Modularized soil column experimental device for simulating migration of micro / nano plastic in porous medium

Abstract

The invention discloses a modular soil column experimental device for micro / nano plastic migration simulation in a porous medium, and belongs to the technical field of porous medium experimental equipment.The modular soil column experimental device comprises an air compressor, a liquid storage mechanism, a permeation simulation mechanism and a percolate collection mechanism, the liquid storage mechanism is connected with the permeation simulation mechanism through a guide pipe, and the permeation simulation mechanism is connected with the percolate collection mechanism through a guide pipe. According to the modularized soil column experimental device for simulating migration of the micro / nano plastic in the porous medium, the experimental efficiency, the data precision and the operation safety are remarkably improved, and the problems that the migration efficiency of the micro / nano plastic in a low-permeability medium is low, experimental parameter control is inaccurate, the sampling error is large and the device flexibility is insufficient are solved; and efficient, accurate and safe migration behavior research is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of porous medium experimental equipment, and in particular to a modular soil column experimental device for simulating the transport of micro / nano plastics in porous media. Background Technique

[0002] Plastic waste gradually degrades into micro / nano plastics (MNPs) with a particle size less than 5 mm under long-term physical, chemical, and biological actions. These MNPs can leak into the surrounding soil through the landfill liner system, resulting in the deterioration of soil structure and fertility, and carrying toxic pollutants due to their strong adsorption ability, posing a potential threat to the ecosystem and human health.

[0003] Compacted clay, as the most widely used anti-seepage barrier material in current landfills, its low permeability can effectively block the migration of pollutants in the short term. However, under the action of working conditions such as non-uniform load and uneven settlement of the foundation, cracks are easily formed in the compacted clay layer, destroying its continuous structure, significantly increasing the migration rate of MNPs, resulting in a decline in anti-seepage performance, and further affecting the overall environmental safety of the landfill.

[0004] At present, two technical paths, numerical simulation and soil column experiment, are mainly used to study the transport behavior of micro / nano plastics in porous media. Numerical simulation can efficiently predict the transport trend, but its accuracy highly depends on boundary conditions and parameter settings, and still requires experimental data for calibration and verification. In contrast, as a direct physical simulation method, the soil column experiment can provide more real observations of the migration process and data support, and has been widely used in the study of seepage pollution migration.

[0005] Traditional soil column test devices mostly adopt a rigid pipe body structure, fill homogeneous or layered soil samples, control seepage through a constant head or a constant flow pump, apply a pollutant solution or a colloidal suspension to the upper part of the column, and the seepage is from top to bottom. Liquid samples are regularly collected at the outlet of the column to analyze the breakthrough curve and migration behavior of pollutants. Some advanced devices also introduce a temperature control system or a pH adjustment unit for carrying out migration research under multi-field coupling conditions. However, the above methods still have technical defects: (1) The migration rate of MNPs in low-permeability media is relatively low, and the experimental period is long. There are problems such as large head fluctuations and fast colloidal sedimentation in traditional gravity water supply or single-stage water pump systems, which easily cause non-uniform transport processes and affect data accuracy and repeatability; (2) The existing devices have limited means of adjusting key parameters such as the concentration of colloidal suspensions, head gradient, and temperature, and it is difficult to perform high-precision control. At the same time, the sampling process is complex and has a large disturbance, with large errors and difficulties in experimental repetition; (3) The migration of MNPs in the landfill environment is usually affected by the combined effects of seepage, chemical reactions (such as ion exchange, adsorption), and microbial activities. Traditional devices are mostly single physical seepage systems, which cannot comprehensively reflect the complexity of the actual migration process and limit the research depth. Summary of the Invention

[0006] The object of the present invention is to provide a modular soil column experimental device for simulating the migration of micro / nano plastics in porous media, which significantly improves the experimental efficiency, data accuracy, and operation safety, solves the problems of low migration efficiency of micro / nano plastics in low-permeability media, inaccurate control of experimental parameters, large sampling errors, and insufficient flexibility of the device, and realizes efficient, accurate, and safe research on migration behavior.

