 r / min, and ensure the oxygen concentration in the tank. Continue stirring for 1 day. After fermentation is completed, a gel-like bacterial cellulose film is formed on the wall of the fermenter. After standing for 2 hours, the film is removed; S2. Bacterial cellulose purification: The removed bacterial cellulose membrane is repeatedly washed with deionized water to remove the culture medium and bacteria; the bacterial cellulose membrane is then placed in a 1% NaOH solution and heated to 80°C to repeatedly wash away residual proteins and other impurities on the surface; the washed bacterial cellulose membrane is then immersed in a prepared hydrogen peroxide solution, heated to 90°C, and slowly stirred for 1 hour before removal to remove organic impurities from the bacterial cellulose; finally, the bacterial cellulose membrane is rinsed with deionized water until neutral; the purified bacterial cellulose is crushed by a high-speed homogenizer to obtain bacterial cellulose suspensions of varying concentrations; S3. Preparation of bacterial cellulose-based gel: Deionized water was heated to 60°C in a water bath. Sodium alginate powder, bacterial cellulose suspension, and KH590 were then added in the appropriate proportions. Stirring was continued for 4 hours at a speed of 1000-1400 rpm to form a viscous gel. After ultrasonic dispersion, the gel was removed and aged in a refrigerator at 4°C for 2 hours to enhance mechanical properties and crosslinking strength. S4. Solvent replacement: Immerse the aged wet gel in anhydrous ethanol solution. After 4 hours, remove the supernatant and pour it into anhydrous ethanol again. Repeat 3-5 times. S5. Freeze-drying: Pour the wet gel after solution replacement into a customized mold and perform temperature-layered direction freezing. The aerogel is directionally frozen in three different layers to control the regional distribution of pore size. After the wet gel is directionally frozen for a certain period of time according to the prepared thickness, usually 10 minutes, it is taken out and placed in a refrigerator for further freezing. After 4 hours, it is taken out and placed in a freeze dryer and dried at -60°C and 1 Pa for 48 hours to obtain bacterial cellulose-based aerogel with directionally distributed pore size. Furthermore, the bacterial cellulose-based aerogel uses bacterial cellulose as its structural base, strengthens the skeleton by adding sodium alginate, enhances the cross-linking effect by adding a silane coupling agent, and undergoes hydrophobic modification, with a dynamic contact angle of 100°. KH590 cross-links only on the surface of the bacterial cellulose and sodium alginate complex. After the addition of sodium alginate and KH590, the aerogel crystal structure exhibits a more amorphous distribution, but the overall cellulose I-type crystal structure is still maintained. Furthermore, the HS culture medium uses carbon sources including but not limited to glucose and fructose, nitrogen sources including but not limited to yeast extract and peptone, disodium hydrogen phosphate and citric acid as buffers, and the rest are sodium chloride, calcium chloride, and ultrapure water; the pH needs to be adjusted to 6 before use, and sterilized at high temperature and high pressure; Furthermore, the continuous stirred fermentation system includes a fermentation tank, a stirring paddle, a pH sensor, a temperature sensor, an air inlet pipe, a liquid inlet pipe, an oxygen concentration sensor, etc., and the relevant sensors monitor the various fermentation parameters in the tank in real time to keep the fermentation parameters within the set range; the stirring paddle adopts a double-layer inclined paddle design, which can form an effective disturbance area to increase the contact surface between the bacterial liquid and oxygen; Furthermore, the concentration of the hydrogen peroxide solution used for bacterial cellulose membrane purification is generally 2-4 g / L; sodium silicate is added as a stabilizer to prevent hydrogen peroxide from decomposing too quickly; and the pH value is adjusted to 10-11 to obtain the best bleaching effect and reduce fiber damage; Furthermore, the skeleton strengthening component includes but is not limited to plant polysaccharides such as sodium alginate and konjac glucomannan, wherein the higher the polarity of the plant polysaccharide, the better the binding effect with bacterial cellulose; the cross-linking unit strengthening component includes but is not limited to silane coupling agent KH590, methyltrimethoxysilane, etc., wherein the higher the polarity of the silane, the better the surface cross-linking effect and the higher the filtration efficiency; Furthermore, the layered directional freezing method divides the freezing area into three layers by using baffles. The central area is frozen with liquid nitrogen, the middle area is frozen with ethanol, and the outermost layer is made of ice cubes made of clean water. Each layer uses a polytetrafluoroethylene material baffle. The lower the freezing temperature, the faster the ice crystals form, the smaller the diameter, and the smaller the pore size in the wet gel. Furthermore, the custom mold can be designed as required to include but not limited to a cylinder, with a bottom made of brass or other highly thermally conductive metals and surrounded by polytetrafluoroethylene for high stability and thermal insulation. The height usually determines the thickness of the aerogel. A smaller thickness results in a lower pressure drop but poorer filtration efficiency, so it is usually set to 1-3 mm. During directional freezing, it is placed on a layered annular freezing table, with the other side of the freezing table in contact with the low-temperature freezing liquid to achieve simultaneous layered freezing. Furthermore, the bacterial cellulose-based aerogel can not only be prepared by pore size zoning, but also by fixed pore size preparation at a fixed freezing temperature. In this case, only liquid nitrogen is used as the freezing liquid, which can achieve rapid freezing. After 10 minutes, it can be taken out and directly dried, which can be changed according to the dust concentration, dust type, and internal flow field characteristics of the dust collector.

