Method and device for continuously extracting and separating soil micro-plastics with different particle sizes

Abstract

The invention provides a method and a device for continuously extracting and separating soil micro-plastics with different particle sizes, and belongs to the technical field of soil micro-plastic treatment. According to the method, a special device for continuously extracting and separating the soil micro-plastics is used and comprises a mounting main frame, a rotary mounting frame arranged on one side of the mounting main frame and a driving unit arranged on the mounting main frame and rotationally connected with the rotary mounting frame through a connecting shaft, and an extracting and separating barrel is arranged in the rotary mounting frame; the extraction and separation cylinder, the filter membrane and the circulating material return pipe in the device are combined with the micro-plastic particle gradient separation and liquid recycling steps in the method, micro-plastics with different particle sizes can be effectively separated, the extraction and separation cylinder is repeatedly reversed up and down, continuous extraction and separation of the soil micro-plastics are sequentially completed, and the separation efficiency of the soil micro-plastics is improved. According to the continuous operation mode, errors and time waste possibly caused by links such as sample transfer and equipment resetting in traditional step-by-step operation are avoided, and the efficiency of the whole micro-plastic extraction and separation process is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil microplastic treatment, and specifically relates to a method and a device for continuously extracting and separating soil microplastics of different particle sizes. Background Art

[0002] With the extensive use of plastic products, microplastics are increasingly distributed in the environment. As an important part of the ecosystem, soil is also polluted by microplastics. Microplastics can enter the soil through a variety of pathways, such as sewage irrigation, sludge application, decomposition of plastic films, and atmospheric deposition. Microplastic pollution of varying degrees has been detected in soils in a variety of environments, including agriculture, industry, and cities. This may affect the physical, chemical, and biological properties of the soil, thereby threatening the health and function of the soil ecosystem.

[0003] Microplastics in the soil may change the structure of the soil, affecting its aeration, water retention and fertility. They may also absorb pollutants in the soil, such as heavy metals and organic pollutants, and change the mobility and bioavailability of these pollutants, thereby producing toxic effects on soil organisms, including microorganisms, earthworms, etc., interfering with the food chain transmission in the soil ecosystem, and ultimately affecting the stability and biodiversity of the entire ecosystem.

[0004] Traditional soil sampling methods often do not fully consider the representativeness of sampling when studying soil microplastics. Some sampling methods may only randomly select a few sampling points, or do not standardize the sampling volume of each sampling point, resulting in the collected soil samples not being able to 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, resulting in inaccurate separation results. The operation process is relatively complicated, usually requiring multiple steps and frequent sample transfers between equipment, and the efficiency of the entire microplastic extraction and separation process is low. Summary of the invention

[0005] In response to the above-mentioned problems, the present invention provides a method and device for continuously extracting and separating soil microplastics of different particle sizes.

[0006] The technical solution of the present 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] A plurality of sampling points are set up in a grid distribution manner within the sampling area, and soil samples are collected at a predetermined depth at each sampling point to ensure that the amount of soil collected at each sampling point is consistent;

[0009] S2. Soil sample pretreatment

[0010] First, the solid impurities in the collected soil samples are sieved and cleaned, and the soil samples after the solid impurities are removed are evenly spread out in a well-ventilated indoor environment for air drying, and the soil samples are regularly turned over, 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 extract are then mixed and stirred evenly with a magnetic stirrer to obtain a mixed slurry sample, wherein 1L of the extract is added to every 50kg of the sieved soil particles, the speed of the magnetic stirrer is 3000-5000r / min, and the centrifugation time is 10-20min;

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

[0012] The mixed slurry sample is added to the extraction and separation cylinder, and flows through filter membranes with increasing mesh sizes from top to bottom, and microplastic particles of multiple particle size ranges in the mixed slurry sample are separated by each filter membrane. The separated liquid is reused as the extraction liquid, and the direction in the extraction and separation cylinder is rotated to turn it upside down. At this time, the microplastic particles on each filter membrane are received by the receiving plate, thereby 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, pull out each receiving plate 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 / cm 3 , the density of zinc iodide solution is 1.8-2.0g / cm 3 .

[0016] Note: The extract can destroy the agglomeration between soil particles, making the soil particles evenly dispersed in the solution, so that the microplastic particles in the soil can be more fully exposed to the solution, facilitating subsequent separation operations.

