Separation and enrichment device and method for micro-plastics in sediment

Abstract

The invention discloses a device and method for separating and enriching micro-plastics in sediment, the device comprises a flotation separation part and a filtering and enriching part, the flotation separation part comprises a flotation separation chamber, a stirring mechanism is installed in the flotation separation chamber, and a motor and an air pump are installed at the bottom of the flotation separation chamber; the motor is connected with the stirring mechanism through a transmission shaft and a hollow rotating shaft, an air outlet is formed in the stirring mechanism, and the air pump is connected with the hollow rotating shaft through an air conveying hose; a volume adjusting mechanism is installed at the top of the flotation separation chamber and detachably connected with a stop valve, and the top of the stop valve is detachably connected with a glass cup with an opening in the top. The filtering and enriching part comprises a collecting bottle, and the top of the collecting bottle is connected with a multi-stage filtering module through a sand core filtering head. According to the device and the method disclosed by the invention, the separation efficiency of the micro-plastics can be effectively improved, and secondary damage to the micro-plastics in the sediments can be effectively avoided by virtue of airflow stirring.

Description

Technical Field

[0001] The present invention relates to the field of microplastic separation, and particularly to a device and method for separating and enriching microplastics in sediments. Background Art

[0002] With the development of technology, plastic products have been widely used in daily life. During the application process of plastic products, there will inevitably be natural wear and weathering processes, which will cause some plastics to fall off and gradually turn into tiny microplastic particles left in the natural environment. In addition, there are a large number of abrasive plastic particles in cosmetics and cleaning products used, the weathering of agricultural mulch films, and the application of organic fertilizers, all of which will generate a large number of plastic particles. These plastic particles will gradually converge into river, lake, and marine environments through ways such as domestic sewage, rainwater, and atmospheric deposition. In the water environment, microplastics will undergo physical, chemical, and biological reactions such as drifting, biological migration, and adsorption of organic pollutants. During the above reaction processes, microplastics will be swallowed by multi-level food chains, settle with biological feces, and finally accumulate in the sediment environment. Since microplastics cannot be digested and are difficult to degrade, microplastic pollution in sediments has seriously threatened the survival of marine benthic organisms and human health.

[0003] In order to provide accurate data support for marine environmental detection and pollution control departments, it is necessary to study the size and morphology characterization, chemical element composition, and distribution of microplastics in sediments. At present, the collection and enrichment methods of microplastics in marine sediments have not been standardized. The traditional microplastic separation method is to put sediment samples into a container filled with a separation liquid, stir manually, and use the density separation method to separate particles such as organic matter, biological matter, and microplastics from the sediment samples. After standing for a period of time, the particles such as organic matter, biological matter, and microplastics floating on the surface of the separation liquid are filtered and extracted using a microfiltration membrane, and then transferred to a digestion container to digest the organic matter and biological matter therein to obtain a relatively pure microplastic sample. The entire process has a lot of manual intervention, the phenomenon of human pollution during the process is uncontrollable, and the separation effect seriously depends on the stirring situation of the operator, the separation effect is uncontrollable, it takes more time, and the separation efficiency is low. With the emergence of simple density flotation separation devices, semi-automatic separation of microplastics can be achieved, but there are still problems such as large floor area of the separation device, difficult cleaning process of the separation equipment, and troublesome waste treatment process. Most separation equipment does not have the function of simultaneous digestion, and manual transfer of samples to the digestion device for digestion work is still required, and the problem of a lot of manual intervention is still prominent; moreover, most separation devices mainly rely on mechanical stirring for microplastic separation. During the process, severely weathered microplastics may be broken again under the action of the collision force of the impeller and decomposed into microplastic particles with smaller particle sizes, and the size and morphology characterization of the original microplastics are damaged, and the analysis results cannot reflect the actual characteristics of the sediment samples. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a device and method for separating and enriching microplastics in sediment, aiming to improve the separation efficiency and avoid secondary damage to the microplastics in the sediment.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A device for separating and enriching microplastics in sediment includes a flotation separation part and a filtration enrichment part. The flotation separation part includes a flotation separation chamber, inside which a stirring mechanism is installed. An air outlet is opened on the stirring mechanism, and a motor and an air pump are installed at the bottom. The motor is connected to the stirring mechanism through a transmission shaft and a hollow rotating shaft, and the air pump is connected to the hollow rotating shaft through an air delivery hose. A volume adjustment mechanism is installed at the top of the flotation separation chamber. The volume adjustment mechanism is detachably connected to a stop valve, and the top of the stop valve is detachably connected to a glass cup with an open top. The filtration enrichment part includes a collection bottle, and the top of the collection bottle is connected to a multi-stage filtration module through a sintered filter head.

