Water-soluble high cationic charge density active compound, its preparation method and application

Abstract

The application discloses a water-soluble high cationic charge density active compound and a preparation method and application thereof. The water-soluble high cationic charge density compound molecule is prepared from a silane coupling agent, polyethylene imine and a glycidyl compound. The prepared product structure contains active siloxane groups, quaternary ammonium salt cation groups and a large number of amine groups. The active siloxane groups reserved in the structure of the compound can be chemically grafted with porous filter materials with reactive groups on the surface, and can also occur condensation reaction to form polymers in the drying process, so as to endow the porous filter material with a persistent high cationic charge density on the surface after graft modification. The modified filter material has excellent removal performance on nano-plastics in water and excellent antibacterial performance, and has a wide application prospect in the field of water filtration.

Description

Technical Field

[0001] This invention relates to the fields of organic chemistry and filtration and separation technology, specifically to a water-soluble compound with high cationic charge density, its preparation method, and its application in the field of water filtration and separation. Background Technology

[0002] Micro- and nano-plastics have become a major environmental concern globally, classified as emerging pollutants. They are not only widely distributed in aquatic environments such as lakes and rivers, but also difficult to decompose, persisting in the environment for many years and worsening pollution over time. Nanoplastics (smaller than 1 micrometer) have been found to cause harm at the cellular and molecular levels, significantly impacting the growth, development, and reproduction of organisms. Micro- and nano-plastics can even penetrate the cell walls of the human gastrointestinal tract and enter the human body, posing a significant potential threat to human health. Studies have also found that tap water and bottled water contain micro- and nano-plastics, which can directly enter the human body. Therefore, the removal of micro- and nano-plastics from water has become an urgent and pressing issue.

[0003] As an emerging pollutant, there is currently a lack of targeted removal methods for both environmental water and tap water. Typical current water treatment processes for micro- and nano-plastics include traditional methods such as coagulation, sand filtration, adsorption, and biological treatment. However, these methods are ineffective at removing small-sized micro- and nano-plastics; and biological treatment processes are demanding and costly. Membrane filtration can effectively remove micro- and nano-plastics, but its removal mechanism is mainly based on the size repulsion effect driven by pressure difference. Its biggest drawback is membrane fouling, which can lead to a rapid increase in membrane resistance and a decrease in membrane flux, affecting membrane efficiency and causing rapid failure. Porous filter materials, with their excellent pore structure, offer superior filtration performance and pollutant holding capacity, making them promising candidates for nano-plastic removal. Glass fiber filter materials, made from glass fiber and glass wool using a wet papermaking process, exhibit superior filtration performance compared to other filter materials, with uniform pore distribution and high dirt-holding capacity.

[0004] Studies have found that most micro- and nano-plastics in the environment are negatively charged. Therefore, constructing a surface with a positive charge and utilizing the electrostatic interaction between the filter material surface and the micro- and nano-plastics can improve the filtration performance of the filter material for micro- and nano-plastics. For example, the literature [Xia Xue, Li Guoping, Luo Jiyue, Ma Yiwen. Grafting of quaternary ammonium salts to improve the zeta potential of glass fiber membranes, Water Purification Technology, 2020, 39(03):82-88] uses glass fiber membranes as the matrix, and prepares positively charged glass fiber membranes by plasma treatment and then chemically grafting organosilicon quaternary ammonium salts with antibacterial agents and tetraethyl orthosilicate reagent. However, this method requires two processing steps, which is relatively complicated, and the highest zeta potential of the filter material after treatment is only 27.35mV. Chinese patent CN116249581A, "Polycharged Filter Material with Excellent Removal Performance for Charged Particles and its Preparation Method", discloses that a polyamine compound is compounded with a crosslinking agent to treat the surface of the filter material to make it positively charged, which has selective removal performance for negatively charged organic / inorganic particles, heavy metal ions and pathogenic microorganisms in water. This method also requires multiple process steps, and the preparation of its modifier uses chemical solvents, which is not an environmentally friendly product.

[0005] Furthermore, water contains a large number of bacteria and microorganisms. These microorganisms attach to the filter media, grow and multiply, leading to filter media failure. Therefore, if the filter media has good antibacterial properties, it can improve the performance and lifespan of the filter media. As can be seen from the above, modifying the surface of the filter media with high cationic charge density compounds to form a high positive charge is key to achieving efficient removal of nanoplastics.

