A method and apparatus for continuous extraction and separation of soil microplastics of different particle sizes

Abstract

The application provides a method and device for continuous extraction and separation of soil microplastics with different particle sizes, and belongs to the technical field of soil microplastic treatment. The method uses a special device for continuous extraction and separation of soil microplastics. The device comprises a mounting main frame, a rotating mounting frame arranged on one side of the mounting main frame, a driving unit rotatably connected to the rotating mounting frame through a connecting shaft and arranged on the mounting main frame, and an extraction and separation cylinder arranged in the rotating mounting frame. The extraction and separation cylinder, the filter membrane and the circulating return pipe in the device are combined with the microplastic particle gradient separation and liquid reuse steps in the method, so that different particle sizes of microplastics can be effectively separated. The extraction and separation cylinder is repeatedly inverted, and the continuous extraction and separation of soil microplastics are sequentially completed. This continuous operation mode avoids errors and time waste caused by sample transfer and equipment reconfiguration in traditional step-by-step operation, and improves the efficiency of the entire microplastic extraction and separation process.

Description

Technical Field

[0001] This invention belongs to the field of soil microplastic treatment technology, specifically a method and apparatus for the continuous extraction and separation of soil microplastics of different particle sizes. Background Technology

[0002] With the widespread use of plastic products, microplastics are increasingly distributed in the environment, and soil, as an important component of the ecosystem, has also been polluted by microplastics. Microplastics can enter the soil through various pathways, such as wastewater irrigation, sludge application, decomposition of plastic films, and atmospheric deposition. Different levels of microplastic pollution have been detected in soils in various environments, including agriculture, industry, and urban areas. This can affect the physical, chemical, and biological properties of the soil, thereby threatening the health and function of the soil ecosystem.

[0003] Microplastics in soil can alter soil structure, affecting soil aeration, water retention, and fertility. They can also adsorb pollutants in the soil, such as heavy metals and organic pollutants, altering the mobility and bioavailability of these pollutants, thereby having toxic effects on soil organisms, including microorganisms and earthworms, interfering with food chain transmission in the soil ecosystem, and ultimately potentially affecting the stability and biodiversity of the entire ecosystem.

[0004] Traditional soil sampling methods often fail to adequately consider the representativeness of soil samples when studying soil microplastics. Some sampling methods may only randomly select a few sampling points or fail to standardize the sampling volume at each sampling point. As a result, the collected soil samples cannot accurately reflect the microplastic pollution status of the entire sampling area. In terms of microplastic extraction and separation, existing devices may not be able to effectively separate microplastics of different particle size ranges, leading to inaccurate separation results. The operation process is relatively complex, usually requiring multiple steps and frequent sample transfer between devices, resulting in low efficiency of the entire microplastic extraction and separation process. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method and apparatus for the continuous extraction and separation of soil microplastics of different particle sizes.

[0006] The technical solution of this invention is: a method for continuous extraction and separation of soil microplastics of different particle sizes, comprising the following steps:

[0007] S1. Soil Sample Collection

[0008] Multiple sampling points are set up in a grid distribution within the sampling area. Soil samples are collected at each sampling point at a predetermined depth to ensure that the amount of soil collected at each sampling point is consistent.

[0009] S2, Soil Sample Pretreatment

[0010] First, the collected soil samples were sieved to remove solid impurities. The soil samples, after solid impurities were removed, were then spread evenly in a well-ventilated indoor environment to air dry, turning them over periodically. The air drying time was 3-5 days. Second, the air-dried soil samples were ground and sieved to obtain soil particles with a particle size of 0.1-5 mm. The sieved soil particles were then mixed with the extract and stirred evenly using a magnetic stirrer to obtain a mixed slurry sample. 1 L of extract was added to every 50 kg of sieved soil particles. The magnetic stirrer was operated at a speed of 3000-5000 r / min, and the centrifugation time was 10-20 min.

[0011] S3. Gradient separation of microplastic particles in soil samples

[0012] The mixed slurry sample is added to the extraction separation cylinder and flows from top to bottom through a series of filter membranes with progressively increasing mesh sizes. Microplastic particles of multiple particle size ranges in the mixed slurry sample are separated through each filter membrane. The separated liquid is reused as the extraction liquid. The direction inside the extraction separation cylinder is rotated to invert it. At this time, the microplastic particles located on each filter membrane are collected by the receiving tray, thus completing the gradient separation of microplastic particles in the soil sample.

[0013] S4. Extraction of microplastic particles from soil samples

[0014] Open the sealing cover, extract each receiving tray from the extraction and separation cylinder, and collect the microplastic particles separated from the soil sample.