[0017] The present invention also discloses a device 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, comprising a mounting main frame, a rotating mounting frame arranged on one side of the mounting main frame, and a driving unit arranged on the mounting main frame and rotatably connected to the rotating mounting frame through a connecting shaft, wherein the extraction and separation cylinder is arranged in the rotating mounting frame;

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

[0019] The receiving plate includes a receiving frame, a folding sliding plate slidably connected to the receiving frame and composed of a plurality of parallel spliced ​​support plates, a sliding bar arranged 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 driving the sliding bar to slide.

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

[0021] Note: Because the rotating mounting frame and the extraction and separation cylinder are arranged on one side of the main mounting frame, a reinforcement base is arranged at the bottom of the main mounting frame and corresponding to the lower end of the rotating mounting frame and the extraction and separation cylinder to prevent them from sinking, shifting, tipping, etc. due to their own weight or dynamic force during operation, thereby enhancing the installation stability of the rotating mounting frame and the extraction and separation cylinder. At the same time, an anti-slip friction layer is provided at the bottom of the reinforcement base to increase the friction between the reinforcement base and the ground, prevent the reinforcement base from sliding in the horizontal direction, and thereby avoid horizontal shift of the rotating mounting frame and the extraction and separation cylinder.

[0022] Furthermore, the adding port is connected through a mixing box, and a magnetic stirrer is arranged in the mixing box.

[0023] Note: Before extracting microplastics from the soil, the soil and extract are added to the mixing box in proportion and stirred with a magnetic stirrer to obtain a mixed slurry sample. This can evenly disperse the extract in the soil sample and make the microplastics dissolve more quickly in the extract, thereby improving the extraction efficiency of microplastics.

[0024] Furthermore, the side wall of the receiving frame is provided with a fastening clamping strip, and the upper and lower ends of the fastening clamping strip are respectively provided with clamping grooves, and the inner wall of the blocking cover plate and corresponding to each receiving frame are respectively provided with a clamping fastening component, and the clamping fastening component includes two horizontal mounting plates arranged parallel to the upper and lower ends of each fastening clamping strip, and two clamping plates connected to the two horizontal mounting plates through an electric telescopic rod and relatively distributed, and the two relatively distributed clamping plates match the clamping grooves located at the upper and lower ends of the same fastening clamping strip.

[0025] Description: When the receiving frame is installed in the extraction and separation cylinder, it will move synchronously with the up and down flipping of the extraction and separation cylinder. In order to improve the installation reliability of the receiving frame, a fastening clamping strip is provided on the receiving frame, and a snap-on fastening assembly is provided on the blocking cover plate. The two clamping plates are driven to move toward each other and into the clamping groove by two electric telescopic rods located at the upper and lower ends of the same fastening clamping strip, and the upper and lower ends of the fastening clamping strip are clamped and fixed, so that the receiving frame will not shake or displace during the flipping process, and can be stably maintained in a suitable position to ensure its normal receiving function.

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

[0027] Description: When the two clamping plates move toward each other and move into the clamping groove, an elastic soft rubber strip is arranged at the bottom end of the clamping plate, which has a certain elasticity and flexibility. The elastic soft rubber strip can fit tightly with the inner wall of the clamping groove and fill the tiny gap that may exist between the clamping plate and the clamping groove, thereby increasing 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 likely to shake or displace. A receiving vertical plate is provided on each side wall at the bottom of the receiving frame. When the receiving frame is turned upside down with the extraction and separation cylinder, a containing cavity is formed between the receiving frame and the folding sliding plate to prevent the microplastic particles separated on each filter membrane from falling to the outside of the receiving frame.

[0028] Furthermore, a plurality of placement bars are provided on the inner wall of the extraction and separation cylinder and on the side opposite to the blocking cover plate, a placement groove opposite to the receiving plate is provided at the upper end of the placement bar, and the plurality of placement bars are connected to the plurality of receiving frames in a one-to-one correspondence.

[0029] Note: When the receiving tray is installed, one end is fixed to the fastening clamping strip by a clamping fastening assembly, and the other end is placed in the placement groove on the placement strip for support, forming a two-point support and fixing structure, so that the receiving tray has better stability after installation.

