CN109228022B - Enrichment device for rapidly and continuously separating microplastic and application method thereof - Google Patents

Abstract

An enrichment device for rapidly and continuously separating microplastic and a use method thereof. The device comprises a flotation solution circulation part and a sample separation and enrichment part; the flotation liquid circulation part comprises a peristaltic pump, a liquid storage bottle, a flowmeter, a filter pumping cylinder, a vacuum pump and a guide pipe, the sample separation and enrichment part comprises an ultrasonic wave generating device, a sample bottle, a flotation tube, a stirring rod and a multi-stage screening disc, and the filter pumping cylinder is arranged in the ultrasonic wave generating device; placing the sample bottle in a filter suction cylinder, assembling a flotation tube on the sample bottle, and finally nesting a plurality of screening discs on the outer side of the flotation tube; extending the stirring rod into the sample bottle; the filter cylinder is connected with a vacuum pump, and a filter screen or a filter membrane with different particle diameters is placed in the screening disc. The invention is designed based on the density separation principle and is characterized in that: the flotation liquid is recycled among the three, so that the economic cost is reduced, and secondary pollution is avoided; the multistage screening disc can be used for continuously subdividing the micro plastic particles with different particle sizes, and the separation efficiency is high.

Description

Enrichment device for rapidly and continuously separating microplastic and application method thereof

Technical Field

The invention relates to an extraction device for rapidly separating microplastic, in particular to an enrichment device for rapidly and continuously separating microplastic and a use method thereof.

Background

Plastic products are low in cost, have a large weight strength, a low thermal conductivity, durability, and bio-inertness, as compared with materials such as wood, metal, etc., and are used in various fields, for example, from household products to personal hygiene products, and from packaging industries to construction materials. While enjoying great convenience brought by plastic products, the problem of garbage pollution of a large number of plastic products also plagues people. A large amount of plastic waste is discharged into the aquatic environment, especially in the ocean. Large plastic products are gradually decomposed into small-particle plastics in marine environments through the actions of photodegradation, bioerosion, physical degradation and the like, and the plastic material fibers, particles, fragments and the like with the size smaller than 5mm are defined as microplastic. The problem of contamination of small particle plastics was not addressed until the beginning of the 70 s of the 20 th century.

The presence of microplastic has been detected in polar regions, islands, continental shelves and deep sea ocean bottoms, even in common salt. Because the large-quantity and shape-and-color-diversified microplastic migrates among different environmental media, especially after entering the ocean, the microplastic with large specific surface area easily adsorbs pollutants (persistent organic pollutants, heavy metal ions and the like) and microorganisms in the seawater, and becomes a carrier of the pollutants and the microorganisms. And the microplastic with different particle sizes can generate different toxicological effects, such as: the nano-level micro-plastic can penetrate the cell wall to perform cell interior, and is harmful to organisms, and the micro-plastic with the same size as plankton is easy to be absorbed by marine organisms, so that the micro-plastic is transmitted among all nutrition levels through a food chain, and the whole ecological system can be possibly influenced. Therefore, the method for efficiently collecting the microplastic with different particles and evaluating the harm of the microplastic with different particles to the environment becomes the primary problem of the research in the field, so that the research policy of microplastic pollution control is developed.

Most of the current microplastic extraction devices are designed based on the density separation principle by utilizing the density difference between the target and the impurities. For example: the continuous separating and enriching device for microplastic in China patent (patent number: CN 108177273A) utilizes gas medium and density liquid to mix into a flotation agent carrying microplastic, so as to achieve the purpose of separating microplastic, but the microplastic with different particle diameters cannot be screened, and the microplastic wrapped in sludge cannot be extracted and enriched effectively. In addition, china patent (patent number: CN 108202428A) is a microplastic extracting device based on an electrostatic technology, and can effectively extract microplastic in sediment, but cannot effectively extract microplastic with small particles and microplastic wrapped in sediment and pollutant, and cannot separate microplastic with different particle sizes. Although most of the microplastic separating and extracting devices can realize automatic continuous separation of the microplastic from the sediment, in the actual experimental process, the microplastic is often attached to the surface of the vessel and is not easy to fall off, and the coated microplastic is not easy to extract, so that the actual difference of the final separating and extracting microplastic results is very large.

