Cellulose fiber-based sandwich structure filter material for removing micro-plastics and preparation method of cellulose fiber-based sandwich structure filter material

Abstract

The invention discloses a cellulose fiber-based sandwich structure filter material for removing micro-plastics and a preparation method of the cellulose fiber-based sandwich structure filter material, and belongs to the field of micro-plastic filtration. The preparation method comprises the following steps: (1) uniformly mixing cellulose long fibers and cellulose short fibers, and then carrying out suction filtration to respectively prepare an upper-layer fiber membrane and a lower-layer fiber membrane; (2) preparing a covalent cross-linking mixture from cellulose nanofibers as a base material, a silane coupling agent, an amino-containing polymer and water; (3) coating a fiber membrane with the covalent cross-linking mixture, and assembling to obtain a sandwich structure; and (4) freezing the obtained sandwich structure, and drying at normal pressure to obtain the cellulose fiber-based sandwich structure filter material. The obtained cellulose fiber-based sandwich structure filter material can effectively filter multi-scale micro-plastics in a graded manner, can effectively filter various micro-plastics and micro-plastics in various real water samples, and provides a novel environment-friendly solution for micro-plastic pollution abatement.

Description

Technical Field

[0001] This invention relates to the field of microplastic filtration, and in particular to a cellulose fiber-based sandwich structure filter material for removing microplastics and its preparation method. Background Technology

[0002] Plastics, with their excellent mechanical properties, corrosion resistance, and low cost, have become core materials in food packaging, medical devices, and other fields, with polyolefin polymers accounting for over 60%. However, their high chemical stability leads to a natural degradation cycle of hundreds of years, and under environmental stresses such as light, heat, and mechanical friction, they gradually decompose into microplastic pollutants (MPs) with a particle size of less than 5 mm. Notably, secondary microplastics with a particle size of less than 20 µm, due to their large specific surface area and significant surface charge characteristics, are more likely to form complex toxicity carriers by adsorbing heavy metals and organic pollutants, exacerbating ecological risks.

[0003] Current microplastic pollution control systems encompass technologies such as screening, chemical flocculation, adsorption, biodegradation, and photocatalytic decomposition. While screening can physically intercept particles, nanoscale microplastics easily penetrate them, and membrane pores are prone to clogging by retained pollutants, leading to flux decline. Chemical flocculation relies on flocculants such as aluminum or iron salts, which can rapidly aggregate suspended particles, but residual metal ions may exacerbate the ecological burden on aquatic bodies. Adsorption methods, relying on functionalized porous materials, can target and capture microplastics, but single adsorbents face the risk of desorption in dynamic water flow. Biodegradation and photocatalytic degradation suffer from long degradation cycles and stringent reaction conditions. For example, patent CN119735785A uses biomass-modified polyurethane foam to adsorb microplastics, utilizing its porous structure, but it relies on petroleum-based polymer materials with poor biodegradability and a high carbon footprint. While the magnetic chitosan / polydopamine aerogel reported in patent CN113952899A achieves microplastic adsorption through hydrogen bonding / electrostatic synergy, it suffers from low mechanical strength, collapse, and poor stability due to the easy degradation of chitosan in acidic wastewater, as well as high raw material costs. Patent CN119972001A removes microplastics using magnetically modified biochar, but the biochar is prone to detachment leading to secondary pollution, and the high-temperature carbonization process is energy-intensive, hindering large-scale application. Patent CN118223330B prepares a filterable micro / nanoplastics filter by loading cellulose onto filter paper, but this may result in large particles of the target precipitate causing blockage, while small particles penetrate and leak. In contrast, a composite filtration system combining physical interception and adsorption processes achieves hierarchical treatment of "large particle interception - small particle adsorption" through a gradient pore structure, addressing multi-scale microplastic pollution while avoiding the structural-functional contradiction between high-adsorption-capacity materials with low mechanical strength and high-strength substrates with insufficient removal efficiency. Summary of the Invention

[0004] Technical issues Current materials for removing microplastics are mostly designed for single-size plastic contaminants, and face problems such as low process economics, performance-stability imbalance, and functional limitations. Therefore, there is a need to develop a material that can achieve hierarchical retention of a wide particle size range from nanometer to micrometer within a single material, and that is low-cost, simple to process, and possesses both high removal rates and structural stability.