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

[0031] Description: After the extraction and separation of microplastics in the mixed slurry sample, the remaining residual liquid flows out from the discharge port and then flows back to the temporary storage box through the circulation return pipe for storage, which is convenient for reuse and treatment next time. In addition, since the extraction and separation cylinder will turn upside down during use, due to the one-way conduction characteristics of the one-way valve, the residual liquid can only flow into the temporary storage box from the bottom and flow out of the temporary storage box from the top, ensuring that the temporary storage box can stably store the residual liquid, and there will be no leakage of residual liquid due to the flipping of the extraction and separation cylinder, thereby ensuring the normal function of the temporary storage box.

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

[0033] The present invention provides a method for continuous extraction and separation of soil microplastics of different particle sizes. Several sampling points are set in a sampling area according to a grid distribution, and the amount of soil collected at each sampling point is kept consistent. This sampling method can comprehensively and evenly obtain soil samples in the sampling area, ensuring that the samples are representative. A gradient separation method is adopted to make the soil flow through filter membranes with increasing mesh sizes, which can effectively separate microplastic particles of several particle size ranges, and the separated liquid can be reused as an extract. This recycling method saves resources and reduces costs. The method also uses a special device for continuous extraction and separation of soil microplastics. The device The extraction and separation cylinder, filter membrane, circulating return pipe and other components in the method are combined 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 circulating return pipe realizes the reuse of liquid, which improves the efficiency of the entire process, reduces resource waste, and reduces costs. During the use of the device, the driving unit drives the extraction and separation cylinder to repeatedly turn it upside down to complete the continuous extraction and separation of soil microplastics in turn. This continuous operation method avoids the errors and time waste that may be caused by sample transfer, equipment re-setting and other links in traditional step-by-step operations, and improves the efficiency of the entire microplastic extraction and separation process. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0037] Figure 4 It is a structural schematic diagram of the receiving plate when the receiving vertical plate of the present invention is installed;

[0038] Figure 5 It is a schematic diagram of the installation structure of the clamping fastening assembly of the present invention on the blocking cover plate;

[0039] Figure 6 It is a schematic diagram of the connection structure between the clamping fastening assembly and the fastening clamping strip of the present invention.

[0040] Among them, 1-installation main frame, 10-reinforcement base, 11-anti-slip friction layer, 2-rotation installation frame, 3-drive unit, 4-extraction separation cylinder, 40-addition port, 400-mixing box, 401-magnetic stirrer, 402-fastening clamping strip, 403-clamping groove, 404-receiving vertical plate, 405-holding chamber, 41-discharging port, 42-blocking cover plate, 420-clamping fastening component, 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-joining support plate, 442-folding sliding plate, 443-sliding bar, 444-hydraulic rod, 45-circulation return pipe, 450-check valve, 451-liquid pump, 46-placing bar, 460-placing trough, 47-temporary storage box. DETAILED DESCRIPTION

[0041] In order to further understand the content of the present invention, the present invention is described in detail below through examples.

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

[0043] S1. Soil sample collection

[0044] The length and width of the sampling area were divided into 4 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 15 cm underground, and the amount of soil collected at each sampling point was kept at 2 kg.

[0045] S2. Soil sample pretreatment

[0046] First, the solid impurities in the collected soil samples were sieved through a 4-mesh sieve, and the soil samples after the solid impurities were removed were evenly spread out in a well-ventilated indoor environment for air drying, and the soil samples were turned over once every 4 hours, wherein the air drying time was 3 days; secondly, the air-dried soil samples were ground and sieved to obtain soil particles; furthermore, the sieved soil particles were mixed with the extract, and stirred evenly with a magnetic stirrer 401 to obtain a mixed slurry sample, wherein 1L of the extract was added to every 50kg of the sieved soil particles, the speed of the magnetic stirrer 401 was 3000r / min, the centrifugation time was 10min, and the extract was a saturated sodium chloride solution or a zinc iodide solution, wherein the density of the saturated sodium chloride solution was 1.0g / cm 3, the density of zinc iodide solution is 1.8g / cm 3 The extract can destroy the agglomeration force between soil particles, so that the soil particles are evenly dispersed in the solution, so that the microplastic particles in the soil can be more fully exposed to the solution, which is convenient for subsequent separation operations. The magnetic stirrer 401 adopts the 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 and separation cylinder 4, and flows through the filter membranes 43 with increasing mesh sizes from top to bottom, and the microplastic particles with a particle size range of 0.1-0.5mm, 0.5-1mm, and 1-5mm in the mixed slurry sample are separated by the filter membranes 43 respectively, and the separated liquid is reused as the extracting liquid, and the direction in the extraction and separation cylinder 4 is rotated so that it is turned upside down. At this time, the microplastic particles on each filter membrane 43 are received by the receiving plate 44, so as to complete the gradient separation of the microplastic particles in the soil sample, wherein the filter membrane 43 adopts the existing stainless steel filter membrane, the extraction and separation cylinder 4 adopts the existing cylindrical structure, the filter membrane 43 is arranged in the extraction and separation cylinder 4, the receiving plate 44 corresponds to the filter membrane 43 one by one and is located at the upper end of the filter membrane 43, the receiving plate 44 adopts the existing receiving structure, and the bottom of the receiving structure is provided with an automatic opening and closing plate structure;