[0007] In the above solution, the flotation separation chamber includes a separation cone and a threaded guiding neck welded to the top of the separation cone. The bottom of the separation cone is connected to a chassis through a clamp one. The hollow rotating shaft passes through the center of the chassis and is installed on the chassis through a rotating shaft end cover. A seal one, a rotating shaft bearing, and a seal two are installed between the rotating shaft end cover and the chassis.

[0008] In a further technical solution, a support plate is installed at the bottom of the chassis, and the transmission shaft passes through the support plate. The bottom of the support plate is connected to a power system installation chamber, and the motor and the air pump are located in the power system installation chamber. An air flow channel is opened on the support plate, and the air delivery hose passes through the air flow channel and is connected to the hollow rotating shaft.

[0009] In an even further technical solution, a stepped chassis card slot and a rotating shaft end cover card slot are opened on the top of the support plate. The chassis and the rotating shaft end cover are respectively located in the chassis card slot and the rotating shaft end cover card slot. A transmission shaft end cover card slot is opened at the bottom of the support plate, and a transmission shaft end cover is provided in the transmission shaft end cover card slot. The transmission shaft passes through the transmission shaft end cover and is connected to the hollow rotating shaft. The bottom of the transmission shaft end cover is installed in the support plate through a fixing plate. A seal three and a transmission shaft bearing are installed between the transmission shaft end cover and the transmission shaft.

[0010] In a further technical solution, the volume adjustment mechanism includes a sliding joint, a knurled outer cover, a rotating screw disk, a thrust bearing, and a sealing ring IV; the sliding joint is sleeved on the threaded guiding neck, the top of the sliding joint is connected to the lower end of the stop valve through a second clamp, and the top of the stop valve is connected to the glass through a third clamp; the sealing ring IV is arranged between the threaded guiding neck and the sliding joint; the rotating screw disk is located below the sliding joint and is threadedly connected to the threaded guiding neck, the knurled outer cover is fixedly connected to the outside of the rotating screw disk through screws and is clamped on the sliding joint; the thrust bearing is arranged in the cavity formed by the sliding joint, the knurled outer cover, the rotating screw disk, and the threaded guiding neck.

[0011] In the above solution, the stirring mechanism includes a rotating hub, and hollow stirring claws with different lengths are connected to the rotating hub. The air outlet is located at the end of the stirring claws, and the rotating hub is connected to a hollow stirring shaft.

[0012] In a further technical solution, stirring blades are connected between adjacent stirring claws.

[0013] In the above solution, the multi-stage filtration module includes an upper pressing plate, a lower pressing plate, and a plurality of filter membrane support disks and filter membranes arranged between the upper pressing plate and the lower pressing plate. The filter membranes are installed downward on the plurality of filter membrane support disks in order from largest to smallest pore size. A conversion disk for connecting to a sand core filter head is installed below the bottommost filter membrane support disk. The top of the upper pressing plate is connected to a chuck; the upper pressing plate and the lower pressing plate are connected through compression screws and wing nuts.

[0014] In the above solution, the sand core filter head can be connected to an air extraction pump.

[0015] A method for separating and enriching microplastics in sediment, using the device for separating and enriching microplastics in sediment as described above, includes the following steps:

[0016] (1) Put the sediment sample into the top inlet of the flotation separation chamber, then put in the standard separation liquid, and install the stop valve and the glass with an open top in sequence. The stop valve is in an open state.

[0017] (2) Start the motor and the air pump. The stirring mechanism and the rotating air flow fully stir the sediment sample. After a period of time, turn off the air pump, add the standard separation liquid in batches, and continue flotation until the liquid level reaches the middle position of the glass.

[0018] (3) When the separation liquid in the glass becomes clear, turn off the motor and the stop valve, adjust the volume adjustment mechanism, gradually raise the stop valve and the glass to the topmost position, and drain the liquid in the cavity at the lower end of the stop valve.