[0005] Technical content To address the aforementioned technical problems, this invention proposes a cellulose-based fiber sandwich structure filter material prepared by atmospheric pressure drying, providing an innovative solution for green and sustainable microplastic remediation. The sandwich structure of this invention can handle microplastic particle size range (nm→μm) pollution while balancing filtration performance and stability, solving problems such as structural collapse or adsorbate shearing in flow systems caused by hydraulic shearing in porous structures. The fiber membrane and aerogel filter material prepared from natural biomass fibers in this invention possess biodegradability advantages, making it a highly promising microplastic filter material. Furthermore, it is adaptable to atmospheric pressure drying, avoiding reliance on specialized drying equipment, reducing production costs, and increasing yield.

[0006] The first objective of this invention is to provide a method for preparing a cellulose fiber-based sandwich structure filter material, comprising the following steps: (1) The long cellulose fibers and short cellulose fibers were mixed evenly to obtain a fiber dispersion, and then filtered to obtain an upper fiber membrane and a lower fiber membrane respectively. (2) Using cellulose nanofibers as a substrate, a covalently crosslinked mixture was prepared with a silane coupling agent, an amino-containing polymer, and water; (3) The covalently cross-linked mixture is coated onto the fiber membrane and assembled to obtain a sandwich structure; (4) The obtained sandwich structure is frozen and then dried at normal pressure to obtain cellulose fiber-based sandwich structure filter material.

[0007] Furthermore, the cellulose long fibers mentioned in step (1) are selected from one or more of bamboo pulp fiber, wood cellulose fiber, bagasse long fiber, kenaf fiber, reed fiber, and coconut shell fiber.

[0008] Further, the cellulose long fibers mentioned in step (1) have a length of 0.5 mm to 5 mm and a diameter of 10 μm to 50 μm.

[0009] Furthermore, the cellulose short fibers mentioned in step (1) are selected from one or more of the following: lignocellulose nanofibers, bamboo cellulose nanofibers, and bacterial cellulose nanofibers. Further, the cellulose short fibers described in step (1) have a length of 10 μm to 100 μm and a diameter of 20 nm to 200 nm.

[0010] Further, in step (1), the mass ratio of long cellulose fibers to short cellulose fibers in the fiber dispersion is 1:0.01~0.5.

[0011] Further, in step (1), the mass ratio of the total mass of cellulose long fibers and cellulose short fibers to water in the fiber dispersion is 1:50~150.

[0012] Further, the volume of the fiber dispersion in step (1) is 60~100 mL.

[0013] Further, in step (1), the mass ratio of long cellulose fibers to short cellulose fibers in the upper fiber membrane is 1:0.01~0.05.

[0014] Further, the mass ratio of long cellulose fibers to short cellulose fibers in the lower fiber membrane described in step (1) is 1:0.1~0.15.

[0015] Furthermore, the cellulose nanofibers mentioned in step (2) are selected from one or more of the following: lignocellulose nanofibers, bamboo cellulose nanofibers, Tempo oxidized carboxylated cellulose nanofibers, and bacterial cellulose nanofibers.

[0016] Furthermore, the cellulose nanofibers described in step (2) have a length of 10 µm to 50 µm and a diameter of 20 nm to 100 nm.

[0017] Further, the silane coupling agent in step (2) is selected from one or more of methyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0018] Further, the amino-containing polymer in step (2) is selected from one or more of polydopamine, polyethyleneimine, polyacrylamide, 2-3-epoxypropyltrimethylammonium chloride, hydroxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide.

[0019] Further, the mass ratio of cellulose nanofibers and crosslinking agent in step (2) is 1:0.5~1.5.

[0020] Further, the mass ratio of cellulose nanofibers and amino polymers in step (2) is 1:0.5~2.

[0021] Furthermore, the mass ratio of cellulose nanofibers to water in step (2) is 1:40~120.

[0022] Further, the amount of the covalently crosslinked mixture described in step (3) coated on the fiber membrane is 500~600 mg / cm². 2 .

