Dispersion extraction aid for micro / nano plastic in soil and application of dispersion extraction aid

Abstract

The invention provides a dispersion extraction auxiliary agent for micro / nano plastic in soil and application of the dispersion extraction auxiliary agent, and belongs to the technical field of pollutant detection and treatment. The dispersion extraction auxiliary agent provided by the invention is prepared from the following preparation raw materials in percentage by mass: 1 to 30 percent of polyphosphate, 1 to 10 percent of sodium percarbonate, 0 to 1 percent of surfactant and 59 to 98 percent of water, the surface active agent is a nonionic surface active agent or a zwitterionic surface active agent. According to the invention, the polyphosphate dispersant is adopted to disperse the soil aggregate and release the micro / nano plastic wrapped by the soil aggregate; the sodium percarbonate solid oxidizing agent can pre-oxidize organic substances in soil, improve the dispersion effect on soil aggregates and release micro / nano plastic wrapped in the soil aggregates; the zwitterionic surfactant or the nonionic surfactant can reduce the electrostatic adsorption force between the micro / nano plastic and the vessel in the extraction process of the micro / nano plastic in the soil.

Description

Technical Field

[0001] The invention belongs to the technical field of pollutant detection and treatment, and specifically relates to a dispersion extraction auxiliary for micro / nano plastics in soil and application thereof. Background Art

[0002] The pollution of microplastics (particle size <5mm) and nanoplastics (particle size <1μm) caused by the irregular production, use of plastic products and disposal of plastic waste has attracted global attention. Soil is an important gathering place for micro / nanoplastics. Many studies have confirmed that micro / nanoplastics (≤2μm) can be absorbed by crop roots and transferred to above-ground tissues, indicating that micro / nanoplastic pollution in the soil-plant system will trigger food chain transmission risks. Limited by the separation and analysis technology of microplastics in soil, most current studies only analyze microplastics with a particle size of >20μm in soil, and do not consider the effect of soil aggregates on the extraction efficiency of microplastics due to their encapsulation effect, especially the effect on small-sized micro / nanoplastics (particle size less than 20μm) in soil.

[0003] For example, related technologies use pressurized fluid extraction or thermal pyrolysis chromatography combined with mass spectrometry to quantify micro / nano plastics in soil, but these two methods cannot obtain information such as the size and shape of micro / nano plastics, which are important characteristics that distinguish micro / nano plastics from other pollutants; related technologies use high-density flotation reagents (saturated sodium chloride solution, saturated zinc chloride solution, and saturated sodium iodide, etc.) to float soil, remove dense mineral particles in the soil, and use oxidizing reagents to digest organic matter in the soil. The high recovery rate of microplastic recovery is based on standard microplastic particles and fibers with hydrophobic surfaces (particle size range of 100μm to 5mm). Studies have shown that soil is mainly composed of inorganic mineral particles and organic matter of different particle sizes. Through the adhesion of organic matter, most of the micro / nano plastics that enter the soil will be combined with soil aggregates, and only 28% of the micro / nano plastics exist in the form of dispersed particles. However, the above-mentioned density flotation-based separation and analysis method for micro / nanoplastics in soil does not pay attention to the influence of soil aggregates on the extraction of micro / nanoplastics in soil, and it is difficult to achieve efficient extraction of micro / nanoplastics wrapped in soil aggregates in actual soil. Summary of the invention

[0004] The purpose of the present invention is to provide a dispersion and extraction aid for micro / nanoplastics in soil and its application. The dispersion and extraction aid provided by the present invention can disperse soil aggregates and release micro / nanoplastics wrapped in soil aggregates, thereby realizing efficient recovery and extraction of micro / nanoplastics in soil.

[0005] In order to achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0006] A dispersion extraction aid for micro / nano plastics in soil, comprising the following preparation raw materials by mass fraction:

[0007] 1-30% polyphosphate, 1-10% sodium percarbonate, 0-1% surfactant and 59-98% water; the surfactant is a nonionic surfactant or a zwitterionic surfactant.

[0008] Preferably, the polyphosphate is sodium hexametaphosphate.

[0009] Preferably, the zwitterionic surfactant is a betaine surfactant; and the nonionic surfactant is an alkyl glycoside.

[0010] The present invention also provides the use of the dispersing extraction aid for separating micro / nano plastics in soil described in the above technical solution to separate and extract plastics in soil.

