A silver nanowire / silk fibroin fiber / glass fiber composite filter paper, its preparation method and application

Abstract

This invention discloses a silver nanowire / silk fibroin fiber / glass fiber composite filter paper, its preparation method, and its application. The method includes: using natural silkworm cocoons as raw material, preparing multi-scale silk fibroin fibers from top to bottom using solvent and mechanical methods; preparing a silver nanowire / silk fibroin fiber composite material through electrostatic assembly between silver nanowires and silk fibroin fibers; and using glass fiber as a filter framework, preparing silver nanowire-multi-scale silk fibroin fiber / glass fiber air filter paper with silver nanowires / silk fibroin fibers through a wet papermaking process. The silver nanowire-multi-scale silk fibroin fiber / glass fiber air filter paper obtained by this invention has high strength, good toughness, and excellent antibacterial properties, and can form a spiderweb-like filter network, effectively filtering air pollutants such as fine particulate matter and bioaerosols.

Description

Technical Field

[0001] This invention relates to the field of air filtration, and in particular to a method for preparing and applying antibacterial air filtration filter paper. Background Technology

[0002] Glass fiber filter materials are widely used internationally as air filtration materials, with their main advantages including good moisture resistance, chemical resistance, heat resistance, high dust holding capacity, and resistance to bio-erosion. However, glass fiber also has some disadvantages, such as high brittleness, easy breakage, and poor flexibility. Furthermore, traditional glass fiber filter materials capture particles from polluted gases through their internally disordered fiber layers, but achieving a balance between filtration efficiency and pressure drop is difficult. To improve filtration efficiency, air permeability is often sacrificed, resulting in a significant pressure drop. Therefore, controlling the microstructure of glass fiber filter paper to simultaneously achieve good air resistance and filtration efficiency is currently a key technology and industry trend in the development of glass fiber air filter paper.

[0003] Multiscale silk fibroin fibers, as a fundamental component of natural silk fibers, possess not only the advantages of natural abundance and mechanical toughness, but also adjustable biodegradability and good biocompatibility, making them potential functional materials. Current reports often describe the complete dissolution of degummed silk fibroin fibers from natural silk cocoons to form regenerated multiscale silk fibroin fibers, inevitably sacrificing the natural properties of the original silk fibroin fibers. Another method involves dissolving silk fibroin fibers to prepare aerogels, but this method is limited by low porosity, weak resilience, and high brittleness. By maintaining the structural stability of silk fibroin fibers, exfoliating them into multiscale silk fibroin fibers using solvent and mechanical methods can preserve good mechanical strength and toughness. Compared to regenerated silk fibroin solutions, multiscale silk fibroin fibers exhibit good natural toughness and intact fiber shape. Therefore, utilizing multiscale silk fibroin fibers to control the micro-nanopore structure in glass fiber filter materials holds promise for improving their folding and abrasion resistance, achieving an effective balance between high filtration efficiency and pressure resistance, and extending the lifespan of the filter media.

[0004] In addition to organic pollutants and particulate matter, air also contains pathogenic bacteria, viruses, and other microorganisms. Filter media can intercept these microorganisms, which then accumulate on the media, feeding on other organic pollutants and forming colonies that can enter indoor spaces with the airflow, causing secondary pollution. Silver nanowires possess excellent broad-spectrum antibacterial properties. By electrostatically assembling silver nanowires with silk fibroin fibers, antibacterial properties can be effectively provided. Increasing fiber roughness can improve the filtration performance of the filter media without excessively affecting the material's air permeability. This study used a top-down method to prepare multi-scale silk fibroin fibers from natural silkworm cocoons and then electrostatically assembled them with silver nanowires to obtain silver nanowire / silk fibroin antibacterial nanofibers. Due to steric hindrance and hydrogen bonding, silver nanowire / silk fibroin antibacterial nanofibers spontaneously form a spiderweb-like entanglement structure with glass fibers. Therefore, silver nanowire / silk fibroin fibers impart strength to glass fiber filter media while achieving good flexibility and excellent antibacterial effects. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing silver nanowire / silk fibroin fiber / glass fiber composite filter paper and its application in air filtration.

