Preparation method of modified activated carbon filter membrane for filter device

Abstract

The invention discloses a preparation method of a modified activated carbon filter membrane for a filter device. Comprising the following steps: step 1, mixing banana peel powder with phosphoric acid, soaking under a dark condition, drying, carbonizing, washing and drying to obtain banana peel activated carbon; step 2, adding modified polyvinylidene fluoride powder into N, N-dimethylacetamide, stirring at 60 DEG C, then adding polyvinylpyrrolidone, continuously stirring, finally adding banana peel activated carbon, stirring at room temperature, standing in vacuum, and defoaming to obtain a membrane casting solution; and 3, uniformly coating a glass plate with the membrane casting solution, rapidly immersing the glass plate in a coagulating bath, keeping for 1-2 hours, stripping, washing, and drying to obtain the modified activated carbon filter membrane. The preparation method has the beneficial effects that the banana peel powder is used as a raw material to prepare the activated carbon, and the filter membrane is prepared by compounding the modified polyvinylidene fluoride powder and the activated carbon and combining a specific process; the antibacterial performance and the filtering efficiency of the filter membrane are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of filter membranes, and in particular, relates to a method for preparing a modified activated carbon filter membrane for a filter device. Background Art

[0002] Activated carbon membranes are widely used in water treatment due to their excellent adsorption properties. However, they still suffer from several key drawbacks. First, traditional activated carbon membranes typically utilize coal-based or wood-based activated carbon, resulting in uneven pore size distribution, which limits filtration efficiency and insufficient selective adsorption of heavy metals and organic pollutants. Second, conventional activated carbon membranes lack antimicrobial properties, making them susceptible to microbial growth over long-term use, causing secondary contamination and shortening the membrane's service life. Furthermore, while polyvinylidene fluoride (PVDF)-based membranes commonly used in existing technologies possess excellent mechanical strength and chemical stability, they are highly hydrophobic and easily clogged by contaminants, leading to significant flux attenuation. While some studies have attempted to improve membrane performance through physical blending or surface modification, these modification methods are complex and struggle to achieve both filtration efficiency and antimicrobial performance. For example, some commercially available membranes incorporate antimicrobial agents, but these suffer from issues such as easy dissolution and poor stability, preventing them from achieving long-term antimicrobial efficacy.

[0003] Therefore, in order to solve the above problems, the present invention provides a method for preparing a modified activated carbon filter membrane for a filtration device. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing a modified activated carbon filter membrane for a filtration device.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a modified activated carbon filter membrane for a filter device comprises the following steps: Step 1: Mix banana peel powder with phosphoric acid, soak in the dark for 24 hours, then dry in a 105°C oven for 24 hours, transfer to a muffle furnace for carbonization for 23 hours, wash, and dry to obtain banana peel activated carbon; Step 2: Add modified polyvinylidene fluoride powder to N,N-dimethylacetamide, stir in a 60°C water bath for 1-2 hours, then add polyvinyl pyrrolidone, continue stirring for 40-50 minutes, and finally add banana peel activated carbon, stir at room temperature for 10-12 hours, stand in vacuum, degas, and obtain a casting solution; Step 3: Evenly coat the casting liquid on the glass plate, quickly immerse the coated membrane in a coagulation bath, keep it for 1-2 hours, peel it off and wash it, and dry it naturally at room temperature to obtain a modified activated carbon filter membrane.

[0006] More optimally, the mass ratio of the banana peel powder to the phosphoric acid solution is 1:3; wherein the concentration of the phosphoric acid solution is 85wt%.

[0007] More optimally, the casting liquid raw materials include the following components: by weight, 10-12 parts of modified polyvinylidene fluoride powder, 80-100 parts of N,N-dimethylacetamide, 1-2 parts of polyvinylpyrrolidone, and 2-5 parts of banana peel activated carbon; the coagulation bath is composed of equal volumes of deionized water and anhydrous ethanol.