[0011] Preferably, the application method of the dispersion extraction aid comprises the following steps:

[0012] The soil to be extracted and the dispersion extraction aid for micro / nano plastics in the soil are mixed, and a first liquid phase and a first solid phase are obtained after solid-liquid separation;

[0013] Density separation of the first solid phase to obtain a second liquid phase and a second solid phase;

[0014] The first liquid phase and the second liquid phase are microfiltered to obtain micro / nano plastics; the pore size of the filter membrane used for the microfiltration is 0.1 to 20 μm.

[0015] Preferably, the pH of the soil to be extracted is 4.0-8.0.

[0016] Preferably, the mass ratio of the soil to be extracted to the dispersion extraction aid is 1:2-4.

[0017] Preferably, the reagent used for density separation is sodium chloride or zinc chloride.

[0018] Preferably, digestion is further included after the microfiltration; the reagent used for the digestion is hydrogen peroxide.

[0019] The invention provides a dispersion extraction aid for micro / nano plastics in soil, which comprises the following raw materials by mass fraction: 1-30% polyphosphate, 1-10% sodium percarbonate, 0-1% surfactant and 59-98% water; the surfactant is a nonionic surfactant or a zwitterionic surfactant. The invention adopts polyphosphate as a dispersant, which can disperse soil aggregates, release micro / nano plastics wrapped in soil aggregates, and improve the extraction and recovery efficiency of micro / nano plastics in soil; adopts sodium percarbonate as a solid oxidant, which can pre-oxidize organic matter in soil, has a dispersing effect on soil aggregates, and further releases micro / nano plastics wrapped in soil aggregates; further, the invention adopts zwitterionic betaine surfactants and nonionic alkyl glycosides with the advantages of antistatic, biocompatibility and environmental friendliness, which can reduce the electrostatic adsorption between micro / nano plastics and utensils, soil particles and plant residues in the process of extracting micro / nano plastics in soil, and further improve the extraction and recovery efficiency of micro / nano plastics in soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 The dispersion effects of different dispersion and extraction aids on soil aggregates in fluvo-aquic soil;

[0022] Figure 2 The dispersion effects of different dispersion and extraction aids on soil aggregates in ferro-alumina soil;

[0023] Figure 3 The recovery and extraction effects of different dispersion and extraction aids on microplastics in fluvo-aquic soil;

[0024] Figure 4 The recovery and extraction effects of different dispersion and extraction aids on microplastics in ferroalumina;

[0025] Figure 5 The recovery and extraction effect of different dispersion and extraction aids on nanoplastics in ferroalumina. DETAILED DESCRIPTION

[0026] The present invention provides a dispersion and extraction aid for micro / nano plastics in soil, which comprises the following preparation raw materials by mass fraction:

[0027] 1-30% of polyphosphate, 1-10% of sodium percarbonate, 0-1% of surfactant and 59-98% of water; the surfactant is a nonionic surfactant or a zwitterionic surfactant.

[0028] In the present invention, unless otherwise specified, all preparation raw materials are preferably commercially available products well known to those skilled in the art.

[0029] In the present invention, the raw materials for preparing the dispersion and extraction aid include 1-30% polyphosphate by mass fraction, and in specific embodiments, it can be 1.5%, 5%, 10% or 15%; the polyphosphate can be sodium hexametaphosphate.

[0030] In the present invention, polyphosphate carries a large amount of negative charge and can exchange ions with positively charged metal ions (such as calcium and magnesium ions) on the surface of soil particles. This will destroy the cohesion between soil particles, thereby dispersing them; the polyphosphate used in the present invention is a strong chelating agent and can form a stable complex with metal ions. When polyphosphate chelates with metal ions in the soil, the activity of these ions is reduced, thereby reducing their cohesive effect on soil particles; at the same time, polyphosphate has the effect of a wetting agent and can reduce the surface tension of soil particles, which makes it easier for water to penetrate between soil particles, further promoting the dispersion of particles.

[0031] In the present invention, the raw material for preparing the dispersion and extraction aid includes 1-10% sodium percarbonate by mass fraction, and in specific embodiments, it can be 1%, 3%, 5% or 10%. In the present invention, sodium percarbonate, as a solid oxidant, can pre-oxidize organic matter in the soil (such as plant roots or humus), has a dispersing effect on soil aggregates, and further releases micro / nano plastics wrapped in soil aggregates.