[0015] Furthermore, the extract is a saturated sodium chloride solution or a zinc iodide solution, wherein the density of the saturated sodium chloride solution is 1.0-1.4 g / cm³. 3 The density of zinc iodide solution is 1.8-2.0 g / cm³. 3 .

[0016] Explanation: The extract can break down the agglomeration forces between soil particles, allowing them to be evenly dispersed in the solution. This enables the microplastic particles in the soil to be more fully exposed in the solution, facilitating subsequent separation operations.

[0017] The present invention also discloses an apparatus for continuous extraction and separation of soil microplastics of different particle sizes, which is used to realize a method for continuous extraction and separation of soil microplastics of different particle sizes. The apparatus includes a main frame, a rotating mounting frame disposed on one side of the main frame, and a drive unit disposed on the main frame and rotatably connected to the rotating mounting frame via a connecting shaft. The extraction and separation cylinder is disposed inside the rotating mounting frame.

[0018] The extraction and separation cylinder is provided with an addition port and a discharge port at its upper and lower ends, respectively. A sealing cover plate is hinged to one side of the extraction and separation cylinder. Multiple filter membranes with progressively increasing mesh sizes are arranged in the extraction and separation cylinder from top to bottom, and each filter membrane is provided with a receiving plate at its upper end. The addition port and discharge port of the extraction and separation cylinder are connected by a circulation return pipe, and a one-way valve and a liquid pump are provided at the connection point.

[0019] The receiving plate includes a receiving frame, a folding sliding plate slidably connected within the receiving frame and composed of multiple parallel splicing support plates, a sliding strip disposed on one side of the folding sliding plate and capable of sliding left and right along the inner wall of the receiving frame, and a hydraulic rod for driving the sliding strip to slide.

[0020] Furthermore, a reinforcing base is provided at the bottom of the main mounting frame and directly below the rotating mounting frame, and the bottom of the reinforcing base is provided with an anti-slip friction layer.

[0021] Note: Because the rotating mounting frame and the extraction / separation cylinder are located on one side of the main mounting frame, a reinforcing base is installed at the bottom of the main mounting frame, corresponding to the lower ends of the rotating mounting frame and the extraction / separation cylinder. This prevents them from sinking, shifting, or tipping due to their own weight or dynamic forces during operation, thereby enhancing the installation stability of the rotating mounting frame and the extraction / separation cylinder. At the same time, an anti-slip friction layer is provided at the bottom of the reinforcing base, which increases the friction between the reinforcing base and the ground, preventing the reinforcing base from sliding in the horizontal direction, and thus avoiding horizontal displacement of the rotating mounting frame and the extraction / separation cylinder.

[0022] Furthermore, a mixing chamber is connected through the addition port, and a magnetic stirrer is installed inside the mixing chamber.

[0023] Note: Before extracting microplastics from soil, soil and extractant are added to a mixing tank in a specific ratio and stirred using a magnetic stirrer to obtain a mixed slurry sample. This allows the extractant to be evenly dispersed in the soil sample, making the dissolution of microplastics in the extractant more rapid and thus improving the extraction efficiency of microplastics.

[0024] Furthermore, the receiving frame sidewall is provided with a fastening clamping strip, and the upper and lower ends of the fastening clamping strip are respectively provided with clamping grooves. The inner wall of the sealing cover plate is provided with a snap-fit ​​fastening assembly corresponding to each receiving frame. The snap-fit ​​fastening assembly includes two horizontal mounting plates provided parallel to the upper and lower ends of each fastening clamping strip, and two clamping plates connected to the two horizontal mounting plates by an electric telescopic rod and distributed opposite to each other. The two clamping plates distributed opposite to each other match the clamping grooves located at the upper and lower ends of the same fastening clamping strip.

[0025] Note: After the receiving frame is installed inside the extraction and separation cylinder, it will move synchronously with the up and down rotation of the extraction and separation cylinder. In order to improve the installation reliability of the receiving frame, a fastening clamping strip is set on the receiving frame, and a snap-fit ​​fastening component is set on the sealing cover plate. Two electric telescopic rods located at the upper and lower ends of the same fastening clamping strip drive the two clamping plates to move towards each other and into the clamping groove, clamping and fixing the upper and lower ends of the fastening clamping strip. This ensures that the receiving frame will not shake or shift during the rotation process, and can be stably maintained in a suitable position to ensure its normal receiving function.

[0026] Furthermore, the bottom end of the clamping plate is provided with an elastic soft rubber strip, and each side wall of the bottom end of the fastening clamping strip is provided with a receiving vertical plate. Each receiving vertical plate, the receiving frame, and the folding sliding plate form a holding cavity, and each receiving vertical plate abuts against the bottom end of the corresponding filter membrane.