[0008] More optimally, the preparation process of the modified polyvinylidene fluoride powder is: S1: Add polyvinylidene fluoride powder to sodium hydroxide solution, stir and react at 60-70°C for 1-2 hours, filter, wash, dry, transfer to acetonitrile under protective atmosphere, add α-bromoisobutyryl bromide and triethylamine, increase the temperature to 60-70°C, react for 4-5 hours, filter, wash, and dry to obtain brominated polyvinylidene fluoride powder; S2: Ethylenediamine, 6-bromo-1-hexene, and anhydrous acetonitrile were mixed, and triethylamine was added dropwise at 0°C. After the addition was complete, the mixture was stirred at room temperature for 12-20 hours. The solvent was removed by distillation under reduced pressure, and the mixture was filtered, concentrated, and purified by column chromatography to obtain an aminoolefin compound. S3: Mix α,α′-dibromo-p-xylene, 4-pyridinecarboxaldehyde, and 1,2-dichloroethane, raise the temperature to 85-90°C, reflux for 48 hours, cool to room temperature after the reaction is complete, remove the solvent by distillation under reduced pressure, filter, purify, mix with aminoolefin compound and dichloromethane, raise the temperature to 50-60°C, react for 3-4 hours, cool to room temperature after the reaction is complete, filter, wash, and dry to obtain a quaternary ammonium salt monomer; S4: Under a protective atmosphere, brominated polyvinylidene fluoride powder, quaternary ammonium salt monomer, 2,2'-bipyridine, cuprous bromide, and acetonitrile are mixed, the temperature is raised to 60-70° C., the mixture is reacted for 10-12 hours, filtered, washed, and dried to obtain modified polyvinylidene fluoride powder.

[0009] In the scheme, an amino group of ethylenediamine attacks the bromination site of 6-bromo-1-hexene (SN2 reaction), generating an amino compound with an olefin at the end; triethylamine acts as a base to capture the generated HBr. The specific reaction process is shown below: In the scheme, the bromomethyl group of dibromo-p-xylene undergoes nucleophilic substitution with the pyridine nitrogen of 4-pyridinecarboxaldehyde, and then the aldehyde group contained therein undergoes a condensation reaction with the amino group of the aminoolefin compound to form an olefin-containing quaternary ammonium salt monomer, the structural formula of which is shown below: In the scheme, the initiation site of brominated polyvinylidene fluoride undergoes atom transfer radical polymerization (ATRP) with the olefin of the quaternary ammonium salt monomer in the presence of 2,2'-bipyridine to form a polymer with quaternary ammonium side chains grafted onto the PVDF main chain, thereby obtaining modified polyvinylidene fluoride powder.

[0010] More optimally, the brominated polyvinylidene fluoride powder raw material includes the following components: by weight, 100-120 parts of polyvinylidene fluoride powder, 10-15 parts of sodium hydroxide solution, 200-250 parts of acetonitrile, 23-25 ​​parts of α-bromoisobutyryl bromide, and 10-12 parts of triethylamine; wherein the concentration of the sodium hydroxide solution is 10wt%.

[0011] More optimally, the aminoolefin compound raw material includes the following components: by weight, 10-12 parts of ethylenediamine, 28-30 parts of 6-bromo-1-hexene, 100-150 parts of anhydrous acetonitrile, and 16-18 parts of triethylamine.

[0012] More optimally, the quaternary ammonium salt monomer raw material includes the following components: by weight, 10-12 parts of α,α′-dibromo-p-xylene, 47-50 parts of pyridine carboxaldehyde, 100-120 parts of 1,2-dichloroethane, 5-8 parts of aminoolefin compound, and 200-250 parts of dichloromethane.

[0013] More optimally, the modified polyvinylidene fluoride powder raw material includes the following components: by weight, 10-12 parts of brominated polyvinylidene fluoride powder, 25-38 parts of quaternary ammonium salt monomer, 2-3 parts of 2,2'-bipyridine, 1-1.5 parts of cuprous bromide, and 200-250 parts of acetonitrile.