2. The bacterial cellulose-based aerogel for filtration and dust removal and the preparation method thereof according to claim 1, characterized in that: The bacterial cellulose production strains include but are not limited to Acetobacter xylinum and Gluconoacetobacter; the bacterial cellulose is fermented through stirring, and its diameter is 50-70nm.

3. The bacterial cellulose-based aerogel for filtration and dust removal and the preparation method thereof according to claim 1, characterized in that: The oxygen concentration monitoring value of the continuous fermentation device is set to 15% saturation; after the fermentation is completed, the Acetobacter xylinum or other bacterial species used to produce bacterial cellulose can be reused by collecting the residual liquid at the bottom of the fermentation tank, continuing to inoculate the strain into it and replenishing the culture medium, which will help reduce costs.

4. The bacterial cellulose-based aerogel for filtration and dust removal and the preparation method thereof according to claim 1, characterized in that: The bacterial cellulose membrane is slightly transparent white, and its transparency will be further increased after purification.

5. The bacterial cellulose-based aerogel for filtration and dust removal and the preparation method thereof according to claim 1, characterized in that: The composition ratio of bacterial cellulose, sodium alginate and KH590 is usually 1:1.5:

1. The pore size can also be controlled by changing the composition ratio. The general trend is that the higher the sodium alginate concentration, the smaller the pore size. The pore size can usually be between 1 μm and 30 μm.

6. The bacterial cellulose-based aerogel for filtration and dust removal prepared according to claims 1-5, characterized in that: The bacterial cellulose-based aerogel can rebound to its original shape after being compressed to 20-80% of its volume for multiple times.

7. The bacterial cellulose-based aerogel for filtration and dust removal prepared according to claims 1-5, characterized in that: The bacterial cellulose-based aerogel can remain stable at a high temperature of 200° C., with a decomposition mass of less than 10%; and maintains internal channel flow when the humidity is less than 70% RH.

8. The bacterial cellulose-based aerogel for filtration and dust removal prepared according to claims 1-5, characterized in that: The bacterial cellulose-based aerogel has an initial filtration efficiency of over 99% for PM10 and over 98% for PM2.5 in a high-concentration dust environment. Moreover, the filtration efficiency only decreases by 1% after being cleaned and reused five times.

9. The bacterial cellulose-based aerogel for filtration and dust removal prepared according to claims 1-5, characterized in that: The bacterial cellulose-based aerogel has an area of degradation exceeding 50% after being embedded in soil for ten days, and has excellent biodegradability.

10. The bacterial cellulose-based aerogel for filtration and dust removal prepared according to claims 1-5, characterized in that: The main application steps of the bacterial cellulose-based aerogel include: a. Prepare the bacterial cellulose-based aerogel into a full-section filter membrane or an annular filter cartridge. For the full-section filter membrane, it is mounted directly on the rear section of the dust collector using a fixture to ensure that the entire section is covered by the aerogel. At this point, the filtration rate should be kept low. For the annular filter cartridge, it is fixed to a clamped polytetrafluoroethylene baffle, which is then connected to the inner wall of the dust collector. b. When the dust collector is in operation, if the internal flow field is swirling, the aerogel with fixed pore size is prepared; if the internal flow field is relatively stable, aerogel with fixed pore size is prepared as needed; c. Adjust the wind speed of the dust collector, and after running to the limit pressure drop, open the reverse blowing cleaning device to clean the dust and reuse it.

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