[0006] Therefore, there is an urgent need to develop a technology and materials that are simple to prepare, low in cost, environmentally friendly, have good removal function for micro and nano-plastics in water, and have good antibacterial properties. This is of great significance for ensuring the safety of the water environment and drinking water and protecting people's health. Summary of the Invention

[0007] The technical problem this invention aims to solve is to overcome the issues of high resistance and short lifespan in existing membrane filtration materials that remove nanoplastic pollutants from water through surface filtration. This invention prepares a water-soluble, high-cationic charge density active compound and applies it to porous filtration materials (such as glass fiber filter media). First, by chemically modifying the surface of the glass fiber filter media and introducing a large number of cationic and amine groups, the glass fiber filter media is endowed with a durable high-density positive charge, which can efficiently remove nanoplastics from water through electrostatic adsorption. Second, the prepared water-soluble, high-cationic charge density active compound contains reactive silanol groups in its molecular structure. Besides undergoing its own condensation reaction to form a macromolecular adhesive that reinforces the glass fiber filter media, it can also undergo a grafting reaction with the hydroxyl groups on the glass fiber surface to form covalent bonds, further enhancing its bonding force with the glass fiber substrate and ensuring the durability of its surface positive charge. Finally, the cationic groups in the molecular structure contain quaternary ammonium salt groups with excellent antibacterial properties, thus also endowing the modified glass fiber filter media with excellent antibacterial properties.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] This invention provides a water-soluble active compound with high cationic charge density and applies it to porous filter materials with active reactive groups on the surface, giving them long-lasting high cationic charge density performance and excellent removal performance for micro- and nano-plastics with a particle size of less than or equal to 1 μm in water.

[0010] This invention provides a water-soluble, highly cationic charge-density active compound, which is prepared by the following method:

[0011] Add polyethyleneimine to 10-20 times its weight of water, then add glycidyl group compound, heat to 60-70℃ and react for 3-4 hours, then control the temperature at 70-75℃, continue to add silane coupling agent, and continue to react for 2-4 hours to prepare the target water-soluble high cationic charge density active compound.

[0012] Preferably, the polyethyleneimine is a branched polyethyleneimine with a molecular weight of 1800-10000.

[0013] Preferably, the glycidyl compound is one of glycidyltrimethylammonium chloride, glycidyltriethylammonium chloride, or glycidyltripropylammonium chloride.

[0014] Preferably, the glycidyl group compound is added at a mass of 20-40 wt% of polyethyleneimine.

[0015] Preferably, the silane coupling agent is a silane coupling agent containing an epoxy group at one end and a siloxane group at the other end. The epoxy group at one end of the silane coupling agent of the present invention can react with PEI to generate the target substance, and the siloxane group at the other end, after hydrolysis, becomes a silanol group, thus enabling it to react with the substrate and undergo its own condensation reaction.

[0016] More preferably, the silane coupling agent is one of 3-glycidoxypropyltrimethoxysilane (A-187), 3-(2,2-epoxypropane)propyltriethoxysilane (A-1871), β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (A-186), and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane (A-1861).

[0017] Preferably, the added mass of the silane coupling agent is 25-45 wt% of polyethyleneimine.

[0018] The above preparation method yields a water-soluble, high-cationic-charge-density active compound whose molecular structure contains active siloxane groups, quaternary ammonium salt cationic groups, and a large number of amine groups. When used to modify porous filter media, it imparts a durable, high-density positive charge to the filter media, achieving highly efficient removal of micro- and nano-plastics from water. Furthermore, the modified filter media exhibits excellent antibacterial properties.

[0019] This invention also provides a filter material modified based on the above-mentioned water-soluble high cationic charge density active compound, which is prepared by the following method:

[0020] A porous filter material with active groups on its surface that can react with silanol groups is immersed in the above-mentioned water-soluble high cationic charge density active compound. The pH is adjusted to 4-5 by adding acid, and the material is soaked for 1-3 hours. Then it is taken out and dried at 100-150°C to obtain a porous filter material with water-soluble high cationic charge density active compound on its surface.

[0021] Preferably, the porous filter material having reactive groups that can react with silanol groups is a glass fiber filter material.