[0032] In the present invention, the raw materials for preparing the dispersion extraction aid include 0-1% surfactant by mass fraction, and in a specific embodiment, it can be 0%, 0.5% or 1%; the surfactant is a nonionic surfactant alkyl glycoside or a zwitterionic surfactant; the nonionic surfactant is an alkyl glycoside; the zwitterionic surfactant is a betaine surfactant; the betaine surfactant can be one of lauroyl amide propyl betaine, citric acid betaine and cocamidopropyl betaine. In the present invention, the surfactant has the advantages of antistatic, biocompatibility and environmental friendliness, and can reduce the electrostatic adsorption between micro / nano plastics and vessels during the extraction of micro / nano plastics in soil.

[0033] The present invention has no particular limitation on the preparation method of the dispersion and extraction aid. In a specific embodiment of the present invention, the dispersion and extraction aid can be obtained by mixing polyphosphate, sodium percarbonate, a surfactant and water in the above proportions.

[0034] The present invention also provides the use of the dispersion extraction aid described in the above technical solution for separating and extracting plastics in soil.

[0035] In the present invention, the application method of the dispersion and extraction aid comprises the following steps:

[0036] The soil to be extracted and the dispersion extraction aid for micro / nano plastics in the soil are mixed, and a first liquid phase and a first solid phase are obtained after solid-liquid separation;

[0037] Density separation of the first solid phase to obtain a second liquid phase and a second solid phase;

[0038] The first liquid phase and the second liquid phase are microfiltered to obtain micro / nano plastics; the pore size of the filter membrane used for the microfiltration is 0.1 to 20 μm.

[0039] The present invention mixes the soil to be extracted with the dispersion extraction aid described in the above technical solution, and obtains a first liquid phase and a first solid phase after solid-liquid separation. The present invention does not specifically limit the type of the soil to be extracted. In a specific embodiment of the present invention, it can be tidal soil or iron-alumina soil containing micro / nano plastics; the microplastics can be plastic fibers, plastic fragments or plastic particles with a particle size of less than 5 mm, and in a specific embodiment, the particle size can be 100 μm, 150 μm, 500 μm or 600 μm; the nanoplastics can be plastic fibers, plastic fragments or plastic particles with a particle size of less than 1 μm, and in a specific embodiment, the particle size can be 200 nm, 300 μm, 500 nm or 600 nm; the micro / nanoplastics can be polyethylene, polystyrene, polypropylene or polycarbonate.

[0040] In the present invention, the pH of the soil to be extracted can be 4.0-8.0, and in a specific embodiment, can be 4.96 or 7.32; the present invention has no special limitation on the content of micro / nanoplastics in the soil to be extracted.

[0041] In the present invention, the mass ratio of the soil to be extracted to the dispersion extraction aid can be 1:2-4, and in a specific embodiment, can be 1:2, 1:3 or 1:4.

[0042] The present invention has no special limitation on the mixing method of the soil to be extracted and the dispersion extraction aid. In a specific embodiment, a stirrer or a vortexer is used for stirring and mixing; the stirring and mixing time can be 0.5 to 30 minutes. The present invention has no special limitation on the solid-liquid separation method, and a method well known to those skilled in the art can be used.

[0043] After obtaining the first solid phase, the present invention performs density separation on the first solid phase to obtain a second liquid phase and a second solid phase. In the present invention, the density separation method is to use an aeration separation device or a static flotation method for separation; the reagent used for the density separation can be sodium chloride or zinc chloride, and in a specific embodiment, it can be saturated sodium chloride.

[0044] After obtaining the first liquid phase and the second liquid phase, the present invention microfilters the first liquid phase and the second liquid phase to obtain micro / nano plastics. In the present invention, the pore size of the filter membrane used for microfiltration can be 0.1 to 20 μm, and in a specific embodiment, it can be 0.1 μm, 1 μm or 20 μm; the microfiltration method is suction filtration. In the present invention, if the mixed system after microfiltration contains precipitates, it also includes performing secondary density separation on the precipitates using a reagent with a higher density, and the density separation method is consistent with the above-mentioned density separation.

[0045] In the present invention, the solid phase obtained after microfiltration is digested to obtain micro / nano plastics. In the present invention, the reagent used for the digestion can be hydrogen peroxide; the concentration of the hydrogen peroxide is 30%; the temperature of the digestion can be 60-70°C, and the time can be 2-3 days.