[0019] (4) Disassemble the stop valve and the volume adjustment mechanism, translate the stop valve and the glass cup to the multi-stage filtration module, and after fixing, open the stop valve. Under the action of gravity, the separation liquid passes through the multi-stage filtration module and the sand core filter head and flows into the collection bottle. The organic matter, biological matter, and microplastics in the sediment sample are retained in the multi-stage filtration module;

[0020] (5) Close the stop valve, pour the digestion solution from the top of the glass cup to completely cover the multi-stage filtration module, and use the digestion solution to completely digest the organic matter and biological matter in the sediment sample. Then open the stop valve again. Under the action of gravity, the digestion solution passes through the multi-stage filtration module and the sand core filter head and flows into the collection bottle, and the microplastics therein are retained in the multi-stage filtration module.

[0021] Through the above technical solutions, a device and method for separating and enriching microplastics in sediment provided by the present invention have the following beneficial effects:

[0022] 1. The present invention uses rotating air flow as the main power to stir the sediment sample, stirs the sediment more fully, floats the microplastics more thoroughly, can effectively improve the separation efficiency of microplastics, and the stirring of the air flow can effectively avoid secondary damage to the microplastics in the sediment;

[0023] 2. The present invention adopts a volume adjustment mechanism to make the volume space of the flotation separation chamber adjustable, so that the liquid level of the separation liquid can be adjusted, and the problem of overflow of the separation liquid during the transfer of microplastics can be effectively avoided;

[0024] 3. The multi-stage filtration module of the present invention has both filtration and digestion functions, can effectively improve the separation speed of microplastics in sediment, shorten the separation time of microplastics in sediment, and improve the work efficiency of laboratory staff;

[0025] 4. The device of the present invention adopts a modular design, and the modules are connected by quick-connect chucks, making the processes of feeding, treating waste, and cleaning the equipment more simple and fast.

[0026] 5. The present invention can select a suitable stirring mechanism according to the characteristics of the sediment sample (sandy mud sample, muddy mud sample) to improve the separation efficiency. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0028] Figure 1 It is a schematic diagram of a device for separating and enriching microplastics in sediment disclosed in an embodiment of the present invention. (a) is the flotation separation part, and (b) is the filtration and enrichment part;

[0029] Figure 2Schematic diagram of the stirring mechanism, (a) is the stirring claw for sandy samples, and (b) is the stirring claw for muddy samples;

[0030] Figure 3 Schematic diagram of the flotation separation chamber;

[0031] Figure 4 Schematic diagram of the hollow rotating shaft and the transmission shaft, (a) is the hollow rotating shaft, and (b) is the transmission shaft;

[0032] Figure 5 Schematic diagram of the support disk;

[0033] Figure 6 Schematic diagram of the outside of the power system installation chamber;

[0034] Figure 7 Schematic diagram of the volume adjustment mechanism, (a) before adjustment and (b) after adjustment;

[0035] Figure 8 Schematic diagram of the multi-stage filtration module;

[0036] Figure 9 Schematic diagram after the multi-stage filtration module is connected to the stop valve.

[0037] In the figure, 1. Glass; 2. Stop valve; 3. Volume adjustment mechanism; 4. Flotation separation chamber; 5. Stirring mechanism; 6. Hollow rotating shaft; 7. Transmission shaft; 8. Motor; 9. Air pump; 10. Power system installation chamber; 11. Transmission shaft end cover assembly; 12. Air delivery hose; 13. Rotating shaft end cover assembly; 14. Support disk; 15. Clamp 1; 16. Clamp 2; 17. Multi-stage filtration module; 18. Sand core filter head; 19. Collection bottle; 20. Clamp 3;

[0038] 301. Slip joint; 302. Knurled outer cover; 303. Rotating screw disk; 304. Thrust bearing; 305. Seal ring 4; 306. Expansion chamber;

[0039] 401. Threaded guide neck; 402. Separation cone; 403. Seal ring 5; 404. Chassis;

[0040] 501. Rotating hub; 502. Long stirring claw; 503. Short stirring claw; 504. Stirring blade;

[0041] 601. Rotating shaft slot; 602. Hollow air delivery channel; 603. Threaded head;

[0042] 701. Transmission shaft slot;

[0043] 1001. Housing; 1002. Power switch; 1003. Cyclone switch;

[0044] 1101. Seal ring three; 1102. Transmission shaft bearing; 1103. Transmission shaft end cover;

[0045] 1301. Seal ring one; 1302. Rotating shaft bearing; 1303. Seal ring two; 1304. Rotating shaft end cover;

[0046] 1401. Chassis card slot; 1402. Rotating shaft end cover card slot; 1403. Transmission shaft end cover card slot; 1404. Fixed plate; 1405. Hose press head; 1406. Air flow channel;

[0047] 1701. Quick-connect chuck one; 1702. Filter membrane support disc; 1703. Filter membrane; 1704. Conversion disc; 1705. Seal ring six; 1706. Upper pressure plate; 1707. Compression screw; 1708. Lower pressure plate; 1709. Wing nut. Specific implementation mode

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0049] The present invention provides a device for separating and enriching microplastics in sediments, as Figure 1 shown, including a flotation separation part and a filtration enrichment part.

