A system and method for recovering microplastics at a water-sediment interface

Abstract

The present application relates to a kind of slurry interface microplastic recovery system and control method, fully consider the mixed scene of microplastic particles in slurry, design the device structure under the link of collection, stirring, slurry filtration, microplastic filtration, achieve the full design and efficient application of each link, and then the application of structure under global contact, microplastic particles in slurry are efficiently extracted;While the present application further designs the control method based on structured system, emphatically analyzes and designs slurry filtration link and microplastic particle extraction link, by repeatedly filtering slurry, fully separates the dirt in it and the liquid containing microplastic particles, while for each level microplastic filtration device, based on the structure design, the microplastic particle separation method under the joint action of plastic desorption liquid and protective gas is further improved the extraction efficiency of microplastic particles in slurry;The present application scheme is efficiently matched between structure and method, in practical application, microplastic particles in slurry are efficiently extracted.

Description

Technical Field

[0001] This invention relates to a microplastic recycling system and control method for mud-water interface, belonging to the field of mud-water microplastic particle recycling technology. Background Technology

[0002] The slow decomposition of plastic products produces numerous smaller fragments called microplastics, typically defined as plastic particles smaller than 5 millimeters. Microplastics in the environment can be classified as "primary" or "secondary" based on their size. Many primary microplastics are directly produced and used in personal care products or cosmetics, while secondary microplastics are small fragments formed from the decomposition of larger plastics by various abiotic factors. Microplastics are abundant in aquatic and terrestrial environments and can accumulate in birds, mammals, fish, and reptiles through various pathways, causing direct physical damage and potential toxic effects. Because the materials used to manufacture plastics have different chemical and physical properties, the resulting microplastics will vary significantly in composition, density, shape, and buoyancy. Microplastics with a density greater than water, or those whose density increases through biological processes by organisms, will sink in water bodies, posing a potential hazard. Although sediments are one of the important accumulation sites for microplastics, much research still focuses on the water surface, with limited attention paid to microplastics at the mud-water interface in natural water bodies.

[0003] Existing microplastic collection devices are mostly designed to collect microplastics from the surface of water bodies or soil on land. Moreover, their filter membranes have limited particle size and structure, making them unsuitable for collecting microplastics from the mud-water interface in natural water bodies. Furthermore, they cannot separate the collected material from the mud and water or perform effective deep processing on different subjects, resulting in inefficient and incomplete extraction of microplastics. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a microplastics recovery system for mud-water interface. Considering the collection, stirring, mud-water filtration and microplastic filtration of each stage, the system performs local and global structural design to efficiently extract microplastic particles in practical applications.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The present invention designs a mud-water interface microplastic recovery system and control method for absorbing mud-water to be treated and extracting microplastics from it. The system is characterized by comprising a front-end absorption subsystem, a mud-water mixing subsystem, a mud-water filtration subsystem, and a microplastic filtration subsystem. The front-end absorption subsystem is used to absorb mud-water from a target location for pretreatment to obtain mud-water to be treated, and then transport it to the mud-water mixing subsystem. The mud-water mixing subsystem receives the mud-water to be treated from the front-end absorption subsystem, mixes it, and then transports it to the mud-water filtration subsystem. The mud-water filtration subsystem receives the mud-water to be treated from the mud-water mixing subsystem, filters out mud impurities, obtains liquid to be treated, and then transports it to the microplastic filtration subsystem. The microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem and filters and extracts microplastic particles from the liquid.

[0006] As a preferred embodiment of the present invention: the front-end suction subsystem includes a front-end suction device and a water pump, wherein the front-end suction device includes a front-end plate, a front-end rigid pipe, a front-end flexible pipe, a pipe support structure, at least two electro-hydraulic push rod devices, at least one electro-hydraulic agitator, and at least one stage of pre-filter; the front-end plate has through holes penetrating its two sides, and the diameter of one port of the front-end flexible pipe is adapted to the diameter of the through hole on the front-end plate surface, and this port of the front-end flexible pipe is connected to the through hole on the front-end plate surface; the other port of the front-end flexible pipe is connected to the front-end rigid pipe via a connecting ring. One port; each electrically controlled mud mixer is positioned around the through-hole on the surface of the front-end plate facing away from the pre-connected rigid pipe, with the working end of each electrically controlled mud mixer facing away from the pre-connected rigid pipe. Based on the surface of the front-end plate facing away from the pre-connected rigid pipe contacting the target position, the working end of each electrically controlled mud mixer stirs the target position; each level of pre-filter screen is arranged along the direction of the pre-connected rigid pipe, with its edge circumferentially aligned with the inner wall of the pipe. The filter diameter of each level of pre-filter screen decreases sequentially along the direction away from the front-end plate, and the filter diameter of each level of pre-filter screen decreases sequentially. The minimum filter opening diameter in the filter screen is larger than the diameter of the mud impurities; the pipe support structure is set around the outside of the front rigid pipe, and the positions of the pipe support structure and the front rigid pipe are fixed. Each electro-hydraulic push rod device is located between the front end plate and the pipe support structure, and surrounds the outside of the front flexible pipe and the front rigid pipe. The end of the motor of each electro-hydraulic push rod device facing away from the connected push rod is fixed to the position facing the pipe support structure. The end of the push rod of each electro-hydraulic push rod device facing away from its connected motor is fixedly connected to the surface of the front end plate it faces. The operation of the motor in each electro-hydraulic push rod device controls the connected... The movement of the push rod causes the front-end plate to move in a manner that changes its distance from the pre-installed rigid pipe. The other end of the pre-installed rigid pipe is connected to the water pump inlet via a pipeline, and the water pump outlet constitutes the output end of the front-end suction subsystem. The output end of the front-end suction subsystem is connected to the input port of the mud-water mixing subsystem via a detachable pipeline. Based on the operation of the water pump, mud-water from the target location is sucked up through the surface through-holes on the front-end plate that are connected to the pre-installed rigid pipe. The mud-water is then filtered through various pre-filters to remove impurities larger than the diameter of the mud impurities, resulting in mud-water to be treated. This mud-water is then transported to the mud-water mixing subsystem from the output end of the front-end suction subsystem.

