A porous composite fiber filter element and its preparation method

Abstract

This invention relates to a porous composite fiber filter element and its preparation method, belonging to the technical field of fiber filter elements. A porous composite fiber filter element is made from biodegradable composite fibers, which comprise the following components: biodegradable resin, glycidyl methacrylate-ethylene copolymer, modified styrax fiber, fumed silica, and an antioxidant. The biodegradable resin is one or more of PBS, PBAT, PHB, PES, PHA, PBT, PLA, PPC, PHV, PHBV, PCL, PBSA, PVA, and PBAD. The porous composite fiber filter element of this invention is not limited to using biodegradable materials; furthermore, it ensures that the prepared fibers possess good mechanical strength. The development of this porous composite fiber filter element aims to provide a fiber filter element that is both environmentally friendly and practical.

Description

Technical Field

[0001] This invention belongs to the technical field of fiber filter elements, and relates to a porous composite fiber filter element and its preparation method. Background Technology

[0002] In the production of filter cartridges, materials that are not easily decomposed, such as PP, PA, PE, and PET, are typically used. However, the non-degradable nature of these materials means that their widespread use can cause permanent environmental damage. Furthermore, filter cartridge materials are also used to manufacture components such as humidifier absorbers, aromatherapy diffusers, e-cigarette filters, and oil-collecting foam, requiring filter cartridge materials to possess both excellent filtration capabilities and good mechanical strength.

[0003] Caragana korshinskii, a type of wood, yields natural fibers. Due to the abundance of hydroxyl groups in its cellulose, Caragana korshinskii can be used as a modifier for some adsorbent materials. Given its hard core, the fibers are expected to possess good toughness, making them a suitable reinforcing agent for polymer materials, enhancing their mechanical properties. However, the compatibility between Caragana korshinskii fibers and polymers is poor, and direct mixing often fails to achieve the desired bonding effect. Summary of the Invention

[0004] The purpose of this invention is to provide a porous composite fiber filter element and its preparation method. The porous composite fiber filter element of this invention is not limited to the use of biodegradable materials, but also ensures that the prepared fibers possess good mechanical strength. The development of this porous composite fiber filter element aims to provide a fiber filter element that is both environmentally friendly and practical.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A porous composite fiber filter element is made from biodegradable composite fiber, wherein the biodegradable composite fiber comprises the following components by weight: 90-110 parts of biodegradable resin, 7-10 parts of glycidyl methacrylate-ethylene copolymer, 12-16 parts of modified styrax fiber, 2-3 parts of fumed silica, and 1.0-1.5 parts of antioxidant.

[0007] As a preferred embodiment of the present invention, the biodegradable resin is one or more of PBS, PBAT, PHB, PES, PHA, PBT, PLA, PPC, PHV, PHBV, PCL, PBSA, PVA and PBAD.

[0008] As a preferred embodiment of the present invention, the antioxidant is composed of antioxidant 1010, antioxidant 1076 and antioxidant 168 mixed in a mass ratio of 1.6-2.0:1.0-1.2:0.6-0.8.

[0009] The preparation method of the modified Caragana korshinskii includes the following steps:

[0010] Step 1: Place the Caragana fibers in an activation solution for heating treatment, ultrasonic treatment, filtration, washing, and vacuum drying to obtain pre-made Caragana fibers;

[0011] Step 2: The pre-made Caryota fiber and chitosan solution are ultrasonically treated, heated and stirred, filtered to obtain the solid, and then vacuum dried to obtain the composite.

[0012] Step 3: Mix the complex and ethanol solution, preheat, add the mixed monomers and stir at a constant temperature, filter, wash, and vacuum dry to obtain modified Caragana fibers.

[0013] As a preferred embodiment of the present invention, in step one, the heating treatment is heating at a temperature of 70-75°C for 15-20 minutes; the ultrasonic treatment is treatment at a power of 600-800W for 2-3 minutes; and the vacuum drying is vacuum drying at a temperature of 70°C to constant weight.