[0014] Beneficial effects of the present invention: The present invention prepares activated carbon from banana peel powder, composites the activated carbon with modified polyvinylidene fluoride powder, and combines it with a specific process to produce a filter membrane, effectively improving the membrane's antibacterial properties and filtration efficiency. The details are as follows: First, phosphoric acid reacts with the cellulose and hemicellulose in banana peels at high temperatures to form an esterification reaction. Phosphoric acid acts as a dehydrating agent to promote the formation of a carbon skeleton. This process produces a rich microporous and mesoporous structure. This multi-level pore structure greatly enhances the adsorption capacity of the activated carbon, effectively improving the efficiency of intercepting organic pollutants and heavy metal ions in water. Second, in this scheme, quaternary ammonium groups are grafted onto polyvinylidene fluoride chains through an ATRP reaction. The positively charged nitrogen atoms in these groups can interact electrostatically with the phospholipid bilayer on the bacterial cell membrane. This interaction can disrupt the integrity of the cell membrane and cause leakage of cellular contents. At the same time, the long-chain alkyl groups in the quaternary ammonium groups can insert into the bacterial cell membrane, further exacerbating the destruction of the membrane structure through a "zipper effect," thereby achieving a broad-spectrum antibacterial effect. Third: The quaternary ammonium salt groups on the molecular chain of modified polyvinylidene fluoride powder form hydrogen bonds or ion-dipole interactions with the oxygen-containing functional groups (such as carboxyl and hydroxyl) on the surface of banana peel activated carbon. This interfacial bonding not only improves the mechanical strength of the material; at the same time, it creates an "adsorption-sterilization" synergistic site: the activated carbon first enriches pollutants and bacteria, and then the quaternary ammonium salt groups kill the captured bacteria. This cascade effect significantly improves the filtration efficiency and service life. DETAILED DESCRIPTION

[0015] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0016] Example 1: A method for preparing a modified activated carbon filter membrane for a filtration device, comprising the following steps: Step 1: Banana peel powder was mixed with phosphoric acid, soaked in the dark for 24 hours, then dried in a 105°C oven for 24 hours, transferred to a muffle furnace for carbonization for 23 hours, washed, and dried to obtain banana peel activated carbon; the mass ratio of banana peel powder to phosphoric acid solution was 1:3; the concentration of the phosphoric acid solution was 85wt%; Step 2: Add 10 parts of modified polyvinylidene fluoride powder to 80 parts of N,N-dimethylacetamide, stir in a water bath at 60°C for 1 hour, then add 1 part of polyvinyl pyrrolidone, continue stirring for 40 minutes, and finally add 2 parts of banana peel activated carbon, stir at room temperature for 10 hours, stand in vacuum, and degas to obtain a casting solution; Step 3: The casting solution is evenly coated on a glass plate, and the coated membrane is quickly immersed in a coagulation bath and kept for 1 hour. After peeling and washing, it is naturally dried at room temperature to obtain a modified activated carbon filter membrane; the coagulation bath is composed of equal volumes of deionized water and anhydrous ethanol; The preparation process of modified polyvinylidene fluoride powder is as follows: S1: Add 100 parts of polyvinylidene fluoride powder to 10 parts of sodium hydroxide solution (concentration of 10 wt%), stir and react at 60°C for 1 hour, filter, wash, and dry, then transfer to 200 parts of acetonitrile under a protective atmosphere, add 23 parts of α-bromoisobutyryl bromide and 10 parts of triethylamine, raise the temperature to 60°C, react for 4 hours, filter, wash, and dry to obtain brominated polyvinylidene fluoride powder; S2: 10 parts of ethylenediamine, 28 parts of 6-bromo-1-hexene, and 100 parts of anhydrous acetonitrile were mixed, and 16 parts of triethylamine were added dropwise at 0°C. After the addition was complete, the mixture was stirred at room temperature for 12 hours. The solvent was removed by distillation under reduced pressure, and then filtered, concentrated, and purified by column chromatography to obtain an aminoolefin compound; S3: 10 parts of α,α′-dibromo-p-xylene, 47 parts of pyridine carboxaldehyde, and 100 parts of 1,2-dichloroethane were mixed, the temperature was raised to 85°C, and the mixture was refluxed for 48 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by distillation under reduced pressure. The mixture was filtered and purified, and then mixed with 5 parts of an amino olefin compound and 200 parts of dichloromethane. The mixture was heated to 50°C and reacted for 3 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, and dried to obtain a quaternary ammonium salt monomer. S4: Under a protective atmosphere, 10 parts of brominated polyvinylidene fluoride powder, 25 parts of quaternary ammonium salt monomer, 2 parts of 2,2'-bipyridine, 1 part of cuprous bromide, and 200 parts of acetonitrile were mixed, the temperature was raised to 60°C, the reaction was carried out for 10 hours, and the mixture was filtered, washed, and dried to obtain modified polyvinylidene fluoride powder.