[0007] As a preferred embodiment of the present invention: the mud-water mixing subsystem includes a tank and an electrically controlled mixing device; wherein, the tank includes a tank body with an open top and a tank cover matching the diameter of the open top of the tank body, the electrically controlled mixing device includes an electrically controlled motor and a mixing paddle, the electrically controlled motor is fixed to the upper surface of the tank cover, the end of the drive rod of the electrically controlled motor passes through the surface of the tank cover and connects to the end of the mixing paddle located below the tank cover, and the straight line of the drive rod of the electrically controlled motor is collinear with the straight line of the mixing paddle; a through hole penetrating the inner and outer spaces of the tank is provided on the side of the tank at a predetermined distance relative to its open top, and a valve 1 is connected to the outer end of the through hole to form the mud-water mixing subsystem. The system has an input port for receiving mud and water to be treated from the front-end suction subsystem; a through hole is provided at the bottom of the tank, and valve 2 is connected to the outer end of the through hole to form the output port of the mud and water mixing subsystem. The output port of the mud and water mixing subsystem is connected to the input port of the mud and water filtration subsystem via a pipeline; based on the tank cover being located at the open top of the tank and the closure of valve 2, the electric motor in the electric control mixing device drives the mixing paddle to rotate and mix the mud and water to be treated from the front-end suction subsystem in the tank. After the mixing is completed, the mud and water to be treated after mixing is transported to the mud and water filtration subsystem through the output port of the mud and water mixing subsystem by opening valve 2.

[0008] As a preferred embodiment of the present invention: the mud-water mixing subsystem further includes at least one liquid storage spray device and at least one electrically controlled ultrasonic oscillator; each electrically controlled ultrasonic oscillator is disposed on the inner wall of the tank body; each liquid storage spray device includes a liquid storage tank and an electrically controlled spray head, each liquid storage tank is fixed to the upper surface of the tank cover, and the delivery port of each liquid storage tank passes through the surface of the tank cover and connects to the corresponding electrically controlled spray head located below the tank cover; each liquid storage tank is used to store pure water; based on the tank cover being located at the open top of the tank body, each electrically controlled spray head operates to spray water into the tank body, and based on the closure of valve 2, each electrically controlled ultrasonic oscillator operates to vibrate the mud-water to be treated from the front-end suction subsystem inside the tank body.

[0009] As a preferred embodiment of the present invention: the mud and water filtration subsystem includes a filtration chamber, at least one primary intermediate filter screen, and at least one electrically controlled ultrasonic oscillator; each electrically controlled ultrasonic oscillator is disposed on the inner wall of the filtration chamber; an inlet is provided at the top of the filtration chamber, constituting the inlet of the mud and water filtration subsystem; the intermediate filters of each stage are arranged in the filtration chamber from top to bottom, with their edges detachably connected to the inner wall of the side of the filtration chamber, and the filtration aperture of each intermediate filter screen decreases sequentially from top to bottom, and the smallest filtration aperture of each intermediate filter screen is larger than the aperture of the microplastic particles; a through hole is provided at the bottom of the filtration chamber, and a valve 6 is connected to the outer end of the through hole, constituting the outlet of the mud and water filtration subsystem; the inlet of the mud and water filtration subsystem receives the mud and water to be treated from the mud and water mixing subsystem, and passes it sequentially through the intermediate filters of each stage inside the filtration chamber from top to bottom, filtering out mud impurities in the mud and water to be treated with an aperture larger than the aperture of the microplastic particles, obtaining the liquid to be treated, and then transporting it to the microplastic filtration subsystem through the outlet of the mud and water filtration subsystem.

[0010] As a preferred embodiment of the present invention: the mud and water filtration subsystem further includes at least one electrically controlled heating and drying device, each electrically controlled heating and drying device being disposed on the inner wall of the filtration chamber; a through hole is provided below the filter screen at the lowest position on the side wall of the filtration chamber, the outer end of the through hole being connected to valve 4 and valve 5 respectively, the end of valve 5 facing away from the filtration chamber being used to connect to the plastic desorption liquid, and the end of valve 4 facing away from the filtration chamber being used to connect to the protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane; an exhaust port is provided at the top of the filtration chamber, and the outer end of the exhaust port is connected to valve 3, forming the exhaust port of the filtration chamber.

[0011] As a preferred embodiment of the present invention: the microplastic filtration subsystem includes at least one stage of microplastic filtration device. Each stage of the microplastic filtration device has the same structure, and each stage includes a housing, a terminal filter, and at least one electrically controlled ultrasonic oscillator. In the structure of each stage of the microplastic filtration device: the terminal filter is installed inside the housing with its edge circumferentially aligned with the inner wall of the housing, dividing the interior of the housing into upper and lower spaces. The surface of the terminal filter is sloped. Each electrically controlled ultrasonic oscillator is installed inside the housing. The microplastic filtration devices are connected in series. In the first stage of the microplastic filtration device, an inlet is provided at the top of the housing, and the outer end of this inlet is connected to valve 7, forming the inlet of the microplastic filtration subsystem. In the last stage of the microplastic filtration device, a through hole is provided at the bottom of the housing, and the outer end of this through hole is connected to valve 13, forming the outlet of the microplastic filtration subsystem. The devices are connected in series. In the adjacent microplastic filtration devices of the structure, the bottom of the housing of the upper-level microplastic filtration device is provided with at least one output port, and the same number of input ports are provided at the top of the housing of the lower-level microplastic filtration device. Each output port at the bottom of the housing of the upper-level microplastic filtration device is connected to the corresponding input port at the top of the housing of the lower-level microplastic filtration device through a series of valves 12. From the first-level microplastic filtration device to the last-level microplastic filtration device, the filtration diameter of the end filter screen in each level of microplastic filtration device decreases sequentially. Each end filter screen is used to filter and extract microplastic particles of the corresponding filtration diameter in the liquid to be treated. The input port of the microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem and passes it sequentially through the end filter screens in the housing of each level of microplastic filtration device. Each end filter screen filters and extracts the microplastic particles of the corresponding filtration diameter in the liquid to be treated.

