CN115178105A - Long-acting filtering membrane with uniformly distributed biological electrets on polylactic acid nanofiber surface and preparation method thereof - Google Patents

Abstract

The invention discloses a long-acting filter membrane in which biological electrets are evenly distributed on the surface of polylactic acid nanofibers and a preparation method thereof. The biological electret material is efficiently synthesized and evenly distributed on the surface of polylactic acid nanofibers, thereby comprehensively improving the The technical scheme of mechanical properties, surface potential and air filtration efficiency, the biological electret material is hydroxyapatite nanowhisker synthesized by microwave-assisted biomimetic mineralization, surface activation and high dispersibility are obtained by plasma treatment, and then mist It is synthesized and deposited on the surface of synchronous electrospinning polylactic acid nanofibers, and finally a fully degradable nanofiber membrane with high surface potential, high mechanical properties, high filtration efficiency and long-term filtration is obtained. The method can well control the microstructure of the biological electret, inhibit the self-agglomeration of the nano-scale electret or local agglomeration during the molding process, so as to ensure the good processability of the electrospinning polylactic acid fiber film and improve the fiber film's performance. Surface potential, filtration properties and mechanical properties.

Description

A long-term filter membrane with biological electrets uniformly distributed on the surface of polylactic acid nanofibers and preparation method thereof

technical field

The invention relates to the technical field of functional materials, in particular to a long-acting filter membrane in which biological electrets are evenly distributed on the surface of polylactic acid nanofibers and a preparation method thereof.

Background technique

Air pollution is a long-term global problem that endangers the atmospheric environment and human health, and air filtration is a key and effective way to improve air quality. Nanofiber-based filtration media have the advantages of small diameter, high specific surface area, and high porosity, which improve the durability of filtration mainly through physical sieving, and have been widely used in the field of air filtration. One of the most typical technologies for producing nanofibers is electrospinning, and large-scale industrial production has been achieved. However, traditional electrospun polymer materials are difficult to degrade in nature, posing a huge challenge to environmental protection. As a new bio-based degradable material, polylactic acid has excellent properties such as high mechanical properties, good biocompatibility and biodegradability, and has shown a good application prospect in the field of air filter materials to replace traditional polymer materials.

Ordinary fiber filter materials mainly rely on mechanical interception such as Brownian diffusion, interception, inertial collision, and gravity sedimentation to filter particles in the air, but the filtering effect of sub-micron particles is not ideal. Therefore, an electret is often added to the fiber, which not only provides a general mechanical interception effect, but also uses the Coulomb force generated by its own charge to capture particles, and the filtration efficiency is much higher than that of ordinary fibers, especially in filtering sub-micron. It is more obvious when the particles are graded.

Commonly used electret materials are divided into two categories: inorganic and organic: inorganic electret materials include tourmaline, magnets, inorganic silicon, etc., which have problems of poor application effect and high cost; organic electret materials include plexiglass , high-molecular polymers, etc., face the problems of difficult degradation and serious decay of stored charge. As natural bio-electret materials, materials such as bone and protein can maintain a polarized or charged state for a long time. Therefore, high-charge-storage bio-electret materials with excellent biocompatibility and friendliness to the human body and the environment are urgently needed.

Hydroxyapatite is the main inorganic component of human and animal bones. It can achieve chemical bonding with body tissues at the interface, has a certain solubility in the body, can release ions that are harmless to the body and participate in body metabolism. It has excellent properties. Biocompatibility and Bioactivity. Under different conditions, its crystals are granular, fibrous, needle-like or fibrous aggregates, with diameters as low as several nanometers and lengths up to several millimeters. The higher ionic activity endows the hydroxyapatite with good polarization potential, which facilitates the implementation of a fast and simple electret effect, resulting in a higher surface potential and filtration effect.

Therefore, to provide a bio-electret that is uniformly introduced into the polylactic acid electrospinning nanofiber membrane by atomization and deposition, so as to realize the high performance and multifunctionalization of the fully degradable nanofiber membrane on the surface of the polylactic acid nanofiber The uniform distribution of long-term filter membrane and its preparation method is a problem worthy of study.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a kind of bio-electret which is uniformly introduced into polylactic acid electrospinning nanofiber membrane by means of atomization and deposition, so as to realize the high performance and multifunctionalization of fully degradable nanofiber membrane in polylactic acid. A long-term filter membrane with uniform distribution on the surface of nanofibers and a preparation method thereof.