The micro plastic separation and enrichment device which has the advantages of simple structure, wide application, low cost, convenient disassembly and assembly and low maintenance difficulty is developed, and the micro plastic separation and enrichment device is a primary problem which needs to be solved in micro plastic research. The invention relates to a device for rapidly, efficiently and continuously separating microplastic with different particle diameters based on a density separation principle. The method can realize screening and enrichment of the target object according to the requirements, has high screening efficiency, can obviously reduce the consumption of the solution by recycling the flotation liquid, reduces the economic cost, and has small secondary pollution to the environment.

Disclosure of Invention

The invention mainly aims to provide a device for separating and enriching microplastic in sediment, and secondarily aims to provide a using method for separating microplastic in sediment by using the device.

The invention is designed based on the density separation principle and is characterized in that: 1. the flotation liquid is recycled among the three, so that the economic cost is reduced, and secondary pollution is avoided; 2. the multistage screening disc can be used for continuously subdividing micro plastic particles with different particle diameters, so that the separation efficiency is high; the device has simple structure, easy disassembly and convenient installation, carrying and maintenance.

The technical scheme of the invention is as follows.

An enrichment device for rapidly and continuously separating microplastic, recycling flotation liquid and continuously separating microplastic particles with different particle diameters. Comprises a flotation solution circulation part and a sample separation and enrichment part; the flotation liquid circulation part comprises a peristaltic pump, a liquid storage bottle, a flowmeter, a filter pumping cylinder, a vacuum pump and a guide pipe, the sample separation and enrichment part comprises an ultrasonic generating device, a sample bottle, a flotation tube, a stirring rod and a multi-stage screening disc, ports of a glass part in the device are all made by grinding, and random disassembly and assembly can be carried out among the parts. Wherein, the liquid storage bottle is connected with the branch port at the bottom of the filter cylinder by a conduit with a water stop clamp; a conduit is arranged in the liquid storage bottle and connected to the peristaltic pump, a flowmeter is arranged in the middle of the conduit so as to control the flow rate of the flotation liquid, and the other end of the conduit is led into the bottom of the sample bottle; placing the suction cartridge in an ultrasonic wave generating device; placing the sample bottle in a filter pumping cylinder, sequentially assembling the flotation tubes on the sample bottle from bottom to top, and finally nesting a plurality of screening discs on the outer side of the flotation tubes; extending the stirring rod into the sample bottle; and finally, connecting a branch port at the top end of the filter cylinder with a vacuum pump, wherein filter screens or filter membranes with different particle diameters are placed in the screening disc so as to realize screening separation and enrichment of micro-plastic targets.

Further, the sediment sample which is optimized in advance is placed in a sample bottle, a proper amount of floatation liquid is added, and a stirring rod and ultrasonic waves are started, so that the sample and the floatation liquid are uniformly mixed to form suspension.

Further, the frequency range of the ultrasonic wave generating device is 300 MHz-500 MHz.

Further, the flotation liquid medium is saturated liquid of sodium chloride, sodium iodide or zinc chloride and degradable surfactant salt solution, and the connection between the liquid storage bottle and the filter cylinder enables the flotation liquid to be recycled, so that the economic cost is reduced, and secondary environmental pollution is avoided.

Furthermore, the arrangement of the screening disc can rapidly and continuously separate and enrich the microplastic with different specifications in the sediment according to actual demands. Changing filter membranes or filter screens with different particle diameters according to requirements, for example, the apertures of micro plastic particles contained in sediments in a beach area are larger, and the filter screens with the apertures in the range of 4-200 meshes can be selected; in the water body, the nano-sized micro-plastic particles may be contained, and a filter membrane with the pore diameter ranging from 0.45 μm to 335 μm can be selected.

Further, the number of the screening trays (10) is determined according to the length of the flotation tubes (8) (one screening tray can be arranged at each flotation tube 10cm long, and the flotation tubes are long enough to enable the suspension to be separated on the screening tray more quickly and better).

Furthermore, the assembly mode between the flotation liquid circulation part and the separation and enrichment part of the sample is detachable and convenient to carry.