[0050] As Figure 1 shown in (a), the flotation separation part includes a flotation separation chamber 4. A stirring mechanism 5 is installed inside the flotation separation chamber 4, and a motor 8 and an air pump 9 are installed at the bottom. The motor 8 is connected to the stirring mechanism 5 through a transmission shaft 7 and a hollow rotating shaft 6. An air outlet is provided on the stirring mechanism 5, and the air pump 9 is connected to the hollow rotating shaft 6 through an air delivery hose 12. The stirring mechanism 5 is driven by the motor 8 to stir the sediments, and the air pump 9 delivers air flow to the stirring mechanism 5 to float the microplastics in the sediments during the stirring process.

[0051] As Figure 2 shown, the stirring mechanism 5 includes a rotating hub 501. A hollow long stirring claw 502 and a short stirring claw 503 are connected to the rotating hub 501. The ends of the long stirring claw 502 and the short stirring claw 503 are air outlets. The rotating hub 501 is connected to the hollow rotating shaft 6, and air flow can be discharged from the ends of the long stirring claw 502 and the short stirring claw 503 through the hollow rotating shaft 6 and the rotating hub 501, so as to float the sediments. Figure 2 The sandy sample stirring claw shown in (a) is suitable for the case where the sediment sample has large-sized sand grains or more stones. When the sediment sample is muddy, another muddy sample stirring claw can be selected, as Figure 2 shown in (b), that is, stirring blades 504 are connected between adjacent long stirring claws 502 and short stirring claws 503.

[0052] As shown Figure 3 in the figure, the flotation separation chamber 4 includes a separation cone barrel 402 and a threaded guiding neck 401 welded to the top of the separation cone barrel 402. The bottom of the separation cone barrel 402 is connected to the chassis 404 through a first clamp 15, and the two are sealed under the action of a fifth sealing ring 403; the hollow rotating shaft 6 is connected to the chassis 403 through a rotating shaft end cover assembly 13. The rotating shaft end cover assembly 13 includes a rotating shaft end cover 1304, a first sealing ring 1301, a rotating shaft bearing 1302, and a second sealing ring 1303; the hollow rotating shaft 6 passes through the center of the chassis 404. The hollow rotating shaft 6 is installed on the chassis 404 through the rotating shaft end cover 1304. A second sealing ring 1301, a rotating shaft bearing 1302, and a second sealing ring 1303 are installed between the rotating shaft end cover 1304 and the chassis 404. The rotating shaft end cover 1304 is fixed to the bottom surface of the chassis 404 by screws.

[0053] As shown Figure 4 in the figure, the ends of the hollow rotating shaft 6 and the transmission shaft 7 are designed with a rotating shaft slot 601 and a transmission shaft slot 701 that cooperate with each other. As shown Figure 4 in (a) of the figure, the middle part of the hollow rotating shaft 6 is a hollow air transmission channel 602, and the other end is a threaded head 603, which is connected to the rotating hub 501. As shown Figure 4 in (b) of the figure, the other end of the transmission shaft 7 is connected to the motor 8.

[0054] As shown Figure 1 and Figure 5 in the figure, a support disk 14 is installed at the bottom of the chassis 404, and the transmission shaft 7 passes through the support disk 14; the bottom of the support disk 14 is connected to the power system installation chamber 10. The motor 8 and the air pump 9 are located in the power system installation chamber 10. As shown Figure 6 in the figure, a power switch 1002 and a cyclone switch 1003 are arranged outside the housing 1001 of the power system installation chamber 10, which are used to control the motor 8 and the air pump 9 respectively. An air flow channel 1406 is opened on the support disk 14, and the air delivery hose 12 passes through the air flow channel 1406 and is connected to the hollow rotating shaft 6. A hose press head 1405 is arranged at the end of the air flow channel 1406 for fixing the air delivery hose 12.