The object of the present invention is achieved in this way:

A long-term filtration membrane in which biological electrets are evenly distributed on the surface of polylactic acid nanofibers, including a polylactic acid fiber membrane, the surface of the polylactic acid nanofiber membrane is evenly distributed with biological electrets, and biological electrets are evenly distributed on the surface of the polylactic acid nanofibers. The electret content is 0.05-30 wt %, and the biological electret is a hydroxyapatite nanowhisker synthesized by microwave-assisted biomimetic mineralization.

The diameter of the hydroxyapatite nanowhisker is 1-20 nm, and the aspect ratio of the hydroxyapatite nanowhisker is 5-200.

The thickness of the polylactic acid fiber film is 40-800 μm, and the diameter of the nanofibers in the polylactic acid fiber film is 5-100 nm.

A preparation method of a long-term filtration membrane in which biological electrets are evenly distributed on the surface of polylactic acid nanofibers, comprising the following steps:

S1. Preparation of hydroxyapatite nanowhiskers: add water-soluble calcium salt, water-soluble phosphate and template agent into water, stir and dissolve evenly, put it into a microwave reactor, and conduct microwave-assisted biomimetic mineralization under stirring chemical reaction, and cooling after the reaction finishes to obtain an aqueous solution deposited with hydroxyapatite nanowhiskers;

S2. Preparation of hydroxyapatite nanowhisker dispersion: using plasma equipment to directly process the hydroxyapatite nanowhisker aqueous solution obtained in step S1 to obtain a hydroxyapatite nanowhisker dispersion;

S3. Preparation of polylactic acid nanofiber membrane with uniform distribution of biological electrets: polylactic acid dissolved in organic solvent is prepared by electrospinning technology to prepare nanofiber membrane, and the step of atomization is applied during the spinning process. S2 hydroxyapatite The nano-whisker dispersion liquid is obtained to obtain a polylactic acid nanofiber membrane with a uniform distribution of biological electrets.

In the step S1, the water-soluble calcium salt is at least one of calcium chloride, calcium nitrate, calcium acetate, and calcium hypochlorite, and the concentration of the water-soluble calcium salt is 0.01 to 2 mol/liter; the water-soluble phosphate is phosphoric acid At least one of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and the molar ratio of calcium ion to phosphate ion is 2:1~1:1 ; The plate agent is at least one of cetyltrimethylammonium bromide, stearic acid, oleic acid, sodium lauryl sulfate, sodium dodecylbenzenesulfonate and octylphenyl polyoxyethylene ether, The mass fraction of the template agent in the solution is 0.001 wt %~0.1 wt %, which can act as a structure directing agent to grow hydroxyapatite into rod-like one-dimensional nanowhiskers along the c-axis.

In the step S1, the reaction temperature of the microwave-assisted synthesis is 100-250 °C, and the reaction time is 1-30 minutes; the diameter of the hydroxyapatite nanowhisker obtained in the step S1 is 1-20 nm, and the aspect ratio is 5-200.

In the step S2, the plasma processing equipment is at least one of the normal pressure jet type, the dielectric barrier discharge type, and the rotary type normal pressure type, the plasma discharge voltage is 1-80 kV, and the plasma working gas is argon. , at least one of helium, hydrogen, nitrogen, and oxygen, and the treatment temperature is 10 to 50 °C, and the treatment temperature is 10 seconds to 30 minutes.

In the step S3, the organic solvent is at least one of methylene chloride, trichloromethane, dimethylformamide, N-methylpyrrolidone, hexafluoroisopropanol, methanol, ethanol, isopropanol, and glycerol , the polylactic acid concentration in the mixed solution was 0.5-22 wt %; the electrospinning module voltage was 15-60 kV, the receiving voltage was –15-0 kV, and the spinning dope consumption rate was 1-60 mL/min.

In the step S3, the atomization speed of the bio-electret is 0.5-50 mL/min, the diameter of the obtained bio-electret-modified polylactic acid nanofiber is 5-100 nm, and the bio-electret in the polylactic acid nanofiber has a diameter of 5-100 nm. The content is 0.05-30 wt %, and the thickness of the obtained PLA fiber film is 40-800 μm.

