Device and method for efficient flotation and grading separation of micro-plastics

Abstract

The invention discloses an efficient flotation grading separation device and method for microplastics, and belongs to the field of pretreatment research of microplastic pollutants. Comprising an iron stand; the flotation separation mechanism is arranged on the iron stand and is used for carrying out overflow operation on flotation liquid containing the micro-plastics; the impurity collecting assembly is arranged on the iron stand and located at the opening in the lower end of the flotation separation mechanism; the flotation liquid collecting assembly is located below the overflow outlet of the flotation separation mechanism and used for collecting the overflow flotation liquid; and the graded filtering mechanism is located on one side of the flotation separation mechanism and used for filtering flotation liquid overflowing out of the flotation separation mechanism in a graded mode. The flotation liquid used in the method is non-toxic and harmless, the density is moderate, large-density micro-plastics can be conveniently extracted, the flotation liquid is convenient to recycle and can be repeatedly used, energy is saved, consumption is reduced, and meanwhile the influence on the surrounding environment is reduced.

Description

Technical Field

[0001] The present invention belongs to the research field of pre-treatment of microplastic pollutants, and specifically relates to a device and method for efficient flotation and graded separation of microplastics. Background Art

[0002] Microplastics are plastic particles with a diameter of less than 5mm and are identified as an emerging pollutant. Due to its wide distribution, large quantity, and difficulty in degradation, the microplastic pollution problem has attracted widespread attention from government departments, academic institutions, social environmental protection organizations, and the public, and has been listed by the United Nations Environment Assembly as a global environmental pollution problem that needs to be solved urgently.

[0003] At present, there have been relevant studies on microplastics in the ocean, lakes, rivers and other ecological environments, but there is not enough attention paid to sediments that contain more microplastic pollutants and the impact of microplastics on the health of organisms in freshwater environments. Microplastics are not only harmful in themselves, but can also absorb other pollutants in freshwater environments (such as heavy metals and persistent organic pollutants) to form complex pollutants, causing harm to the health of freshwater organisms, and can even be transmitted to higher trophic levels through the food chain, thus posing a potential threat to human health.

[0004] It has been confirmed that microplastic pollutants are widely present in water bodies, atmosphere, soil, sediments, and even polar ice. In view of the characteristics of microplastics themselves, the extraction methods of microplastics in environmental samples are mostly traditional manual screening, acid and alkali and other chemical reagents to digest impurities combined with flotation agents for density separation (patent application numbers: 202223416854.7, 201910747902.4, 201810604532.4, 202210696388.8, 202211452303.8). This type of method has the disadvantages of complex microplastic separation devices, low extraction rates of high-density microplastics (such as PET and PVC), cumbersome operations, and difficulty in recovering flotation agents. In addition, the extraction methods of microplastics from water bodies and soil are difficult to be directly used for the extraction of microplastics from freshwater biological tissue samples.

[0005] Therefore, there is an urgent need for a method and device that is simple to operate, energy-saving and environmentally friendly, and can quickly and efficiently separate microplastics from freshwater biological tissue samples. Summary of the invention

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A device for efficient flotation and fractionation of microplastics, comprising:

[0008] Iron frame platform;

[0009] A flotation separation mechanism, which is arranged on the iron frame and is used to perform overflow operation on the flotation liquid containing microplastics;

[0010] An impurity collecting assembly, which is arranged on the iron frame and located at the lower opening of the flotation separation mechanism;

[0011] A flotation liquid collecting assembly, the flotation liquid collecting assembly is located below the overflow outlet of the flotation separation mechanism and is used to collect overflowed flotation liquid;

[0012] The grading filtering mechanism is located at one side of the flotation separation mechanism and is used for grading and filtering the flotation liquid overflowing from the flotation separation mechanism.

[0013] Furthermore, the flotation separation mechanism includes a funnel-shaped conical bottle body and an overflow pipe;

[0014] The funnel-shaped conical flask is arranged on the iron frame; the lower end opening of the funnel-shaped conical flask is located above the open end of the impurity collecting assembly, and a glass piston is arranged at the lower end opening of the funnel-shaped conical flask;

[0015] The upper side wall of the funnel-shaped conical flask is provided with an opening matching the overflow pipe; the opening of the funnel-shaped conical flask is connected to one end of the overflow pipe, and the other end of the overflow pipe is located above the opening of the flotation liquid collecting assembly.