[0014] As a preferred embodiment of the present invention, in step one, the mass ratio of the Caragana korshinskii fiber to the activation liquid is 8-10:40-45; the activation liquid is a mixture of propylene glycol, acetic acid and deionized water in a mass ratio of 4.8-5.2:0.5-0.7:20-24.

[0015] As a preferred embodiment of the present invention, under high temperature conditions, the Caragana korshinskii fibers swell and become soft, which facilitates the removal of impurities. Furthermore, ultrasonic treatment enhances the efficiency of the acetic acid reaction, further removing impurities from the lignin. Simultaneously, the combined use of propylene glycol and ultrasound significantly increases the hydroxyl content on the surface of the Caragana korshinskii fibers.

[0016] As a preferred embodiment of the present invention, in step two, the ultrasonic treatment is performed at a power of 800-1000W for 3-5 minutes; the heating and stirring is performed at a temperature of 50-60℃ and a speed of 500-600rpm for 30-45 minutes; and the vacuum drying is performed at a temperature of 80℃ to constant weight.

[0017] As a preferred embodiment of the present invention, in step two, the mass ratio of the pre-made Caragana korshinskii fiber to the chitosan solution is 12-15:50-60; the chitosan solution is composed of chitosan and a 2wt% aqueous acetic acid solution in a mass ratio of 1.0-1.3:35-40.

[0018] As a preferred technical solution of the present invention, under the action of ultrasound, chitosan forms small molecule water-soluble chitosan, which releases more amino groups and promotes the combination of chitosan and hydroxyl groups on the surface of the citronella fiber through hydrogen bonding and electrostatic interaction. This facilitates the entry of chitosan into the porous structure of the citronella fiber, forming a multi-dimensional network structure and significantly improving the mechanical strength of the filter element.

[0019] As a preferred embodiment of the present invention, in step three, the stirring and mixing is carried out at a speed of 800-1000 rpm for 20-30 minutes; the preheating is carried out at a temperature of 40°C; the constant temperature stirring is carried out at a temperature of 45-55°C and a speed of 400-600 rpm for 4-6 hours; the washing is carried out by rinsing three times with anhydrous ethanol; and the vacuum drying is carried out at a temperature of 80-90°C until constant weight is achieved.

[0020] As a preferred embodiment of the present invention, in step three, the mass ratio of the complex, ethanol solution, and mixed monomers is 15-16:50-60:2.5-3.0; the mixed monomers are composed of 2-furan acrolein and coniferaldehyde mixed in a mass ratio of 1.5-1.8:2.5-3.0; and the concentration of the ethanol solution is 30 wt%.

[0021] As a preferred embodiment of the present invention, the surface of Caragana korshinskii fibers is modified with chitosan, 2-furan acrolein, and coniferaldehyde, and glycidyl methacrylate-ethylene copolymer is used as a compatibilizer to introduce functional groups that can chemically react with the polymer, thereby significantly improving the interfacial bonding force between the Caragana korshinskii fibers and the polymer. This modified Caragana korshinskii fiber not only disperses better in the polymer matrix but also effectively enhances the mechanical strength of the filter element while maintaining its good filtration performance.

[0022] As a preferred embodiment of the present invention, the GMA content of the glycidyl methacrylate-ethylene copolymer is 6 wt%.

[0023] A method for preparing a porous composite fiber filter element includes the following steps: placing a biodegradable resin, glycidyl methacrylate-ethylene copolymer, modified citronella fiber, fumed silica, and antioxidant in an extruder and spinning them in a twin-screw spinning machine at a temperature of 190-210℃ to obtain biodegradable composite fibers; forming the biodegradable composite fibers into a fiber web, reinforcing it into a nonwoven fabric, heating and melting it, and then placing it in a filter element mold for shaping treatment to obtain the final product.