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

[0050] The sealing cover 42 is opened, each receiving plate 44 is pulled out from the extraction and separation cylinder 4, and the microplastic particles separated from the soil sample are collected, wherein the sealing cover 42 is opened using the existing sealing structure.

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

[0052] S1. Soil sample collection

[0053] The length and width of the sampling area were divided into 4 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 a predetermined depth of 15 cm underground at each sampling point, and the amount of soil collected at each sampling point was kept at 2 kg.

[0054] S2. Soil sample pretreatment

[0055] First, the solid impurities in the collected soil samples were sieved through a 3-mesh sieve, and the soil samples after the solid impurities were removed were evenly spread out in a well-ventilated indoor environment for air drying, and the soil samples were turned over once every 5 hours, wherein the air drying time was 4 days; secondly, the air-dried soil samples were ground and sieved to obtain soil particles; furthermore, the sieved soil particles and the extract were mixed, and stirred evenly with a magnetic stirrer 401 to obtain a mixed slurry sample, wherein 1L of the extract was added to every 50kg of the sieved soil particles, the speed of the magnetic stirrer 401 was 4000r / min, the centrifugation time was 15min, and the extract was a saturated sodium chloride solution or a zinc iodide solution, wherein the density of the saturated sodium chloride solution was 1.2g / cm 3 , the density of zinc iodide solution is 1.9 g / cm 3 The extract can destroy the agglomeration between soil particles, making the soil particles evenly dispersed in the solution, so that the microplastic particles in the soil can be more fully exposed to the solution, facilitating subsequent separation operations;

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

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

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

[0059] The sealing cover 42 is opened, each receiving tray 44 is pulled out from the extraction and separation cylinder 4, and the microplastic particles separated from the soil sample are collected.

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

[0061] S1. Soil sample collection

[0062] The length and width of the sampling area were divided into 4 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 15 cm underground, and the amount of soil collected at each sampling point was kept at 2 kg.

[0063] S2. Soil sample pretreatment

[0064] First, the solid impurities in the collected soil samples were sieved through a 2-mesh sieve, and the soil samples after the solid impurities were evenly spread out in a well-ventilated indoor environment for air drying, and the soil samples were turned over once every 6 hours, wherein the air drying time was 5 days; secondly, the air-dried soil samples were ground and sieved to obtain soil particles; furthermore, the sieved soil particles were mixed with the extract, and stirred evenly with a magnetic stirrer 401 to obtain a mixed slurry sample, wherein 1L of the extract was added to every 50kg of the sieved soil particles, the speed of the magnetic stirrer 401 was 5000r / min, the centrifugation time was 20min, and the extract was a saturated sodium chloride solution or a zinc iodide solution, wherein the density of the saturated sodium chloride solution was 1.4g / cm 3 , the density of zinc iodide solution is 2.0g / cm 3 The extract can destroy the agglomeration between soil particles, making the soil particles evenly dispersed in the solution, so that the microplastic particles in the soil can be more fully exposed to the solution, facilitating subsequent separation operations;

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

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

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

[0068] The sealing cover 42 is opened, each receiving tray 44 is pulled out from the extraction and separation cylinder 4, and the microplastic particles separated from the soil sample are collected.