[0023] Further, the assembly in step (3) includes first coating the covalently cross-linked mixture onto the lower fiber membrane and then covering it with the upper fiber membrane, or coating the covalently cross-linked mixture onto the upper fiber membrane and then covering it with the lower fiber membrane.

[0024] Furthermore, the freezing temperature of the freezing treatment in step (4) is -196 ℃ to -20 ℃, and the freezing time is 60 min to 240 min.

[0025] Furthermore, in step (4), the drying temperature of the atmospheric pressure drying is 25 ℃~75 ℃, the pressure is 98~105 kPa, and the drying time is 1.5 h~4.5 h.

[0026] A second objective of this invention is to provide a cellulose fiber-based sandwich structure filter material prepared according to the above-described preparation method.

[0027] A third objective of this invention is to provide the application of the aforementioned cellulose fiber-based sandwich structure filter material in the field of multi-scale microplastic removal.

[0028] Furthermore, the microplastic is selected from one or more of polypropylene (PP), polyamide (PA), polyethylene (PE), polyurethane (PU), polystyrene (PS), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), and polyethylene terephthalate (PET).

[0029] Furthermore, the microplastics have a size of 50 nm to 20 µm.

[0030] Furthermore, the concentration of the microplastics is 10~100 mg / L.

[0031] Furthermore, the dispersion solution of the microplastic pollutant liquid is selected from one or more of deionized water, tap water, rainwater, snow water, seawater, lake water, and river water.

[0032] Furthermore, the cellulose fiber-based sandwich structure filter material achieves a removal efficiency of over 93% for single-scale microplastics and over 96% for mixed microplastics of different particle sizes.

[0033] Beneficial effects 1. The cellulose fiber-based sandwich structure filter material of the present invention avoids the problems of structural collapse or adsorbate shearing caused by hydraulic shear in a flow system.

[0034] 2. The cellulose fiber-based sandwich structure filter media of this invention achieves graded filtration of microplastics of mixed sizes, with a removal efficiency of over 93%. The removal efficiency of PS, PET, PMMA, and PVC microplastics is also over 93%, and the removal efficiency of microplastics dispersed in actual water samples such as lake water, seawater, tap water, and rainwater is also over 93%.

[0035] 3. The cellulose fiber-based sandwich structure filter material of the present invention uses natural and renewable cellulose as the base material, which has low preparation cost and does not require critical drying equipment in the preparation process, providing a new environmentally friendly solution for the treatment of microplastic pollution. Attached Figure Description

[0036] Figure 1 The image shown is a characterization result of Example 1, and is an SEM image of the cellulose fiber-based sandwich structure filter material. Figure 2 The characterization results of Example 4, wherein Figure 2 (a) SEM image of the upper fiber membrane of the cellulose fiber-based sandwich structure filter material for filtering mixed microplastic contaminants at a ratio of 100 nm:1 μm:10 μm = 5:2.5:2.5; Figure 2 (b) is a SEM image of the surface of the middle aerogel. Figure 2 (c) is a SEM image of the cross-section of the middle layer aerogel; Figure 2 (d) is a SEM image of the bottom fiber membrane.

[0037] Figure 3 The aerogel characterization results for Comparative Example 4 are shown in the image below.

[0038] Figure 4 The aerogel characterization results for Comparative Example 5 are shown in the image below.

[0039] Figure 5 The following is a SEM image of the aerogel monolayer filter material used in Comparative Example 6, which represents the characterization results.

[0040] Figure 6 The SEM image of the cellulose fiber-based bilayer filter material in Comparative Example 7 shows the characterization results. Detailed Implementation

[0041] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0042] Source of raw materials Bacterial cellulose nanofibers (BC, average length 20 μm, diameter 50–100 nm) were purchased from Guilin Qihong Technology Co., Ltd. (3-glycidyloxypropyl)trimethoxysilane (GPTMS) was purchased from Sinopharm Chemical Reagent Co., Ltd. Polyethyleneimine (PEI, Mw = 750,000 Da) was purchased from Sigma Reagent Co., Ltd. Fluorescent microplastics were purchased from Nantong Zhichuan Microsphere Biotechnology Co., Ltd. Seawater was purchased from Jiyuan Baicaoxian Trading Studio.