[0012] As a preferred embodiment of the present invention: In each stage of the microplastic filtration device, a through hole is provided on the side of the housing at a preset height position corresponding to the end filter screen. The outer ends of the through holes are respectively connected to valves 10 and 11. The end of valve 11 facing away from the housing is used to connect to the external plastic desorption liquid, and the end of valve 10 facing away from the housing is used to connect to the external protective gas that does not chemically react with the plastic desorption liquid, plastic particles, or filter membrane. In each stage of the microplastic filtration device, an exhaust hole is provided on the top surface of the housing, and the outer ends of each exhaust hole are respectively connected to valve 8, forming the exhaust port of each housing. In each stage of the microplastic filtration device, a through hole is provided on the side of the housing at a preset height position corresponding to the end filter screen. The outer ends of the through holes are respectively connected to end caps.

[0013] Corresponding to the above, the technical problem that this invention also needs to solve is to provide a control method for a microplastic recycling system based on the mud-water interface. Based on the application of the global process, this invention focuses on analyzing and designing methods for the mud-water filtration process and the microplastic particle extraction process to improve the efficiency of practical applications.

[0014] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: The present invention designs a control method for a mud-water interface microplastic recovery system. Based on the fact that valves 3, 4, and 5, as well as valves 8, end caps, 10, and 11 in each level of microplastic filtration devices are all closed, the front-end suction subsystem sucks mud-water from the target location, and after passing through the mud-water mixing subsystem, mud-water filtration subsystem, and plastic filtration subsystem in sequence, the control method includes a microplastic recovery method. For each level of microplastic filtration device, the following steps are performed to achieve the extraction of microplastic particles of the corresponding filtration diameter in each level of microplastic filtration device.

[0015] Step A. For the microplastic filter device, close the valves connected to each inlet at the top of the housing and each outlet at the bottom, and then proceed to Step B;

[0016] Step B. For the microplastic filtration device, open valve 11 connected to the housing to deliver plastic desorption liquid into the housing; at the same time, open valve 10 connected to the housing to introduce a protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane into the housing, and open valve 8 connected to the housing for venting; turn on the electrically controlled ultrasonic oscillator; then proceed to step C.

[0017] Step C. After the plastic desorption liquid has submerged the end filter screen in the tank, stop the delivery of the plastic desorption liquid and close valve 11. Continue to deliver the protective gas and keep the electrically controlled ultrasonic oscillator running. After the preset delay time, stop the delivery of the protective gas and close valve 10. Then proceed to step D.

[0018] Step D. For the microplastic filtration device, open the end cap connected to the housing, use the extraction device to connect the pipeline through the end cap to the housing, draw up the plastic desorption liquid in the housing, and then extract the microplastic particles in the plastic desorption liquid that meet the corresponding microplastic particle diameter.

[0019] As a preferred technical solution of the present invention: based on the fact that valves 3, 4, 5, and valves 8, end caps, 10, and 11 in each level of microplastic filtration device are all closed, the front-end suction subsystem sucks up mud and water from the target location and transports it to the mud and water filtration subsystem via the mud and water mixing subsystem. The control method for the mud and water filtration subsystem to the plastic filtration subsystem is executed according to the following steps.

[0020] Step i. The mud-water filtration subsystem receives the mud-water to be treated from the mud-water mixing subsystem, filters out mud impurities from the mud-water to be treated, obtains the liquid to be treated, and delivers it to the microplastic filtration subsystem; the microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem, filters out microplastic particles from the liquid to be treated, discharges the remaining liquid, and then proceeds to step ii.

[0021] Step ii. Close valve 2 connected to the tank of the mud-water mixing subsystem, and close valve 6 connected to the filter chamber for the mud-water filtration subsystem, then proceed to step iii;

[0022] Step iii. For the mud and water filtration subsystem, turn on the electrically controlled heating and drying device in the filter chamber, dry the mud and impurities attached to the intermediate filter screens of each stage in the filter chamber for the preset time, then turn off the electrically controlled heating and drying device, and then proceed to step iv.

[0023] Step iv. For the mud and water filtration subsystem, open valve 5 connected to the filtration chamber to deliver plastic desorption liquid into the filtration chamber; at the same time, open valve 4 connected to the filtration chamber to introduce protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane into the filtration chamber, and turn on the electrically controlled ultrasonic oscillator in the filtration chamber, and open valve 3 connected to the filtration chamber for venting the filtration chamber; then proceed to step v.

[0024] Step v. Keep the electrically controlled ultrasonic oscillator running. After the plastic desorption liquid has submerged the central filter screen at the highest position in the filter chamber, stop the delivery of the plastic desorption liquid and close valve 5. Continue to deliver the protective gas for the preset delay time, then stop the delivery of the protective gas and close valve 4. Then proceed to step vi.

[0025] Step vi. For the mud and water filtration subsystem, open valve 6 connected to the filter chamber. The plastic desorption liquid in the filter chamber passes through the intermediate filter screens of each stage inside the filter chamber from top to bottom, filtering out mud impurities in the plastic desorption liquid with a diameter larger than that of microplastic particles, obtaining the liquid to be treated, and then transporting it to the microplastic filtration subsystem through the mud and water filtration subsystem output port, and then proceeding to step vii.