[0055] The transmission shaft 7 is connected to the support disk 14 through the transmission shaft end cover assembly 11. The transmission shaft end cover assembly 11 includes a transmission shaft end cover 1103, a fixing plate 1404, a third sealing ring 1101, and a transmission shaft bearing 1102. A stepped chassis card slot 1401 and a rotating shaft end cover card slot 1402 are formed at the top of the support disk 14. The chassis 404 and the rotating shaft end cover 1304 are respectively located in the chassis card slot 1401 and the rotating shaft end cover card slot 1402. A transmission shaft end cover card slot 1403 is formed at the bottom of the support disk 14. The transmission shaft end cover 1103 is arranged in the transmission shaft end cover card slot 1403. The transmission shaft 7 passes through the transmission shaft end cover 1103 and is connected to the hollow rotating shaft 6. The bottom of the transmission shaft end cover 1103 is installed in the support disk 14 through the fixing plate 1404. A third sealing ring 1101 and a transmission shaft bearing 1102 are installed between the transmission shaft end cover 1103 and the transmission shaft 7.

[0056] As Figure 7 shown, the volume adjustment mechanism 3 includes a sliding joint 301, a knurled outer cover 302, a rotating screw disk 303, a thrust bearing 304, and a fourth sealing ring 305. The sliding joint 301 is sleeved on the threaded guiding neck 401 at the top of the flotation separation chamber 4. The fourth sealing ring 305 is arranged between the threaded guiding neck 401 and the sliding joint 301. The top of the sliding joint 301 is connected to the lower end of the stop valve 2 through a second clamp 16. The top of the stop valve 2 is connected to the glass cup 1 through a third clamp 20. The rotating screw disk 303 is located below the sliding joint 301 and is threadedly connected to the threaded guiding neck 401. The knurled outer cover 302 is fixedly connected to the outside of the rotating screw disk 303 through screws and is clamped on the sliding joint 301. The thrust bearing 304 is arranged in the cavity formed by the sliding joint 301, the knurled outer cover 302, the rotating screw disk 303, and the threaded guiding neck 401. When the knurled outer cover 302 is turned, the rotating screw disk 303 moves up and down along the threaded guiding neck 401. Under the action of the thrust bearing 304, the sliding joint 301 also moves up and down. At this time, the volume of the expansion chamber 306 formed by the sliding joint 301 and the threaded guiding neck 401 becomes larger or smaller, as Figure 7 shown in (a) and (b).

[0057] As Figure 1 shown in (b), the filtration and enrichment part includes a collection bottle 19. The top of the collection bottle 19 is connected to the multi-stage filtration module 17 through a sand core filter head 18. To achieve rapid filtration, a manual air pump 9 can be connected to the sand core filter head 18. By using the form of manual exhaust, the pressure difference between the inside and outside of the collection bottle 19 is increased to achieve rapid filtration.

[0058] As Figure 8As shown in the figure, the multi-stage filtration module 17 includes an upper pressing plate 1706, a lower pressing plate 1708, and a plurality of filter membrane support discs 1702 and filter membranes 1703 disposed between the upper pressing plate 1706 and the lower pressing plate 1708. The filter membranes 1703 are sequentially installed downward on the plurality of filter membrane support discs 1702 according to the decreasing pore size, and are sealed by a sixth sealing ring 1705. A conversion disc 1704 for connecting with a sand core filter head 18 is installed below the lowermost filter membrane support disc 1702. The top of the upper pressing plate 1706 is connected to a chuck 1701, and the chuck 1701 can be connected to the stop valve 2; the upper pressing plate 1706 and the lower pressing plate 1708 are connected by a pressing screw 1707 and a wing nut 1709.