[0007] To achieve the above object, the present invention provides a modular soil column experimental device for simulating the migration of micro / nano plastics in porous media, including an air compressor, a liquid storage mechanism, a seepage simulation mechanism, and a leachate collection mechanism. The air compressor is connected to the liquid storage mechanism through a conduit, the liquid storage mechanism is connected to the seepage simulation mechanism through a conduit, and the seepage simulation mechanism is connected to the leachate collection mechanism through a conduit.

[0008] Preferably, the liquid storage mechanism includes a pressure regulating valve, a deflation valve, a liquid storage tank, a first magnetic stirrer, and a liquid level display tube. The liquid storage tank is placed above the first magnetic stirrer. The pressure regulating valve and the deflation valve are installed on the top of the liquid storage tank. A first liquid outlet is opened in the center of the top of the liquid storage tank, and a conduit is connected to the first liquid outlet. The liquid level display tube is installed on the side wall of the liquid storage tank. The pressure regulating valve is installed on the top of the liquid storage tank and is connected to the air compressor through a conduit.

[0009] Preferably, the seepage simulation mechanism includes a pressure gauge, a fixing component, and a simulation component. The simulation component includes an upper metal flange, a lower metal flange, a sample column, an upper sealing cover, a lower sealing cover, a screen, an upper rubber ring, and a lower rubber ring. The upper metal flange and the lower metal flange are respectively installed above and below the sample column. The lower metal flange is in contact with the screen. The lower sealing cover is arranged outside the screen, and a lower rubber ring is installed between the lower sealing cover and the screen. An upper rubber ring is installed between the upper metal flange and the upper sealing cover. Connecting holes are opened on both the upper metal flange and the lower metal flange.

[0010] Preferably, the fixing component includes a base, a lead screw, and a fixing nut. The lead screw is fixedly installed on the base. The lead screw sequentially passes through the connecting holes of the lower metal flange and the upper metal flange and is fixedly connected to the metal flange through the fixing nut.

[0011] Preferably, a liquid inlet and a pressure gauge installation port are opened on the upper sealing cover. The pressure gauge is installed at the pressure gauge installation port. A second liquid outlet is opened on the lower sealing cover.

[0012] Preferably, the effusion collection mechanism includes a sampling tank, a second magnetic stirrer, an exhaust valve, a sampling tube, and a glass syringe. The sampling tank is placed above the second magnetic stirrer. The exhaust valve is installed in the middle of the top cover of the sampling tank. The glass syringe is connected to the sampling tank through the sampling tube, and the sampling tube is inserted below the liquid level in the sampling tank.

[0013] Preferably, the exhaust valve includes an exhaust port and a valve switch. The exhaust port is metal honeycomb-shaped, the exhaust valve is a ball valve, and the valve switch is fixedly connected to the sphere inside the exhaust valve.

[0014] Preferably, the number of lead screws is four, and they are evenly distributed on the base. The lead screws respectively match the connection holes on the upper metal flange and the lower metal flange, and the number is the same.

[0015] Preferably, a micro / nano plastic suspension is contained in the liquid storage tank.

[0016] Therefore, the modular soil column experimental device for simulating the migration of micro / nano plastics in the above-mentioned porous medium of the present invention has the following beneficial effects: (1) The closed-loop pressure regulating module formed by the air compressor, the pneumatic pressure regulating valve, and the pressure gauge dynamically maintains the experimental air pressure stable through the automatic start-stop function, and accelerates the migration efficiency of micro / nano plastics in the low-permeability medium; (2) The linkage design of the liquid storage tank and the honeycomb-shaped exhaust valve keeps the water head constant through liquid level compensation, and at the same time uses the porous diversion structure, that is, the honeycomb-shaped exhaust valve, to reduce the influence of liquid evaporation on the sample concentration; (3) The first magnetic stirrer and the second magnetic stirrer can ensure the uniform distribution of the colloidal suspension. The glass syringe is calibrated with volume, and can realize the function of timed and quantitative collection, so as to achieve unbiased interception of samples; (4) The upper metal flange and the lower metal flange are detachable flanges, which can quickly replace the sample columns of different porous media. After the test, the honeycomb-shaped exhaust valve and the liquid storage tank are used to relieve pressure together to eliminate the potential safety hazard of residual air pressure.