The beneficial effects of the present invention are as follows: the present invention proposes a technical route for efficiently synthesizing biological electrets with high surface activity, high dispersibility and uniform distribution on the fiber surface, in order to improve the surface potential and electrostatic adsorption of polylactic acid nanofiber membranes The effect provides a new way to help expand the application and development of degradable polymer materials in the field of long-term air filter materials.

Description of drawings

Fig. 1 is the flow chart of the present invention;

Fig. 2 is the hydroxyapatite nanowhisker morphology of the plasma treatment solution observed in Example 1 by transmission electron microscope of the present invention;

Fig. 3 is the image of commercially available conventional hydroxyapatite in comparative example 1 observed by scanning electron microscope of the present invention;

Fig. 4 is the image of the polylactic acid fiber film obtained in Example 1 observed by scanning electron microscope of the present invention;

5 is an image of the polylactic acid fiber membrane obtained in Comparative Example 1 observed by a scanning electron microscope of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Example 1:

As shown in Figure 1, a long-term filtration membrane in which biological electrets are uniformly distributed on the surface of polylactic acid nanofibers and a preparation method thereof, comprising the following steps:

S1. Preparation of hydroxyapatite nanowhiskers: add calcium chloride (0.01 mol/L), ammonium dihydrogen phosphate (0.01 mol/L) and stearic acid (0.001 wt %) into water, mix well, put In the microwave reaction kettle, in a stirring state, the temperature is raised to 250 ° C, the reaction is performed for 1 minute, and the reaction is cooled to obtain an aqueous solution with hydroxyapatite nanowhiskers deposited;

S2. Preparation of hydroxyapatite nanowhisker dispersion: Using dielectric barrier discharge plasma equipment (working voltage 1 kV, working gas is argon/nitrogen gas mixture, temperature 15~30 ℃), the aqueous solution obtained from S1 was treated for 30 minutes to obtain a hydroxyapatite nanowhisker dispersion;

S3. Preparation of polylactic acid nanofiber membrane with uniform distribution of biological electrets: polylactic acid was dissolved in dichloromethane/N-methylpyrrolidone (mass ratio 7:3) as a spinning dope, and electrospinning technology ( The module voltage was 20 kV, the receiving voltage was –15 kV, and the consumption rate of the stock solution was 0.5 mL/min) to prepare nanofibers, while the dispersion obtained from S2 was atomized (speed 0.5 mL/min) until the bioelectret content reached 0.05 wt % , the fiber membrane thickness reaches 800 μm.

Example 2

A long-acting filter membrane in which biological electrets are evenly distributed on the surface of polylactic acid nanofibers and a preparation method thereof, comprising the following steps:

S1. Preparation of hydroxyapatite nanowhiskers: calcium nitrate (2 mol/L), disodium hydrogen phosphate (1 mol/L) and oleic acid (0.1 wt %) were added to water, mixed well, and placed in a microwave reaction In the kettle, under stirring, the temperature was raised to 100° C., reacted for 30 minutes, and cooled after the reaction to obtain an aqueous solution deposited with hydroxyapatite nanowhiskers;

S2. Preparation of hydroxyapatite nanowhisker dispersion: using a rotary atmospheric pressure plasma equipment (working voltage 80 kV, working gas argon, temperature 25-35 °C), the aqueous solution obtained in S21 was treated for 10 minutes to obtain Hydroxyapatite nanowhisker dispersion;

S3. Preparation of polylactic acid nanofiber membrane with uniform distribution of biological electrets: polylactic acid was dissolved in chloroform/dimethylformamide (mass ratio 6:4) as a spinning dope, and electrospinning technology ( The module voltage was 60 kV, the receiving voltage was 0 kV, and the stock solution consumption rate was 60 mL/min) to prepare nanofibers. At the same time, the dispersion obtained from S22 was atomized (speed 50 mL/min) until the bioelectret content reached 30 wt %, and the fibers The film thickness reaches 40 μm.