[0024] The beneficial effects of this invention are:

[0025] The porous composite fiber filter element involved in this invention is not limited to the use of biodegradable materials in its preparation process; moreover, it ensures that the prepared fibers possess good mechanical strength. The development of this porous composite fiber filter element aims to provide an environmentally friendly and practical fiber filter element to meet the current societal demands for sustainable development and environmental protection. This invention successfully combines the environmentally friendly characteristics of biodegradable materials with the mechanical properties of fibers, thereby ensuring the strength and durability of the fibers in practical applications while meeting environmental requirements. Detailed Implementation

[0026] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0027] Example 1

[0028] A porous composite fiber filter element is made from biodegradable composite fibers. The biodegradable composite fibers comprise the following components by weight: 90 parts biodegradable resin, 7 parts glycidyl methacrylate-ethylene copolymer, 12 parts modified *Caragana korshinskii* fiber, 2 parts fumed silica, and 1.0 part antioxidant. The biodegradable resin is PBS. The antioxidant is a mixture of antioxidant 1010, antioxidant 1076, and antioxidant 168 in a mass ratio of 1.6:1.0:0.6.

[0029] The preparation method of the modified Caragana korshinskii includes the following steps:

[0030] Step 1: Place the Caragana korshinskii fibers in an activation solution for heat treatment, ultrasonic treatment, filtration, washing, and vacuum drying to obtain pre-made Caragana korshinskii fibers; wherein, the heat treatment is performed at 70°C for 15 minutes; the ultrasonic treatment is performed at 600W power for 2 minutes; the vacuum drying is performed at 70°C until constant weight; the mass ratio of Caragana korshinskii fibers to activation solution is 8:40; the activation solution is a mixture of propylene glycol, acetic acid, and deionized water in a mass ratio of 4.8:0.5:20.

[0031] Step 2: The pre-prepared *Caragana korshinskii* fiber and chitosan solution are ultrasonically treated, heated and stirred, filtered to obtain the solid, and then vacuum dried to obtain the composite. The ultrasonic treatment is performed at 800W power for 3 minutes; the heating and stirring is performed at 50℃ and 500rpm for 30 minutes; the vacuum drying is performed at 80℃ to constant weight; the mass ratio of the pre-prepared *Caragana korshinskii* fiber to the chitosan solution is 12:50; the chitosan solution is composed of chitosan and a 2wt% aqueous acetic acid solution at a mass ratio of 1.0:35.

[0032] Step 3: Mix the composite and ethanol solution, preheat, add the mixed monomers, stir at a constant temperature, filter, wash, and vacuum dry to obtain modified Caragana korshinskii fiber; the mixing is carried out at 800 rpm for 20 min; the preheating is carried out at 40℃; the constant temperature stirring is carried out at 45℃ and 400 rpm for 4 h; the washing is carried out by rinsing three times with anhydrous ethanol; the vacuum drying is carried out at 80℃ to constant weight; the mass ratio of the composite, ethanol solution, and mixed monomers is 15:50:2.5; the mixed monomers are composed of 2-furan acrolein and coniferaldehyde mixed at a mass ratio of 1.5:2.5; the concentration of the ethanol solution is 30 wt%.

[0033] A method for preparing a porous composite fiber filter element includes placing a biodegradable resin, glycidyl methacrylate-ethylene copolymer, modified citronella fiber, fumed silica, and antioxidant in an extruder and spinning them in a twin-screw extruder at 190°C to obtain biodegradable composite fibers. The biodegradable composite fibers are then formed into a fiber web, reinforced into a nonwoven fabric, heated and melted, and then placed in a filter element mold for shaping treatment to obtain the final product.

[0034] Example 2

[0035] A porous composite fiber filter element is made from biodegradable composite fibers. The biodegradable composite fibers comprise the following components by weight: 97 parts biodegradable resin, 8 parts glycidyl methacrylate-ethylene copolymer, 13 parts modified *Caragana korshinskii* fiber, 2.3 parts fumed silica, and 1.2 parts antioxidant. The biodegradable resin is PBS. The antioxidant is a mixture of antioxidant 1010, antioxidant 1076, and antioxidant 168 in a mass ratio of 1.7:1.1:0.65.