[0046] In the present invention, the digestion further includes washing and drying the obtained product; the reagent used for the washing may be ultrapure water; and the drying temperature may be room temperature.

[0047] In order to further illustrate the present invention, the plastic dispersion extraction aid and the method for extracting micro / nano plastics in soil provided by the present invention are described in detail below in combination with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present invention.

[0048] Example 1

[0049] Weigh 10g of tidal soil (pH 7.32±0.13) and add it to a 50mL centrifuge tube, and add 20mL of deionized water, 20mL of sodium hexametaphosphate solution, 20mL of sodium hexametaphosphate and sodium percarbonate mixed solution, 20mL of sodium hexametaphosphate and alkyl glucoside mixed solution, 20mL of sodium hexametaphosphate, alkyl glucoside and lauramide propyl betaine mixed solution, 20mL of sodium percarbonate and alkyl glucoside mixed solution, 20mL of sodium percarbonate, alkyl glucoside and lauramide propyl betaine mixed solution. Among them, the concentration of sodium hexametaphosphate is 15%, the concentration of lauramide propyl betaine is 0.35%, the concentration of alkyl glucoside is 1%, and the concentration of sodium percarbonate is 1%. The dispersion effect of different reagents on soil aggregates in tidal soil is tested, and the results are as follows: Figure 1 shown.

[0050] Figure 1 The dispersion effects of different dispersion and extraction aids on soil aggregates in fluvo-aquic soil are shown in Figure 2. Figure 1It can be seen that compared with the blank control group with only deionized water added, the addition of different separation and extraction aid formulas promoted the dispersion of large aggregates in the soil, especially the separation and extraction aid containing sodium hexametaphosphate. After treatment, the water-stable aggregates with a particle size below 0.25 mm increased from 45.82% to 59.39%~68.89%, and the powdery clay particles with a particle size below 0.053 mm increased from 16.63% to 35.34%~39.08%.

[0051] Example 2

[0052] Weigh 10g of ferroaluminous soil (pH 4.96±0.08) and add it to a 50mL centrifuge tube. Then add 20mL of deionized water, 20mL of sodium hexametaphosphate solution, 20mL of sodium percarbonate solution, 20mL of a mixed solution of sodium hexametaphosphate and sodium percarbonate, and 20mL of a mixed solution of sodium hexametaphosphate, sodium percarbonate, and lauroyl amide propyl betaine. The concentration of sodium hexametaphosphate is 1.5%, the concentration of lauroyl amide propyl betaine is 0.175%, and the concentration of sodium percarbonate is 1%. The dispersion effect of different reagents on soil aggregates in ferroaluminous soil was tested. The results are as follows: Figure 2 shown.

[0053] Figure 2 The dispersion effects of different dispersion and extraction aids on soil aggregates in ferro-alumina soil are shown in Figure 2. Figure 2 It can be seen that compared with the blank control group with only deionized water added, the separation and extraction agents with different formulations have a good dispersing effect on soil aggregates, increasing the proportion of soil water-stable aggregates with a particle size below 0.25 mm, especially increasing the proportion of powdery clay particles with a particle size below 0.053 mm. Powdery clay particles only accounted for 9.34% in the blank control treatment group with only water added, while the proportion of powdery clay particles increased to 38.8%~49.7% after adding different dispersing and extracting agents.

[0054] Example 3

[0055] Weigh 200g of air-dried damp soil (pH 7.32±0.13) into a 500mL beaker, weigh 0.1g of 150μm polyethylene microplastic particles and mix them into the soil, add 10mL of water and stir the soil to allow the microplastics to fully contact the soil. After leaving it for 1 day, soil containing polyethylene microplastics was obtained.