Example 3

As shown in Figure 1, a long-acting filtration membrane in which biological electrets are uniformly distributed on the surface of polylactic acid nanofibers and a preparation method thereof, comprising the following steps:

S1. Preparation of hydroxyapatite nanowhiskers: add calcium acetate (0.05 mol/L), potassium dihydrogen phosphate (0.04 mol/L) and cetyltrimethylammonium bromide (0.01 wt%) into water and mix well Then, it was placed in a microwave reactor, heated to 150° C. under stirring, and reacted for 15 minutes, and cooled after the reaction to obtain an aqueous solution deposited with hydroxyapatite nanowhiskers;

S2. Preparation of hydroxyapatite nanowhisker dispersion: Using atmospheric jet plasma equipment (working voltage 20 kV, working gas argon, temperature 25-50 °C), the aqueous solution obtained in S1 was treated for 30 minutes to obtain hydroxyl groups Apatite nanowhisker dispersion;

S3. Preparation of polylactic acid nanofiber membrane with uniform distribution of biological electrets: polylactic acid was dissolved in dimethylformamide/hexafluoroisopropanol (mass ratio 5:5) as a spinning dope, and electrospinned by electrospinning Technology (module voltage 40 kV, receiving voltage –10 kV, stock solution consumption rate 30 mL/min) to prepare nanofibers, while the dispersion obtained from S2 was atomized (speed 30 mL/min) until the biological electret content reached 10 wt %, and the thickness of the fiber membrane reaches 80 μm.

Example 4

A long-acting filter membrane in which biological electrets are evenly distributed on the surface of polylactic acid nanofibers and a preparation method thereof, comprising the following steps:

S1. Preparation of hydroxyapatite nanowhiskers: calcium hypochlorite (0.2 mol/L), ammonium hydrogen phosphate (0.15 mol/L) and octylphenylethoxylate (0.05 wt%) were added to water, mixed After homogeneous, put it into a microwave reactor, under stirring, heat up to 200 ° C, react for 5 minutes, and cool down after the reaction to obtain an aqueous solution with hydroxyapatite nanowhiskers deposited;

S2. Preparation of hydroxyapatite nanowhisker dispersion: Using dielectric barrier discharge plasma equipment (working voltage 40 kV, working gas is argon/nitrogen gas mixture, temperature 20~40 °C), the aqueous solution obtained from S1 was treated for 15 minutes to obtain a hydroxyapatite nanowhisker dispersion;

S3. Preparation of polylactic acid nanofiber membrane with uniform distribution of biological electrets: polylactic acid was dissolved in N-methylpyrrolidone/dimethylformamide (mass ratio 7:3) as a spinning dope, and electrospinned by electrospinning Technology (module voltage 35 kV, receiving voltage 0 kV, stock solution consumption rate 20 mL/min) to prepare nanofibers, while the dispersion obtained from S2 was atomized (speed 10 mL/min) until the biological electret content reached 15 wt %, and the thickness of the fiber membrane reaches 100 μm.

Example 5

A long-acting filter membrane in which biological electrets are evenly distributed on the surface of polylactic acid nanofibers and a preparation method thereof, comprising the following steps:

S1. Preparation of hydroxyapatite nanowhiskers: add calcium acetate (0.8 mol/L), ammonium dihydrogen phosphate (0.5 mol/L) and sodium dodecylbenzenesulfonate (0.08 wt %) into water and mix well Then, put it into a microwave reaction kettle, and under stirring, the temperature was raised to 140° C., reacted for 20 minutes, and cooled after the reaction was completed to obtain an aqueous solution deposited with hydroxyapatite nanowhiskers;

S2. Preparation of hydroxyapatite nanowhisker dispersion: Using dielectric barrier discharge plasma equipment (working voltage 10 kV, working gas is helium, temperature 20-30 °C), the aqueous solution obtained in S1 was treated for 25 minutes to obtain hydroxyl groups Apatite nanowhisker dispersion;

S3. Preparation of polylactic acid nanofiber membrane with uniform distribution of biological electrets: polylactic acid was dissolved in dichloromethane/hexafluoroisopropanol (mass ratio 9:1) as a spinning dope, and electrospinning technology ( The module voltage was 45 kV, the receiving voltage was 0 kV, and the stock solution consumption rate was 20 mL/min) to prepare nanofibers, and the dispersion obtained from S2 was atomized at the same time (speed 15 mL/min) until the biological electret content reached 18 wt %. The film thickness reaches 500 μm.