[0026] Step vii; The microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem, filters the microplastic particles in the liquid to be treated by the microplastic filtration subsystem, discharges the remaining liquid, and then proceeds to step viii;

[0027] Step viii. Determine whether the operations in steps ii to vii have reached the preset number of cycles. If yes, end the filtration operation that sequentially passes through the mud-water mixing subsystem, mud-water filtration subsystem, and plastic filtration subsystem; otherwise, return to step ii.

[0028] The microplastics recycling system and control method at the mud-water interface described in this invention, compared with the prior art, has the following technical advantages:

[0029] This invention presents a microplastic recovery system for the mud-water interface. It fully considers the mixing of microplastic particles in mud-water and designs the device structure for each stage: collection, stirring, mud-water filtration, and microplastic filtration. This ensures the efficient design and application of each stage, and allows for the application of the overall interconnected structure to efficiently extract microplastic particles from mud-water. Furthermore, this invention designs a control method based on a structured system, focusing on the analysis and design of the mud-water filtration and microplastic particle extraction stages. Through repeated filtration of the mud-water, mud impurities and liquid containing microplastic particles are fully separated. Simultaneously, for each stage of the microplastic filtration device, a microplastic particle separation method based on the combined action of plastic desorption liquid and protective gas is designed to further improve the extraction efficiency of microplastic particles from mud-water. Through the efficient matching design between structure and method, this invention achieves highly efficient extraction of microplastic particles from mud-water in practical applications. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the architecture of the mud-water interface microplastic recycling system designed in this invention;

[0031] Figure 2 This is a schematic diagram of the front-end absorption subsystem in the design of this invention;

[0032] Figure 3 This is a schematic diagram of the mud-water mixing subsystem in the design of this invention;

[0033] Figure 4 This is a schematic diagram of the mud and water filtration subsystem in the design of this invention;

[0034] Figure 5 This is a schematic diagram of the microplastic filtration subsystem in the design of this invention. Detailed Implementation

[0035] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0036] This invention designs a microplastic recovery system for the mud-water interface, used to absorb mud-water to be treated and extract microplastics from it. In practical applications, such as... Figure 1As shown, the system includes a front-end suction subsystem, a mud-water mixing subsystem, a mud-water filtration subsystem, and a microplastic filtration subsystem. The front-end suction subsystem is used to suction mud-water from a target location for pretreatment, obtaining mud-water to be treated, and then conveying it to the mud-water mixing subsystem. The mud-water mixing subsystem receives the mud-water to be treated from the front-end suction subsystem, mixes it, and then conveys it to the mud-water filtration subsystem. The mud-water filtration subsystem receives the mud-water to be treated from the mud-water mixing subsystem, filters out mud impurities from the mud-water to obtain liquid to be treated, and then conveys it to the microplastic filtration subsystem. The microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem and filters out microplastic particles from the liquid to be treated.

[0037] In practical applications, such as Figure 2As shown, the front-end suction subsystem includes a front-end suction device and a water pump. The front-end suction device includes a front-end plate, a front-end rigid pipe, a front-end flexible pipe, a pipe support structure, at least two electro-hydraulic push rod devices, at least one electro-hydraulic agitator, and at least one stage of pre-filter. The front-end plate has through holes on both sides. The diameter of one port on the front-end flexible pipe matches the diameter of the through hole on the front-end plate, and this port on the front-end flexible pipe is connected to the through hole on the front-end plate. The other port on the front-end flexible pipe is connected to one port on the front-end rigid pipe via a connecting ring. Each electro-hydraulic agitator... The agitators are positioned around the through holes on the surface of the front-end plate facing away from the pre-connected rigid pipe, with the working ends of each electrically controlled mud mixer facing away from the pre-connected rigid pipe. Since the surface of the front-end plate facing away from the pre-connected rigid pipe is in contact with the target location, the working ends of each electrically controlled mud mixer agitate the target location. Various levels of pre-filters are arranged along the direction of the pre-connected rigid pipe, with their edges circumferentially aligned with the inner wall of the pipe. The filter diameter of each level of pre-filter decreases sequentially along the direction away from the front-end plate, with the smallest filter among all levels being... The filter inlet diameter is larger than the diameter of the mud impurities; the pipe support structure is set around the outside of the front rigid pipe, and the positions of the pipe support structure and the front rigid pipe are fixed. Each electro-hydraulic push rod device is located between the front end plate and the pipe support structure, and surrounds the outside of the front flexible pipe and the front rigid pipe. In each electro-hydraulic push rod device, the end of the motor facing away from the connected push rod is fixed to the position facing the pipe support structure. In each electro-hydraulic push rod device, the end of the push rod facing away from its connected motor is fixedly connected to the surface of the front end plate it faces. The operation of the motor in each electro-hydraulic push rod device controls the push rod connected to it. The front-end plate moves by changing its distance from the pre-installed rigid pipe. The other end of the pre-installed rigid pipe is connected to the water pump inlet via a pipeline. The water pump outlet constitutes the output end of the front-end suction subsystem. The output end of the front-end suction subsystem is connected to the input port of the mud-water mixing subsystem via a detachable pipeline. Based on the operation of the water pump, mud-water from the target location is sucked up through the surface through-holes on the front-end plate that are connected to the pre-installed rigid pipe. The mud-water is then filtered through various pre-filters to remove impurities larger than the diameter of the mud impurities, resulting in mud-water to be treated. This mud-water is then transported to the mud-water mixing subsystem from the output end of the front-end suction subsystem.

[0038] In practical applications, the front-end absorbing subsystem, such as Figure 2As shown, a flexible protective sleeve can be designed on the outermost periphery of the corresponding front rigid pipe and front flexible pipe positions in the entire device. In addition, layout compartments can be set up outside the pipes for the electrical control circuits of each electro-hydraulic push rod device and electro-stirring device to achieve the independence of the space where each device is located. In actual application, the electro-stirring device uses a combination of motor 5IK60GU-CT and rotor BAP400R 125-40-7T.