[0017] Example 2: A method for preparing a modified activated carbon filter membrane for a filtration device, comprising the following steps: Step 1: Banana peel powder was mixed with phosphoric acid, soaked in the dark for 24 hours, then dried in a 105°C oven for 24 hours, transferred to a muffle furnace for carbonization for 23 hours, washed, and dried to obtain banana peel activated carbon; the mass ratio of banana peel powder to phosphoric acid solution was 1:3; the concentration of the phosphoric acid solution was 85wt%; Step 2: Add 12 parts of modified polyvinylidene fluoride powder to 100 parts of N,N-dimethylacetamide, stir in a water bath at 60°C for 2 hours, then add 2 parts of polyvinyl pyrrolidone, continue stirring for 50 minutes, and finally add 5 parts of banana peel activated carbon, stir at room temperature for 12 hours, let stand in vacuum, degas, and obtain a casting solution; Step 3: The casting solution is evenly coated on a glass plate, and the coated membrane is quickly immersed in a coagulation bath and kept for 2 hours. After peeling and washing, it is naturally dried at room temperature to obtain a modified activated carbon filter membrane; the coagulation bath is composed of equal volumes of deionized water and anhydrous ethanol; The preparation process of modified polyvinylidene fluoride powder is as follows: S1: Add 120 parts of polyvinylidene fluoride powder to 15 parts of sodium hydroxide solution (concentration of 10 wt%), stir and react at 70°C for 2 hours, filter, wash, and dry, then transfer to 250 parts of acetonitrile under a protective atmosphere, add 25 parts of α-bromoisobutyryl bromide and 12 parts of triethylamine, raise the temperature to 70°C, react for 5 hours, filter, wash, and dry to obtain brominated polyvinylidene fluoride powder; S2: 12 parts of ethylenediamine, 30 parts of 6-bromo-1-hexene, and 150 parts of anhydrous acetonitrile were mixed, and 18 parts of triethylamine were added dropwise at 0°C. After the addition was complete, the mixture was stirred at room temperature for 20 hours. The solvent was removed by distillation under reduced pressure, and the mixture was filtered, concentrated, and purified by column chromatography to obtain an aminoolefin compound; S3: 12 parts of α,α′-dibromo-p-xylene, 50 parts of pyridine carboxaldehyde, and 120 parts of 1,2-dichloroethane were mixed, the temperature was raised to 90°C, and the reaction was refluxed for 48 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by distillation under reduced pressure. The mixture was filtered and purified, and the mixture was mixed with 8 parts of an amino olefin compound and 250 parts of dichloromethane. The mixture was heated to 60°C and the reaction was carried out for 4 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, and dried to obtain a quaternary ammonium salt monomer. S4: Under a protective atmosphere, 12 parts of brominated polyvinylidene fluoride powder, 38 parts of quaternary ammonium salt monomer, 3 parts of 2,2'-bipyridine, 1.5 parts of cuprous bromide, and 250 parts of acetonitrile were mixed, the temperature was raised to 70°C, the reaction was carried out for 12 hours, and the mixture was filtered, washed, and dried to obtain modified polyvinylidene fluoride powder.