[0069] Example 4: This example describes a device used in the method for continuous extraction and separation of soil microplastics of different particle sizes in Example 2, such as Figure 1 As shown, it includes a mounting main frame 1, a rotating mounting frame 2 arranged on one side of the mounting main frame 1, a driving unit 3 arranged on the mounting main frame 1 and rotatably connected to the rotating mounting frame 2 through a connecting shaft, and an extraction and separation cylinder 4 is arranged in the rotating mounting frame 2, wherein the driving unit 3 adopts the existing technology, for example, the existing rotary motor with the model YB2-631-2 can be adopted;

[0070] like Figure 2 As shown, the upper and lower ends of the extraction and separation cylinder 4 are respectively provided with an addition port 40 and a discharge port 41, a sealing cover plate 42 is hingedly connected to one side of the extraction and separation cylinder 4, three filter membranes 43 with increasing mesh sizes are arranged in sequence from top to bottom in the extraction and separation cylinder 4, and a receiving plate 44 is arranged on the upper end of each filter membrane 43, the addition port 40 and the discharge port 41 of the extraction and separation cylinder 4 are connected by a circulation return pipe 45, and a one-way valve 450 and a liquid pump 451 are arranged at the connection, wherein the one-way valve 450 and the liquid pump 451 both adopt the existing technology, for example, the one-way valve 450 can adopt the one-way valve of model DIF-L10H1-S, and the liquid pump 451 can adopt the 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 which is slidably connected to the receiving frame 440 and is composed of 25 mutually parallel splicing support plates 441, a sliding bar 443 which is arranged on one side of the folding sliding plate 442 and can slide left and right along the inner wall of the receiving frame 440, and a hydraulic rod 444 which drives the sliding bar 443 to slide, wherein the hydraulic rod 444 adopts the existing technology, for example, a hydraulic rod with a size of Φ140 / 100-800 can be adopted;

[0072] A reinforcement base 10 is provided at the bottom of the installation main frame 1 and located directly below the rotating installation frame 2, and an anti-skid friction layer 11 is provided at the bottom of the reinforcement base 10. Because the rotating installation frame 2 and the extraction separation cylinder 4 are arranged on one side of the installation main frame 1, the reinforcement base 10 is provided at the bottom of the installation main frame 1 and corresponding to the lower end of the rotating installation frame 2 and the extraction separation cylinder 4. It can prevent them from sinking, deflecting, tipping, etc. due to their own weight or dynamic forces during operation, thereby enhancing the installation stability of the rotating installation frame 2 and the extraction separation cylinder 4. At the same time, an anti-skid friction layer 11 is provided at the bottom of the reinforcement base 10, which can increase the friction between the reinforcement base 10 and the ground, prevent the reinforcement base 10 from sliding in the horizontal direction, and thereby avoid the horizontal deviation of the rotating installation frame 2 and the extraction separation cylinder 4. The material used for the anti-skid friction layer 11 is polyvinyl chloride.

[0073] The adding port 40 is connected to a mixing box 400, and a magnetic stirrer 401 is provided in the mixing box 400. Before extracting microplastics in the soil, the soil and the extract are added to the mixing box 400 in proportion, and stirred by the magnetic stirrer 401 to obtain a mixed slurry sample, which can make the extract evenly dispersed in the soil sample, so that the microplastics are dissolved more quickly in the extract, thereby improving the extraction efficiency of the microplastics. The magnetic stirrer 401 adopts the existing technology, for example, a magnetic stirrer of model QMS50 can be used;

[0074] The working principle of the device 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) adding soil and extract into a mixing box 400 according to a certain proportion, and stirring them by a magnetic stirrer 401 to obtain a 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 in sequence, so as to separate microplastic particles with a particle size range of 0.1-0.5 mm, 0.5-1 mm, and 1-5 mm in the mixed slurry sample. The separated microplastics can be retained on each filter membrane 43, and 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) The driving unit 3 drives the rotating mounting frame 2 to rotate, so that the extraction and separation cylinder 4 is turned upside down. At this time, the corresponding sliding bar 443 is driven to move along the inner wall of the receiving frame 440 to the side opposite to the blocking cover plate 42 through the extension of each hydraulic rod 444, so that the folding sliding plate 442 is unfolded to block the bottom end 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 blocking cover 42, pull out each receiving tray 44 from the extraction and separation cylinder 4, and pour out and collect the separated microplastic particles on the receiving tray 44. Finally, drive the rotating mounting frame 2 to rotate through the driving unit 3 to reset the extraction and separation cylinder 4.