Further, the ultrasonic wave is started, so that the falling-off of the substances loaded on the surface of the microplastic is facilitated, and the microplastic can be separated.

Further, the screening disc is divided into an upper layer, a middle layer and a lower layer, wherein the screening disc can be replaced with filter screens or filter membranes with different particle diameters so as to facilitate the step-by-step continuous separation and enrichment of the microplastic with different particles, and the general principle is that the upper layer is provided with the filter screen with 4-80 meshes, the middle layer is provided with the filter screen with 100-200 meshes, and the lower layer is provided with the filter membrane with 0.45-335 mu m.

Further, a sealing device is required to be formed between the lower screening disc and the filter cylinder, and a filter membrane is placed on the lowest screening disc, so that when the flotation liquid and the microplastic reach the lower screening disc, a decompression vacuum pump is started to perform decompression and suction filtration, and separation of fine silt, nano-grade microplastic and the flotation liquid is facilitated, so that the aim of secondary purification of the flotation liquid is fulfilled.

Further, for the purpose of secondary purification of the flotation liquid, a filter membrane can be placed in the lower layer screening tray, thus ensuring the separation of fine silt and nano-sized micro plastic particles from the flotation liquid.

Further, at the same time as the vacuum pump is turned on, the water stop clip also needs to be opened to pump the flotation liquid in the filter cartridge to circulate to the liquid storage bottle.

The application method of the enrichment device for rapidly and continuously separating microplastic is characterized by comprising the following steps of:

(1) And (3) device assembly: selecting a proper experiment table top, respectively assembling all parts, assembling the parts in a left-right and bottom-up principle, and connecting all the parts into a whole through a guide pipe;

(2) The tightness of the device was checked: adding a proper amount of distilled water into the sample bottle and the liquid storage bottle, starting the device, and checking the reading of the vacuum pump to ensure the normal use of the vacuum pump;

(3) Sample adding: adding a sediment sample which is treated in advance into a sample bottle, adding a flotation liquid, starting a stirrer and an ultrasonic generating device, and uniformly mixing the sample and the flotation liquid to form a suspension;

(4) Screening of microplastic: starting a peristaltic pump, pumping the flotation liquid in the liquid storage bottle into a sample bottle, regulating a flow meter within a range of 1-3 mL/min to enable the flotation liquid to enter the sample bottle at a constant speed, so as to ensure that the suspension slowly overflows from the top end of a flotation tube and passes through a screening disc; when the suspension reaches the lowest screening disc, a vacuum pump is started to quickly separate the flotation liquid containing fine silt and nano-grade microplastic; finally, a water stop clamp is opened to enable the flotation liquid to be recycled between the storage bottle and the filter suction cylinder, so that micro plastic particles of the flotation liquid are enriched in different screening discs;

(5) Cleaning the micro plastic: and replacing the flotation liquid with deionized water, and respectively collecting the micro-plastic particles with different particle diameters for drying and detecting in order to ensure that the solute of the flotation liquid adsorbed on the surface of the micro-plastic is removed.

Compared with the prior art, the invention has the advantages that:

1) According to the physical and chemical properties of the existing flotation liquid preparation base and samples, the flotation liquid is selected, and the flotation liquid is recycled, so that the economic cost and the cost for secondary treatment of waste liquid are further reduced;

2) Ultrasonic treatment is selected to treat the sample so as to better remove impurities deposited on the surface of the micro plastic for a long time, thus being beneficial to obtaining original micro plastic particles;

3) The purpose of selecting a multi-layer screening disc for screening is convenient for separating the microplastic with different particles at one time, and the concentration of the microplastic can be enriched efficiently;

4) The use of the vacuum pump improves the separation efficiency of nano-sized substances and flotation liquid, and nano-sized micro-plastic particles can be further enriched;

5) The device has the advantages of simple structure, low cost, easy assembly, easy carrying and moving and high separation efficiency, realizes continuous and rapid separation and enrichment of the micro plastic particles with different specifications in the sediment, and is convenient for popularization and use.

Drawings

FIG. 1 is a schematic diagram of an enrichment apparatus for rapid and continuous separation of microplastic according to the present invention;

FIG. 2 is a schematic view of the flotation tube (left) and screening tray (right) of the present invention;

FIG. 3 is a schematic drawing of a filter cartridge according to the present invention.