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing an antibacterial air filter paper, specifically a silver nanowire / silk fibroin fiber / glass fiber composite filter paper with both filtration and antibacterial properties.

[0007] The present invention also aims to provide a method for preparing a silver nanowire / silk fibroin fiber / glass fiber composite filter paper and its application in air filtration. This preparation method uses a top-down approach to prepare multi-scale silk fibroin fibers from natural silkworm cocoons, which are then electrostatically assembled with silver nanowires to obtain silver nanowire-silk fibroin antibacterial nanofibers. Through steric hindrance and hydrogen bonding with glass fibers, a spiderweb-like entanglement structure is spontaneously formed, resulting in an antibacterial air filter paper with high filtration and antibacterial properties.

[0008] The objective of this invention is achieved by at least one of the following technical solutions.

[0009] This invention utilizes multi-scale silk fibroin fibers to prepare antibacterial air filter paper, and uses a wet papermaking process to prepare air filter paper with long-lasting antibacterial effect.

[0010] The present invention provides a silver nanowire / silk fibroin fiber / glass fiber composite filter paper and its preparation method. The method uses a top-down approach to prepare multi-scale silk fibroin fibers from natural silkworm cocoons, and then electrostatically assembles them with silver nanowires to obtain silver nanowire-silk fibroin antibacterial nanofibers. Through the spatial steric hindrance and hydrogen bonding between the nanofibers and glass fibers, a spider web-like entanglement structure is spontaneously formed, resulting in an antibacterial air filter paper with high filtration and antibacterial properties.

[0011] This invention provides a method for preparing silver nanowire / silk fibroin fiber / glass fiber composite filter paper, comprising the following steps:

[0012] (1) Wash, chop and degumme natural silkworm cocoons to obtain coarse silk fibroin fibers. Swell the obtained coarse silk fibroin fibers by solvent method, then crush them by mechanical method under alkaline conditions, and dialyze them with deionized water to obtain a multi-scale silk fibroin fiber dispersion.

[0013] (2) Using polypyrrolidone and ethylene glycol as template and reducing agent, polypyrrolidone was dissolved in ethylene glycol and silver nitrate was reduced under high temperature oil bath conditions. After being thoroughly washed with acetone, it was dispersed in deionized water to obtain silver nanowire solution.

[0014] (3) Under stirring conditions, the silver nanowire solution described in step 2 is added dropwise to the multi-scale silk fibroin fiber dispersion described in step 1, and the multi-scale silver nanowire / silk fibroin fiber dispersion is obtained by electrostatic assembly.

[0015] (4) Disperse glass fibers in an acidic aqueous solution to obtain a glass fiber aqueous dispersion. Add the multi-scale silver nanowire / silk fibroin fiber dispersion obtained in step 3 to the glass fiber aqueous dispersion and stir thoroughly to obtain a silver nanowire / silk fibroin fiber / glass fiber dispersion. Use this dispersion through a wet papermaking process to obtain silver nanowire / silk fibroin fiber / glass fiber antibacterial air filter paper.

[0016] Furthermore, in step (1), the cocoon fragments are approximately 1-2 cm in size, the sodium bicarbonate concentration used for degumming is 1%-2%, and the degumming time is 30-60 min.

[0017] Further, in step (1), the scale of the multi-scale silk fibroin fiber is 100nm-2μm; the alkaline condition is a 1%-5% sodium hydroxide solution; and the mechanical crushing time is 5min-30min.

[0018] Further, in step (1), the solvent method specifically involves preparing a ternary solution of water / anhydrous ethanol / calcium chloride with a molar ratio of 1:2:8 to 1:4:8, and immersing 2g to 4g of degummed silk fibroin fibers in the ternary solution for 24-48 hours to allow them to swell.

[0019] Further, in step (2), the mass percentage concentration of the silver nanowires is 1%-2%; the specific conditions of the high-temperature oil bath are 130-150℃; the concentration of polypyrrolidone in ethylene glycol is 1.0-8.0 g / L, and the concentration of silver nitrate in ethylene glycol is 5.0-10.0 g / L.

[0020] Further, in step (3), the amount of silver nanowire solution added and the amount of multi-scale silk fibroin fiber added are: the amount of silver nanowire solution added is 5-10 ml, and the amount of multi-scale silk fibroin fiber dispersion added is 50 mL-100 mL.