[0036] The preparation method of the modified Caragana korshinskii includes the following steps:

[0037] Step 1: Place the Caragana korshinskii fibers in an activation solution for heating and ultrasonic treatment, filter, wash, and vacuum dry to obtain pre-made Caragana korshinskii fibers; wherein, the heating treatment is performed at 72°C for 15 minutes; the ultrasonic treatment is performed at 660W for 2.5 minutes; the vacuum drying is performed at 70°C until constant weight; the mass ratio of Caragana korshinskii fibers to activation solution is 8.7:42; the activation solution is a mixture of propylene glycol, acetic acid, and deionized water in a mass ratio of 5.0:0.55:21.

[0038] Step 2: The pre-prepared *Caragana korshinskii* fiber and chitosan solution are ultrasonically treated, heated and stirred, filtered to obtain the solid, and then vacuum dried to obtain the composite. The ultrasonic treatment is performed at 860W power for 3.5 minutes; the heating and stirring is performed at 53℃ and 530rpm for 35 minutes; the vacuum drying is performed at 80℃ to constant weight; the mass ratio of the pre-prepared *Caragana korshinskii* fiber to the chitosan solution is 13:53; the chitosan solution is composed of chitosan and a 2wt% acetic acid aqueous solution at a mass ratio of 1.1:37.

[0039] Step 3: Mix the composite and ethanol solution, preheat, add the mixed monomers, stir at a constant temperature, filter, wash, and vacuum dry to obtain modified Caragana korshinskii fiber; the mixing was carried out at 860 rpm for 25 min; the preheating was carried out at 40℃; the constant temperature stirring was carried out at 48℃ and 460 rpm for 4.5 h; the washing was carried out by rinsing three times with anhydrous ethanol; the vacuum drying was carried out at 83℃ to constant weight; the mass ratio of the composite, ethanol solution, and mixed monomers was 15.5:53:2.7; the mixed monomers were composed of 2-furan acrolein and coniferaldehyde mixed at a mass ratio of 1.6:2.7; the concentration of the ethanol solution was 30 wt%.

[0040] A method for preparing a porous composite fiber filter element includes placing a biodegradable resin, glycidyl methacrylate-ethylene copolymer, modified citronella fiber, fumed silica, and antioxidant in an extruder and spinning them in a twin-screw extruder at 197°C to obtain biodegradable composite fibers. The biodegradable composite fibers are then formed into a fiber web, reinforced into a nonwoven fabric, heated and melted, and then placed in a filter element mold for shaping treatment to obtain the final product.

[0041] Example 3

[0042] A porous composite fiber filter element is made from biodegradable composite fibers. The biodegradable composite fibers comprise the following components by weight: 103 parts biodegradable resin, 9 parts glycidyl methacrylate-ethylene copolymer, 15 parts modified *Caragana korshinskii* fiber, 2.7 parts fumed silica, and 1.3 parts antioxidant. The biodegradable resin is PBS. The antioxidant is a mixture of antioxidant 1010, antioxidant 1076, and antioxidant 168 in a mass ratio of 1.9:1.15:0.75.

[0043] The preparation method of the modified Caragana korshinskii includes the following steps:

[0044] Step 1: Place the Caragana korshinskii fibers in an activation solution for heating and ultrasonic treatment, filter, wash, and vacuum dry to obtain pre-made Caragana korshinskii fibers; wherein, the heating treatment is performed at 73°C for 18 minutes; the ultrasonic treatment is performed at 730W for 2.5 minutes; the vacuum drying is performed at 70°C until constant weight; the mass ratio of the Caragana korshinskii fibers to the activation solution is 9.3:43; the activation solution is a mixture of propylene glycol, acetic acid, and deionized water in a mass ratio of 5.1:0.65:23.