[0043] Test methods The surface morphology of the fiber membrane / aerogel was observed using scanning electron microscopy. The tensile properties of the fiber membrane / aerogel were tested using an electronic universal testing machine. The pore size distribution, porosity, and average pore size of the fiber membrane and aerogel were obtained using a high-performance automated porosimeter. The fluorescence intensity of the fluorescent microsphere suspension was measured using fluorescence spectroscopy, and a curve showing the change in standard concentration of microplastics as a function of fluorescence intensity was plotted. The Zeta potentials of the fiber membrane, aerogel, and microplastics were measured using a potential and particle size analyzer.

[0044] Example 1 This embodiment describes a method for preparing high-porosity cellulose fiber-based sandwich structure filter media using an atmospheric pressure drying method. The specific steps are as follows: Step 1: Lignocellulose fibers (BNP, 20 μm) and bacterial nanocellulose fibers (BC, 1.5 mm) were separately mixed with water and stirred evenly to obtain a 0.1 wt% lignocellulose fiber dispersion and a 0.8 wt% bacterial nanocellulose fiber dispersion. Then, the two fiber dispersions were mixed at BNP:BC mass ratios of 1:0.05 and 1:0.1, respectively, to prepare fiber dispersion 1 and fiber dispersion 2. Next, 80 mL of fiber dispersion 1 and fiber dispersion 2 were respectively used for vacuum-assisted filtration to prepare 35 mm diameter fiber membranes, which served as the upper and lower layers of a sandwich-structured filter material. The upper fiber membrane had a BNP:BC ratio of 1:0.05, and the lower fiber membrane had a BNP:BC ratio of 1:0.1.

[0045] Step 2: Take 20 mL of a 1 wt% bacterial nanocellulose fiber (BC) dispersion, 97 wt% (3-glycidyloxypropyl)trimethylsilane (GPTMS), and 20 wt% polyethyleneimine (PEI), and stir uniformly to prepare a biomass fiber covalent crosslinking mixture. The mass ratio of GPTMS to BC is 1:1, and the mass ratio of PEI to BC is 1:1.

[0046] Step 3: After coating 5 g of covalently crosslinked mixture onto the prepared lower fiber membrane, the upper fiber membrane is placed on top, followed by freezing treatment at -25 ℃ for 3 h. After freezing, it is dried under normal pressure at 60 ℃ for 4 h to obtain cellulose fiber-based sandwich structure filter material, denoted as SND5 filter material. Its longitudinal interface morphology is as follows. Figure 1 As shown.

[0047] The cellulose fiber-based sandwich structure filter material has a tensile strength of 12738.50 kPa and removal efficiencies of 93.96%, 95.21%, and 99.98% for PS microplastics with sizes of 100 nm, 1 µm, and 10 µm, respectively.

[0048] Example 2: Filtration effect of mixed microplastics with different particle size ratios Mixed microplastic contamination solutions with different particle size ratios of 100 nm : 1 μm : 10 μm = 5:2.5:2.5, 2.5:5:2.5, and 2.5:2.5:5 were prepared respectively. 10 mL of each of the above solutions were taken and microplastic filtration experiments were conducted using the cellulose fiber-based sandwich filter material SND5 prepared in Example 1 through a vacuum filtration device. Filtration was carried out at a pressure of -0.1 bar. The filtrate was collected and recovered through a receiving bottle, and the microplastic concentration of the treated water sample was tested.