[0022] Preferably, the amount of the water-soluble high cationic charge density active compound is 5%-7% of the weight of the porous filter media material.

[0023] This invention employs a simple two-step feeding method, controlling the proportions and molecular weights of various raw materials within appropriate ranges, to prepare the target water-soluble high cationic charge density active compound. When applied to modified glass fiber filter materials, this compound exhibits excellent filtration performance for micro / nanoplastics in water and possesses antibacterial properties. First, by introducing quaternary ammonium salt groups into the PEI molecular structure, in addition to further increasing the cationic density of PEI, the quaternary ammonium salt groups also possess excellent antibacterial functions, endowing the product with superior antibacterial properties. Second, based on the quaternary ammonium salt-modified PEI product, further modification is achieved by adding a silane coupling agent containing epoxy and siloxane groups, thereby introducing siloxane groups into the product structure. Finally, utilizing the fact that siloxane groups can hydrolyze into active hydroxyl groups under appropriate acidic conditions, these groups can undergo grafting reactions with the filter material surface and simultaneously undergo condensation reactions to form polymers, thus endowing the filter material surface with a persistent high cationic charge density, achieving high filtration efficiency and excellent antibacterial properties for nanoplastics. Although the principle is simple, the inventors conducted repeated research and experiments on the order of addition, material ratio, and molecular weight of PEI. They discovered that the order of introducing quaternary ammonium salt groups and the two modifying materials containing epoxy and siloxane groups must strictly follow the sequence of "quaternary ammonium salt modification first, followed by silane coupling agent modification containing epoxy and siloxane groups." If the silane coupling agent is added first, the siloxane groups in the silane coupling agent will undergo a certain degree of hydrolysis at high temperatures, leading to unstable conditions such as flocculation in the prepared material. Furthermore, if the ratio of the two modifying raw materials or the molecular weight of the PEI raw material is unsuitable, the resulting product will either be insoluble in water and therefore unstable, or its application performance will be significantly deteriorated.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The water-soluble, high-cationic-charge-density active compound of this invention is an environmentally friendly aqueous compound. Its quaternary ammonium salt and amine groups impart a high positive charge density. Furthermore, the silanol groups in the molecular structure are reactive, not only forming chemical bonds with porous substrates to enhance their bonding strength with glass fiber substrates and maintain their surface positive charge, but also undergoing condensation reactions to form macromolecular adhesives that reinforce the glass fiber filter media. The quaternary ammonium salt groups in the molecular structure possess excellent antibacterial properties, imparting superior antibacterial properties to the modified glass fiber filter media, effectively controlling the growth and reproduction of microorganisms, and extending the service life of the filter media. The positively charged porous filter material prepared by the method of this invention can achieve highly efficient filtration of nanoplastic pollutants with a particle size of 1 μm or less in water under low resistance, and has broad application prospects. Attached Figure Description

[0026] The present invention will now be described in detail with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram illustrating the preparation mechanism of the water-soluble high-cation-density active compound described in this invention and its surface modification process on glass fiber filter media.

[0028] Figure 2 This is a structural design diagram of the water filtration performance test bench for the filter media of the present invention. Wherein: 1-Test tank; 2-High-speed stirrer; 3-Thermometer; 4-Stop valve; 5-Coarse filter; 6-Hydraulic pump; 7-Throttle valve; 8-Sampling valve; 9-Flow meter; 10-Pressure gauge; 11-Differential pressure sensor; 12-Filter media clamp; 13-Collection tank.

[0029] Figure 3 SEM image of fiberglass base paper.

[0030] Figure 4 Example 5: SEM image of the filter media.

[0031] Figure 5 SEM image of the modified glass fiber filter material of Comparative Example 4. Detailed Implementation

[0032] The following specific embodiments further illustrate a water-soluble, high-cationic-charge-density active compound, its preparation method, and its applications. Those skilled in the art will understand that these embodiments are for illustrative purposes only, but the scope of protection of the present invention is not limited thereto.

[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available products.

[0034] The following examples illustrate the preparation methods and related testing techniques used for glass base paper:

[0035] Preparation of glass fiber base paper: 475-79 glass wool and chopped glass fibers were mixed at a mass ratio of 7:3 and then decomposed using a decomposition machine at 10,000 revolutions. The pH was controlled at 2.5-3.5, and the basis weight was 48±1 g / m³. 2 After being evenly dispersed, the slurry is poured into a forming machine, dehydrated, formed, and then dried in a flat sheet to obtain the glass fiber filter material base paper. The average pore size of the glass fiber base paper was measured to be 3.03 μm.