Comparative example 1 (adding conventional hydroxyapatite filler)

The method of Example 1 was basically used to prepare the hydroxyapatite dispersion and the polylactic acid fiber membrane. The difference is that this example does not use the hydroxyapatite nanowhisker synthesized by the microwave-assisted biomimetic mineralization method, but adds commercially available hydroxyapatite powder (purity 99%, average diameter 2 nm, Xi'an Tongze Biotechnology). Ltd). Specifically, after directly stirring and dispersing the hydroxyapatite powder in water, a dielectric barrier discharge plasma equipment (working voltage of 1 kV, working gas of argon/nitrogen gas mixture, temperature of 15-30 °C) was used for 30 minutes. , to obtain a stably dispersed aqueous solution; polylactic acid was dissolved in dichloromethane/N-methylpyrrolidone (mass ratio 7:3) as a spinning dope, and electrospinning technology (module voltage 20 kV, receiving voltage –15 At the same time, the dispersion of hydroxyapatite was atomized (speed 0.5 mL/min) until the content of hydroxyapatite reached 0.05 wt % and the thickness of the fiber film reached 0.05 wt %. 800 μm.

Comparative Example 2 (without using plasma treatment technology to disperse the biological electret)

Basically, the method of Example 2 was used to prepare biological electret and polylactic acid nanofiber membrane. The difference is that this example does not use plasma treatment technology to disperse hydroxyapatite nanowhiskers. Specifically, polylactic acid was dissolved in chloroform/dimethylformamide (mass ratio 6:4) as a spinning dope solution, and electrospinning technology (module voltage 60 kV, receiving voltage 0 kV, dope consumption rate 60 mL/min) to prepare nanofibers, while the dispersion obtained from S21 was atomized (speed 50 mL/min) until the bioelectret content reached 30 wt % and the fiber film thickness reached 40 μm.

Comparative Example 3 (without adding biological electret)

The polylactic acid nanofiber membrane was basically prepared by the method of Example 3, except that no electret was added in this example. Specifically, polylactic acid was dissolved in dimethylformamide/hexafluoroisopropanol (mass ratio 5:5) as a spinning dope, and electrospinning technology (module voltage 40 kV, receiving voltage -10 kV, The stock solution consumption rate was 30 mL/min) to prepare nanofibers until the thickness of the fiber membrane reached 80 μm.

Structural Characterization and Performance Testing

Transmission electron microscope observation: The microstructure and dispersed morphology of plasma-treated hydroxyapatite nanowhiskers were observed using a transmission electron microscope (model Hitachi HT7700, Hitachi Electronics, Japan) (Fig. 2).

Scanning electron microscope observation: The microstructure of commercially available conventional hydroxyapatite nanoparticles (Fig. 3), and the microstructure of the polylactic acid fiber film (Fig. 4) were observed by a field emission scanning electron microscope (model JSM-7900F, JEOL). and 5).

Tensile property test: The obtained fiber film was cut out to obtain a tensile spline, according to the plastic tensile property test standard in ASTM D638-2003 of the American Society for Testing and Materials, using a universal tensile machine (model 4403, sensor 100 from Instron, USA) N) Testing the tensile properties of the composites. At least 3 parallel test samples are guaranteed for each group, and the average value of the results is taken.

Surface potential test: A non-contact electrostatic meter (VM54XQS, Quatek, USA) was used to test the surface potential of the nanofiber membrane (area 100 mm2), the test height was 2 cm, and the temperature and humidity were constant at 25 °C and 45% for each sample. Twenty data points were randomly collected and averaged.

Filtration performance test: LZC-K automatic filter material tester (Suzhou Huada Instrument Equipment Co., Ltd.) was used to test the air filtration performance of the nanofiber membrane (area 100 cm2), the gas flow rate was set to 85 L/min, and the aerosol generator was used. The resulting NaCl atomized particles ranged in size from 0.1 to 10 μm. At least 3 different positions were tested for each group of fibrous membranes, and the results were averaged.

Table 1. Test results of mechanical properties and filtration performance of PLA nanofiber membranes

Experimental results: As shown in Fig. 2, the hydroxyapatite nanowhisker synthesized by microwave-assisted biomimetic mineralization has good structural regularity and crystallinity, and the whisker diameter and aspect ratio are also well controlled, which lays a solid foundation for its role as a nano-whisker. Structural basis of biological electrets, and in combination with plasma treatment, good dispersion morphology can be obtained. In obvious contrast, the commercially available hydroxyapatite nanoparticles have obvious agglomeration, and it is difficult to obtain a good dispersed morphology (Figure 3).