[0039] In practical applications, such as Figure 3 As shown, the slurry mixing subsystem includes a tank, an electrically controlled mixing device, at least one liquid storage spraying device, and at least one electrically controlled ultrasonic oscillator. The tank includes a tank body with an open top and a tank cover matching the diameter of the open top. The electrically controlled mixing device includes an electrically controlled motor and a mixing paddle. The electrically controlled motor is fixed to the upper surface of the tank cover, and the end of the motor's drive rod passes through the surface of the tank cover and connects to the end of the mixing paddle located below the tank cover. The straight line of the motor's drive rod is collinear with the straight line of the mixing paddle. A through-hole penetrating the inner and outer spaces of the tank is provided on the side of the tank at a predetermined distance from its open top. A valve 1 is connected to the outer end of this through-hole, forming the input port of the slurry mixing subsystem for receiving slurry from the front-end suction subsystem. A through-hole is provided at the bottom of the tank, and a valve 2 is connected to the outer end of this through-hole, forming the output port of the slurry mixing subsystem. The output port of the slurry mixing subsystem is connected to a slurry filter via a pipeline. The system has an input port; based on the open opening at the top of the tank with the tank lid and the closure of valve 2, the electric motor in the electric stirring device drives the stirring paddle to rotate and stir the mud and water to be treated from the front-end suction subsystem inside the tank. After the stirring is completed, the mud and water to be treated is transported to the mud and water filtration subsystem through the output port of the mud and water stirring subsystem by opening valve 2. Each electric ultrasonic oscillator is set on the inner wall of the tank. Each liquid storage spray device includes a liquid storage tank and an electric spray head. Each liquid storage tank is fixed on the upper surface of the tank lid. The delivery port of each liquid storage tank passes through the surface of the tank lid and connects to the corresponding electric spray head located below the tank lid. Each liquid storage tank is used to store pure water. Based on the open opening at the top of the tank with the tank lid, each electric spray head sprays into the tank. Based on the closure of valve 2, each electric ultrasonic oscillator vibrates the mud and water to be treated from the front-end suction subsystem inside the tank.

[0040] In practical applications, based on the closure of valve 2, after the mud-water mixing subsystem receives the mud-water to be treated from the front-end suction subsystem, valve 1 can be closed to prevent liquid backflow. Then, the electrically controlled mixing device is controlled to work, which thoroughly mixes the mud-water to be treated in the tank. Accompanying the mixing action, the operation of the electrically controlled ultrasonic oscillator can also accelerate the mixing effect. Furthermore, the addition of the liquid storage spray device allows pure water to be added to the tank during the mixing process. Alternatively, while opening valve 2 to discharge the mud-water to be treated downwards, the liquid storage spray device can be used to flush the residual mud-water to be treated in the tank and transport it to the mud-water filtration subsystem.

[0041] In practical applications, such as Figure 4 As shown, the sludge filtration subsystem includes a filter chamber, at least one primary intermediate filter screen, at least one electrically controlled ultrasonic oscillator, and at least one electrically controlled heating and drying device. Each electrically controlled ultrasonic oscillator is mounted on the inner wall of the filter chamber. An inlet is located at the top of the filter chamber, forming the inlet of the sludge filtration subsystem. The intermediate filter screens are arranged sequentially from top to bottom within the filter chamber, with their edges detachably connected to the inner wall of the filter chamber's side. The filtration diameter of each intermediate filter screen decreases sequentially from top to bottom, and the smallest filtration diameter among the intermediate filter screens is larger than the diameter of the microplastic particles. A through-hole is located at the bottom of the filter chamber, with a valve 6 connected to the outer end of the through-hole, forming the outlet of the sludge filtration subsystem. The inlet of the sludge filtration subsystem is also shown. The system receives sludge from the sludge mixing subsystem and passes it sequentially through various centrally located filters inside the filtration chamber from top to bottom. This filters out impurities in the sludge with a diameter larger than that of the microplastic particles, resulting in a liquid to be treated. This liquid is then transported from the sludge filtration subsystem output to the microplastic filtration subsystem. Each electrically controlled heating and drying device is installed on the inner wall of the filtration chamber. A through-hole is located below the lowest centrally located filter on the side wall of the filtration chamber. The outer ends of this through-hole connect to valves 4 and 5, respectively. The end of valve 5 facing away from the filtration chamber is used to connect to the external plastic desorption liquid, and the end of valve 4 facing away from the filtration chamber is used to connect to a protective gas that does not chemically react with the plastic desorption liquid, plastic particles, or filter membrane. An exhaust port is located at the top of the filtration chamber, and the outer end of this exhaust port connects to valve 3, forming the exhaust port of the filtration chamber.