[0036] Tensile strength testing (including tensile strength before and after water immersion) was performed according to GB / T12914-2018. A tensile strength tester (model: CE062, L&W, Sweden) was used to test the tensile strength and elongation at break of the glass fiber filter paper. The sample length was 100 mm and the width was 15 mm. The treated filter material was immersed in deionized water at room temperature for one month, then dried, and the tensile strength of the glass fiber filter material was re-measured as the strength performance after water immersion.

[0037] Zeta potential (including zeta potential before and after water immersion) testing of fiberglass filter media: The test was conducted using a flow potentiometer (model: SZP-06, Mütek, Germany). The fiberglass filter media was slurried and prepared into a 500ml solution, with the slurry concentration controlled below 4%. The surface charge of the fiberglass slurry was then measured. The treated filter media was then immersed in deionized water at room temperature for one month, then removed, dried, and the zeta potential of the fiberglass filter media was measured again; this was the zeta potential after water immersion.

[0038] The antibacterial properties of the filter media (including antibacterial properties before and after soaking in water) were tested using the shaking method: 5 mL of bacterial solution with a concentration of 1×10⁻⁶ was taken. 8 cfu / mL ~5×10 8 A CFU / mL bacterial suspension (Staphylococcus aureus) was prepared in an Erlenmeyer flask containing 70 mL of 0.03 mol / L PBS buffer (2.84 g disodium hydrogen phosphate, 1.36 g potassium dihydrogen phosphate, and 1000 mL water). 0.75 g of chopped filter media sample was added. The flask was placed on a constant-temperature water bath shaker and incubated at (24±1) °C with shaking at 150 rpm for different time periods. After the specified time, the experimental mixture was diluted to an appropriate concentration with 0.03 mol / L PBS buffer, transferred to nutrient agar medium, and incubated at (37±1) °C for 24 h. The antibacterial rate was then counted and calculated. The treated filter media was then immersed in deionized water at room temperature for one month, dried, and the antibacterial properties of the glass fiber filter media were re-evaluated.

[0039] Filtration performance (filtration efficiency and resistance of nanoplastics): Referring to European standard EN 13443-2 "Water conditioning equipment inside buildings - mechanical filters", a test bench for water filtration performance of filter media was designed using the single-pass method, and the corresponding test methods were specified. The water filtration performance test bench is as follows: Figure 2 As shown, where: 1-test tank; 2-high-speed stirrer; 3-thermometer; 4-stop valve; 5-coarse filter; 6-hydraulic pump; 7-throttle valve; 8-sampling valve; 9-flow meter; 10-pressure gauge; 11-differential pressure sensor; 12-filter media clamp; 13-collection tank.

[0040] The experimental conditions for water filtration efficiency testing are as follows: water flow rate 75 L / h, test time 60 min, and test area 78.5 cm². 2 The test medium was deionized water, and the contaminant was a suspension of polystyrene latex balls with an average particle size of 300 nm (i.e., nanoscale plastic with a particle size of 0.3 μm). The polystyrene latex ball suspension, diluted to a particle concentration of approximately 20,000 particles / ml, was passed through the filter media at a surface flow rate of 10 cm / min. The number of experimental particles upstream and downstream of the filter paper sample was measured, and the water filtration efficiency of the filter media was calculated. Samples were taken every 10 minutes at both the upstream and downstream sampling points, and the filtration efficiency of the filter media was obtained by calculating the number of particles upstream and downstream. The test duration was 1 hour. The pressure difference at the start of the test and the resistance change after 1 hour were recorded, expressed as the increase in resistance. The treated filter media was then immersed in deionized water at room temperature for one month, dried, and the filtration performance of the glass fiber filter media was re-measured to determine the filtration performance after water immersion.

[0041] The purpose of this invention is to prepare a water-soluble, high-cationic-charge-density active compound and apply it to porous filter materials with active reactive groups on their surface. The water-soluble, high-cationic-density active compound of this invention is prepared by reacting polyethyleneimine of a suitable molecular weight with appropriate amounts of silane coupling agents and glycidyl compounds. The resulting product has a molecular structure containing both active siloxane groups, quaternary ammonium salt cationic groups, and a large number of amino groups. The preparation mechanism of this compound and its surface modification process on glass fiber filter materials are described below. Figure 1 As shown.