[0045] Step 2: The pre-prepared *Caragana korshinskii* fiber and chitosan solution are ultrasonically treated, heated and stirred, filtered to obtain the solid, and then vacuum dried to obtain the composite. The ultrasonic treatment is performed at 930W power for 4.5 minutes; the heating and stirring is performed at 57℃ and 560rpm for 40 minutes; the vacuum drying is performed at 80℃ to constant weight; the mass ratio of the pre-prepared *Caragana korshinskii* fiber to the chitosan solution is 14:57; the chitosan solution is composed of chitosan and a 2wt% acetic acid aqueous solution at a mass ratio of 1.2:38.

[0046] Step 3: Mix the composite and ethanol solution, preheat, add the mixed monomers, stir at a constant temperature, filter, wash, and vacuum dry to obtain modified Caragana korshinskii fiber; the mixing was carried out at 930 rpm for 25 min; the preheating was carried out at 40℃; the constant temperature stirring was carried out at 52℃ and 530 rpm for 5.5 h; the washing was carried out by rinsing three times with anhydrous ethanol; the vacuum drying was carried out at 87℃ to constant weight; the mass ratio of the composite, ethanol solution, and mixed monomers was 15.8:57:2.8; the mixed monomers were composed of 2-furan acrolein and coniferaldehyde mixed at a mass ratio of 1.7:2.8; the concentration of the ethanol solution was 30 wt%.

[0047] A method for preparing a porous composite fiber filter element includes placing a biodegradable resin, glycidyl methacrylate-ethylene copolymer, modified citronella fiber, fumed silica, and antioxidant in an extruder and spinning them in a twin-screw extruder at 203°C to obtain biodegradable composite fibers. The biodegradable composite fibers are then formed into a fiber web, reinforced into a nonwoven fabric, heated and melted, and then placed in a filter element mold for shaping treatment to obtain the final product.

[0048] Example 4

[0049] A porous composite fiber filter element is made from biodegradable composite fibers. The biodegradable composite fibers comprise the following components by weight: 110 parts biodegradable resin, 10 parts glycidyl methacrylate-ethylene copolymer, 16 parts modified citronella fiber, 3 parts fumed silica, and 1.5 parts antioxidant. The biodegradable resin is PBS. The antioxidant is a mixture of antioxidant 1010, antioxidant 1076, and antioxidant 168 in a mass ratio of 2.0:1.2:0.8.

[0050] The preparation method of the modified Caragana korshinskii includes the following steps:

[0051] Step 1: Place the Caragana korshinskii fibers in an activation solution for heat treatment, ultrasonic treatment, filtration, washing, and vacuum drying to obtain pre-made Caragana korshinskii fibers; wherein, the heat treatment is performed at 75°C for 20 minutes; the ultrasonic treatment is performed at 800W power for 3 minutes; the vacuum drying is performed at 70°C to constant weight; the mass ratio of Caragana korshinskii fibers to activation solution is 10:45; the activation solution is a mixture of propylene glycol, acetic acid, and deionized water in a mass ratio of 5.2:0.7:24.

[0052] Step 2: The pre-prepared *Caragana korshinskii* fiber and chitosan solution are ultrasonically treated, heated and stirred, filtered to obtain the solid, and then vacuum dried to obtain the composite. The ultrasonic treatment is performed at 1000W power for 5 minutes; the heating and stirring is performed at 60℃ and 600rpm for 45 minutes; the vacuum drying is performed at 80℃ to constant weight; the mass ratio of the pre-prepared *Caragana korshinskii* fiber to the chitosan solution is 15:60; the chitosan solution is composed of chitosan and a 2wt% acetic acid aqueous solution at a mass ratio of 1.3:40.

[0053] Step 3: Mix the composite and ethanol solution, preheat, add the mixed monomers, stir at a constant temperature, filter, wash, and vacuum dry to obtain modified Caragana korshinskii fiber; the mixing is carried out at 1000 rpm for 30 min; the preheating is carried out at 40℃; the constant temperature stirring is carried out at 55℃ and 600 rpm for 6 h; the washing is carried out by rinsing three times with anhydrous ethanol; the vacuum drying is carried out at 90℃ to constant weight; the mass ratio of the composite, ethanol solution, and mixed monomers is 16:60:3.0; the mixed monomers are composed of 2-furan acrolein and coniferaldehyde mixed at a mass ratio of 1.8:3.0; the concentration of the ethanol solution is 30 wt%.