[0016] Furthermore, it also includes a funnel, which is arranged on the iron frame, and an ellipsoidal buffer is arranged above the lower opening of the funnel to reduce the flow rate of the flotation liquid entering the funnel-shaped conical flask; the lower opening of the funnel is connected to the opening of the funnel-shaped conical flask.

[0017] Furthermore, the overflow pipe is arranged on the funnel-shaped conical flask in a downwardly inclined manner, and one end of the overflow pipe close to the flotation liquid collecting assembly is arranged with a flat mouth upward at an elevation angle of 45°.

[0018] Furthermore, the graded filtration mechanism includes a graded filtration cup, a vacuum filtration pump, a filter head and a recovery bottle;

[0019] The lower opening of the grading filter cup is sealedly connected to the upper opening of the filter head, and the lower opening of the filter head is connected to the recovery bottle; the side wall of the filter head is provided with an air suction nozzle, and the air suction nozzle is connected to the vacuum filtration pump through a pipeline.

[0020] Furthermore, the graded filter cup includes a filter cup, a stainless steel interface and two filter membranes;

[0021] The lower opening of the filter cup is sealed and connected to the upper opening of the filter head; wherein the stainless steel interface is arranged 0.5-1.0 cm above the lower opening of the filter cup; one of the filter membranes is installed at the stainless steel interface through a stainless steel fixture, and the other filter membrane is installed between the lower opening of the filter cup and the filter head through a fixing clip.

[0022] Furthermore, the impurity collection component is a glass culture dish.

[0023] Furthermore, the flotation liquid collecting component is a beaker.

[0024] A method for efficient flotation and fractionation separation of microplastics, comprising the following steps:

[0025] S1. Close the glass piston and add the sample into the funnel-shaped conical flask. 3 Add the potassium formate flotation liquid into the funnel-shaped conical flask to 30-50mm below the upper interface of the overflow pipe, and seal the upper opening of the funnel-shaped conical flask with aluminum foil, and then let it stand for more than 12 hours;

[0026] S2. Open the aluminum foil and add fresh 1.5g / cm 3 The potassium formate flotation liquid flows into the flotation liquid collection assembly through the overflow pipe; after the overflow is completed, the flotation liquid is added to the funnel-shaped conical flask again to 30-50 mm below the upper end interface of the overflow pipe, and the operation is repeated after standing for 2 hours, and the overflow operation is repeated 3 times;

[0027] S3, slowly pour the flotation liquid in the flotation liquid collection component into the graded filter cup of the graded filter mechanism, and start the vacuum filtration pump to filter at the same time, and then repeatedly rinse the flotation liquid collection component with ultrapure water, and also pour all the ultrapure water rinse liquid into the graded filter cup;

[0028] S4. Collect the residues on the filter membrane and observe the residual substances on the filter membrane using a stereo microscope. Use Fourier transform micro-infrared spectroscopy to identify whether the suspected microplastic particles are microplastic particles;

[0029] S5. Open the glass piston to allow the flotation liquid containing impurities at the bottom of the funnel-shaped conical flask to flow into the impurity collection assembly, and then close the glass piston to retain the remaining flotation liquid in the funnel-shaped conical flask.

[0030] Preferably, the flotation liquid in the recovery bottle and the funnel-type conical bottle of the graded filtration mechanism can be reused after being filtered through a 1 μm glass cellulose membrane.

[0031] Beneficial effects of the present invention:

[0032] (1) The present invention designs a related microplastic separation flotation device based on the principles of density separation, overflow and vacuum filtration, which effectively separates the microplastic particles in freshwater biological tissue (such as fish) samples, thereby solving the problems that traditional microplastic separation methods are difficult to directly apply to freshwater biological tissue (such as fish), are complicated to operate, have low extraction rates of high-density microplastics (such as PET, PVC), and are difficult to recover flotation reagents.