The individual components in the figure are as follows: peristaltic pump 1, stock solution bottle 2, flowmeter 3, stagnant water clamp 4, ultrasonic wave generating device 5, sample bottle 6, take out and strain a section of thick bamboo 7, flotation tube 8, stirring rod 9, screening dish 10, vacuum pump 11, pipe 12.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but embodiments of the present invention are not limited thereto, and may be performed with reference to conventional techniques for process parameters that are not specifically noted.

As shown in fig. 1 to 3, a device for separating and enriching microplastic in sediment designed based on a density separation principle is provided, wherein a flotation solution is recycled and microplastic particles with different particle diameters are continuously separated. Comprises a flotation solution circulation part and a sample separation and enrichment part; the flotation liquid circulation part comprises a peristaltic pump 1, a liquid storage bottle 2, a flowmeter 3, a filter cartridge 7, a vacuum pump 11 and a guide pipe 12, the sample separation enrichment part comprises an ultrasonic generating device 5, a sample bottle 6, a flotation tube 8, a stirring rod 9 and a multi-stage screening disc 10, ports of a glass part in the device are all made by grinding, and all parts can be disassembled and assembled at will. Wherein, the liquid storage bottle 2 is connected with the branch opening at the bottom of the filter cartridge 7 by a conduit 12 with a water stop clamp 4; a conduit 12 is arranged in the liquid storage bottle 2 and connected to the peristaltic pump 1, a flowmeter 3 is arranged in the middle of the conduit so as to control the flow rate of the flotation liquid, and the other end of the conduit is led into the bottom of the sample bottle 6; placing the extraction cartridge 7 in the ultrasonic wave generating device 5; placing the sample bottle 6 in a filter pumping cylinder 7, sequentially assembling a flotation tube 8 with the length of 30cm on the sample bottle 6 from bottom to top, and finally nesting a plurality of screening discs 10 on the outer side of the flotation tube 8; a stirring rod 9 with the length of 40cm is stretched into the sample bottle 6; finally, the branch port at the top end of the filter cartridge 7 is connected with a vacuum pump 11, and a filter screen or a filter membrane with different particle diameters is placed in the screening disc 10 so as to realize screening separation and enrichment of micro-plastic targets. The frequency range of the ultrasonic wave generating device 5 is 300 MHz-500 MHz. The flotation liquid medium is saturated liquid of sodium chloride, sodium iodide or zinc chloride and degradable surfactant salt solution, and the liquid storage bottle 2 is connected with the filter cylinder (7), so that the flotation liquid can be recycled, the economic cost is reduced, and secondary environmental pollution is avoided. The assembly mode between the flotation liquid circulation part and the separation and enrichment part of the sample is detachable and convenient to carry. The sieving disk 10 is divided into an upper layer, a middle layer and a lower layer, wherein the sieving disk 10 can be replaced with filter screens or filter membranes with different particle diameters so as to facilitate the step-by-step continuous separation and enrichment of microplastic with different particles, and the general principle is that the upper layer is provided with a 4-80-mesh filter screen, the middle layer is provided with a 100-200-mesh filter screen, and the lower layer is provided with a 0.45-335 mu m filter membrane.

A separation method for separating microplastic with different specifications by a microplastic separation device in sediment comprises the following steps:

1) Adding the prepared saturated density flotation solution into a liquid storage bottle, pretreating to obtain sediment, and placing the sediment into a sample bottle

Wherein, the density of seawater is 1.03×10 ³ kg/m ³ The density of the flotation liquid is chosen here to be greater than the density of seawater. According to the principle of economy and no secondary pollution, saturated sodium chloride and sodium iodide solution are generally selected, and meanwhile, solutions of biodegradable surfactant salts, such as sophorolipid, rhamnolipid and the like, are selected so that some carriers on the surface of the microplastic are degraded and shed.

Weighing 500g of sediment, drying in a baking oven at 105 ℃, grinding in a mortar, and screening by using a steel screen with the aperture of 10mm to obtain sediment A; and weighing 300g of sediment A, dropwise adding 30mL of 30% hydrogen peroxide, soaking for 3-5 hours, and drying for later use.