[0021] Furthermore, in step (4), the mass percentage concentration of the silver nanowires / silk fibroin fibers is between 10% and 20%.

[0022] Further, in step (4), the acidic aqueous solution is a 10%-20% sulfuric acid aqueous solution; the mass percentage concentration of the glass fiber aqueous dispersion is 0.05%-0.10%; the addition amount of the multi-scale silver nanowire / silk fibroin fiber and the glass fiber aqueous dispersion satisfies the following: the mass ratio between the multi-scale silver nanowire / silk fibroin fiber and the glass fiber aqueous dispersion is 10%-20%; and the drying temperature of the wet drying process is 90℃-95℃.

[0023] This invention provides an antibacterial air filter paper made of silver nanowires / silk fibroin fiber / glass fiber by the above preparation method. It can effectively filter out 99% of PM2.5, bacteria and other air pollutants, and can kill bacteria to prevent bacteria from multiplying on the filter paper and causing secondary pollution.

[0024] This invention provides an antibacterial air filter paper made of silver nanowires / silk fibroin fibers / glass fibers by the above preparation method, which can meet the requirements of antibacterial air filter paper.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The silk fibroin fiber used in this invention is safe and non-toxic, and has good biocompatibility and biodegradability;

[0027] (2) The present invention uses a top-down method to prepare silk fibers from natural silkworm cocoons into multi-scale silk fibroin fibers, and electrostatically assembles them with silver nanowires to obtain silver nanowire-silk fibroin antibacterial nanofibers. Through the spatial steric hindrance and hydrogen bonding between the nanofibers and glass fibers, a spider web-like entanglement structure is spontaneously formed to obtain antibacterial air filter paper with high filtration performance and antibacterial properties.

[0028] (3) The preparation method of the present invention is simple and easy to operate, with low energy consumption, which is conducive to large-scale industrial production;

[0029] (4) The silver nanowire / silk fibroin fiber / glass fiber antibacterial air filter paper prepared by the present invention can effectively filter out 99% of PM2.5, bacteria and other air pollutants, and can prevent secondary pollution. Attached Figure Description

[0030] Figure 1 Example 2 is an electron microscope image of silver nanowires / silk fibroin fibers / glass fibers.

[0031] Figure 2 The diagram shows the antibacterial effects of glass fiber, silk fibroin / glass fiber obtained in Example 4, and silver nanowire / silk fibroin / glass fiber on Escherichia coli.

[0032] Figure 3 The diagram shows the antibacterial effects of glass fiber, silk fibroin / glass fiber obtained in Example 4, and silver nanowire / silk fibroin / glass fiber on Staphylococcus aureus. Detailed Implementation

[0033] The specific implementation of the present invention will be further described below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0034] Example 1

[0035] A method for preparing a silver nanowire / silk fibroin fiber / glass fiber composite filter paper includes the following steps:

[0036] (1) Wash natural silkworm cocoons, chop them into pieces of 1-2 cm, degumm them for 0.5 h to obtain crude silk fibroin fibers. The obtained crude silk fibroin fibers are then subjected to solvent method, i.e., by preparing a ternary solution with a molar ratio of 1:2:8 (water / anhydrous ethanol / calcium chloride), 2 g of the degummed silk fibroin fibers are soaked in the ternary solution and soaked for 24 hours to swell. Then, under alkaline conditions of pH 9.0, they are mechanically crushed for 10 min and dialyzed with deionized water to obtain 4 wt% multiscale silk fibroin fibers.

[0037] (2) Reduce 0.1 g silver nitrate in a 1.6 g / L polypyrrolidone glycol solution under an oil bath at 130 °C. After washing thoroughly with acetone, disperse the solution in 10 mL of deionized water to obtain a 2 wt% silver nanowire solution.

[0038] (3) Under stirring conditions, the 2wt% silver nanowire solution described in step 2 is added dropwise to the 50mL multiscale silk fibroin fiber described in step 1 containing 4wt% silver nanowire / silk fibroin fiber, and multiscale silver nanowire / silk fibroin fiber is obtained by electrostatic assembly.