[0054] A method for preparing a porous composite fiber filter element includes placing a biodegradable resin, glycidyl methacrylate-ethylene copolymer, modified citronella fiber, fumed silica, and antioxidant in an extruder and spinning them in a twin-screw extruder at 210°C to obtain biodegradable composite fibers. The biodegradable composite fibers are then formed into a fiber web, reinforced into a nonwoven fabric, heated and melted, and then placed in a filter element mold for shaping treatment to obtain the final product.

[0055] Comparative Example 1

[0056] Compared with Example 3, Comparative Example 1 differs in that deionized water is used instead of the activation solution in step one, while the remaining components, preparation steps and parameters are the same.

[0057] Comparative Example 2

[0058] Compared with Example 3, Comparative Example 2 differs in that chitosan is not used in step two, while the other components, preparation steps and parameters are the same.

[0059] Comparative Example 3

[0060] Compared with Example 3, Comparative Example 3 differs in that step two does not involve ultrasonic treatment, while the remaining components, preparation steps, and parameters are the same.

[0061] Comparative Example 4

[0062] Compared with Example 3, Comparative Example 4 differs in that coniferaldehyde is used instead of 2-furan acrolein in step three, while the other components, preparation steps and parameters are the same.

[0063] Comparative Example 5

[0064] Compared with Example 3, Comparative Example 5 differs in that 2-furan acrolein is used instead of coniferaldehyde in step three, while the other components, preparation steps and parameters are the same.

[0065] Comparative Example 6

[0066] Compared with Example 3, Comparative Example 6 differs in that step three does not use mixed monomers, while the remaining components, preparation steps and parameters are the same.

[0067] Comparative Example 7

[0068] Compared with Example 3, Comparative Example 7 differs in that it does not use glycidyl methacrylate-ethylene copolymer, while the other components, preparation steps and parameters are the same.

[0069] The biodegradable composite fibers prepared in Examples 1-4 and Comparative Examples 1-7 were subjected to tensile strength tests, and the test results are shown in Table 1.

[0070] Tensile strength test: according to GB / T19975-2005, the clamping distance is 500 mm and the speed is 250 mm / min. The test results are shown in Table 1.

[0071] Table 1

[0072]

[0073]

[0074] As can be seen from the test results in Table 1, compared with Comparative Examples 1-7, the biodegradable composite fiber prepared by the present invention has excellent tensile strength, and the filter element prepared by it has high mechanical strength.

[0075] This invention utilizes an interwoven network structure formed by chitosan and Caryophyllum fibers to significantly improve the mechanical strength of the composite fibers. Simultaneously, it introduces amino, carboxyl, and more active hydroxyl groups. The amino groups can form covalent bonds with the acrolein phase of the mixed monomers composed of 2-furan acrolein and coniferaldehyde, enabling organic coating modification of the Caryophyllum fiber surface. This significantly increases the dispersibility and interfacial bonding of the Caryophyllum fibers in the polymer material. Furthermore, the invention, through the compounding of furan acrolein and coniferaldehyde, utilizes the different ring structures of furan and benzene rings to form crosslinking points of varying sizes and rigidities. The complementary stacking of these different ring structures may reduce structural defects. This invention improves the overall uniformity of the material, thereby forming a denser and more uniformly distributed three-dimensional network structure in the composite material, which can more effectively disperse stress and improve tensile strength. By introducing the acrolein phase of the mixed monomers, this invention increases the compatibility between Caryophyllum fibers, glycidyl methacrylate-ethylene copolymer, and biodegradable resin. The epoxy groups of glycidyl methacrylate-ethylene copolymer can not only react with the carboxyl and hydroxyl groups in the modified Caryophyllum fibers and fumed silica, but also form chemical grafts with the active groups of the biodegradable resin, further improving the modification effect of the modified Caryophyllum fibers on the biodegradable resin and improving the mechanical strength of the composite fiber.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A porous composite fiber filter element, characterized in that, The porous composite fiber filter element is made from biodegradable composite fibers, which include the following components by weight: 90-110 parts of biodegradable resin, 7-10 parts of glycidyl methacrylate-ethylene copolymer, 12-16 parts of modified styrax fiber, 2-3 parts of fumed silica, and 1.0-1.5 parts of antioxidant; the biodegradable resin is one or more of PBS, PBAT, PHB, PHA, PLA, PPC, PHV, PHBV, PCL, PBSA, and PVA; the antioxidant is a mixture of antioxidant 1010, antioxidant 1076, and antioxidant 168 in a mass ratio of 1.6-2.0:1.0-1.2:0.6-0.