[0033] (2) The microplastic separation flotation device has been optimized. The iron frame, fixed iron ring, funnel, flotation separation mechanism, impurity collection component and flotation liquid collection component are easy to disassemble and assemble. The flotation process does not require an additional power device, which reduces costs. The graded filtration mechanism can flexibly place stainless steel filter membranes of different pore sizes according to target requirements. The small-pore stainless steel filter membrane is located below the large-pore stainless steel filter membrane of the graded filtration mechanism, which improves the efficiency of subsequent microplastic separation and identification and broadens the application scenarios.

[0034] (3) The flotation fluid used in the present invention is non-toxic and harmless, and has a moderate density, which is convenient for extracting high-density microplastics. The flotation fluid is easy to recycle and can be reused, which saves energy and reduces consumption while reducing the impact on the surrounding environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the structure of the flotation separation mechanism provided by the present invention;

[0036] Figure 2 A schematic diagram of the structure of the graded filtering mechanism provided by the present invention;

[0037] Figure 3 A detailed view of the graded filter cup provided by the present invention;

[0038] In the figure: 1. iron frame; 2. fixed iron ring; 3. funnel; 4. flotation separation mechanism; 41. funnel-type conical bottle; 42. overflow pipe; 43. glass piston; 5. impurity collection assembly; 6. flotation liquid collection assembly; 7. graded filtration mechanism; 71. graded filtration cup; 711. stainless steel holder; 72. filter membrane; 73. filter head; 74. recovery bottle; 75. vacuum filtration pump. DETAILED DESCRIPTION

[0039] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0040] Example 1

[0041] refer to Figure 1-Figure 3 , a device for efficient flotation and fractionation of microplastics, comprising:

[0042] Iron frame 1;

[0043] A flotation separation mechanism 4, which is disposed on the iron frame 1 and is used to perform an overflow operation on a flotation liquid containing microplastics;

[0044] An impurity collecting assembly 5, which is arranged on the iron frame 1 and is located at the lower opening of the flotation separation mechanism 4;

[0045] A flotation liquid collecting assembly 6, which is located below the overflow outlet of the flotation separation mechanism 4 and is used to collect the overflowed flotation liquid;

[0046] The grading filtering mechanism 7 is located at one side of the flotation separation mechanism 4 and is used for grading and filtering the flotation liquid overflowing from the flotation separation mechanism 4 .

[0047] Preferably, the flotation separation mechanism 4 includes a funnel-shaped conical bottle body 41 and an overflow pipe 42;

[0048] The funnel-shaped conical flask 41 is disposed on the iron frame 1; the lower opening of the funnel-shaped conical flask 41 is located above the opening end of the impurity collecting assembly 5, and a glass piston 43 is disposed at the lower opening of the funnel-shaped conical flask 41;

[0049] The upper side wall of the funnel-shaped conical flask 41 is provided with an opening matching the overflow pipe 42 ; the opening of the funnel-shaped conical flask 41 is connected to one end of the overflow pipe 42 , and the other end of the overflow pipe 42 is located above the opening of the flotation liquid collecting assembly 6 .

[0050] Preferably, it also includes a funnel 3, which is arranged on the iron frame 1, and an ellipsoidal buffer portion is arranged above the lower end opening of the funnel 3, which is used to reduce the flow rate of the flotation liquid entering the funnel-shaped conical bottle body 41, and prevent the liquid from flowing in too quickly to disturb the lower layer of liquid and cause the surface microplastics to sink; the lower end opening of the funnel is connected to the opening of the funnel-shaped conical bottle body.

[0051] In this embodiment, the ellipsoidal buffer portion is arranged about 2 cm above the lower end opening of the funnel 3 .

[0052] In this embodiment, the iron frame 1 is provided with two fixed iron rings 2 which are matched with the funnel 3 and the funnel-shaped conical bottle body 41 respectively from top to bottom.

[0053] Preferably, the overflow pipe 42 is arranged on the funnel-shaped conical bottle 41 in a downwardly inclined manner, and one end of the overflow pipe 42 close to the flotation liquid collecting assembly 6 is flat and arranged upward at an elevation angle of 45°.