[0027] Explanation: When the two clamping plates move towards each other and into the clamping groove, an elastic soft rubber strip is provided at the bottom of the clamping plate. This strip has a certain degree of elasticity and flexibility and can fit tightly against the inner wall of the clamping groove, filling any small gaps that may exist between the clamping plate and the clamping groove. This increases the friction and contact area between the clamping plate and the receiving frame, making the receiving frame more stable during the flipping process and less prone to shaking or displacement. Each side wall at the bottom of the receiving frame is provided with a receiving vertical plate. When the receiving frame is flipped up and down with the extraction separation cylinder, it forms a holding cavity with the receiving frame and the folding sliding plate, preventing the microplastic particles separated on each filter membrane from falling outside the receiving frame.

[0028] Furthermore, the inner wall of the extraction and separation cylinder and the side opposite to the sealing cover are provided with multiple placement strips. The upper end of each placement strip is provided with a placement groove opposite to the receiving plate. The multiple placement strips are connected to the multiple receiving frames one by one.

[0029] Note: When the receiving plate is installed, one end is fixed to the fastening clamping strip by the snap-fit ​​fastening component, while the other end is placed in the placement groove on the placement strip for support, forming a two-point support and fixation structure, which makes the receiving plate have good stability after installation.

[0030] Furthermore, a temporary storage box is provided on the side wall of the extraction and separation cylinder. The upper and lower ends of the extraction and separation cylinder are respectively connected to the extraction and separation cylinder through the circulating return pipe. There are two one-way valves, which are distributed at the upper and lower ends of the temporary storage box, one above the other.

[0031] Note: After the microplastics in the mixed slurry sample are extracted and separated, the remaining liquid flows out through the outlet and is then returned to the temporary storage tank through the circulation return pipe for storage, facilitating future reuse. Because the extraction and separation cylinder rotates up and down during use, the one-way valve ensures that the residual liquid can only flow into the temporary storage tank from the bottom and out from the top. This ensures that the temporary storage tank can stably store the residual liquid and prevents leakage due to the rotation of the extraction and separation cylinder, guaranteeing the normal functioning of the temporary storage tank.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] This invention discloses a method for continuous extraction and separation of soil microplastics of different particle sizes. Several sampling points are set up in a grid distribution within a sampling area, ensuring a consistent amount of soil sampled at each point. This sampling method comprehensively and uniformly acquires soil samples from the sampling area, guaranteeing sample representativeness. A gradient separation method is employed, allowing the sample to flow through filter membranes with progressively increasing mesh sizes, effectively separating microplastic particles across several particle size ranges. Furthermore, the separated liquid can be reused as the extraction liquid, a recycling method that saves resources and reduces costs. The method also utilizes a specialized device for continuous extraction and separation of soil microplastics. The extraction and separation cylinder, filter membrane, and recycling pipe are integrated with the microplastic particle gradient separation and liquid reuse steps in the method. The filter membrane can effectively separate microplastics of different particle sizes, and the recycling pipe enables liquid reuse, improving the efficiency of the entire process, reducing resource waste, and lowering costs. During the use of the device, the extraction and separation cylinder is repeatedly inverted by the drive unit to continuously extract and separate soil microplastics. This continuous operation avoids the errors and time waste that may be caused by sample transfer and equipment reset in traditional step-by-step operations, thus improving the efficiency of the entire microplastic extraction and separation process. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0035] Figure 2 This is a schematic diagram of the internal structure of the extraction and separation cylinder of the present invention;

[0036] Figure 3 This is a schematic diagram of the receiving plate structure when the receiving vertical plate of the present invention is not installed;

[0037] Figure 4 This is a schematic diagram of the receiving plate structure during the installation of the receiving vertical plate according to the present invention;

[0038] Figure 5 This is a schematic diagram of the installation structure of the snap-fit ​​fastening assembly of the present invention on the sealing cover plate;

[0039] Figure 6 This is a schematic diagram of the connection structure between the snap-fit ​​fastening component and the fastening clamping strip of the present invention.

[0040] Among them, 1-Main mounting frame, 10-Reinforced base, 11-Anti-slip friction layer, 2-Rotating mounting frame, 3-Drive unit, 4-Extraction and separation cylinder, 40-Adding port, 400-Mixing box, 401-Magnetic stirrer, 402-Fastening clamping strip, 403-Clamping groove, 404-Supporting vertical plate, 405-Containing cavity, 41-Discharge port, 42-Sealing cover plate, 420-Snap-fit ​​fastening assembly, 421 - Horizontal mounting plate, 422-Clamping plate, 4220-Electric telescopic rod, 4221-Elastic soft rubber strip, 43-Filter membrane, 44-Receiving plate, 440-Receiving frame, 441-Splicing support plate, 442-Folding sliding plate, 443-Sliding strip, 444-Hydraulic rod, 45-Circulating return pipe, 450-One-way valve, 451-Liquid pump, 46-Placement strip, 460-Placement trough, 47-Temporary storage box. Detailed Implementation

[0041] To further understand the content of the present invention, the present invention will be described in detail below through embodiments.