[0049] The cellulose fiber-based sandwich filter media SND5 achieved removal efficiencies of 96.32%, 98.13%, and 98.45% for particles of 100 nm: 1 μm: 10 μm = 5:2.5:2.5, 2.5:5:2.5, and 2.5:2.5:5, respectively. Particle distribution analysis of the surface and cross-section of each layer after retention was performed using SEM. Figure 2 The following pattern was observed: the upper fibrous membrane ( Figure 2 (a) : Preferentially retains 10 μm particles, its large-pore network (10-50 μm) achieves large particle interception through physical sieving; the intermediate aerogel layer ( Figure 2 (b), (c): Some microplastic particles migrate to the pore walls, where retention is enhanced by electrostatic adsorption between the positive charge of the PEI-modified surface (BGP, +14.59 mV) and the microplastics (PS, -43.57 mV); the lower fiber membrane ( Figure 2 (d): The dense stacking between fibers further intercepts 100 nm particles penetrating the aerogel, and the rejection rate remains at 96.32% even when the input 100 nm proportion is the highest. Example 3: Different types of microplastics and their filtration effect in actual water samples. Microplastic contamination solutions of 50 mg / L each were prepared for PPS, PET, PMMA, and PVC. A 50 mg / L PS microplastic contamination solution was prepared using deionized water, tap water, rainwater, lake water, and seawater. 10 mL of each of these solutions was used to conduct microplastic filtration experiments using the cellulose fiber-based sandwich filter media SND5 prepared in Example 1 through a vacuum filtration device at a pressure of -0.1 bar. The filtrate was collected and recovered through a receiving bottle, and the microplastic concentration of the treated water samples was tested.

[0050] The cellulose fiber-based sandwich filter media SND5 exhibits a removal efficiency of 95.21% for PS microplastics, 98.76% for PVC microplastics, 97.40% for PET microplastics, and 93.98% for PMMA microplastics. Its filtration efficiencies for microplastics in deionized water, tap water, rainwater, lake water, and seawater are 95.21%, 95.88%, 95.97%, 93.82%, and 93.52%, respectively. This demonstrates the advantages of this invention: wide applicability and high removal efficiency.

[0051] Comparative Example 1 This comparative example follows the preparation process described in Example 1, except that the BC content in the fiber dispersion in the first step is adjusted to 0%.

[0052] The final cellulose fiber-based sandwich structure filter material has a tensile strength of 1122.25 kPa and removal efficiencies of 20.91%, 44.54%, and 89.78% for PS microplastics with sizes of 100 nm, 1 µm, and 10 µm, respectively.

[0053] Comparative Example 2 This embodiment follows the preparation process described in Example 1, except that the mass ratio of BNP to BC in the fiber dispersion in the first step is adjusted. Specifically, the mass ratio of BNP to BC in the fiber dispersion 2 is adjusted to 1:0.05.

[0054] The final cellulose fiber-based sandwich structure filter material has a tensile strength of 9969.03 kPa and removal efficiencies of 61.67%, 75.31%, and 94.28% for PS microplastics with sizes of 100 nm, 1 µm, and 10 µm, respectively.

[0055] Comparative Example 3 This embodiment follows the preparation process described in Example 1, except that the mass ratio of BNP to BC in the fiber dispersion 1 is adjusted to 1:0.1.

[0056] The final cellulose fiber-based sandwich structure filter material was completely clogged and could not perform normal filtration when mixed with microplastics.

[0057] Comparative Example 4 This comparative example follows the preparation process described in Example 1, except that the amount of GPTMS added in the second step is adjusted to 0.

[0058] The final filter material cannot be formed ( Figure 3 ).

[0059] Comparative Example 5 This comparative example follows the preparation process described in Example 1, except that the amount of PEI added in the second step is adjusted to 0.

[0060] The final filter material cannot be formed ( Figure 4 ).

[0061] Comparative Example 6 This comparative example follows the preparation process described in Example 1, except that only the fiber membrane was removed in step 3, leaving the aerogel to form a single-layer aerogel structure. Figure 5 ).

[0062] The final filter material had a tensile strength of 66.27 kPa and removal efficiencies of 12.28%, 22.93%, and 84.38% for PS microplastics with sizes of 100 nm, 1 µm, and 10 µm, respectively.

[0063] Comparative Example 7 This comparative example follows the preparation process described in Example 1, except that only the fiber membrane and the covalently cross-linked mixture from step three are combined to form a bilayer filter material. The longitudinal interface morphology is as follows: Figure 6 As shown.

[0064] The final filter media had a tensile strength of 7684.77 kPa and removal efficiencies of 62.49%, 69.63%, and 94.18% for PS microplastics with sizes of 100 nm, 1 µm, and 10 µm, respectively.