[0054] In this embodiment, the funnel-shaped conical flask body 41 is used to contain the flotation liquid containing microplastics, and the overflow pipe 42 is located on the upper side wall of the funnel-shaped conical flask body 41 and is higher than the liquid level of the flotation liquid; the glass piston 43 and the funnel-shaped conical flask body 41 and the inside of the glass piston 43 are all frosted surface sealed connections, and the internal liquid flow hole size of the glass piston 43 is 30-50mm to prevent impurities such as gravel from clogging the liquid flow hole, thereby improving the subsequent flotation liquid recovery efficiency.

[0055] Preferably, the graded filtration mechanism 7 comprises a graded filtration cup 71, a vacuum filtration pump 75, a filter head 73 and a recovery bottle 74;

[0056] The lower opening of the grading filter cup 71 is sealedly connected to the upper opening of the filter head 73, and the lower opening of the filter head 73 is connected to the recovery bottle 74; the side wall of the filter head 73 is provided with an air suction nozzle, which is connected to the vacuum filtration pump 75 through a pipeline.

[0057] Preferably, the graded filter cup 71 comprises a filter cup, a stainless steel interface and two filter membranes 72;

[0058] The lower opening of the filter cup is sealed and connected to the upper opening of the filter head 73; wherein, the stainless steel interface is arranged 0.5-1.0 cm above the lower opening of the filter cup; one of the filter membranes 72 is installed at the stainless steel interface through a stainless steel fixture 711, and the other filter membrane 72 is installed between the lower opening of the filter cup and the filter head through a fixing clip.

[0059] In this embodiment, the pore sizes of the two filter membranes 72 are different. The graded filtration mechanism 7 can flexibly place filter membranes 72 with different pore sizes according to target requirements, wherein the filter membrane with a small pore size is located below the filter membrane with a large pore size of the graded filtration mechanism 7, thereby improving the subsequent microplastic separation and identification efficiency and broadening the application scenarios.

[0060] Preferably, the impurity collecting component 5 is a glass culture dish.

[0061] Preferably, the flotation liquid collecting component 6 is a beaker.

[0062] In this embodiment, the iron frame 1 and the fixed iron ring 2 are common devices in this field; the funnel 3 is a glass funnel containing an ellipsoidal buffer portion, which is used to buffer the flow rate of the flotation solution entering the funnel-shaped conical flask 41, preventing the liquid from flowing in too quickly and causing the surface microplastics to sink; the flotation separation mechanism 4 is a customized glass device containing a funnel-shaped conical flask 41, an overflow pipe 42 and a glass piston 43.

[0063] The impurity collection component 5 and the flotation liquid collection component 6 are preferably glass culture dishes and beakers, and other containers for containing fluids can also be selected; wherein, the filter membrane 72 is a stainless steel filter membrane, and other filter membranes can also be selected; it should be noted that: each component in the selected microplastic efficient flotation and grading separation device cannot cause microplastic pollution.

[0064] Example 2

[0065] A method for efficient flotation and fractionation of microplastics. This embodiment is based on the device for efficient flotation and fractionation of microplastics in Example 1. The method for efficient flotation and fractionation of microplastics comprises the following steps:

[0066] S1. Close the glass piston 43, add the sample into the funnel-shaped conical flask 41, and at the same time add a flask with a density of 1.5 g / cm 3 The potassium formate flotation liquid is added into the funnel-shaped conical flask 41 to a position 30-50 mm below the upper interface of the overflow pipe 42, and the upper opening of the funnel-shaped conical flask 41 is sealed with aluminum foil, and then allowed to stand for more than 12 hours;

[0067] S2, open the aluminum foil, add an appropriate amount of fresh 1.5g / cm 3 The potassium formate flotation liquid flows into the flotation liquid collecting assembly 6 through the overflow pipe 42; after the overflow is completed, the flotation liquid is added to the funnel-shaped conical flask 41 again to 30-50mm below the upper end interface of the overflow pipe 42, and the operation is repeated after standing for 2h, and the overflow operation is repeated 3 times;