[0042] In practical applications, such as Figure 5As shown, the microplastic filtration subsystem includes at least one stage of microplastic filtration device. Each stage of the microplastic filtration device has the same structure, including a housing, a terminal filter, and at least one electrically controlled ultrasonic oscillator. In each stage's structure: the terminal filter is positioned within the housing with its edge circumferentially aligned with the inner wall of the housing, dividing the interior of the housing into upper and lower spaces. The surface of the terminal filter is sloped. Each electrically controlled ultrasonic oscillator is located within the housing. The microplastic filtration devices are connected in series. The top of the housing in the first stage of the microplastic filtration device... An input port is provided, with its outer end connected to valve 7, forming the input port of the microplastic filtration subsystem. A through-hole is provided at the bottom of the housing in the last-stage microplastic filtration device, with its outer end connected to valve 13, forming the discharge port of the microplastic filtration subsystem. In the series structure, adjacent microplastic filtration devices at different stages have at least one output port at the bottom of the housing in the previous stage, and the same number of input ports are provided at the top of the housing in the corresponding next-stage microplastic filtration device. Each output port at the bottom of the housing in the previous stage is connected to the corresponding next-stage microplastic filtration device via a pipeline connected to valve 12. The filter unit has inlets at the top of the housing; from the first stage to the last stage, the filtration aperture of the end filters in each stage decreases sequentially, and each end filter is used to filter and extract microplastic particles of the corresponding aperture size from the liquid to be treated; the inlet of the microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem, and it passes sequentially through the end filters in the housing of each stage of the microplastic filtration unit, where each end filter filters and extracts microplastic particles of the corresponding aperture size from the liquid to be treated; the side of the housing of each stage of the microplastic filtration unit corresponds to the end... A through hole is provided at a preset height position below the filter screen. The outer ends of the through hole are respectively connected to valve 10 and valve 11. The end of valve 11 facing away from the box is used to connect to the plastic desorption liquid, and the end of valve 10 facing away from the box is used to connect to the protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane. Each stage of the microplastic filtration device has an exhaust hole on the top surface of the box, and the outer ends of each exhaust hole are respectively connected to valve 8 to form the exhaust port of each box. A through hole is provided on the side of the box of each stage of the microplastic filtration device at a preset height position corresponding to the end filter screen. The outer ends of the through hole are respectively connected to the end cap.

[0043] In practical applications, for the housings of each level of the microplastic filtration device, an openable door is also provided on its side to facilitate later maintenance of the terminal filters. Furthermore, in practical applications, a central column can be designed to run through the housing of each level of the microplastic filtration device. The terminal filters in each housing are arranged around the central column, meaning the terminal filters have a centrally open structure. The inner edge of the central through-hole of the terminal filter connects to the central column, and the outer edge of the terminal filter connects to the inner side of the housing. Figure 5 As shown, the layout of the end filter screen is designed as a conical shape, that is, the surface of the screen is sloped, which can accelerate the flow of liquid on the surface and improve the filtration effect of the end filter screen on microplastic particles in the liquid to be treated.

[0044] Along with the discharge port of the corresponding microplastic filtration subsystem on the last stage microplastic filtration device, a filtrate collection box can be further designed to connect to this discharge port in practical applications. Depending on actual needs, such as collecting the last discharged filtrate, other detection can be further realized.

[0045] In practical applications, based on the above structural design, the front-end suction subsystem sucks up the mud and water from the target location for pretreatment to obtain mud and water to be treated, and then transports it to the mud and water mixing subsystem. The mud and water mixing subsystem receives the mud and water to be treated from the front-end suction subsystem, mixes it, and then transports it to the mud and water filtration subsystem. The mud and water filtration subsystem receives the mud and water to be treated from the mud and water mixing subsystem, filters out mud and impurities from the mud and water to obtain the liquid to be treated, and then transports it to the microplastic filtration subsystem. The microplastic filtration subsystem receives the liquid to be treated from the mud and water filtration subsystem. The liquid to be treated is filtered and extracted by the microplastic filtration subsystem. Based on the microplastic recovery system at the mud-water interface designed above, this invention further designs control methods for the two stages of mud-water filtration and microplastic particle extraction. Regarding mud-water filtration, with valves 3, 4, and 5, as well as valves 8, end caps, 10, and 11 in each stage of the microplastic filtration device closed, the front-end suction subsystem sucks up the mud-water at the target location and transports it to the mud-water filtration subsystem via the mud-water mixing subsystem. The control method for the mud-water filtration subsystem to the plastic filtration subsystem is executed according to the following steps.

[0046] Step i. The mud-water filtration subsystem receives the mud-water to be treated from the mud-water mixing subsystem, filters out mud impurities from the mud-water to be treated, obtains the liquid to be treated, and transports it to the microplastic filtration subsystem; the microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem, filters out microplastic particles from the liquid to be treated, discharges the remaining liquid, and then proceeds to step ii.

[0047] Step ii. Close valve 2 connected to the tank of the mud-water mixing subsystem, and close valve 6 connected to the filter chamber for the mud-water filtration subsystem, then proceed to step iii.

[0048] Step iii. For the mud and water filtration subsystem, turn on the electrically controlled heating and drying device in the filter chamber, dry the mud and impurities attached to the intermediate filter screens of each stage in the filter chamber for the preset time, then turn off the electrically controlled heating and drying device, and then proceed to step iv.

[0049] Step iv. For the mud-water filtration subsystem, open valve 5 connected to the filtration chamber to deliver plastic desorption liquid into the filtration chamber; at the same time, open valve 4 connected to the filtration chamber to introduce a protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane into the filtration chamber, and turn on the electrically controlled ultrasonic oscillator in the filtration chamber, and open valve 3 connected to the filtration chamber for venting the filtration chamber; then proceed to step v.

[0050] Step v. Keep the electrically controlled ultrasonic oscillator running. After the plastic desorption liquid has submerged the central filter screen at the highest position in the filter chamber, stop the delivery of the plastic desorption liquid and close valve 5. Continue to deliver the protective gas for the preset delay time, then stop the delivery of the protective gas and close valve 4. Then proceed to step vi.

[0051] Step vi. For the mud-water filtration subsystem, open valve 6 connected to the filtration chamber. The plastic desorption liquid in the filtration chamber passes through the intermediate filter screens of each stage inside the filtration chamber from top to bottom, filtering out mud impurities in the plastic desorption liquid with a diameter larger than that of microplastic particles, obtaining the liquid to be treated, and then transporting it to the microplastic filtration subsystem through the output port of the mud-water filtration subsystem, and then proceeding to step vii.

[0052] Step vii: The microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem, filters the microplastic particles in the liquid to be treated by the microplastic filtration subsystem, discharges the remaining liquid, and then proceeds to step viii.