[0056] The above-mentioned soil containing polyethylene microplastics and 400mL of dispersion and extraction aid (the formulas are deionized water, sodium hexametaphosphate solution, sodium hexametaphosphate and sodium percarbonate mixed solution, sodium hexametaphosphate and alkyl glucoside mixed solution, sodium hexametaphosphate, alkyl glucoside and lauramide propyl betaine mixed solution, sodium percarbonate and alkyl glucoside mixed solution, sodium percarbonate, alkyl glucoside and lauramide propyl betaine mixed solution). Among them, the concentration of sodium hexametaphosphate is 15%, the concentration of lauramide propyl betaine is 0.35%, the concentration of alkyl glucoside is 1%, and the concentration of sodium percarbonate is 1%. Use a stirrer to stir at a uniform speed for 30 minutes, and after standing and stratification, obtain the first upper liquid phase and the first lower solid phase; use a vacuum filtration device to filter the first upper liquid phase along the wall of the beaker (the filter membrane uses a nylon filter membrane with a pore size of 20μm); then use saturated sodium chloride to float the first lower solid phase precipitate, and after standing and stratification, obtain the second upper liquid phase and filter it along the wall (the filter membrane uses a nylon filter membrane with a pore size of 20μm) onto the filter membrane of the above-mentioned first upper liquid phase, transfer all the substances on the filter membrane to a 200mL glass beaker, add 100mL of 30% hydrogen peroxide solution, seal with aluminum foil, digest on a hot plate at 60℃ for 2d, remove the filter membrane with toothless stainless steel tweezers and transfer it to a 60mm clean glass culture dish, dry at room temperature, and wait for analysis and identification, wherein the spiked recovery rate of polyethylene microplastics is calculated by subtracting the mass of the filter membrane in the control treatment group where no polyethylene microplastics are added throughout the process, and the analysis results are shown below.

[0057] Figure 3 The recovery and extraction effects of different dispersion and extraction aids on microplastics in fluvo-aquic soil are shown in Table 1. Figure 3 The results showed that adding only sodium hexametaphosphate to the tidal soil reduced the recovery rate of microplastics, while adding the oxidant sodium percarbonate and the surfactants alkyl glycoside and betaine could promote the extraction and recovery of polyethylene microplastics in the soil. In particular, in the treatment group containing the oxidant sodium percarbonate, the recovery and extraction rate of microplastics was 78.77% to 95.27%.

[0058] Example 4

[0059] Weigh 200g of air-dried ferroalumina (pH 4.96±0.08) into a 500mL beaker, weigh 0.1g of 150μm polyethylene microplastic particles and mix them into the soil, add 10mL of water and stir the soil to allow the microplastics to fully contact the soil. After leaving it for 1 day, soil containing polyethylene microplastics was obtained.

[0060] The above soil containing polyethylene microplastics and 400 mL of dispersion and extraction aid (the formulas are deionized water, sodium hexametaphosphate solution, sodium percarbonate solution, sodium hexametaphosphate and sodium percarbonate mixed solution, sodium hexametaphosphate, sodium percarbonate and lauramide propyl betaine mixed solution). Among them, the concentration of sodium hexametaphosphate is 1.5%, the concentration of lauramide propyl betaine is 0.175%, and the concentration of sodium percarbonate is 1%. Use a stirrer to stir at a uniform speed for 30 minutes, and after standing and stratification, obtain the first upper liquid phase and the first lower solid phase; use a vacuum filtration device to filter the first upper liquid phase along the wall of the beaker (the filter membrane uses a nylon filter membrane with a pore size of 20μm); then use saturated sodium chloride to float the first lower solid phase precipitate, and after standing and stratification, obtain the second upper liquid phase and filter it along the wall (the filter membrane uses a nylon filter membrane with a pore size of 20μm) onto the filter membrane of the above-mentioned first upper liquid phase, transfer all the substances on the filter membrane to a 200mL glass beaker, add 100mL of 30% hydrogen peroxide solution, seal with aluminum foil, digest on a hot plate at 60℃ for 2d, remove the filter membrane with toothless stainless steel tweezers and transfer it to a 60mm clean glass culture dish, dry at room temperature, and wait for analysis and identification, wherein the spiked recovery rate of polyethylene microplastics is calculated by subtracting the mass of the filter membrane in the control treatment group where no polyethylene microplastics are added throughout the process, and the analysis results are shown below.

[0061] Figure 4 The recovery and extraction effects of different dispersion and extraction aids on microplastics in ferroalumina are shown in Table 1. Figure 4 The results showed that adding only sodium hexametaphosphate to ferroalumina slightly reduced the recovery rate of polyethylene microplastics, while the addition of oxidant sodium percarbonate and surfactant lauramide propyl betaine reduced the impact of sodium hexametaphosphate, and the recovery rate of polyethylene microplastics reached 85.0% to 97.9%.

[0062] Example 5

[0063] Weigh 10 g of air-dried iron-alumina soil (pH 4.96 ± 0.08) into a 50 mL centrifuge tube, add 1 mL of 20 mg / L rare earth europium-labeled polystyrene nanoplastic microspheres (200 nm) and mix into the soil to allow the microplastics to fully contact the soil. Leave for 1 day to obtain polystyrene nanoplastic soil.