[0017] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of Embodiment 1 of the modular soil column experimental device for simulating the migration of micro / nano plastics in the porous medium of the present invention; Figure 2 is a schematic structural diagram of the simulation component of Embodiment 1 of the modular soil column experimental device for simulating the migration of micro / nano plastics in the porous medium of the present invention; Figure 3 is a schematic structural diagram of the exhaust valve of the modular soil column experimental device for simulating the migration of micro / nano plastics in the porous medium of the present invention in the embodiment.

[0019] Reference numerals 1. Air compressor; 2. First magnetic stirrer; 3. Bleed valve; 4. Pneumatic pressure regulating valve; 5. First liquid outlet; 6. Liquid storage tank; 7. Sample column; 8. Upper metal flange; 9. Upper sealing cover; 10. Upper rubber ring; 11. Lower metal flange; 12. Lower sealing cover; 13. Lower rubber ring; 14. Screen; 15. Pressure gauge; 16. Base; 17. Screw rod; 18. Nut; 19. Sample collection tank; 20. Glass syringe; 21. Exhaust valve; 22. Second magnetic stirrer; 23. Sampling tube; 24. Liquid level display tube; 25. Connection hole; 26. Valve switch; 27. Exhaust port. Detailed implementation manners

[0020] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0021] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the field to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0022] Embodiment 1 As Figure 1 shown, the present invention provides a modular soil column experimental device for simulating the migration of micro / nano plastics in porous media, including an air compressor 1, a liquid storage mechanism, a permeability simulation mechanism, and an effluent collection mechanism. The air compressor 1 is connected to the liquid storage mechanism through a conduit, the liquid storage mechanism is connected to the permeability simulation mechanism through a conduit, and the permeability simulation mechanism is connected to the effluent collection mechanism through a conduit. The air compressor 1 is used to provide a stable air pressure and is the power source of the device. The liquid storage mechanism is used to store the suspension. The permeability simulation mechanism is used to simulate the migration process of micro / nano plastics in porous media and observe their permeability characteristics. The effluent collection mechanism is used to collect the effluent after passing through the porous media and analyze the change in the penetration rate concentration or aggregation state of micro / nano plastics.

[0023] The liquid storage mechanism includes a pneumatic regulating valve 4, a gas release valve 3, a liquid storage tank 6, a first magnetic stirrer 2, and a liquid level display tube 24. The liquid storage tank 6 is placed above the first magnetic stirrer 2, and a micro / nano plastic suspension is contained in the liquid storage tank 6. The first magnetic stirrer 2 is used to prevent particle sedimentation in the suspension and maintain concentration uniformity. A pneumatic regulating valve 4 and a gas release valve 3 are installed at the top of the liquid storage tank 6. The gas release valve 3 is used to release the air pressure in the liquid storage tank 6. A first liquid outlet 5 is provided in the center of the top of the liquid storage tank 6, and a conduit is connected to the first liquid outlet 5 to transport the suspension in the liquid storage tank 6 to the osmosis simulation mechanism. A liquid level display tube 24 is installed on the side wall of the liquid storage tank 6, and the liquid level display tube 24 is used to monitor the liquid level change in the liquid storage tank 6 in real time. The pneumatic regulating valve 4 is installed at the top of the liquid storage tank 6 and is connected to the air compressor 1 through a conduit. The pneumatic regulating valve 4 is used to control the air pressure input into the liquid storage tank 6 and regulate the migration process of the fluid under different pressure conditions.

[0024] The osmosis simulation mechanism includes a pressure gauge 15, a fixing component, and a simulation component. The simulation component is used to simulate the situation where the permeating liquid penetrates through the porous medium, and the fixing component is used to fix the simulation component.

[0025] As Figure 2 shown, the simulation component includes an upper metal flange 8, a lower metal flange 11, a sample column 7, an upper sealing cover 9, a lower sealing cover 12, a screen 14, an upper rubber ring 10, and a lower rubber ring 13. The upper metal flange 8 and the lower metal flange 11 are respectively installed above and below the sample column 7. A porous medium (such as compacted clay) is filled in the sample column 7. The upper metal flange 8 and the lower metal flange 11 are used to fix the sample column 7, and the upper metal flange 8 and the lower metal flange 11 are detachable flanges, which can be quickly disassembled to replace the sample column 7 with different porous media.