[0018] Example 3: A method for preparing a modified activated carbon filter membrane for a filtration device, comprising the following steps: Step 1: Banana peel powder was mixed with phosphoric acid, soaked in the dark for 24 hours, then dried in a 105°C oven for 24 hours, transferred to a muffle furnace for carbonization for 23 hours, washed, and dried to obtain banana peel activated carbon; the mass ratio of banana peel powder to phosphoric acid solution was 1:3; the concentration of the phosphoric acid solution was 85wt%; Step 2: Add 11 parts of modified polyvinylidene fluoride powder to 90 parts of N,N-dimethylacetamide, stir in a water bath at 60°C for 1.5 hours, then add 1.5 parts of polyvinyl pyrrolidone, continue stirring for 45 minutes, and finally add 3.5 parts of banana peel activated carbon, stir at room temperature for 11 hours, stand in vacuum, and degas to obtain a casting solution; Step 3: The casting solution is evenly coated on a glass plate, and the coated membrane is quickly immersed in a coagulation bath and maintained for 1.5 hours. After peeling and washing, it is naturally dried at room temperature to obtain a modified activated carbon filter membrane; the coagulation bath is composed of equal volumes of deionized water and anhydrous ethanol; The preparation process of modified polyvinylidene fluoride powder is as follows: S1: Add 110 parts of polyvinylidene fluoride powder to 12.5 parts of sodium hydroxide solution (concentration of 10 wt%), stir and react at 65°C for 1.5 hours, filter, wash, and dry. Then, transfer to 225 parts of acetonitrile under a protective atmosphere, add 24 parts of α-bromoisobutyryl bromide and 11 parts of triethylamine, raise the temperature to 65°C, react for 4.5 hours, filter, wash, and dry to obtain brominated polyvinylidene fluoride powder; S2: 11 parts of ethylenediamine, 29 parts of 6-bromo-1-hexene, and 125 parts of anhydrous acetonitrile were mixed, and 17 parts of triethylamine were added dropwise at 0°C. After the addition was complete, the mixture was stirred at room temperature for 16 hours. The solvent was removed by distillation under reduced pressure, and the mixture was filtered, concentrated, and purified by column chromatography to obtain an aminoolefin compound; S3: 11 parts of α,α′-dibromo-p-xylene, 48.5 parts of pyridine carboxaldehyde, and 110 parts of 1,2-dichloroethane were mixed, the temperature was raised to 87.5°C, and the mixture was refluxed for 48 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was removed by distillation under reduced pressure. The mixture was filtered and purified, and the mixture was mixed with 6.5 parts of an amino olefin compound and 225 parts of dichloromethane. The mixture was heated to 55°C and the mixture was reacted for 3.5 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, washed, and dried to obtain a quaternary ammonium salt monomer. S4: Under a protective atmosphere, 11 parts of brominated polyvinylidene fluoride powder, 31.5 parts of quaternary ammonium salt monomer, 2.5 parts of 2,2'-bipyridine, 1.2 parts of cuprous bromide, and 225 parts of acetonitrile were mixed, the temperature was raised to 65°C, the reaction was carried out for 11 hours, and the mixture was filtered, washed, and dried to obtain modified polyvinylidene fluoride powder.