[0059] A method for separating and enriching microplastics in sediments, using a device for separating and enriching microplastics in sediments according to any one of the above, includes the following steps:

[0060] (1) Put the sediment sample into the top inlet of the flotation separation chamber 4, and then put in the standard separation liquid (pure saturated brine). Connect the stop valve 2 to the sliding joint 301 of the volume adjustment mechanism 3 through a second clamp 16, and install the glass 1 with an open top on the stop valve 2 through a third clamp 20. Before starting the test, the stop valve 2 is in an open state;

[0061] (2) Turn on the power switch 1002 to start the motor 8, and turn on the air cyclone switch 1003 to start the air pump 9. The motor 8 drives the long stirring claws 502 and short stirring claws 503 of the stirring mechanism 5 to stir the sediment sample through the transmission shaft 7 and the hollow rotating shaft 6. At the same time, the air flow passes through the air delivery hose 12, the hollow rotating shaft 6, and the rotating hub 501 and is discharged from the long stirring claws 502 and short stirring claws 503, so as to float the microplastics in the sediment. The gas can be discharged from the top of the glass 1. After a period of time, turn off the air pump 9, and only keep the mechanical stirring rotating at a low speed. Add the standard separation liquid in portions and continue the flotation until the liquid level reaches the middle position of the glass 1;

[0062] (3) When the separation liquid in the glass 1 becomes clear, turn off the motor 8 and close the stop valve 2. Slowly turn the knurled outer cover 302 of the volume adjustment mechanism 3 to make the rotating screw disc 303 move upward along the threaded guiding neck 401, gradually raise the stop valve 2 and the glass 1, and turn it to the top to form an expansion chamber 306. The separation liquid in the lower cavity of the stop valve 2 is discharged into the expansion chamber 306 to avoid splashing of the separation liquid during the transfer process;

[0063] (4) Open the second clamp 16, disassemble the stop valve 2 and the volume adjustment mechanism 3, and translate the stop valve 2 and the glass 1 onto the multi-stage filtration module 17, as Figure 9As shown, after being fixed by the chuck 1701 and the second clamp 16, the isolation valve 2 is opened. Under the action of gravity, the separation liquid flows through the multi-stage filtration module 17 and the sand core filter head 18 and into the collection bottle 19. Among them, the organic matter, biological substances, and microplastics in the sediment sample are retained in the multi-stage filtration module 17;

[0064] (5) Close the isolation valve 2, and pour the digestion solution (15% concentration H 2 O 2 ) from the top of the glass 1 to completely cover the multi-stage filtration module 17. Use the digestion solution to completely oxidize and reduce the digestion of the organic matter and biological substances in the sediment sample. After standing for a period of time, open the isolation valve 2 again. Under the action of gravity, the digestion solution flows through the multi-stage filtration module 17 and the sand core filter head 18 and into the collection bottle 19. The microplastics therein are retained in the multi-stage filtration module 17;

[0065] (6) With the isolation valve 2 open, repeatedly pour pure water evenly along the inner wall of the glass 1 so that the microplastics adsorbed on components such as the glass 1, the chuck 1701, and the filter membrane support plate 1702 are all washed and retained on the surface of the filter membrane 1703, realizing that different particle microplastics are retained on the corresponding filter screen surface and achieving hierarchical filtration and separation;

[0066] (7) Unscrew the wing nut 1709, take out the filter membrane 1703 containing microplastics in sequence, and transfer it to a professional analytical instrument for subsequent quantitative and qualitative analysis of microplastics;

[0067] (8) After the separation is completed, wash all components with pure water again, and dry them.

[0068] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for separating and enriching microplastics in sediments, characterized in that: It includes a flotation separation part and a filtration and enrichment part. The flotation separation part includes a flotation separation chamber. A stirring mechanism is installed inside the flotation separation chamber. A motor and an air pump are installed at the bottom. The motor is connected to the stirring mechanism through a transmission shaft and a hollow rotating shaft. An air outlet is provided on the stirring mechanism. The air pump is connected to the hollow rotating shaft through an air hose. A volume adjustment mechanism is installed on the top of the flotation separation chamber. The volume adjustment mechanism is detachably connected to a stop valve. The top of the stop valve is detachably connected to a glass cup with an opening on the top. The filtration and enrichment part includes a collecting bottle. The top of the collecting bottle is connected to a multi-stage filtration module through a sand core filter head.

2. The device for separating and enriching microplastics in sediment according to claim 1, characterized in that: The flotation separation chamber includes a separation cone and a threaded guide neck welded to the top of the separation cone, and the bottom of the separation cone is connected to the chassis through a clamp. The hollow rotating shaft passes through the center of the chassis, and the hollow rotating shaft is installed on the chassis through a rotating shaft end cover. A sealing ring 1, a rotating shaft bearing and a sealing ring 2 are installed between the rotating shaft end cover and the chassis.