[0026] The lower metal flange 11 is in contact with the screen 14. The screen 14 is used to filter the exudate to prevent the porous medium from flowing out of the sample column 7 with the exudate, thus causing conduit blockage. A lower sealing cover 12 is provided outside the screen 14. A second liquid outlet is provided on the lower sealing cover 12, and the second liquid outlet is used to output the exudate. A lower rubber ring 13 is installed between the lower sealing cover 12 and the screen 14. The lower sealing cover 12 and the lower rubber ring 13 are arranged so that the exudate will not flow out and can only flow out from the second liquid outlet.

[0027] An upper rubber ring 10 is installed between the upper metal flange 8 and the upper sealing cover 9. An inlet and a pressure gauge installation port are provided on the upper sealing cover 9. The upper sealing cover 9 and the upper rubber ring 10 play a sealing role, so that the suspension can only flow into the sample column 7 through the central inlet. The pressure gauge 15 is installed at the pressure gauge installation port. The pressure gauge installation port is communicated with the inside of the sample column 7 and can monitor the internal air pressure. Connecting holes 25 are provided on both the upper metal flange 8 and the lower metal flange 11.

[0028] The fixing component includes a base 16, a lead screw 17, and a fixing nut 18. The lead screw 17 is fixedly installed on the base 16. The number of lead screws 17 is four, and the four lead screws 17 are evenly distributed on the base 16. The lead screws 17 respectively match the connection holes 25 on the upper metal flange 8 and the lower metal flange 11, and the number is the same. The base 16 is used to support and fix the lead screw 17. The lead screw 17 sequentially passes through the connection hole 25 of the lower metal flange 11 and the connection hole 25 of the upper metal flange 8, and is fixedly connected to the lower metal flange 11 through the fixing nut 18. The upper metal flange 8 and the lower metal flange 11 are fixed on the lead screw 17 through the fixing nut 18 and maintained on a horizontal plane. Connecting four lead screws 17 at one time by the base 16 can achieve the function of stabilizing the device.

[0029] The exudate collection mechanism includes a sampling tank 19, a second magnetic stirrer 22, an exhaust valve 21, a sampling tube 23, and a glass syringe 20. The sampling tank 19 is placed above the second magnetic stirrer 22. The sampling tank 19 is used to collect exudate. The second magnetic stirrer 22 is used for homogenizing the exudate to solve the problem of uneven sampling concentration of the glass syringe 20.

[0030] The exhaust valve 21 is installed in the middle of the top cover of the sampling tank 19. As Figure 3 shown, the exhaust valve 21 includes an exhaust port 27 and a valve switch 26. The exhaust port 27 is metal honeycomb-shaped. The exhaust valve 21 is a ball valve. The valve switch 26 is fixedly connected to the sphere inside the exhaust valve 21. The ventilation and closing of the exhaust valve 21 are controlled by rotating the valve switch 26. The exhaust valve 21 with a metal honeycomb-shaped exhaust port 27 can prevent particle escape. The glass syringe 20 is connected to the sampling tank 19 through the sampling tube 23. The sampling tube 23 is inserted below the liquid level in the sampling tank 19. The glass syringe 20 sucks the exudate through the sampling tube 23. The glass syringe 20 is calibrated with volume, and can realize the function of collecting samples regularly and quantitatively, so as to realize the unbiased interception of exudate.

[0031] When the modular soil column experimental device for simulating the migration of micro / nano plastics in porous media provided by the present invention is used, first fill the porous media into the sample column 7 and complete the installation of the infiltration simulation mechanism. Inject the micro / nano plastic suspension into the liquid storage tank 6, install the whole device, and then start the air compressor 1 and the first magnetic stirrer 2 in sequence. After adjusting to the target pressure value, wait for the suspension to enter the sample column 7 through the conduit. Through the infiltration effect, exudate is obtained. The exudate flows into the conduit through the second liquid outlet below the sample column 7 and enters the sampling tank 19 for collection. At this time, start the second magnetic stirrer 22 to homogenize the exudate. After the migration process is stable, use the glass syringe 20 to regularly collect the exudate samples in the sampling tank 19 for analysis. After the test is completed, quickly release the pressure through the air release valve 3 and the exhaust valve 21 to eliminate the potential safety hazard of residual air pressure.