[0053] Step viii. Determine whether the operations in steps ii to vii have reached the preset number of cycles. If yes, end the filtration operation that sequentially passes through the mud-water mixing subsystem, mud-water filtration subsystem, and plastic filtration subsystem; otherwise, return to step ii.

[0054] Regarding the extraction of microplastic particles, the specific design is based on the closure of valves 3, 4, and 5, as well as valves 8, end caps, 10, and 11 in each level of the microplastic filtration device. The front-end suction subsystem sucks up the mud and water at the target location, and after passing through the mud and water mixing subsystem, mud and water filtration subsystem, and plastic filtration subsystem in sequence, the control method includes a microplastic recovery method. For each level of the microplastic filtration device, the following steps are performed to achieve the extraction of microplastic particles of the corresponding filtration diameter in each level of the microplastic filtration device.

[0055] Step A. For the microplastic filter device, close the valves connected to each inlet at the top of the housing and each outlet at the bottom, and then proceed to Step B.

[0056] Step B. For the microplastic filtration device, open valve 11 connected to the housing to deliver plastic desorption liquid into the housing; at the same time, open valve 10 connected to the housing to introduce a protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane into the housing, and open valve 8 connected to the housing for venting; turn on the electrically controlled ultrasonic oscillator; then proceed to step C.

[0057] Step C. After the plastic desorption liquid has submerged the end filter screen in the tank, stop the delivery of the plastic desorption liquid and close valve 11. Continue to deliver the protective gas and run the electrically controlled ultrasonic oscillator. After the preset delay time, stop the delivery of the protective gas and close valve 10, and then proceed to step D.

[0058] Step D. For the microplastic filtration device, open the end cap connected to the housing, use the extraction device to connect the pipeline through the end cap to the housing, draw up the plastic desorption liquid in the housing, and then extract the microplastic particles in the plastic desorption liquid that meet the corresponding microplastic particle diameter.

[0059] The aforementioned technical solution designs a microplastic recovery system for the mud-water interface, fully considering the mixing scenario of microplastic particles in mud-water. It designs the device structure for each stage—collection, stirring, mud-water filtration, and microplastic filtration—ensuring thorough design and efficient application of each stage. This allows for the application of a globally interconnected structure, enabling efficient extraction of microplastic particles from mud-water. Furthermore, this invention designs a control method based on a structured system, focusing on the analysis and design of the mud-water filtration and microplastic particle extraction stages. Through repeated filtration of the mud-water, mud impurities and liquid containing microplastic particles are fully separated. Simultaneously, for each stage of the microplastic filtration device, a microplastic particle separation method based on the combined action of plastic desorption liquid and protective gas is designed, further improving the extraction efficiency of microplastic particles from mud-water. Through efficient matching design between structure and method, this invention achieves highly efficient extraction of microplastic particles from mud-water in practical applications.

[0060] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A slurry interface microplastic recovery system for drawing in slurry to be treated and extracting microplastics from the slurry to be treated, characterized in that: The system comprises a front-end suction subsystem, a sludge stirring subsystem, a sludge filtering subsystem, and a micro-plastic filtering subsystem; the front-end suction subsystem is used to suck sludge at a target position for pretreatment, to obtain sludge to be treated, and to deliver the sludge to the sludge stirring subsystem; the sludge stirring subsystem is used to receive the sludge to be treated from the front-end suction subsystem, to stir and treat the sludge to be treated by the sludge stirring subsystem, and to deliver the sludge to the sludge filtering subsystem; the sludge filtering subsystem receives the sludge to be treated from the sludge stirring subsystem, filters out sludge impurities in the sludge to be treated by the sludge filtering subsystem, to obtain liquid to be treated, and to deliver the liquid to the micro-plastic filtering subsystem; the micro-plastic filtering subsystem receives the liquid to be treated from the sludge filtering subsystem, filters and extracts micro-plastic particles in the liquid to be treated by the micro-plastic filtering subsystem; The sludge filtering subsystem comprises a filtering cabin, at least one level of middle filtering screen, and at least one electrically-controlled heating and drying device; each electrically-controlled heating and drying device is arranged on the inner wall of the filtering cabin; the side wall of the filtering cabin is provided with a through hole below the lowest middle filtering screen; the outer side end of the through hole is respectively connected to valve four and valve five; the end of valve five away from the filtering cabin is used to externally connect plastic desorption liquid.

2. The system for recovering microplastics at the water-sediment interface according to claim 1, wherein: The front-end suction subsystem comprises a front-end suction device and a water pump, wherein the front-end suction device comprises a front-end plate, a front hard pipe, a front flexible pipe, a pipe body support structure, at least two electrically-controlled hydraulic push rod devices, at least one electrically-controlled mud-water agitator, and at least one front filter screen; the front-end plate is provided with a through hole penetrating through both sides thereof, the diameter of one port of the front flexible pipe is adapted to the diameter of the through hole on the surface of the front-end plate, the one port of the front flexible pipe is connected to the through hole on the surface of the front-end plate, and the other port of the front flexible pipe is connected to one port of the front hard pipe through a connecting ring; each electrically-controlled mud-water agitator is arranged on the surface of the front-end plate away from the through hole connected to the front hard pipe, and the working end of each electrically-controlled mud-water agitator is arranged away from the direction of the front hard pipe; based on the surface of the front-end plate away from the front hard pipe being in contact with the target position, the working end of each electrically-controlled mud-water agitator works on the target position to agitate the target position; each front filter screen is arranged in the front hard pipe in a manner that the edge of the front filter screen is connected to the inner wall of the front hard pipe in sequence, the filtering diameter of each front filter screen decreases in sequence in the direction away from the front-end plate in the front hard pipe, and the smallest filtering diameter of each front filter screen is greater than the diameter of the impurities; the pipe body support structure is arranged around the outside of the front hard pipe, and the pipe body support structure and the front hard pipe are fixed in position; each electrically-controlled hydraulic push rod device is located between the front-end plate and the pipe body support structure and is arranged around the outside of the front flexible pipe and the front hard pipe; the end of the motor of each electrically-controlled hydraulic push rod device away from the connected push rod is fixed to the position of the pipe body support structure facing the motor, and the end of the push rod of each electrically-controlled hydraulic push rod device away from the connected motor is fixed to the surface of the front-end plate facing the push rod; based on the motor of each electrically-controlled hydraulic push rod device working to control the movement of the connected push rod, the front-end plate moves in a manner that the distance between the front-end plate and the front hard pipe changes; the other end of the front hard pipe is connected to the inlet of the water pump through a pipeline, the outlet of the water pump constitutes the output end of the front-end suction subsystem, and the output end of the front-end suction subsystem is detachably connected to the input port of the mud-water agitating subsystem through a pipeline; based on the working of the water pump, the mud-water at the target position is sucked through the through hole on the surface of the front-end plate away from the front hard pipe, and the impurities with a diameter greater than the diameter of the impurities are filtered out from the sucked mud-water through the front filter screens in sequence to obtain the mud-water to be treated, which is then transported to the mud-water agitating subsystem through the output end of the front-end suction subsystem.