As shown in Figure 4, the atomization of the plasma-treated hydroxyapatite nanowhisker dispersion and the combination of electrospinning technology can achieve uniform distribution of biological electrets on the surface of PLA nanofibers. The diameter of the fiber is nanometer, and the distribution is relatively uniform (15~90 nm), while the biological electret is evenly distributed on the surface of the nanofiber, and has a strong interfacial bonding force with the fiber, ensuring high fiber porosity and good three-dimensional connected structure. , while improving the mechanical properties, surface potential and filtration efficiency of nanofibers. Figure 5 shows that the surface properties and geometric dimensions of hydroxyapatite also have important effects: the conventional commercially available nano-hydroxyapatite is very easy to form local agglomeration after introduction, which leads to uneven distribution of fiber diameters, and A large number of micron-scale fibrous structures.

Table 1 compares the tensile test, surface potential test and filterability test results of the polylactic acid nanofiber membranes obtained in the examples and comparative examples. It is twice as high as the pure PLA fiber membrane (2.6 MPa), which reflects the excellent mechanical properties and fully meets the mechanical properties requirements of the PLA fiber membrane in the field of filter materials. However, the breaking strengths of Comparative Examples 1 and 2 were only 3.0 MPa and 4.2 MPa, mainly due to severe agglomeration caused by uncontrollable nanoparticle properties or unsuitable dispersion methods.

It is also of great significance that Examples 1–5 all exhibit extremely high surface potential (6.2 kV~14.5 kV), and almost no decay occurs over time, confirming that they have extremely high long-term stability. In particular, the initial value of the surface potential of Example 2 was as high as 14.5 kV, which was 2.23 times that of Comparative Example 2 and nearly 4.53 times that of Comparative Example 3; and after 90 days, the surface potential of Example 2 remained at 13.9 kV, while the Ratios 2 and 3 attenuate substantially to 0.5 kV and 0.2 kV. The degree of dispersion of the biological electret and the surface potential of the PLA nanofiber membrane are closely related to the filtration performance. Example 2 with the highest surface potential performed the best in the filtration test, and the filtration efficiency of PM0. 99.7% and 99.9%; much higher than the comparative examples 1–3 with lower surface potential (the filtration efficiencies of PM0.3 and PM2.5 are both <90%).

This shows that the technical solution proposed by the present invention enables the biological electret to have good surface properties and structural regularity, as well as the degree of dispersion and efficacy in polylactic acid nanofibers have been significantly improved, which benefits from: (1 ) The structural regularity and uniformity of hydroxyapatite nanowhiskers synthesized by microwave-assisted biomimetic mineralization make it easier to peel and disperse in polylactic acid, thereby better exerting the effect of biological electrets; (2) Plasma treatment The technology promotes the surface activation of nanowhiskers and the ability to disperse them in solution, so that they are evenly distributed on the surface of polylactic acid nanofibers, which is the basis for exerting the function of biological electrets; The extremely high and long-lasting surface potential is achieved in the polar body PLA nanofibers, which helps to improve the filtration efficiency of the fiber membrane and has good application prospects.

Claims (9)