[0032] Therefore, the modular soil column experimental device for simulating the migration of micro / nano plastics in the above-mentioned porous medium is adopted in the present invention, which significantly improves the experimental efficiency, data accuracy and operation safety, solves the problems of low migration efficiency of micro / nano plastics in low-permeability media, inaccurate control of experimental parameters, large sampling errors and insufficient flexibility of the device, and realizes the research on efficient, accurate and safe migration behavior.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A modular soil column experimental device for simulating the migration of micro / nano plastics in porous media, characterized in that: It includes an air compressor, a liquid storage mechanism, a penetration simulation mechanism, and an exudate collection mechanism. The air compressor is connected to the liquid storage mechanism through a conduit. The liquid storage mechanism is connected to the penetration simulation mechanism through a conduit. The penetration simulation mechanism is connected to the exudate collection mechanism through a conduit.

2. The modular soil column experimental device for simulating the transport of micro / nano plastics in porous media according to claim 1, characterized in that: The liquid storage mechanism includes a pressure regulating valve, a deflation valve, a liquid storage tank, a first magnetic stirrer, and a liquid level display tube. The liquid storage tank is placed above the first magnetic stirrer. A pressure regulating valve and a deflation valve are installed on the top of the liquid storage tank. A first liquid outlet is provided in the center of the top of the liquid storage tank, and a conduit is connected to the first liquid outlet. A liquid level display tube is installed on the side wall of the liquid storage tank. The pressure regulating valve is installed on the top of the liquid storage tank and is connected to the air compressor through a conduit.

3. The modular soil column experimental device for simulating the migration of micro / nano plastics in porous media according to claim 1, characterized in that: The penetration simulation mechanism includes a pressure gauge, a fixing component, and a simulation component. The simulation component includes an upper metal flange, a lower metal flange, a sample column, an upper sealing cover, a lower sealing cover, a sieve, an upper rubber ring, and a lower rubber ring. The upper metal flange and the lower metal flange are respectively installed above and below the sample column. The lower metal flange is in contact with the sieve. A lower sealing cover is provided outside the sieve, and a lower rubber ring is installed between the lower sealing cover and the sieve. An upper rubber ring is installed between the upper metal flange and the upper sealing cover. Connecting holes are provided on both the upper metal flange and the lower metal flange.

4. The modular soil column experimental device for simulating the migration of micro / nano plastics in porous media according to claim 3, characterized in that: The fixing component includes a base, a lead screw, and a fixing nut. The lead screw is fixedly installed on the base. The lead screw passes through the connecting holes of the lower metal flange and the upper metal flange in sequence and is fixedly connected to the metal flange through the fixing nut.

5. The modular soil column experimental device for simulating the migration of micro / nano plastics in porous media according to claim 3, characterized in that: An inlet and a pressure gauge installation port are provided on the upper sealing cover. The pressure gauge is installed at the pressure gauge installation port. A second liquid outlet is provided on the lower sealing cover.

6. The modular soil column experimental device for simulating the migration of micro / nano plastics in porous media according to claim 1, characterized in that: The exudate collection mechanism includes a sample collection tank, a second magnetic stirrer, an exhaust valve, a sampling tube, and a glass syringe. The sample collection tank is placed above the second magnetic stirrer. The exhaust valve is installed in the middle of the top cover of the sample collection tank. The glass syringe is connected to the sample collection tank through the sampling tube, and the sampling tube is inserted below the liquid level in the sample collection tank.

7. The modular soil column experimental device for simulating the migration of micro / nano plastics in porous media according to claim 6, characterized in that: The exhaust valve includes an exhaust port and a valve switch. The exhaust port is in a metal honeycomb shape. The exhaust valve is a ball valve, and the valve switch is fixedly connected to the sphere inside the exhaust valve.

8. The modular soil column experimental device for simulating the migration of micro / nano plastics in porous media according to claim 2, characterized in that: A micro / nano plastic suspension is contained in the liquid storage tank.

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