[0068] S3, slowly pour the flotation liquid in the flotation liquid collection component 6 into the grading filter cup 71 of the grading filter mechanism, and start the vacuum filtration pump 75 for filtration, and then repeatedly rinse the flotation liquid collection component 6 with ultrapure water, and also pour all the ultrapure water rinse liquid into the grading filter cup 71;

[0069] S4, collecting the residue on the filter membrane 72, observing the residual substances on the filter membrane 72 using a stereo microscope, and identifying whether the suspected microplastic particles are microplastic particles by Fourier transform micro-infrared spectroscopy technology;

[0070] S5, opening the glass piston to allow the flotation liquid containing impurities at the bottom of the funnel-shaped conical flask to flow into the impurity collecting assembly 5, and then closing the glass piston 43 to retain the remaining flotation liquid in the funnel-shaped conical flask 41.

[0071] Preferably, the flotation liquid in the recovery bottle 74 and the funnel-shaped conical bottle 41 of the graded filtration mechanism 7 can be reused after being filtered through a 1 μm glass cellulose membrane.

[0072] Example 3

[0073] A method for efficient flotation fractionation and separation of microplastics in freshwater biological tissues (such as fish). This embodiment is based on the device for efficient flotation fractionation and separation of microplastics in Example 1. The method for efficient flotation fractionation and separation of microplastics comprises the following steps:

[0074] S1. After cleaning, 5 g of crucian carp tissue sample was placed in a 250 ml glass beaker, 50 ml of 10% potassium hydroxide solution was added, and the glass beaker was sealed with aluminum foil. The beaker was placed in a constant temperature air shaker and fully shaken for 48 hours.

[0075] S2. After digestion is completed, filter the sample in the beaker through a 20 μm stainless steel filter membrane. After filtration, place the filter membrane in a funnel-type conical flask;

[0076] S3. Add about 100 ml of a liquid with a density of 1.5 g / cm2 to the upper opening of the funnel-shaped conical flask. 3 Potassium formate flotation solution, cover the upper opening of the funnel-shaped conical flask with aluminum foil, then ultrasonicate for 30 minutes, and add a density of 1.5 g / cm 3 The potassium formate flotation liquid is added to the position 30-50 mm below the upper interface of the overflow pipe, and then ultrasonicated for 30 minutes, covered with aluminum foil and then left to stand for more than 12 hours;

[0077] S4. Open the aluminum foil and add an appropriate amount of fresh 1.5g / cm 3 The potassium formate flotation liquid is added to the funnel-shaped conical flask, so that the microplastics in the funnel-shaped conical flask flow into the flotation liquid collection assembly through the overflow effect of the flotation liquid. After the overflow is completed, the flotation liquid is added to the funnel-shaped conical flask again to 30-50 mm below the upper end interface of the overflow tube. After standing for 2 hours, the operation is repeated, and the overflow operation is repeated 3 times;

[0078] S5, slowly pouring the flotation liquid in the flotation liquid collection component into the upper filter cup of the graded filtration mechanism, and simultaneously starting the vacuum filtration pump for filtration, and then repeatedly washing the flotation liquid collection component with ultrapure water, and also pouring all the ultrapure water rinse liquid into the filter cup of the graded filtration mechanism;

[0079] S6. Collect the residue on the filter membrane and observe the residual substances on the filter membrane using a stereo microscope. Use Fourier transform micro-infrared spectroscopy to identify whether the suspected microplastic particles are microplastic particles;

[0080] S7. Open the glass piston valve to allow the flotation liquid containing impurities at the bottom of the funnel-shaped conical flask to flow into the impurity collection assembly, and then close the valve to retain the remaining flotation liquid in the funnel-shaped conical flask.

[0081] The results of multiple experiments showed that the recovery rates of low-density microplastics PE, medium-density microplastics PS and high-density microplastics PVC in the spiked experiment of crucian carp biological tissue were 93±5%, 97±1% and 95±3%, respectively.