2) Starting a peristaltic pump and an adjusting flowmeter, putting 200mL of flotation liquid into a sample bottle at the speed of 3mL/min, closing the peristaltic pump, and stopping the flotation liquid from entering the sample bottle;

3) Adding a small amount of flotation liquid into the filter cylinder, and starting an ultrasonic wave and a stirring rod to enable the flotation liquid and a separation sample to fully become suspension;

further, ultrasonic waves of 300W were selected for ultrasonic treatment in the above steps, and the stirring speed of the stirring rod was controlled at 80rpm.

4) After about 15min, starting the peristaltic pump again, and adjusting the flowmeter to pump the flotation liquid into the bottom of the sample bottle at a speed of 1.0mL/min, wherein the suspension with the light floating substances slowly floats upwards, and then the suspension slowly overflows from the top end of the flotation tube;

5) When the suspension overflows from the pipe orifice at the top end, the suspension firstly reaches a filter screen with a large aperture at the upper layer to be filtered, so as to obtain micro plastic particles MPs1 with relatively large blocks, and then the suspension continues to flow downwards, and the micro plastic particles are secondarily separated through a filter screen in the middle to obtain micro plastic MPs2 with medium particles;

further, the pore diameter of the upper and middle layers should be controlled to be 5 mm.ltoreq.R.ltoreq.0.45 μm.

6) When the suspension reaches the filter membrane at the lowest layer, starting a vacuum pump to quickly filter out fine silt and micro plastic particles in the suspension, wherein micro plastic particles MPs3 with nano-scale size are obtained;

further, the liquid level of the flotation liquid in the filter pumping cylinder cannot reach two thirds of that of the ultrafiltration liquid cylinder, and when the liquid level reaches about two thirds, the water stop clamp is opened, so that the flotation liquid flows into the liquid storage bottle from the filter pumping cylinder, the flotation liquid is prevented from being pumped into the vacuum pump, and meanwhile, the flotation liquid is recycled.

7) The flotation liquid in the liquid storage bottle can be replaced by deionized water or other cleaning solution, the micro plastic samples are washed according to the steps 1) to 6), and then the samples on different screening discs are air-dried and stored for testing.

Further, in the step, the circulation time of the cleaning solution is controlled to be 3-5 hours in the cleaning process of the microplastic; the microplastic obtained by separation should be treated by natural air drying.

Example 1

Selecting 5 sampling points (S1, S2, S3, S4 and S5) of a submarine sediment collected by a certain mechanism in a nearby offshore area of China, respectively weighing 500g of crude products, placing the crude products on a surface dish for air drying, and removing massive stones, biomasses and sundries to obtain sediment A; grinding the sediment A in a mortar, and sieving by using a steel sieve with a pore size of 5-10 mm to obtain sediment B; 300g of sediment B is weighed into a beaker, 10mL of deionized water is added into the beaker for stirring, 20mL of 30% hydrogen peroxide is slowly added dropwise, after the reaction is carried out for about 3 hours, the mixture is placed into an oven at 80 ℃ for drying and grinding, and sediment C is obtained and is used as sediment sample of screening microplastic. Preparation of a flotation solution: at room temperature, a saturated sodium chloride solution and an alkaline rhamnolipid aqueous solution are prepared and mixed in a ratio of 8:2 to be used as a flotation solution for standby.

As shown in fig. 1, a sample of the sediment to be separated, which has been treated in advance, was added to the sample bottle 6, the liquid storage bottle was filled with a flotation liquid, the pumping bottle was filled with a flotation liquid of about one-fourth of the volume, the peristaltic pump was turned on and the flow rate of the flowmeter was adjusted so that the flotation liquid was injected into the sample bottle at a rate of 3mL/min, after about 200mL, the injection of the flotation liquid was stopped, and an ultrasonic wave (power 300W) and a stirring bar (rotation speed 80 rpm) were turned on so that the sediment C was thoroughly mixed with the flotation liquid to form a suspension a, which was stirred for 15 min.

Starting a peristaltic pump, adjusting a flowmeter to enable the flotation liquid to be injected into a sample bottle at a speed of 1.0ml/min, adjusting the rotating speed of a stirring rod to be 30rpm, slowly floating the diluted suspension A at a constant speed, and overflowing to the top end of a flotation tube.