[0019] Comparative Example 1: The polyvinylidene fluoride powder was not modified, and the rest was the same as in Example 3, as follows: Step 1: Banana peel powder was mixed with phosphoric acid, soaked in the dark for 24 hours, then dried in a 105°C oven for 24 hours, transferred to a muffle furnace for carbonization for 23 hours, washed, and dried to obtain banana peel activated carbon; the mass ratio of banana peel powder to phosphoric acid solution was 1:3; the concentration of the phosphoric acid solution was 85wt%; Step 2: Add 11 parts of polyvinylidene fluoride powder to 90 parts of N,N-dimethylacetamide, stir in a water bath at 60°C for 1.5 hours, then add 1.5 parts of polyvinyl pyrrolidone, continue stirring for 45 minutes, and finally add 3.5 parts of banana peel activated carbon, stir at room temperature for 11 hours, stand in vacuum, and degas to obtain a casting solution; Step 3: The casting liquid is evenly coated on a glass plate, and the coated membrane is quickly immersed in a coagulation bath and maintained for 1.5 hours. After peeling and washing, it is naturally dried at room temperature to obtain a modified activated carbon filter membrane; the coagulation bath is composed of equal volumes of deionized water and anhydrous ethanol.

[0020] Comparative Example 2: A commercially available activated carbon filter membrane (brand: Qingdao Jianqi, model: JQ-HRP) was used.

[0021] Detection test: (1) First, the pure water flux of the membrane was measured using a cross-flow filtration device. Then, a 12-hour long-term dynamic filtration experiment was conducted using simulated municipal sewage as the feed solution through the cross-flow filtration device to test the flux retention rate. (2) The antibacterial effect of the modified PVDF membrane was evaluated using the colony forming unit (CFU) method with Escherichia coli and Enterococcus faecalis as model strains. The data obtained are shown in the following table: Table 1 Conclusion: This invention significantly improves the antibacterial properties and filtration efficiency of filter membranes prepared from activated carbon using banana peel powder as a raw material and then composited with modified polyvinylidene fluoride. Experimental data show that the flux retention rates of Examples 1 to 3 reached 63.8%, 62.9%, and 65.7%, respectively, significantly exceeding those of Comparative Example 1 (34.5%) and the commercially available Comparative Example 2 (42.7%). Furthermore, the examples exhibited antibacterial rates of 84.8%-87.6% against Escherichia coli and 72.5%-76.9% against Enterococcus faecalis, both exceeding those of Comparative Example 1 (60.7% and 53.5%) and Comparative Example 2 (64.6% and 55.6%). These results verify the significant advantages of the modified activated carbon filter membrane in flux retention and antibacterial properties. Its multi-level pore structure, the antibacterial mechanism of the quaternary ammonium salt group, and the "adsorption-sterilization" synergistic effect work together to enable the filter membrane to exhibit excellent stability and high efficiency in long-term use, making it suitable for the filtration treatment of complex water bodies such as municipal sewage.

[0022] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0023] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a modified activated carbon filter membrane for a filter device, characterized in that: The following steps are involved: Step 1: Mix banana peel powder with phosphoric acid, soak in the dark for 24 hours, then dry in a 105°C oven for 24 hours, transfer to a muffle furnace for carbonization for 23 hours, wash, and dry to obtain banana peel activated carbon; Step 2: Add modified polyvinylidene fluoride powder to N,N-dimethylacetamide, stir in a 60°C water bath for 1-2 hours, then add polyvinyl pyrrolidone, continue stirring for 40-50 minutes, and finally add banana peel activated carbon, stir at room temperature for 10-12 hours, stand in vacuum, degas, and obtain a casting solution; Step 3: Evenly coat the casting liquid on the glass plate, quickly immerse the coated membrane in a coagulation bath, keep it for 1-2 hours, peel it off and wash it, and dry it naturally at room temperature to obtain a modified activated carbon filter membrane.

2. The method for preparing a modified activated carbon filter membrane for a filter device according to claim 1, wherein: The mass ratio of the banana peel powder to the phosphoric acid solution is 1:3; The concentration of the phosphoric acid solution is 85wt%.