[0082] Example 4

[0083] A method for efficient flotation and fractionation separation of microplastics in sediments. This embodiment is based on the device for efficient flotation and fractionation separation of microplastics in Example 1. The method for efficient flotation and fractionation separation of microplastics comprises the following steps:

[0084] S1. Dry the river sediment sample at 55°C; grind the dried sediment sample using a quartz grinder, and then pass it through a stainless steel mesh sieve with a pore size of 5 mm;

[0085] S2. Take 30g of the sieved sediment sample and put it into a funnel-shaped conical flask; add about 100ml of a 1.5g / cm3 solution at the upper opening of the funnel-shaped conical flask. 3 Potassium formate flotation solution, cover the upper opening of the funnel-shaped conical flask with aluminum foil, ultrasonicate for 30 minutes, and add a density of 1.5 g / cm 3 The potassium formate flotation liquid is flowed to 30-50mm below the upper interface of the overflow pipe, ultrasonicated for 30min, covered with aluminum foil and then left to stand for more than 12h;

[0086] S3. Open the aluminum foil and add an appropriate amount of fresh 1.5g / cm 3 The potassium formate flotation liquid is added to the funnel-shaped conical flask, so that the microplastics in the funnel-shaped conical flask flow into the flotation liquid collection component through the overflow of the flotation liquid. After the overflow is completed, the flotation liquid is added to the funnel-shaped conical flask again to 30-50 mm below the upper end interface of the overflow pipe. After standing for 2 hours, the operation is repeated, and the overflow operation is repeated 3 times;

[0087] S4, slowly pouring the flotation liquid in the flotation liquid collection component into the upper filter cup of the graded filtration mechanism, and starting the vacuum filtration pump for filtration, and then repeatedly washing the flotation liquid collection component with ultrapure water, and pouring all the ultrapure water rinse liquid into the filter cup of the graded filtration mechanism, and filtering with the vacuum filtration pump;

[0088] S5. Place the stainless steel filter in a 250 ml beaker, then add 100 ml of 30% H2O2, and then place in a constant temperature shaker and shake at 50°C for 48 hours to completely eliminate organic impurities.

[0089] S6. After digestion is completed, the digestion solution is slowly poured into the upper filter cup of the graded filtration mechanism, and the vacuum filtration pump is started for filtration, and then the flotation liquid collection component is repeatedly rinsed with ultrapure water, and the ultrapure water washing solution is also poured into the filter cup of the graded filtration mechanism;

[0090] S7. Collect the residue on the filter membrane and observe the residual substances on the filter membrane using a stereo microscope. Use Fourier transform micro-infrared spectroscopy to identify whether the suspected microplastic particles are microplastic particles;

[0091] S8. Open the glass piston valve to allow the flotation liquid containing impurities at the bottom of the funnel-shaped conical flask to flow into the impurity collection assembly, and then close the valve to retain the remaining flotation liquid in the funnel-shaped conical flask.

[0092] The recovery rate experimental results showed that the recoveries of low-density microplastics PE and high-density microplastics PVC in the spiking experiment of sediment samples were 94±1% and 97±2%, respectively.

[0093] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A device for efficient flotation and fractionation of microplastics, characterized in that: include: Iron frame platform; A flotation separation mechanism, which is arranged on the iron frame and is used to perform overflow operation on the flotation liquid containing microplastics; An impurity collecting assembly, which is arranged on the iron frame and located at the lower opening of the flotation separation mechanism; A flotation liquid collecting assembly, the flotation liquid collecting assembly is located below the overflow outlet of the flotation separation mechanism and is used to collect overflowed flotation liquid; The grading filtering mechanism is located at one side of the flotation separation mechanism and is used for grading and filtering the flotation liquid overflowing from the flotation separation mechanism.

2. The device for efficient flotation and fractionation of microplastics according to claim 1, characterized in that: The flotation separation mechanism comprises a funnel-shaped conical bottle body and an overflow pipe; The funnel-shaped conical flask is arranged on the iron frame; the lower end opening of the funnel-shaped conical flask is located above the open end of the impurity collecting assembly, and a glass piston is arranged at the lower end opening of the funnel-shaped conical flask; The upper side wall of the funnel-shaped conical flask is provided with an opening matching the overflow pipe; the opening of the funnel-shaped conical flask is connected to one end of the overflow pipe, and the other end of the overflow pipe is located above the opening of the flotation liquid collecting assembly.