[0042] Example 1: As Figure 1 , 2 As shown, a method for continuous extraction and separation of soil microplastics of different particle sizes includes the following steps:

[0043] S1. Soil Sample Collection

[0044] The length and width of the sampling area were divided into four equal parts to form a 4×4 grid, with a total of 16 squares. A sampling point was set at the center of each square. Soil samples were collected at each sampling point at a predetermined depth of 15cm. The amount of soil collected at each sampling point was 2kg.

[0045] S2, Soil Sample Pretreatment

[0046] First, the collected soil samples were sieved through a 4-mesh sieve to remove solid impurities. The soil samples, after solid impurity removal, were then evenly spread out in a well-ventilated indoor environment to air-dry, turning them over every 4 hours for a total of 3 days. Second, the air-dried soil samples were ground and sieved to obtain soil particles. Third, the sieved soil particles were mixed with the extraction solution and stirred thoroughly using a magnetic stirrer 401 to obtain a mixed slurry sample. 1 L of extraction solution was added for every 50 kg of sieved soil particles. The magnetic stirrer 401 was operated at 3000 rpm for 10 minutes. The extraction solution used was either a saturated sodium chloride solution or a zinc iodide solution, with the density of the saturated sodium chloride solution being 1.0 g / cm³. 3The density of the zinc iodide solution is 1.8 g / cm³. 3 The extract can break down the agglomeration force between soil particles, allowing the soil particles to be evenly dispersed in the solution. This allows the microplastic particles in the soil to be more fully exposed in the solution, facilitating subsequent separation operations. The magnetic stirrer 401 uses existing technology, for example, a magnetic stirrer of model QMS50 can be used.

[0047] S3. Gradient separation of microplastic particles in soil samples

[0048] The mixed slurry sample is added into the extraction separation cylinder 4 and flows from top to bottom through a series of filter membranes 43 with progressively increasing mesh sizes. Microplastic particles with particle sizes ranging from 0.1-0.5 mm, 0.5-1 mm, and 1-5 mm are separated from the mixed slurry sample through each filter membrane 43. The separated liquid is reused as the extraction liquid. The direction inside the extraction separation cylinder 4 is rotated to invert it. At this time, the microplastic particles located on each filter membrane 43 are collected by the receiving plate 44, thereby completing the gradient separation of microplastic particles in the soil sample. The filter membrane 43 is an existing stainless steel filter membrane, and the extraction separation cylinder 4 adopts an existing cylindrical structure. The filter membrane 43 is located inside the extraction separation cylinder 4. The receiving plate 44 corresponds to each filter membrane 43 and is located on the upper end of the filter membrane 43. The receiving plate 44 adopts an existing receiving structure, and the bottom of the receiving structure is equipped with an automatic opening and closing plate structure.

[0049] S4. Extraction of microplastic particles from soil samples

[0050] Open the sealing cover 42, extract each receiving plate 44 from the extraction separation cylinder 4, and collect the microplastic particles separated from the soil sample. The sealing cover 42 is opened using an existing sealing structure.

[0051] Example 2: As Figure 1 , 2 As shown, a method for continuous extraction and separation of soil microplastics of different particle sizes includes the following steps:

[0052] S1. Soil Sample Collection

[0053] The length and width of the sampling area were divided into four equal parts to form a 5×5 grid, with a total of 25 squares. A sampling point was set at the center of each square. Soil samples were collected at each sampling point at a predetermined depth of 15cm. The amount of soil collected at each sampling point was 2kg.

[0054] S2, Soil Sample Pretreatment

[0055] First, the collected soil samples were sieved through a 3-mesh sieve to remove solid impurities. The soil samples, after solid impurity removal, were then evenly spread out in a well-ventilated indoor environment to air-dry, turning them over every 5 hours for a total drying time of 4 days. Second, the air-dried soil samples were ground and sieved to obtain soil particles. Third, the sieved soil particles were mixed with the extraction solution and stirred thoroughly using a magnetic stirrer 401 to obtain a mixed slurry sample. 1 L of extraction solution was added for every 50 kg of sieved soil particles. The magnetic stirrer 401 was operated at 4000 rpm for 15 minutes. The extraction solution used was either a saturated sodium chloride solution or a zinc iodide solution, with the density of the saturated sodium chloride solution being 1.2 g / cm³. 3 The density of the zinc iodide solution is 1.9 g / cm³. 3 The extract can break down the agglomeration forces between soil particles, allowing the soil particles to be evenly dispersed in the solution, thus enabling the microplastic particles in the soil to be more fully exposed in the solution, which facilitates subsequent separation operations.