[0042] Examples 1-4 and Comparative Examples 1-7

[0043] Examples 1-4 and Comparative Examples 1-7 prepared a high cationic charge density active compound.

[0044] Examples 1-4 and Examples 1-6 were prepared according to the following steps: Polyethyleneimine was added to 10-20 times its mass of water, then glycidyl quaternary ammonium salt compound was added, the temperature was raised to 65°C and reacted for 3 hours, the temperature was controlled at 73°C, a silane coupling agent was added, and the reaction was continued for 3 hours to obtain the target product.

[0045] Comparative Example 7 used the same reaction raw materials and proportions as Example 1, except that the order of adding the silane coupling agent and the glycidyl quaternary ammonium salt compound was reversed.

[0046] The ingredient lists and product states of Examples 1-4 and Comparative Examples 1-7 are shown in Table 1:

[0047] Table 1. Ingredients and product states of Examples 1-4 and Comparative Examples 1-7

[0048]

[0049]

[0050] As can be seen from the results in Table 1, within the scope of this invention, the high cationic charge density active compounds prepared in Examples 1-4 were all clear and transparent, indicating excellent water solubility and storage stability. The products of Comparative Examples 1-3 also exhibited excellent water solubility and storage stability. However, Comparative Example 4 showed the appearance of flocculent matter, which may be due to the excessively high proportion of glycidyl compounds added, leading to instability in the compound structure. Comparative Example 5 showed a white precipitate, which was due to the excessively high molecular weight of the polyethyleneimine used, resulting in an excessively large molecular weight of the high cationic charge density compound, ultimately leading to a decrease in the product's water solubility, thus causing the precipitation of a white precipitate. The flocculent matter that appeared in Comparative Example 6 after 3 days of storage indicates product instability, which may be due to the excessively high proportion of silane coupling agent used, easily causing the product to continue reacting during storage, leading to system instability and the precipitation of flocculent matter. In Comparative Example 7, because the silane coupling agent first modified PEI with glycidyltrimethylammonium chloride, the siloxane groups reacted for too long at high temperatures, prematurely undergoing a certain degree of hydrolysis, resulting in the prepared substance being prone to flocculation and other unstable states.

[0051] Examples 5-8 and Comparative Examples 8-11

[0052] Examples 5-8 and Comparative Examples 8-10 prepared a glass fiber filter material modified with a water-soluble high cationic charge density active compound, which was prepared by the following method:

[0053] Equal masses of fiberglass base paper were impregnated with stable water-soluble high cationic charge density active compounds prepared in Examples 1-4 and Comparative Examples 1-3, respectively. The pH was adjusted to 4-5, and the impregnation time was 2 hours. The concentration of the water-soluble high cationic charge density active compounds was controlled so that the amount of compound applied to the filter media was within 6 ± 0.5% of the filter media weight, resulting in Examples 5-8 and Comparative Examples 8-10. Additionally, a water filtration membrane with a pore size of 3 μm (purchased from Haining Yibo Filter Material Factory) was selected as Comparative Example 11. Unmodified fiberglass base paper served as a blank control. The tensile strength, zeta potential, filtration efficiency of 300 nm nanoplastics, increase in filtration resistance, and antibacterial properties against Staphylococcus aureus were then tested before and after water immersion. The test results are shown in Table 2.

[0054] Table 2 Performance Test of Filter Media Before Soaking in Water

[0055]

[0056] Table 3 Performance Test of Filter Media After Soaking in Water

[0057]

[0058]

[0059] As can be seen from the test results in Tables 2 and 3, within the scope of this invention, the filter media samples (Examples 5-8) obtained after treatment with the water-soluble high cationic charge density active compounds prepared in Examples 1-4 all exhibit good tensile strength properties. Furthermore, the zeta potential on the filter media surface changed from a negative charge to a higher positive charge state, further demonstrating that the prepared product has a high cationic charge density. The filtration efficiency of the treated filter media all reached approximately 97%, and after filtration for 1 hour, the resistance only increased to approximately 0.80 kPa. Moreover, after soaking in water for one month, the material's properties remained essentially unchanged, indicating that the material prepared by the method of this invention has excellent and durable application performance.