3. The device for efficient flotation and fractionation separation of microplastics according to claim 2, characterized in that: It also includes a funnel, which is arranged on the iron frame, and an ellipsoidal buffer is arranged above the lower opening of the funnel to reduce the flow rate of the flotation liquid entering the funnel-shaped conical flask; the lower opening of the funnel is connected to the opening of the funnel-shaped conical flask.

4. The device for efficient flotation and fractionation separation of microplastics according to claim 2, characterized in that: The overflow pipe is arranged on the funnel-shaped conical flask in a downward tilt, and one end of the overflow pipe close to the flotation liquid collecting assembly is arranged with a flat mouth upward at an elevation angle of 45 degrees.

5. The device for efficient flotation and fractionation separation of microplastics according to claim 1, characterized in that: The graded filtration mechanism comprises a graded filtration cup, a vacuum filtration pump, a filter head and a recovery bottle; The lower opening of the grading filter cup is sealedly connected to the upper opening of the filter head, and the lower opening of the filter head is connected to the recovery bottle; the side wall of the filter head is provided with an air suction nozzle, and the air suction nozzle is connected to the vacuum filtration pump through a pipeline.

6. The device for efficient flotation and fractionation of microplastics according to claim 5, characterized in that: The grading filter cup comprises a filter cup, a stainless steel interface and two filter membranes; The lower opening of the filter cup is sealed and connected to the upper opening of the filter head; wherein the stainless steel interface is arranged 0.5-1.0 cm above the lower opening of the filter cup; one of the filter membranes is installed at the stainless steel interface through a stainless steel fixture, and the other filter membrane is installed between the lower opening of the filter cup and the filter head through a fixing clip.

7. The device for efficient flotation and fractionation of microplastics according to claim 1, characterized in that: The impurity collecting component is a glass culture dish.

8. The device for efficient flotation and fractionation of microplastics according to claim 1, characterized in that: The flotation liquid collecting component is a beaker.

9. A method for efficient flotation and fractionation of microplastics, using the device for efficient flotation and fractionation of microplastics as described in any one of claims 1 to 8, characterized in that: The steps include: S1. Close the glass piston and add the sample into the funnel-shaped conical flask. 3 Add the potassium formate flotation liquid into the funnel-shaped conical flask to 30-50mm below the upper interface of the overflow pipe, and seal the upper opening of the funnel-shaped conical flask with aluminum foil, and then let it stand for more than 12 hours; S2. Open the aluminum foil and add fresh 1.5g / cm 3 The potassium formate flotation liquid flows into the flotation liquid collection assembly through the overflow pipe; after the overflow is completed, the flotation liquid is added to the funnel-shaped conical flask again to 30-50 mm below the upper end interface of the overflow pipe, and the operation is repeated after standing for 2 hours, and the overflow operation is repeated 3 times; S3, slowly pour the flotation liquid in the flotation liquid collection component into the graded filter cup of the graded filter mechanism, and start the vacuum filtration pump to filter at the same time, and then repeatedly rinse the flotation liquid collection component with ultrapure water, and also pour all the ultrapure water rinse liquid into the graded filter cup; S4. Collect the residues on the filter membrane and observe the residual substances on the filter membrane using a stereo microscope. Use Fourier transform micro-infrared spectroscopy to identify whether the suspected microplastic particles are microplastic particles; S5. Open the glass piston to allow the flotation liquid containing impurities at the bottom of the funnel-shaped conical flask to flow into the impurity collecting assembly, and then close the glass piston to retain the remaining flotation liquid in the funnel-shaped conical flask.

10. The method for efficient flotation fractionation and separation of microplastics according to claim 9, characterized in that: The flotation liquid in the recovery bottle and the funnel-type conical bottle of the graded filtration mechanism can be reused after being filtered through a 1 μm glass cellulose membrane.

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