[0079] Embodiment 5: This embodiment differs from Embodiment 4 in that:

[0080] like Figure 5 , 6As shown, 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, and the inner wall of the blocking cover plate 42 and corresponding to each receiving frame 440 are respectively provided with a clamping fastening component 420, and the clamping fastening component 420 includes two horizontal mounting plates 421 arranged 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 through an electric telescopic rod 4220 and relatively distributed, and the two relatively 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 in the extraction and separation cylinder 4, it will be extracted and separated with the separation cylinder 4. The receiving frame 440 is turned upside down and moves synchronously. In order to improve the installation reliability of the receiving frame 440, a fastening clamping strip 402 is provided on the receiving frame 440, and a clamping fastening assembly 420 is provided on the blocking cover plate 42. The two clamping plates 422 are driven to move toward each other and move into the clamping groove 403 by two electric telescopic rods 4220 located at the upper and lower ends of the same fastening clamping strip 402, and the upper and lower ends of the fastening clamping strip 402 are clamped and fixed, so that the receiving frame 440 will not shake or shift during the turning process, and can be stably kept in a suitable position to ensure its normal receiving function. Among them, the electric telescopic rod 4220 adopts the existing technology, for example, the existing screw-driven electric telescopic rod can be adopted;

[0081] The bottom end of the clamping plate 422 is provided with an elastic soft rubber strip 4221, and each side wall at the bottom end of the fastening clamping strip 402 is provided with a receiving vertical plate 404, and each receiving vertical plate 404, the receiving frame 440 and the folding sliding plate 442 form a containing cavity 405, and each receiving vertical plate 404 abuts against the bottom end of the corresponding filter membrane 43. When the two clamping plates 422 move toward each other and move into the clamping groove 403, by arranging an elastic soft rubber strip 4221 at the bottom end of the clamping plate 422, it has a certain elasticity and flexibility, and the elastic soft rubber strip 4221 can fit closely with the inner wall of the clamping groove 403, filling the clamping plate 422 and the clamping groove. The tiny gaps that may exist 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. A receiving vertical plate 404 is provided on each side wall at the bottom of the receiving frame 440. When the receiving frame 440 is turned upside down with the extraction and separation cylinder 4, a holding cavity 405 is formed between the receiving frame 440 and the folding sliding plate 442 to prevent 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 bars 46 are provided on the inner wall of the extraction and separation cylinder 4 and on the side opposite to the blocking cover plate 42. The upper end of the placement bar 46 is provided with a placement groove 460 opposite to the receiving plate 44. The three placement bars 46 are connected to the three receiving frames 440 in a one-to-one correspondence. When the receiving plate 44 is installed, one end is fixed to the fastening clamping bar 402 by the clamping fastening assembly 420, and the other end is placed in the placement groove 460 on the placement bar 46 for support, forming a two-point support and fixing structure, so that the receiving plate 44 has good stability after installation;

[0083] A temporary storage box 47 is provided on the side wall of the extraction and separation cylinder 4. The upper and lower ends of the extraction and separation cylinder 4 are connected to the extraction and separation cylinder 4 through a circulating return pipe 45 respectively. There are two one-way valves 450, and the two one-way valves 450 are respectively distributed at the upper and lower ends of the temporary storage box 47. After the microplastics in the mixed slurry sample are extracted and separated, the remaining residual liquid flows out through the discharge port 41, and then flows back to the temporary storage box 47 through the circulating return pipe 45 for storage, which is convenient for reuse and treatment next time. In addition, since the extraction and separation cylinder 4 will turn upside down when in use, due to the one-way conduction characteristics of the one-way valve 450, the residual liquid can only flow into the temporary storage box 47 from the bottom end and flow out of the temporary storage box 47 from the upper end, ensuring that the temporary storage box 47 can stably store the residual liquid, and there will be no leakage of residual liquid due to the turning over of the extraction and separation cylinder 4, thereby ensuring the normal function of the temporary storage box 47.