3. The device for separating and enriching microplastics in sediments according to claim 2, characterized in that: A support plate is installed at the bottom of the chassis, and the transmission shaft passes through the support plate; the bottom of the support plate is connected to the power system installation room, the motor and the air pump are located in the power system installation room, an air flow channel is opened on the support plate, and the air delivery hose passes through the air flow channel and is connected to the hollow rotating shaft.

4. The device for separating and enriching microplastics in sediments according to claim 3, characterized in that: The top of the support plate is provided with a stepped chassis slot and a rotating shaft end cover slot, and the chassis and the rotating shaft end cover are respectively located in the chassis slot and the rotating shaft end cover slot; the bottom of the support plate is provided with a transfer shaft end cover slot, and a transfer shaft end cover is arranged in the transfer shaft end cover slot, the transfer shaft passes through the transfer shaft end cover and is connected with the hollow rotating shaft, and the bottom of the transfer shaft end cover is installed in the support plate through a fixing plate; a sealing ring and a transfer shaft bearing are installed between the transfer shaft end cover and the transfer shaft.

5. The device for separating and enriching microplastics in sediments according to claim 2, characterized in that: The volume adjustment mechanism includes a sliding joint, a knurled outer cover, a rotating screw disk, a thrust bearing, and a sealing ring four; the sliding joint is sleeved on the threaded guide neck, the top of the sliding joint is connected to the lower end of the stop valve through a clamp two, and the top of the stop valve is connected to the glass cup through a clamp three; the sealing ring four is arranged between the threaded guide neck and the sliding joint; the rotating screw disk is located below the sliding joint and is connected to the threaded guide neck through threads, the knurled outer cover is fixed to the outside of the rotating screw disk by screws, and is clamped on the sliding joint; the thrust bearing is arranged in a cavity surrounded by the sliding joint, the knurled outer cover, the rotating screw disk and the threaded guide neck.

6. The device for separating and enriching microplastics in sediment according to claim 1, characterized in that: The stirring mechanism comprises a rotating hub, and hollow stirring claws of different lengths are connected to the rotating hub. The air outlet is located at the end of the stirring claw, and the rotating hub is connected to the hollow stirring shaft.

7. The device for separating and enriching microplastics in sediments according to claim 6, characterized in that: Adjacent stirring claws are connected with stirring blades.

8. The device for separating and enriching microplastics in sediments according to claim 1, characterized in that: The multi-stage filtration module includes an upper pressure plate, a lower pressure plate, and multiple filter membrane support plates and filter membranes arranged between the upper pressure plate and the lower pressure plate. The filter membranes are installed downward on the multiple filter membrane support plates in descending order according to the pore size. A conversion plate for connecting to a sand core filter head is installed below the bottom filter membrane support plate. The top of the upper pressure plate is connected to a chuck; the upper pressure plate and the lower pressure plate are connected by a tightening screw and a butterfly nut.

9. The device for separating and enriching microplastics in sediment according to claim 1, characterized in that: The sand core filter head can be connected to an air pump.

10. A method for separating and enriching microplastics in sediments, using a device for separating and enriching microplastics in sediments as claimed in any one of claims 1 to 9, characterized in that: The steps include: (1) Place the sediment sample in the top entrance of the flotation separation chamber, then add the standard separation liquid, install the stop valve and the glass cup with the top opening in sequence, and keep the stop valve in the open state; (2) Start the motor and air pump, and use the stirring mechanism and rotating airflow to fully stir the sediment sample. After a period of time, turn off the air pump, add standard separation liquid in batches, and continue flotation until the liquid level reaches the middle of the glass; (3) When the separated liquid in the glass becomes clear, turn off the motor and the stop valve, adjust the volume adjustment mechanism, gradually raise the stop valve and the glass to the top, and discharge the liquid in the cavity at the lower end of the stop valve; (4) Disassemble the stop valve and the volume adjustment mechanism, translate the stop valve and the glass cup onto the multi-stage filtration module, fix them, open the stop valve, and the separation liquid flows into the collection bottle through the multi-stage filtration module and the sand core filter head under the action of gravity. The organic matter, biological matter, and microplastics in the sediment sample are trapped in the multi-stage filtration module; (5) Close the stop valve and pour the digestion solution from the top of the glass to completely cover the multi-stage filtration module. Use the digestion solution to completely digest the organic matter and biological matter in the sediment sample. Open the stop valve again. Under the action of gravity, the digestion solution flows into the collection bottle through the multi-stage filtration module and the sand core filter head. The microplastics in the solution are retained in the multi-stage filtration module.

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