[0060] In Comparative Example 8, the low proportion of glycidyl compounds containing quaternary ammonium groups led to a slight decrease in cation density, resulting in slightly lower zeta potential and filtration efficiency. Furthermore, the reduced proportion of quaternary ammonium groups significantly reduced the antibacterial properties of the filter media. In Comparative Example 9, the low molecular weight of the polyethyleneimine used resulted in minimal enhancement of the filter media's strength after application, leading to low media strength. Additionally, the filter media's performance deteriorated significantly after soaking in water. In Comparative Example 10, the low amount of silane coupling agent resulted in weak bonding with the fiber substrate and weak interactions between compounds, leading to poor material strength, and a significant performance decline after soaking in water. Comparative Example 11, using a traditional water filtration membrane material with a pore size close to that of glass fiber, achieved a filtration efficiency of only about 15%, and the resistance increased significantly after one hour of filtration, further demonstrating the advantages of the material prepared by the method of this invention in water filtration. Regarding antibacterial properties, the filter media in Examples 5-8 exhibited excellent antibacterial performance due to the presence of sufficient quaternary ammonium salt groups, with antibacterial rates all ≥99.9% and no decrease in antibacterial activity after soaking in water. Comparative Examples 8-11 showed poorer antibacterial performance, and their performance further declined after soaking in water.

[0061] In addition, in comparison Figure 3 (glass fiber base paper) and Figure 4 As can be seen in Example 5 (Filter Material), the filter material modified with the water-soluble high cationic charge density active compound prepared within the scope of this invention mainly concentrates on the fiber surface and fiber connections, without clogging. Therefore, it can maintain a good pore structure, maintain good filtration performance, and improve the strength of the filter material. Products outside the scope of this invention do not possess good water solubility (…). Figure 5 (Comparative Example 4: morphology of the modified material) The modified filter material exhibited significant pore clogging, affecting its filtration performance.

[0062] The above embodiments are merely preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a water-soluble, high cationic charge density active compound, characterized in that, The preparation steps include the following: Polyethyleneimine is added to water, followed by the addition of glycidyl group compound. The mixture is heated to 60-70℃ and reacted for 3-4 hours. The temperature is then controlled at 70-75℃, and silane coupling agent is added. The reaction is continued for another 2-4 hours to prepare the target water-soluble high cationic charge density active compound. The polyethyleneimine mentioned is a branched polyethyleneimine with a molecular weight of 1800-10000; The glycidyl compound is one of glycidyltrimethylammonium chloride, glycidyltriethylammonium chloride, and glycidyltripropylammonium chloride; the added mass of the glycidyl compound is 20-40 wt% of polyethyleneimine. The silane coupling agent is a silane coupling agent containing an epoxy group at one end and a siloxane group at the other end, and the added mass of the silane coupling agent is 25-45 wt% of polyethyleneimine.

2. The method for preparing a water-soluble, high cationic charge density active compound according to claim 1, characterized in that, The mass of water added should be 10-20 times the mass of polyethyleneimine.

3. The method for preparing a water-soluble, high cationic charge density active compound according to claim 1, characterized in that, The silane coupling agent is one of 3-glycidoxypropyltrimethoxysilane, 3-(2,2-epoxypropane)propyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

4. A water-soluble, high-cationic-charge-density active compound prepared by the preparation method according to any one of claims 1-3, characterized in that, Its molecular structure contains active siloxane groups, quaternary ammonium salt cationic groups, and a large number of amine groups.

5. The application of the water-soluble high cationic charge density active compound of claim 4 in the preparation of water filtration materials, characterized in that, Filter media modified from water-soluble, high cationic charge density active compounds can be used to filter micro- and nano-plastics with a particle size of less than or equal to 1 μm in water.

6. The application according to claim 5, characterized in that, The preparation method of filter media modified with water-soluble high cationic charge density active compounds is as follows: A porous filter material with active groups on its surface that can react with silanol groups is immersed in the water-soluble high cationic charge density active compound. The amount of the water-soluble high cationic charge density active compound is 5%-7% of the weight of the porous filter material. The pH is adjusted to 4-5 with acid. The material is soaked for 1-3 hours, then removed and dried at 100-150°C to obtain the final product.

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