[0056] S3. Gradient separation of microplastic particles in soil samples

[0057] The mixed slurry sample is added into the extraction separation cylinder 4 and flows from top to bottom through a series of filter membranes 43 with progressively increasing mesh sizes. Microplastic particles with particle sizes ranging from 0.1-0.5 mm, 0.5-1 mm, and 1-5 mm are separated from the mixed slurry sample through each filter membrane 43. The separated liquid is reused as the extraction liquid. The direction inside the extraction separation cylinder 4 is rotated so that it is upside down. At this time, the microplastic particles located on each filter membrane 43 are collected by the receiving tray 44, thereby completing the gradient separation of microplastic particles in the soil sample.

[0058] S4. Extraction of microplastic particles from soil samples

[0059] Open the sealing cover 42, extract each receiving plate 44 from the extraction separation cylinder 4, and collect the microplastic particles separated from the soil sample.

[0060] Example 3: As Figure 1 , 2 As shown, a method for continuous extraction and separation of soil microplastics of different particle sizes includes the following steps:

[0061] S1. Soil Sample Collection

[0062] The length and width of the sampling area were divided into four equal parts to form a 6×6 grid, with a total of 36 squares. A sampling point was set at the center of each square. Soil samples were collected at each sampling point at a predetermined depth of 15cm. The amount of soil collected at each sampling point was 2kg.

[0063] S2, Soil Sample Pretreatment

[0064] First, the collected soil samples were sieved through a 2-mesh sieve to remove solid impurities. The soil samples, after solid impurity removal, were then evenly spread out in a well-ventilated indoor environment to air-dry, turning them over every 6 hours for a total drying time of 5 days. Second, the air-dried soil samples were ground and sieved to obtain soil particles. Third, the sieved soil particles were mixed with the extraction solution and stirred thoroughly using a magnetic stirrer 401 to obtain a mixed slurry sample. 1 L of extraction solution was added for every 50 kg of sieved soil particles. The magnetic stirrer 401 was operated at 5000 rpm for 20 minutes. The extraction solution used was either a saturated sodium chloride solution or a zinc iodide solution, with the density of the saturated sodium chloride solution being 1.4 g / cm³. 3 The density of the zinc iodide solution is 2.0 g / cm³. 3 The extract can break down the agglomeration forces between soil particles, allowing the soil particles to be evenly dispersed in the solution, thus enabling the microplastic particles in the soil to be more fully exposed in the solution, which facilitates subsequent separation operations.

[0065] S3. Gradient separation of microplastic particles in soil samples

[0066] The mixed slurry sample is added into the extraction separation cylinder 4 and flows from top to bottom through a series of filter membranes 43 with progressively increasing mesh sizes. Microplastic particles with particle sizes ranging from 0.1-0.5 mm, 0.5-1 mm, and 1-5 mm are separated from the mixed slurry sample through each filter membrane 43. The separated liquid is reused as the extraction liquid. The direction inside the extraction separation cylinder 4 is rotated so that it is upside down. At this time, the microplastic particles located on each filter membrane 43 are collected by the receiving tray 44, thereby completing the gradient separation of microplastic particles in the soil sample.

[0067] S4. Extraction of microplastic particles from soil samples

[0068] Open the sealing cover 42, extract each receiving plate 44 from the extraction separation cylinder 4, and collect the microplastic particles separated from the soil sample.

[0069] Example 4: This example describes the apparatus used in the continuous extraction and separation method for soil microplastics of different particle sizes described in Example 2, such as... Figure 1 As shown, it includes a main mounting frame 1, a rotating mounting frame 2 located on one side of the main mounting frame 1, and a drive unit 3 located on the main mounting frame 1 and rotatably connected to the rotating mounting frame 2 via a connecting shaft. The extraction separation cylinder 4 is located inside the rotating mounting frame 2. The drive unit 3 adopts existing technology, such as a rotary motor with existing model number YB2-631-2.

[0070] like Figure 2 As shown, the extraction and separation cylinder 4 is provided with an addition port 40 and a discharge port 41 at its upper and lower ends, respectively. A sealing cover plate 42 is hinged to one side of the extraction and separation cylinder 4. Three filter membranes 43 with increasing mesh size are arranged in the extraction and separation cylinder 4 from top to bottom. Each filter membrane 43 is provided with a receiving plate 44 at its upper end. The addition port 40 and the discharge port 41 of the extraction and separation cylinder 4 are connected by a circulation return pipe 45. A one-way valve 450 and a liquid pump 451 are provided at the connection. The one-way valve 450 and the liquid pump 451 adopt existing technologies. For example, the one-way valve 450 can be a one-way valve of model DIF-L10H1-S, and the liquid pump 451 can be an electric liquid pump of model JK-3P.