[0064] The polystyrene nanoplastic soil and 20 mL of a dispersion extraction aid (formulas are deionized water, sodium hexametaphosphate solution, sodium percarbonate solution, a mixed solution of sodium hexametaphosphate and sodium percarbonate, and a mixed solution of sodium hexametaphosphate, sodium percarbonate and lauramide propyl betaine) are added. The concentration of sodium hexametaphosphate is 1.5%, the concentration of lauramide propyl betaine is 0.175%, and the concentration of sodium percarbonate is 1%. All treatment groups were stirred for 30 seconds using a vortexer. After standing and stratifying, the supernatant was filtered along the tube wall using a vacuum filtration device (the filter membrane used was an aluminum oxide filter membrane with a pore size of 0.1 μm, the same below). Then, the lower sediment was floated using a saturated sodium chloride density flotation reagent. After standing and stratifying, the upper clear liquid was filtered along the wall onto a 0.1 μm aluminum oxide filter membrane. The biological residues and other impurities on the filter membrane were rinsed into a beaker with hydrogen peroxide to remove organic matter. All samples were then vacuum filtered, and the filter membrane was placed in a triangular flask. 2 mL of concentrated nitric acid was added to soak the filter membrane. Use a rubber-tipped dropper to absorb 2 mL of concentrated nitric acid to rinse the filter membrane, then remove the filter membrane, and finally add 0.5 mL of concentrated sulfuric acid and heat on an electric hot plate (digest at 180°C for 6 hours, and drive out the acid at 220°C). After the volume is adjusted to 10 mL with 1% dilute nitric acid, a 0.45 μm water filter membrane is used to filter the solution. An inductively coupled plasma mass spectrometer is used to analyze the content of rare earth europium in the soil treated with different separation and extraction agent formulas, and the content is converted into the content of rare earth europium-labeled polystyrene nanoplastic microspheres. The recovery rate is calculated, and the effects of different separation and extraction agents on the separation of polystyrene nanoplastics in soil are analyzed.

[0065] Figure 5 The recovery and extraction effects of different dispersion and extraction aids on nanoplastics in ferroalumina are shown in Table 1. Figure 5 The results show that the addition of dispersant sodium hexametaphosphate and oxidant sodium percarbonate to ferroalumina, and the addition of dispersant sodium hexametaphosphate, oxidant sodium percarbonate and surfactant lauramide propyl betaine all increased the recovery rate of rare earth europium labeled polystyrene nanoplastics to 85.0% to 97.9%.

[0066] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A dispersion and extraction aid for micro / nano plastics in soil, characterized in that: Calculated by mass fraction, the following raw materials are included: 1-30% polyphosphate, 1-10% sodium percarbonate, 0-1% surfactant and 59-98% water; the surfactant is a nonionic surfactant or a zwitterionic surfactant.

2. The dispersion and extraction aid according to claim 1, characterized in that: The polyphosphate is one of sodium hexametaphosphate, sodium metaphosphate, sodium dimetaphosphate and sodium tripolyphosphate.

3. The dispersion and extraction aid according to claim 1, characterized in that: The zwitterionic surfactant is a betaine surfactant; and the nonionic surfactant is an alkyl polyglycoside.

4. Use of the dispersion and extraction aid for micro / nano plastics in soil as described in any one of claims 1 to 3 for separating and extracting plastics in soil.

5. The use according to claim 4, characterized in that: The application method of the dispersion extraction aid comprises the following steps: The soil to be extracted and the dispersion extraction aid for micro / nano plastics in the soil are mixed, and a first liquid phase and a first solid phase are obtained after solid-liquid separation; Density separation of the first solid phase to obtain a second liquid phase and a second solid phase; The first liquid phase and the second liquid phase are microfiltered to obtain micro / nano plastics; the pore size of the filter membrane used for the microfiltration is 0.1 to 20 μm.

6. The use according to claim 5, characterized in that: The pH of the soil to be extracted is 4.0-8.

0.

7. The use according to claim 5, characterized in that: The mass ratio of the soil to be extracted to the dispersion extraction aid is 1:2-4.

8. The use according to claim 5, characterized in that: The reagent used for density separation is sodium chloride or zinc chloride.

9. The use according to claim 5, characterized in that: The method further comprises digestion after the microfiltration; the reagent used for the digestion is hydrogen peroxide.

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