[0039] (4) Disperse 2.5g of glass fiber in water to obtain a glass fiber aqueous dispersion. Add the multi-scale silver nanowires / silk fibroin fibers with a solid content of 0.3g by weight described in step 3 to the glass fiber aqueous dispersion and stir thoroughly to obtain a silver nanowire / silk fibroin fiber / glass fiber dispersion. Use this dispersion to obtain silver nanowire / silk fibroin fiber / glass fiber antibacterial air filter paper (drying temperature at 90-95℃) through a wet papermaking process.

[0040] Example 2

[0041] A method for preparing a silver nanowire / silk fibroin fiber / glass fiber composite filter paper includes the following steps:

[0042] (1) Wash and chop natural silkworm cocoons, degummed for 0.5 h to obtain crude silk fibroin fibers. The obtained crude silk fibroin fibers are then subjected to solvent method, i.e., by preparing a ternary solution with a molar ratio of 1:2:8 (water / anhydrous ethanol / calcium chloride), 2 g of degummed silk fibroin fibers are soaked in the ternary solution and soaked for 24 hours to swell. Then, under alkaline conditions of pH 9.0, they are mechanically crushed for 15 min and dialyzed with deionized water to obtain 4 wt% multiscale silk fibroin fibers.

[0043] (2) 0.3 g silver nitrate was reduced in a 3.2 g / L polypyrrolidone glycol solution under an oil bath at 130 °C. After being thoroughly washed with acetone, the solution was dispersed in 10 mL of deionized water to obtain a 2 wt% silver nanowire solution.

[0044] (3) Under stirring conditions, the 2wt% silver nanowire solution described in step 2 is added dropwise to the 50mL multiscale silk fibroin fiber described in step 1 containing 4wt% silver nanowire / silk fibroin fiber, and multiscale silver nanowire / silk fibroin fiber is obtained by electrostatic assembly.

[0045] (4) Disperse 2.4g of glass fiber in water to obtain a glass fiber aqueous dispersion. Add the 0.4g multi-scale silver nanowires / silk fibroin fibers (by weight) from step 3 to the glass fiber aqueous dispersion and stir thoroughly to obtain a silver nanowire / silk fibroin fiber / glass fiber dispersion. Use this dispersion through a wet papermaking process to obtain silver nanowire / silk fibroin fiber / glass fiber antibacterial air filter paper (drying temperature at 90-95℃). Figure 1 Electron microscopy reveals that silver nanowires / silk fibroin fibers / glass fibers form an interwoven fiber network with glass fibers.

[0046] Example 3

[0047] A method for preparing a silver nanowire / silk fibroin fiber / glass fiber composite filter paper includes the following steps:

[0048] (1) Wash and chop natural silkworm cocoons, degummed for 0.5 h to obtain crude silk fibroin fibers. The obtained crude silk fibroin fibers are then subjected to solvent method, i.e., by preparing a ternary solution with a molar ratio of 1:2:8 (water / anhydrous ethanol / calcium chloride), 2 g of degummed silk fibroin fibers are soaked in the ternary solution and soaked for 24 hours to swell. Then, under alkaline conditions of pH 9, they are mechanically crushed for 20 min and dialyzed with deionized water to obtain 6 wt% multiscale silk fibroin fibers.

[0049] (2) Reduce 0.5 g silver nitrate in a 4.8 g / L polypyrrolidone glycol solution under an oil bath at 130 °C. After washing thoroughly with acetone, disperse the solution in 10 mL of deionized water to obtain a 3 wt% silver nanowire solution.

[0050] (3) Under stirring conditions, the 3 wt% silver nanowire solution described in step 2 is added dropwise to the 50 mL multiscale silk fibroin fiber containing 6 wt% described in step 1, and multiscale silver nanowire / silk fibroin fiber is obtained by electrostatic assembly.

[0051] (4) Disperse 2.3g of glass fiber in water to obtain a glass fiber aqueous dispersion. Add the 0.5g multi-scale silver nanowires / silk fibroin fibers with a solid content obtained in step 3 to the glass fiber aqueous dispersion and stir thoroughly to obtain a silver nanowire / silk fibroin fiber / glass fiber dispersion. Use this dispersion to obtain silver nanowire / silk fibroin fiber / glass fiber antibacterial air filter paper (drying temperature at 90-95℃) through a wet papermaking process.