[0065] Comparative Example 8 This embodiment follows the preparation process described in Example 1, except that the mass of the covalent crosslinked mixture in the third step is adjusted to 2g.

[0066] The final cellulose fiber-based sandwich structure filter material has a tensile strength of 12545.49 kPa and removal efficiencies of 77.70%, 77.87%, and 95.91% for PS microplastics with sizes of 100 nm, 1 µm, and 10 µm, respectively.

[0067] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a cellulose fiber-based sandwich structure filter material, characterized in that, Includes the following steps: (1) A fiber dispersion is obtained by uniformly mixing long cellulose fibers and short cellulose fibers, and then the upper fiber membrane and the lower fiber membrane are obtained by vacuum filtration. The long cellulose fibers have a length of 0.5 mm to 5 mm and a diameter of 10 μm to 50 μm. The short cellulose fibers have a length of 10 μm to 100 μm and a diameter of 20 nm to 200 nm. The mass ratio of long cellulose fibers to short cellulose fibers in the upper fiber membrane is 1:0.01~0.05; the mass ratio of long cellulose fibers to short cellulose fibers in the lower fiber membrane is 1:0.1~0.

15. (2) Using cellulose nanofibers as a substrate, a covalently crosslinked mixture was prepared with a silane coupling agent, an amino-containing polymer, and water; The silane coupling agent is selected from one or more of methyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; The amino-containing polymer is selected from one or more of polydopamine, polyethyleneimine, polyacrylamide, 2-3-epoxypropyltrimethylammonium chloride, hydroxypropyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide; The mass ratio of cellulose nanofibers to crosslinking agent is 1:0.5~1.5; the mass ratio of cellulose nanofibers to amino polymer is 1:0.5~2; the mass ratio of cellulose nanofibers to water is 1:40~120. (3) The covalently cross-linked mixture is coated onto the fiber membrane and assembled to obtain a sandwich structure; the coating amount of the covalently cross-linked mixture on the fiber membrane is 500~600 mg / cm. 2 ; (4) The obtained sandwich structure is frozen and then dried at normal pressure to obtain cellulose fiber-based sandwich structure filter material.

2. The preparation method according to claim 1, characterized in that, The cellulose long fibers mentioned in step (1) are selected from one or more of bamboo pulp fiber, wood cellulose fiber, bagasse long fiber, kenaf fiber, reed fiber, and coconut shell fiber.

3. The preparation method according to claim 1, characterized in that, The cellulose short fibers mentioned in step (1) are selected from one or more of the following: lignocellulose nanofibers, bamboo cellulose nanofibers, and bacterial cellulose nanofibers.

4. The preparation method according to claim 1, characterized in that, The cellulose nanofibers mentioned in step (2) are selected from one or more of the following: lignocellulose nanofibers, bamboo cellulose nanofibers, Tempo oxidized carboxyl cellulose nanofibers, and bacterial cellulose nanofibers; the length of the cellulose nanofibers is 10 µm to 50 µm and the diameter is 20 nm to 100 nm.

5. The preparation method according to claim 1, characterized in that, The assembly described in step (3) includes first coating the covalently cross-linked mixture onto the lower fiber membrane and then covering it with the upper fiber membrane, or coating the covalently cross-linked mixture onto the upper fiber membrane and then covering it with the lower fiber membrane.

6. The preparation method according to claim 1, characterized in that, The freezing temperature in step (4) is -196 ℃ to -20 ℃, and the freezing time is 60 min to 240 min.

7. The preparation method according to claim 1, characterized in that, The drying temperature of the atmospheric pressure drying in step (4) is 25 ℃~75 ℃, the pressure is 98~105 kPa, and the drying time is 1.5 h~4.5 h.

8. A cellulose fiber-based sandwich structure filter material, characterized in that, The cellulose fiber-based sandwich structure filter material is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the cellulose fiber-based sandwich structure filter material as described in claim 8 in the field of microplastic removal.

10. The application according to claim 9, characterized in that, The microplastics include one or more of polypropylene, polyamide, polyethylene, polyurethane, polystyrene, polymethyl methacrylate, polyvinyl chloride, and polyethylene terephthalate; the microplastics have a size of 50 nm to 20 µm.

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