1. the long-term filter membrane that a biological electret is evenly distributed on the surface of polylactic acid nanofiber, it is characterized in that: comprise polylactic acid fiber membrane, and described polylactic acid nanofiber membrane surface is evenly distributed with biological electret, described The content of biological electrets in the polylactic acid nanofibers is 0.05-30 wt %, and the biological electrets are hydroxyapatite nanowhiskers synthesized by microwave-assisted biomimetic mineralization. 2. The long-term filtration membrane in which biological electrets are uniformly distributed on the surface of polylactic acid nanofibers according to claim 1, characterized in that: the diameter of the hydroxyapatite nanowhiskers is 1-20 nm, and the hydroxyl The aspect ratio of the apatite nanowhiskers is 5~200. 3. The long-acting filtration membrane in which biological electrets are uniformly distributed on the surface of polylactic acid nanofibers according to claim 1, wherein the polylactic acid fiber membrane has a thickness of 40-800 μm, and the polylactic acid fibers have a thickness of 40-800 μm. The diameters of the nanofibers in the membrane ranged from 5 to 100 nm. 4. the preparation method of the long-acting filtration membrane that a biological electret is evenly distributed on the surface of the polylactic acid nanofiber, it is characterized in that: comprise the following steps: S1. Preparation of hydroxyapatite nanowhiskers: add water-soluble calcium salt, water-soluble phosphate and template agent into water, stir and dissolve evenly, put it into a microwave reactor, and conduct microwave-assisted biomimetic mineralization under stirring chemical reaction, and cooling after the reaction finishes to obtain an aqueous solution deposited with hydroxyapatite nanowhiskers; S2. Preparation of hydroxyapatite nanowhisker dispersion: using plasma equipment to directly process the hydroxyapatite nanowhisker aqueous solution obtained in step S1 to obtain a hydroxyapatite nanowhisker dispersion; S3. Preparation of polylactic acid nanofiber membrane with uniform distribution of biological electrets: polylactic acid dissolved in organic solvent is prepared by electrospinning technology to prepare nanofiber membrane, and the step of atomization is applied during the spinning process. S2 hydroxyapatite The nano-whisker dispersion liquid is obtained to obtain a polylactic acid nanofiber membrane with a uniform distribution of biological electrets. 5. the preparation method of the long-acting filtration membrane that the biological electret according to claim 4 is evenly distributed on the surface of the polylactic acid nanofiber, it is characterized in that: in the described step S1, the water-soluble calcium salt is calcium chloride, calcium nitrate , at least one of calcium acetate and calcium hypochlorite, the concentration of water-soluble calcium salt is 0.01~2 mol/L; water-soluble phosphate is ammonium dihydrogen phosphate, ammonium hydrogen phosphate, disodium hydrogen phosphate, dihydrogen phosphate At least one of sodium, dipotassium hydrogen phosphate and potassium dihydrogen phosphate, the molar ratio of calcium ion to phosphate ion is 2:1~1:1; the plate agent is cetyltrimethylammonium bromide, stearic acid , at least one of oleic acid, sodium dodecyl sulfate, sodium dodecyl benzene sulfonate and octyl phenyl polyoxyethylene ether, the mass fraction of the template agent in the solution is 0.001 wt % ~ 0.1 wt %, It can be used as a structure directing agent to grow hydroxyapatite into rod-like one-dimensional nanowhiskers along the c-axis. 6. the preparation method of the long-acting filter membrane in which the biological electret is evenly distributed on the surface of the polylactic acid nanofiber according to claim 4, it is characterized in that: the reaction temperature of microwave-assisted synthesis in the described step S1 is 100～250 ℃ , the reaction time is 1-30 minutes; the diameter of the hydroxyapatite nanowhisker obtained in step S1 is 1-20 nm, and the aspect ratio is 5-200. 7. The preparation method of the long-acting filtration membrane in which the biological electret is evenly distributed on the surface of the polylactic acid nanofiber according to claim 4, characterized in that: in the step S2, the plasma treatment equipment is a normal pressure jet type, a medium At least one of a barrier discharge type and a rotary atmospheric pressure type, the plasma discharge voltage is 1 to 80 kV, and the plasma working gas is at least one of argon, helium, hydrogen, nitrogen, and oxygen. The temperature is 10 to 50°C, and the treatment temperature is 10 seconds to 30 minutes. 8. the preparation method of the long-acting filtration membrane that the biological electret according to claim 4 is evenly distributed on the surface of the polylactic acid nanofiber, it is characterized in that: in the described step S3, the organic solvent is methylene chloride, chloroform, At least one of dimethylformamide, N-methylpyrrolidone, hexafluoroisopropanol, methanol, ethanol, isopropanol, and glycerol, and the polylactic acid concentration in the mixed solution is 0.5-22 wt %; electrospinning The module voltage of the silk was 15~60 kV, the receiving voltage was –15~0 kV, and the spinning dope consumption rate was 1~60 mL/min. 9. the preparation method of the long-acting filter membrane in which the biological electret is evenly distributed on the surface of the polylactic acid nanofiber according to claim 4, it is characterized in that: in the step S3, the atomization speed of the biological electret is 0.5~ 50 mL/min, the obtained bio-electret-modified polylactic acid nanofiber has a diameter of 5-100 nm, the bio-electret content in the polylactic acid nanofiber is 0.05-30 wt %, and the obtained polylactic acid fiber membrane has a thickness of 40 nm. ~800 μm.

Images