3. The method for preparing a modified activated carbon filter membrane for a filter device according to claim 1, wherein: The casting solution raw materials include the following components: 10-12 parts by weight of modified polyvinylidene fluoride powder, 80-100 parts by weight of N,N-dimethylacetamide, 1-2 parts by weight of polyvinyl pyrrolidone, and 2-5 parts by weight of banana peel activated carbon; the coagulation bath is composed of equal volumes of deionized water and anhydrous ethanol.

4. The method for preparing a modified activated carbon filter membrane for a filter device according to claim 1, wherein: The preparation process of the modified polyvinylidene fluoride powder is as follows: S1: Add polyvinylidene fluoride powder to sodium hydroxide solution, stir and react at 60-70°C for 1-2 hours, filter, wash, dry, transfer to acetonitrile under protective atmosphere, add α-bromoisobutyryl bromide and triethylamine, increase the temperature to 60-70°C, react for 4-5 hours, filter, wash, and dry to obtain brominated polyvinylidene fluoride powder; S2: Ethylenediamine, 6-bromo-1-hexene, and anhydrous acetonitrile were mixed, and triethylamine was added dropwise at 0°C. After the addition was complete, the mixture was stirred at room temperature for 12-20 hours. The solvent was removed by distillation under reduced pressure, and the mixture was filtered, concentrated, and purified by column chromatography to obtain an aminoolefin compound. S3: Mix α,α′-dibromo-p-xylene, 4-pyridinecarboxaldehyde, and 1,2-dichloroethane, raise the temperature to 85-90°C, reflux for 48 hours, cool to room temperature after the reaction is complete, remove the solvent by distillation under reduced pressure, filter, purify, mix with aminoolefin compound and dichloromethane, raise the temperature to 50-60°C, react for 3-4 hours, cool to room temperature after the reaction is complete, filter, wash, and dry to obtain a quaternary ammonium salt monomer; S4: Under a protective atmosphere, brominated polyvinylidene fluoride powder, quaternary ammonium salt monomer, 2,2'-bipyridine, cuprous bromide, and acetonitrile are mixed, the temperature is raised to 60-70° C., the mixture is reacted for 10-12 hours, filtered, washed, and dried to obtain modified polyvinylidene fluoride powder.

5. The method for preparing a modified activated carbon filter membrane for a filter device according to claim 4, characterized in that: The brominated polyvinylidene fluoride powder raw material comprises the following components: by weight, 100-120 parts of polyvinylidene fluoride powder, 10-15 parts of sodium hydroxide solution, 200-250 parts of acetonitrile, 23-25 ​​parts of α-bromoisobutyryl bromide, and 10-12 parts of triethylamine; wherein the concentration of the sodium hydroxide solution is 10 wt%.

6. The method for preparing a modified activated carbon filter membrane for a filter device according to claim 4, characterized in that: The aminoolefin compound raw material comprises the following components: by weight, 10-12 parts of ethylenediamine, 28-30 parts of 6-bromo-1-hexene, 100-150 parts of anhydrous acetonitrile, and 16-18 parts of triethylamine.

7. The method for preparing a modified activated carbon filter membrane for a filter device according to claim 4, characterized in that: The quaternary ammonium salt monomer raw material comprises the following components: by weight, 10-12 parts of α,α′-dibromo-p-xylene, 47-50 parts of pyridine carboxaldehyde, 100-120 parts of 1,2-dichloroethane, 5-8 parts of aminoolefin compound, and 200-250 parts of dichloromethane.

8. The method for preparing a modified activated carbon filter membrane for a filter device according to claim 4, characterized in that: The modified polyvinylidene fluoride powder raw material comprises the following components: by weight, 10-12 parts of brominated polyvinylidene fluoride powder, 25-38 parts of quaternary ammonium salt monomer, 2-3 parts of 2,2'-bipyridine, 1-1.5 parts of cuprous bromide, and 200-250 parts of acetonitrile.

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