Claims

1. A method for continuous extraction and separation of soil microplastics of different particle sizes, comprising the following steps: S1. Soil sample collection A plurality of sampling points are set up in a grid distribution manner within the sampling area, and soil samples are collected at a predetermined depth at each sampling point to ensure 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 the solid impurities are removed are evenly spread out in a well-ventilated indoor environment for air drying, and the soil samples are regularly turned over, 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 extract are then mixed and stirred evenly with a magnetic stirrer (401) to obtain a mixed slurry sample, wherein 1L of the extract is added to every 50kg of the sieved soil particles, the rotation speed of the magnetic stirrer (401) is 3000-5000r / min, and the centrifugation time is 10-20min; S3. Gradient separation of microplastic particles in soil samples The mixed slurry sample is added into the extraction and separation cylinder (4), and flows through filter membranes (43) with increasing mesh sizes from top to bottom, and microplastic particles of multiple particle size ranges in the mixed slurry sample are separated by each filter membrane (43). The separated liquid is reused as an extracting liquid, and the direction in the extraction and separation cylinder (4) is rotated to turn it upside down. At this time, the microplastic particles on each filter membrane (43) are received by a receiving plate (44), thereby completing the gradient separation of microplastic particles in the soil sample; S4. Extraction of microplastic particles from soil samples The sealing cover plate (42) is opened, each receiving plate (44) is extracted from the extraction and separation cylinder (4), and the microplastic particles separated from the soil sample are collected.

2. The method for continuous extraction and separation of soil microplastics of different particle sizes according to claim 1, characterized in that: 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 / cm 3 , the density of zinc iodide solution is 1.8-2.0g / cm 3 .

3. A device for continuous extraction and separation of soil microplastics of different particle sizes, used to implement the method for continuous extraction and separation of soil microplastics of different particle sizes as described in any one of claims 1-2, characterized in that: It comprises a mounting main frame (1), a rotating mounting frame (2) arranged on one side of the mounting main frame (1), and a driving unit (3) arranged on the mounting main frame (1) and rotatably connected to the rotating mounting frame (2) via a connecting shaft; the extraction and separation cylinder (4) is arranged in the rotating mounting frame (2); The upper and lower ends of the extraction and separation cylinder (4) are respectively provided with a feed port (40) and a discharge port (41); a sealing cover plate (42) is hingedly connected to one side of the extraction and separation cylinder (4); a plurality of filter membranes (43) with increasing mesh sizes are arranged in sequence from top to bottom in the extraction and separation cylinder (4); and a receiving plate (44) is arranged at the upper end of each filter membrane (43); the feed port (40) and the discharge port (41) of the extraction and separation cylinder (4) are connected via a circulation return pipe (45); and a one-way valve (450) and a liquid pump (451) are arranged at the connection; The receiving plate (44) comprises a receiving frame (440), a folding sliding plate (442) slidably connected to the receiving frame (440) and composed of a plurality of mutually parallel spliced ​​support plates (441), a sliding bar (443) provided 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.

4. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 3, characterized in that: A reinforcement base (10) is provided at the bottom end of the main mounting frame (1) and directly below the rotating mounting frame (2), and an anti-skid friction layer (11) is provided at the bottom end of the reinforcement base (10).

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

6. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 3, characterized in that: 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), and the inner wall of the blocking cover plate (42) and corresponding to each receiving frame (440) are respectively provided with a clamping fastening assembly (420), and the clamping fastening assembly (420) includes two horizontal mounting plates (421) arranged 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) through an electric telescopic rod (4220) and arranged oppositely, and the two clamping plates (422) arranged oppositely match the clamping grooves (403) located at the upper and lower ends of the same fastening clamping strip (402).

7. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 6, characterized in that: An elastic soft rubber strip (4221) is provided at the bottom end of the clamping plate (422), and each side wall at the bottom end of the fastening clamping strip (402) is provided with a receiving vertical plate (404). A containing cavity (405) is formed between each receiving vertical plate (404), a receiving frame (440) and a folding sliding plate (442), and each receiving vertical plate (404) abuts against the bottom end of the corresponding filter membrane (43).

8. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 3, characterized in that: A plurality of placement strips (46) are provided on the inner wall of the extraction and separation cylinder (4) and on a side opposite to the blocking cover plate (42); a placement groove (460) opposite to the receiving plate (44) is provided at the upper end of the placement strip (46); and the plurality of placement strips (46) are connected to the plurality of receiving frames (440) in a one-to-one correspondence.

9. The device for continuous extraction and separation of soil microplastics of different particle sizes according to claim 3, characterized in that: A temporary storage box (47) is provided on the side wall of the extraction and separation cylinder (4). The upper and lower ends of the extraction and separation cylinder (4) are respectively connected to the extraction and separation cylinder (4) through the circulation return pipe (45). There are two one-way valves (450), which are respectively distributed at the upper and lower ends of the temporary storage box (47).

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