[0052] Example 4

[0053] A method for preparing a silver nanowire / silk fibroin fiber / glass fiber composite filter paper includes the following steps:

[0054] (1) Wash and chop natural silkworm cocoons, degummed for 0.5 h to obtain crude silk fibroin fibers. The obtained crude silk fibroin fibers are then subjected to solvent method, i.e., by preparing a ternary solution with a molar ratio of 1:2:8 (water / anhydrous ethanol / calcium chloride), 2 g of degummed silk fibroin fibers are soaked in the ternary solution and soaked for 24 hours to swell. Then, under alkaline conditions of pH 9.0, they are mechanically crushed for 25 min and dialyzed with deionized water to obtain 8 wt% multiscale silk fibroin fibers.

[0055] (2) 0.6 g silver nitrate was reduced in a 6.4 g / L polypyrrolidone glycol solution under an oil bath at 130 °C. After being thoroughly washed with acetone, the solution was dispersed in 10 mL of deionized water to obtain a 4 wt% silver nanowire solution.

[0056] (3) Under stirring conditions, the 4 wt% silver nanowire solution described in step 2 is added dropwise to the 50 mL multiscale silk fibroin fiber containing 8 wt% described in step 1, and multiscale silver nanowire / silk fibroin fiber is obtained by electrostatic assembly.

[0057] (4) Disperse 2.2g of glass fiber in water to obtain a glass fiber aqueous dispersion. Add the 0.6g (by weight) multi-scale silver nanowires / silk fibroin fibers from step 3 to the glass fiber aqueous dispersion and stir thoroughly to obtain a silver nanowire / silk fibroin fiber / glass fiber dispersion. Use this dispersion through a wet papermaking process to obtain silver nanowire / silk fibroin fiber / glass fiber antibacterial air filter paper (drying temperature at 90-95℃). Figure 2 , Figure 3 The antibacterial effect of the silver nanowire / silk fibroin fiber / glass fiber antibacterial air filter paper on Escherichia coli and Staphylococcus aureus is shown, indicating that the prepared antibacterial air filter paper has excellent antibacterial effect on Escherichia coli and Staphylococcus aureus.

[0058] Example 5

[0059] A method for preparing a silver nanowire / silk fibroin fiber / glass fiber composite filter paper includes the following steps:

[0060] (1) Wash and chop natural silkworm cocoons, degumming for 0.5 h to obtain crude silk fibroin fibers. The obtained crude silk fibroin fibers are then subjected to solvent method, i.e., by preparing a ternary solution with a molar ratio of 1:2:8 (water / anhydrous ethanol / calcium chloride), 2 g of the degummed silk fibroin fibers are soaked in the ternary solution and soaked for 24 hours to swell. Then, under alkaline conditions of pH 9, they are mechanically crushed for 30 min and dialyzed with deionized water to obtain 10 wt% multiscale silk fibroin fibers.

[0061] (2) 0.7 g silver nitrate was reduced in 8.0 g / L polypyrrolidone glycol solution under oil bath conditions at 130 °C. After being thoroughly washed with acetone, the solution was dispersed in 10 mL of deionized water to obtain a 5 wt% silver nanowire solution.

[0062] (3) Under stirring conditions, the 5 wt% silver nanowire solution described in step 2 is added dropwise to the 50 mL multiscale silk fibroin fiber described in step 1 containing 10 wt% silver nanowire / silk fibroin fiber, and multiscale silver nanowire / silk fibroin fiber is obtained by electrostatic assembly.

[0063] (4) Disperse 2.1g of glass fiber in water to obtain a glass fiber aqueous dispersion. Add the 0.7g multi-scale silver nanowires / silk fibroin fibers with a solid content obtained in step 3 to the glass fiber aqueous dispersion and stir thoroughly to obtain a silver nanowire / silk fibroin fiber / glass fiber dispersion. Use a wet papermaking process to obtain silver nanowire / silk fibroin fiber / glass fiber antibacterial air filter paper (drying temperature at 90-95℃).