[0071] like Figure 3 , 4 As shown, the receiving plate 44 includes a receiving frame 440, a folding sliding plate 442 slidably connected within the receiving frame 440 and composed of 25 parallel splicing support plates 441, a sliding strip 443 disposed on one side of the folding sliding plate 442 and slidable left and right along the inner wall of the receiving frame 440, and a hydraulic rod 444 for driving the sliding strip 443 to slide. The hydraulic rod 444 adopts existing technology, for example, a hydraulic rod with a size of Φ140 / 100-800 can be used.

[0072] A reinforcing base 10 is provided at the bottom of the main frame 1 and directly below the rotating mounting frame 2. The bottom of the reinforcing base 10 is provided with an anti-slip friction layer 11. Since the rotating mounting frame 2 and the extraction separation cylinder 4 are located on one side of the main frame 1, the reinforcing base 10 is provided at the bottom of the main frame 1 and at the corresponding position of the lower ends of the rotating mounting frame 2 and the extraction separation cylinder 4. This can prevent them from sinking, shifting, or tipping due to their own weight or dynamic forces during operation, thereby enhancing the installation stability of the rotating mounting frame 2 and the extraction separation cylinder 4. At the same time, the anti-slip friction layer 11 at the bottom of the reinforcing base 10 can increase the friction between the reinforcing base 10 and the ground, preventing the reinforcing base 10 from sliding in the horizontal direction, thereby avoiding the horizontal shift of the rotating mounting frame 2 and the extraction separation cylinder 4. The anti-slip friction layer 11 is made of polyvinyl chloride.

[0073] A mixing tank 400 is connected through the inlet 40. A magnetic stirrer 401 is installed inside the mixing tank 400. Before the extraction of microplastics from the soil, the soil and extract are added to the mixing tank 400 in a certain proportion and stirred by the magnetic stirrer 401 to obtain a mixed slurry sample. This allows the extract to be evenly dispersed in the soil sample, making the microplastics dissolve more quickly in the extract, thereby improving the extraction efficiency of microplastics. The magnetic stirrer 401 adopts existing technology, for example, a magnetic stirrer of model QMS50 can be used.

[0074] The working principle of the apparatus used in the method for continuous extraction and separation of soil microplastics of different particle sizes in this embodiment includes the following steps:

[0075] (1) Add soil and extract to mixing tank 400 in proportion and stir with magnetic stirrer 401 to obtain mixed slurry sample;

[0076] (2) The mixed slurry sample flows into the extraction and separation cylinder 4 through the addition port 40 and flows through each filter membrane 43 from top to bottom to separate microplastic particles with a particle size range of 0.1-0.5mm, 0.5-1mm and 1-5mm in the mixed slurry sample. The separated microplastics can be trapped on each filter membrane 43. The separated liquid flows out through the discharge port 41 and is pumped into the circulation return pipe 45 by the liquid pump 451, and then flows back into the extraction and separation cylinder 4 through the addition port 40 for reuse.

[0077] (3) Drive the rotating mounting frame 2 to rotate by the drive unit 3, so that the extraction separation cylinder 4 is upside down. At this time, the extension of each hydraulic rod 444 drives the corresponding sliding strip 443 to move along the inner wall of the receiving frame 440 to the side opposite to the sealing cover plate 42, so that the folding sliding plate 442 unfolds and seals the bottom of the receiving frame 440. At the same time, the microplastic particles separated on each filter membrane 43 will fall into the receiving frame 440.

[0078] (4) Open the sealing cover plate 42, pull out each receiving plate 44 from the extraction separation cylinder 4, and pour out and collect the separated microplastic particles on the receiving plate 44. Finally, drive the rotating mounting frame 2 to rotate through the drive unit 3 to reset the extraction separation cylinder 4.

[0079] Example 5: This example differs from Example 4 in that:

[0080] like Figure 5 , 6As shown, the receiving frame 440 has a fastening clamping strip 402 on its side wall. The upper and lower ends of the fastening clamping strip 402 are respectively provided with clamping grooves 403. The inner wall of the sealing cover plate 42 is provided with snap-fit ​​fastening components 420 corresponding to each receiving frame 440. Each snap-fit ​​fastening component 420 includes two horizontal mounting plates 421 parallel to the upper and lower ends of each fastening clamping strip 402, and two clamping plates 422 connected to the two horizontal mounting plates 421 via an electric telescopic rod 4220 and distributed opposite to each other. The two oppositely distributed clamping plates 422 match the clamping grooves 403 located at the upper and lower ends of the same fastening clamping strip 402. When the receiving frame 440 is installed inside the extraction separation cylinder 4, it will move with the extraction separation cylinder 4... To improve the installation reliability of the receiving frame 440, a fastening clamping strip 402 is provided on the receiving frame 440, and a snap-fit ​​fastening assembly 420 is provided on the sealing cover plate 42. Two electric telescopic rods 4220 located at the upper and lower ends of the same fastening clamping strip 402 drive the two clamping plates 422 to move towards each other and into the clamping groove 403, clamping and fixing the upper and lower ends of the fastening clamping strip 402. This ensures that the receiving frame 440 will not shake or shift during the flipping process, and can be stably maintained in a suitable position to ensure its normal receiving function. The electric telescopic rods 4220 adopt existing technology, such as existing screw-driven electric telescopic rods.

[0081] The bottom end of the clamping plate 422 is provided with an elastic soft rubber strip 4221, and each side wall of the bottom end of the fastening clamping strip 402 is provided with a receiving vertical plate 404. The receiving vertical plate 404, the receiving frame 440, and the folding sliding plate 442 form a holding cavity 405. Each receiving vertical plate 404 abuts against the bottom end of the corresponding filter membrane 43. When the two clamping plates 422 move towards each other and move into the clamping groove 403, the elastic soft rubber strip 4221 provided at the bottom end of the clamping plate 422 has a certain elasticity and flexibility. The elastic soft rubber strip 4221 can fit tightly against the inner wall of the clamping groove 403, filling the clamping plate 422 and the clamping groove. The possible tiny gaps between the grooves 403 increase the friction and contact area between the clamping plate 422 and the receiving frame 440, making the receiving frame 440 more stable during the flipping process and less prone to shaking or displacement. Each side wall at the bottom of the receiving frame 440 is provided with a receiving vertical plate 404. When the receiving frame 440 is flipped up and down with the extraction separation cylinder 4, it forms a holding cavity 405 with the receiving frame 440 and the folding sliding plate 442, preventing the microplastic particles separated on each filter membrane 43 from falling to the outside of the receiving frame 440. The material of the elastic soft rubber strip 4221 is EVA / POE polyolefin elastomer.

[0082] Three placement strips 46 are provided on the inner wall of the extraction separation cylinder 4 and on the side opposite to the sealing cover plate 42. The upper end of the placement strip 46 is provided with a placement groove 460 opposite to the receiving plate 44. The three placement strips 46 are connected to the three receiving frames 440 one by one. When the receiving plate 44 is installed, one end is fixed to the fastening clamping strip 402 by the snap fastening component 420, while the other end is placed in the placement groove 460 on the placement strip 46 for support, forming a two-point support and fixing structure, which makes the receiving plate 44 have good stability after installation.

[0083] The extraction and separation cylinder 4 has a temporary storage box 47 on its side wall. The upper and lower ends of the extraction and separation cylinder 4 are connected to the extraction and separation cylinder 4 through the circulation return pipe 45. There are two one-way valves 450, which are distributed at the upper and lower ends of the temporary storage box 47, one above the other. After the microplastics in the mixed slurry sample are extracted and separated, the remaining liquid flows out through the outlet 41 and then flows back to the temporary storage box 47 through the circulation return pipe 45 for storage, which is convenient for reuse next time. Since the extraction and separation cylinder 4 will be flipped up and down during use, due to the one-way conduction characteristic of the one-way valve 450, the residual liquid can only flow into the temporary storage box 47 from the bottom and flow out of the temporary storage box 47 from the top. This ensures that the temporary storage box 47 can stably store the residual liquid and will not leak due to the flipping of the extraction and separation cylinder 4, thus ensuring the normal functioning of the temporary storage box 47.

Claims

1. A device for continuous extraction and separation of soil microplastics of different particle sizes, characterized in that, Including installation main frame (1), be located in the rotating installation frame (2) of installation main frame (1) one side, be located in installation main frame (1) and through connecting shaft with rotating connection of drive unit (3) rotating installation frame (2), extraction separation cylinder (4) is located in rotating installation frame (2) inside; The upper and lower ends of the extraction separation cylinder (4) are respectively provided with an adding port (40) and a discharge port (41), and the extraction separation cylinder (4) is hingedly connected with a blocking cover plate (42) on one side. A plurality of filter membranes (43) with increasing mesh count are sequentially arranged in the extraction separation cylinder (4) from top to bottom, and each filter membrane (43) is provided with a receiving disc (44) at the upper end. The adding port (40) and the discharge port (41) of the extraction separation cylinder (4) are connected by a circulating return pipe (45), and the connection part is provided with a one-way valve (450) and a liquid pump (451). The receiving disc (44) comprises a receiving frame (440), a folding sliding plate (442) slidably connected in the receiving frame (440) and composed of a plurality of parallel splicing support plates (441), a sliding bar (443) arranged on one side of the folding sliding plate (442) and capable of sliding left and right along the inner wall of the receiving frame (440), and a hydraulic rod (444) for driving the sliding bar (443) to slide. The side wall of the receiving frame (440) is provided with a fastening clamping strip (402), and the upper and lower ends of the fastening clamping strip (402) are respectively provided with clamping grooves (403). The inner wall of the blocking cover plate (42) and corresponding each receiving frame (440) are respectively provided with a clamping fastening assembly (420). The clamping fastening assembly (420) comprises two horizontal mounting plates (421) arranged on the upper and lower ends of each fastening clamping strip (402), two clamping plates (422) connected with the two horizontal mounting plates (421) by an electric telescopic rod (4220) and oppositely distributed. The oppositely distributed two clamping plates (422) are matched with the clamping grooves (403) at the upper and lower ends of the same fastening clamping strip (402).

2. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 1, characterized in that, The bottom end of the installation main frame (1) and the lower end of the rotating installation frame (2) are provided with a reinforcing base (10), and the bottom end of the reinforcing base (10) is provided with an anti-skid friction layer (11).

3. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 1, characterized in that, The adding port (40) is connected with a mixing box (400), and the mixing box (400) is provided with a magnetic stirrer (401).

4. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 1, characterized in that, The bottom end of the clamping plate (422) is provided with an elastic soft rubber strip (4221), the bottom end of the fastening clamping strip (402) is provided with a receiving vertical plate (404), and the receiving vertical plate (404), the receiving frame (440) and the folding sliding plate (442) form a containing cavity (405), and the bottom end of each receiving vertical plate (404) abuts against the corresponding filter membrane (43).

5. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 1, characterized in that, The inner wall of the extraction separation cylinder (4) and the opposite side of the blocking cover plate (42) are provided with a plurality of placing strips (46), and the upper end of the placing strip (46) is provided with a placing groove (460) opposite to the receiving disc (44). The plurality of placing strips (46) are connected with the plurality of receiving frames (440) one by one.

6. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 1, characterized in that, The side wall of the extraction and separation cylinder (4) is provided with a temporary storage box (47), the upper and lower ends of the extraction and separation cylinder (4) are respectively communicated with the extraction and separation cylinder (4) through the circulating back material pipe (45), and the two one-way valves (450) are arranged on the upper and lower ends of the temporary storage box (47) in an upper and lower distribution mode.

7. A method for the continuous extraction and separation of soil microplastics of different particle sizes based on a device for the continuous extraction and separation of soil microplastics of different particle sizes according to any one of claims 1 to 6, characterized in that The method comprises the following steps: S1, soil sample collection A plurality of sampling points are arranged in a grid distribution manner in the sampling area, and soil samples are collected at each sampling point according to a predetermined depth, so that the amount of soil collected at each sampling point is consistent; S2, soil sample pretreatment First, the solid impurities in the collected soil samples are sieved and cleaned, and the soil samples after removing the solid impurities are uniformly spread and air-dried in a well-ventilated indoor environment, and the soil samples are turned over regularly, wherein the air-drying time is 3-5 days; secondly, the air-dried soil samples are ground and sieved to obtain soil particles with a particle size of 0.1-5 mm; the sieved soil particles and the extraction liquid are mixed, and a magnetic stirrer (401) is used for uniform stirring to obtain a mixed slurry sample, wherein 1L of extraction liquid is added to every 50kg of sieved soil particles, the rotating speed of the magnetic stirrer (401) is 3000-5000r / min, and the centrifugation time is 10-20min; S3, gradient separation of microplastic particles in the soil sample The mixed slurry sample is added into the extraction and separation cylinder (4), and flows through each filter membrane (43) in turn from top to bottom, each filter membrane (43) separates microplastic particles with different particle size ranges in the mixed slurry sample, the separated liquid is reused as extraction liquid, the direction of rotation in the extraction and separation cylinder (4) is reversed, at this time, the microplastic particles on each filter membrane (43) are collected by the receiving disc (44), thereby completing the gradient separation of microplastic particles in the soil sample; S4, extraction of microplastic particles in the soil sample The blocking cover plate (42) is opened, each receiving disc (44) is pulled out of the extraction and separation cylinder (4), and the separated microplastic particles in the soil sample are collected.

8. The method for continuous extraction and separation of soil microplastics of different particle sizes according to claim 7, characterized in that, The extraction liquid is saturated sodium chloride solution or zinc iodide solution, wherein the density of the saturated sodium chloride solution is 1.0-1.4g / cm³, and the density of the zinc iodide solution is 1.8-2.0g / cm³.

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