Further, the overflowed suspension passes through the upper layer (20 mesh screen) and the middle layer (100 mesh screen) of the screening disc in sequence, at this time, particles are obviously filtered out and marked as particles 1 and 2, and when passing through the lowest layer (0.45 μm filter membrane) of the screening disc, a vacuum pump is started, so that fine particles in the suspension are rapidly filtered, and remain on the filter membrane and marked as particles 3.

Further, when the volume of the flotation solution in the extraction cartridge reaches three-fourths the water stop clamp is opened, allowing the flotation solution to circulate between the holding tank and the extraction cartridge at a constant flow rate.

The flotation liquid in the liquid storage bottle 10 is replaced by deionized water, a peristaltic pump 1 is started, the flow of a flowmeter is regulated to be 10mL/min, a vacuum pump and a water stop clamp are opened, deionized water passes through a three-layer screening disc at a constant flow, particles on a screen are cleaned, the cleaned particles are subjected to air drying treatment, the obtained products are observed by a split microscope, the obtained products are subjected to infrared spectrum, raman spectrum and scanning electron microscope characterization tests, wherein particles of micro plastics are obtained in the screening discs on the upper layer, the middle layer and the lower layer, and the transparent plastics, the colored plastics, the glass fibers and the like are found through the characterization of infrared spectrum, the Raman spectrum and the like.

Table 1, the product count of microplastic particles obtained by sieving five sample points (integrated microscope count)

	S1	S2	S3	S4	S5
						Upper layer plate (granule)	3	0	0	8	1
Middle layer dish (granule)	18	32	19	26	38
						Lower plate (g)	0.023	0.004	0.018	0.001	0.043

Example 2

The purchased linear low density polyethylene particles (particle size about 2-3 mm) were weighed 2.04g, counted under a bulk microscope to 85 particles, added into a 250mL beaker containing 300g of soil, and mixed well to obtain a simulated sediment sample.

Adding the prepared simulated sediment sample into a sample bottle; the prepared flotation liquid is saturated sodium chloride solution; the screens were selected from the upper screen tray (40 mesh screen), the middle screen tray (not placed) and the lower screen tray (house plain filter paper), and the obtained sample was dried in an oven at 80℃and the other operation steps were the same as in example 1.

2.09g of microplastic particles are obtained in total in the three-layer screening, 85 particles are counted under observation of a split microscope, and the obtained plastic particles are dried and treated. The recovery rate of the sample reaches 100%, wherein the middle layer and the lower layer of screening discs are free of micro plastic particles.

Example 3

1.54g of purchased polypropylene plastic particles (with the particle size of 2-3 mm) are weighed, added into a pulverizer for 5min, and all the obtained plastic pulverized particles are added into a 250mL beaker containing 300g of soil and uniformly mixed to be used as a simulated sediment sample.

Adding the prepared simulated sediment sample into a sample bottle; the prepared flotation liquid is saturated sodium chloride solution; the screens were selected from the upper screen tray (40 mesh screen), the middle screen tray (100 mesh screen) and the lower screen tray (0.45 μm filter), and the other steps were the same as in example 1.

In total, 1.46g of microplastic particles are obtained in the final three-layer screening, and the recovery rate of the sample reaches 94.8%, wherein the microplastic particles in the lower-layer screening tray contain a small amount of sediment.

Claims (2)