[0064] The above embodiments are merely preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a silver nanowire / silk fibroin fiber / glass fiber composite filter paper, characterized in that, Includes the following steps: (1) Wash, chop, and degumme natural silkworm cocoons to obtain coarse silk fibroin fibers. Soak the obtained coarse silk fibroin fibers in a solvent method, then break them under alkaline conditions and dialyze them with deionized water to obtain multi-scale silk fibroin fibers. The scale of the multi-scale silk fibroin fibers is 100nm-2μm. The solvent method is as follows: prepare a ternary solution of water / anhydrous ethanol / calcium chloride with a molar ratio of 1:2:8 to 1:4:8, take 2g to 4g of degummed coarse silk fibroin fibers and soak them in the ternary solution for 24-48 hours to swell. (2) Under the conditions of an oil bath at 130-150℃, polypyrrolidone and ethylene glycol were used as templates and reducing agents to reduce silver nitrate. After being thoroughly washed with acetone, the solution was dispersed in deionized water to obtain a silver nanowire solution. (3) Under stirring conditions, the silver nanowire solution obtained in step (2) is added dropwise to the multi-scale silk fibroin fiber dispersion obtained in step (1), and the multi-scale silver nanowire / silk fibroin fiber dispersion is obtained by electrostatic assembly. (4) Disperse glass fibers in water to obtain a glass fiber aqueous dispersion. Add the multi-scale silver nanowire / silk fibroin fiber dispersion obtained in step (3) to the glass fiber aqueous dispersion and stir thoroughly to obtain a silver nanowire / silk fibroin fiber / glass fiber dispersion. Use the silver nanowire / silk fibroin fiber / glass fiber dispersion to obtain silver nanowire / silk fibroin fiber / glass fiber composite filter paper through a wet papermaking process.

2. The method for preparing the silver nanowire / silk fibroin fiber / glass fiber composite filter paper according to claim 1, characterized in that, In step (1), the silkworm cocoons are chopped into pieces of 1-2 cm, the sodium bicarbonate used for degumming has a mass percentage concentration of 1%-2%, and the degumming time is 30-60 min.

3. The method for preparing the silver nanowire / silk fibroin fiber / glass fiber composite filter paper according to claim 1, characterized in that, In step (1), the mechanical crushing time is 5 min to 30 min.

4. The method for preparing the silver nanowire / silk fibroin fiber / glass fiber composite filter paper according to claim 1, characterized in that, In step (2), the mass percentage concentration of the silver nanowires is 1%-2%; the concentration of the polypyrrolidone in ethylene glycol is 1.0-8.0 g / L, and the concentration of silver nitrate in ethylene glycol is 5.0-10.0 g / L.

5. The method for preparing the silver nanowire / silk fibroin fiber / glass fiber composite filter paper according to claim 1, characterized in that, In step (3), the amount of silver nanowire solution added and the amount of multi-scale silk fibroin fiber added are: the amount of silver nanowire solution added is 5-10 ml, and the amount of multi-scale silk fibroin fiber dispersion added is 50 mL-100 mL.

6. The method for preparing the silver nanowire / silk fibroin fiber / glass fiber composite filter paper according to claim 1, characterized in that, In step (4), the mass percentage concentration of the silver nanowires / silk fibroin fibers is between 10% and 20%.

7. The method for preparing the silver nanowire / silk fibroin fiber / glass fiber composite filter paper according to claim 1, characterized in that, In step (4), the mass percentage concentration of the glass fiber aqueous dispersion is 0.05%-0.10%; the amount of multi-scale silver nanowires / silk fibroin fibers added to the glass fiber aqueous dispersion satisfies the following: the mass ratio between the multi-scale silver nanowires / silk fibroin fibers and the glass fiber aqueous dispersion is 10%-20%; and the drying temperature of the wet drying process is 90℃-95℃.

8. The silver nanowire / silk fibroin fiber / glass fiber composite filter paper prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The filter paper can effectively filter out 99% of PM2.5 and bacterial air pollutants, and can kill bacteria to prevent bacteria from multiplying on the filter paper and causing secondary pollution.

9. The silver nanowire / silk fibroin fiber / glass fiber composite filter paper of claim 8 is used for air filtration.

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