8. The method for preparing the modified Caragana korshinskii fiber includes the following steps: Step 1: Place the Caragana korshinskii fibers in an activation solution for heating and ultrasonic treatment, filter, wash, and vacuum dry to obtain pre-made Caragana korshinskii fibers; the mass ratio of the Caragana korshinskii fibers to the activation solution is 8-10:40-45; the activation solution is a mixture of propylene glycol, acetic acid, and deionized water in a mass ratio of 4.8-5.2:0.5-0.7:20-24. Step 2: The pre-prepared Caragana fibers and chitosan solution are ultrasonically treated, heated and stirred, filtered to obtain the solid, and then vacuum dried to obtain the composite. The mass ratio of the pre-prepared Caragana fibers to the chitosan solution is 12-15:50-60. The chitosan solution is composed of chitosan and a 2wt% acetic acid aqueous solution in a mass ratio of 1.0-1.3:35-40. Step 3: Mix the composite and ethanol solution, preheat, add the mixed monomers and stir at a constant temperature, filter, wash, and vacuum dry to obtain modified Caragana korshinskii fiber; the mass ratio of the composite, ethanol solution and mixed monomers is 15-16:50-60:2.5-3.0; the mixed monomers are composed of 2-furan acrolein and coniferaldehyde mixed in a mass ratio of 1.5-1.8:2.5-3.0; the concentration of the ethanol solution is 30wt%.

2. The porous composite fiber filter element according to claim 1, characterized in that: In step one, the heat treatment is heating at 70-75℃ for 15-20 minutes; the ultrasonic treatment is treating at 600-800W power for 2-3 minutes; and the vacuum drying is vacuum drying at 70℃ to constant weight.

3. The porous composite fiber filter element according to claim 1, characterized in that: In step two, the ultrasonic treatment is performed at 800-1000W power for 3-5 minutes; the heating and stirring is performed at 50-60℃ and 500-600rpm for 30-45 minutes; and the vacuum drying is performed at 80℃ to constant weight.

4. The porous composite fiber filter element according to claim 1, characterized in that: In step three, the stirring and mixing is carried out at a speed of 800-1000 rpm for 20-30 minutes; the preheating is carried out at a temperature of 40°C; the constant temperature stirring is carried out at a temperature of 45-55°C and a speed of 400-600 rpm for 4-6 hours; the washing is carried out by rinsing three times with anhydrous ethanol; and the vacuum drying is carried out at a temperature of 80-90°C until constant weight is achieved.

5. A method for preparing a porous composite fiber filter element as described in any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: placing biodegradable resin, glycidyl methacrylate-ethylene copolymer, modified Caragana korshinskii fiber, fumed silica and antioxidant in an extruder and spinning them in a twin-screw spinning machine at a temperature of 190-210℃ to obtain biodegradable composite fiber; forming the biodegradable composite fiber into a fiber web, reinforcing it into a nonwoven fabric, heating and melting it, and then placing it in a filter mold for shaping treatment to obtain the final product.

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