1. An enrichment device for rapidly and continuously separating microplastic is characterized by comprising a flotation liquid circulation part and a sample separation enrichment part; the flotation liquid circulation part comprises a peristaltic pump (1), a liquid storage bottle (2), a flowmeter (3), a filter pumping cylinder (7), a vacuum pump (11) and a guide pipe (12); the sample separation and enrichment part comprises an ultrasonic generating device (5), a sample bottle (6), a flotation tube (8), a stirring rod (9) and a screening disc (10); wherein, the liquid storage bottle (2) is connected with the branch opening at the bottom of the filter cartridge (7) through a conduit (12) with a water stop clamp (4); a conduit (12) is arranged in the liquid storage bottle (2) and connected to the peristaltic pump (1), a flowmeter (3) is arranged in the middle of the conduit so as to control the flow rate of the flotation liquid, and the other end of the conduit is led into the bottle bottom of the sample bottle (6); placing the filter suction cylinder (7) in an ultrasonic wave generating device (5); placing the sample bottle (6) in a filter pumping cylinder (7), sequentially assembling the flotation tubes (8) on the sample bottle (6) from bottom to top, and finally nesting a plurality of screening discs (10) on the outer side of the flotation tubes (8); extending the stirring rod (9) into the sample bottle (6); finally, a branch port at the top end of the filter cartridge (7) is connected with a vacuum pump (11), and a filter screen or a filter membrane with different particle diameters is placed in the screening disc (10) so as to realize screening separation and enrichment of micro-plastic targets;

the frequency range of the ultrasonic wave generating device (5) is 300 MHz-500 MHz;

the flotation liquid medium is more than one of saturated liquid of sodium chloride, saturated liquid of sodium iodide, saturated liquid of zinc chloride and degradable surfactant salt solution; the liquid storage bottle (2) is connected with the filter cylinder (7), so that the flotation liquid can be recycled, the economic cost is reduced, and secondary environmental pollution is avoided;

the number of the screening discs (10) is determined according to the length of the flotation tubes (8), one screening disc is arranged at each flotation tube 10cm long, and the flotation tubes with enough length are used for enabling the suspension to be separated on the screening discs quickly and well;

the assembly mode between the flotation liquid circulation part and the sample separation and enrichment part is detachable and convenient to carry;

the ultrasonic generating device (5) is started, so that the falling of substances loaded on the surface of the microplastic is facilitated, and the microplastic can be separated;

the screening disc (10) is divided into an upper layer, a middle layer and a lower layer, filter screens or filter membranes with different particle diameters can be replaced in the screening disc (10), so that the microplastic with different particles can be continuously separated and enriched step by step, the upper layer is provided with a 4-80-mesh filter screen, the middle layer is provided with a 100-200-mesh filter screen, and the lower layer is provided with a 0.45-335 mu m filter membrane;

a sealing device is required to be formed between the screening disc (10) at the lower layer and the filter cartridge (7), and a filter membrane is placed on the screening disc (10) at the lowest layer, when the flotation liquid and the microplastic reach the screening disc (10) at the lower layer, a vacuum pump (11) is started to perform reduced pressure suction filtration, so that the separation of the fine silt, the nano-grade microplastic and the flotation liquid is facilitated, and the aim of secondary purification of the flotation liquid is fulfilled.

2. The method of using the enrichment apparatus for rapid and continuous separation of microplastic of claim 1, comprising the following steps:

(1) And (3) device assembly: the parts are assembled respectively firstly, the assembly is carried out on the principle of assembling from left to right and from bottom to top, and then the parts are connected into a whole through a conduit;

(2) The tightness of the device was checked: adding a proper amount of distilled water into the sample bottle and the liquid storage bottle, starting the device, and checking the reading of the vacuum pump to ensure the normal use of the vacuum pump;

(3) Sample adding: adding a sediment sample which is treated in advance into a sample bottle, adding a flotation liquid, starting a stirrer and an ultrasonic generating device, and uniformly mixing the sample and the flotation liquid to form a suspension;

(4) Screening of microplastic: starting a peristaltic pump, pumping the flotation liquid in the liquid storage bottle into a sample bottle, regulating a flow meter within a range of 1-3 mL/min to enable the flotation liquid to enter the sample bottle at a constant speed, so as to ensure that the suspension slowly overflows from the top end of a flotation tube and passes through a screening disc; when the suspension reaches the lowest screening disc, a vacuum pump is started to quickly separate the flotation liquid containing fine silt and nano-grade microplastic; finally, a water stop clamp is opened to enable the flotation liquid to be recycled between the liquid storage bottle and the filter suction cylinder, so that micro plastic particles of the flotation liquid are enriched in different screening discs;

(5) Cleaning the micro plastic: and replacing the flotation liquid with deionized water, and respectively collecting the micro-plastic particles with different particle diameters for drying and detecting in order to ensure that the solute of the flotation liquid adsorbed on the surface of the micro-plastic is removed.