3. The system for recovering microplastics at the water-sediment interface according to claim 1, wherein: The mud-water mixing subsystem includes a tank and an electrically controlled mixing device. The tank includes a body with an open top and a tank cover matching the diameter of the open top. The electrically controlled mixing device includes an electric motor and a mixing paddle. The electric motor is fixed to the upper surface of the tank cover, and the end of the motor's drive rod passes through the surface of the tank cover and connects to the end of the mixing paddle located below the tank cover. The straight line of the motor's drive rod is collinear with the straight line of the mixing paddle. A through-hole is provided on the side of the tank at a predetermined distance from its open top, penetrating the inner and outer spaces of the tank. A valve is connected to the outer end of this through-hole, forming the input port of the mud-water mixing subsystem. The system receives sludge from the front-end suction subsystem. A through hole is provided at the bottom of the tank, and valve two is connected to the outer end of the through hole to form the output port of the sludge mixing subsystem. The output port of the sludge mixing subsystem is connected to the input port of the sludge filtration subsystem via a pipeline. Based on the tank cover being located at the open top of the tank and the closure of valve two, the electric motor in the electric mixing device drives the mixing paddle to rotate and mix the sludge from the front-end suction subsystem inside the tank. After the mixing is completed, the sludge is transported to the sludge filtration subsystem through the output port of the sludge mixing subsystem by opening valve two.

4. The system for recovering microplastics at the water-sediment interface according to claim 3, characterized in that: The mud-water mixing subsystem also includes at least one liquid storage spray device and at least one electrically controlled ultrasonic oscillator; Each electrically controlled ultrasonic oscillator is installed on the inner wall of the tank; each liquid storage spray device includes a liquid storage tank and an electrically controlled spray head. Each liquid storage tank is fixed on the upper surface of the tank cover. The delivery port of each liquid storage tank passes through the surface of the tank cover and connects to the corresponding electrically controlled spray head located below the tank cover. Each liquid storage tank is used to store pure water. Based on the open opening at the top of the tank cover, each electrically controlled spray head works to spray water into the tank. Furthermore, based on the closure of valve two, each electrically controlled ultrasonic oscillator works to vibrate the mud and water to be treated from the front-end suction subsystem inside the tank.

5. The system for recovering microplastics at the water-sediment interface according to claim 1, characterized in that: The mud and water filtration subsystem also includes at least one electrically controlled ultrasonic oscillator; Each electrically controlled ultrasonic oscillator is installed on the inner wall of the filter chamber; an inlet is provided at the top of the filter chamber, forming the inlet of the mud-water filtration subsystem; each level of central filter screen is arranged in the filter chamber from top to bottom, with its edge circumferentially connected to the inner wall of the filter chamber side in a detachable manner, and the filtration aperture of each level of central filter screen decreases sequentially from top to bottom, with the smallest filtration aperture of each level of central filter screen being larger than the aperture of the microplastic particles; a through hole is provided at the bottom of the filter chamber, and a valve is connected to the outer end of the through hole, forming the outlet of the mud-water filtration subsystem; the inlet of the mud-water filtration subsystem receives the mud-water to be treated from the mud-water mixing subsystem, and passes it sequentially from top to bottom through each level of central filter screen inside the filter chamber, filtering out mud impurities in the mud-water to be treated with an aperture larger than the aperture of the microplastic particles, obtaining the liquid to be treated, and then transporting it to the microplastic filtration subsystem through the outlet of the mud-water filtration subsystem.

6. The system for recovering microplastics at the water-sediment interface according to claim 5, wherein: The valve four is used to connect a protective gas that does not chemically react with the plastic desorption liquid, plastic particles, or filter membrane at one end facing away from the filter chamber. An exhaust port is provided at the top of the filter chamber, and the outer end of the exhaust port is connected to valve three, which constitutes the exhaust port of the filter chamber.

7. The system for recovering microplastics at the water-sediment interface according to claim 6, wherein: The microplastic filtration subsystem includes at least one stage of microplastic filtration device. Each stage of the microplastic filtration device has the same structure, including a housing, a terminal filter, and at least one electrically controlled ultrasonic oscillator. In each stage, the terminal filter is positioned within the housing with its edge circumferentially aligned with the inner wall of the housing, dividing the interior into upper and lower spaces. The surface of the terminal filter is sloped. Each electrically controlled ultrasonic oscillator is located within the housing. The microplastic filtration devices are connected in series. In the first stage, an inlet is located at the top of the housing, with its outer end connected to valve 7, forming the inlet of the microplastic filtration subsystem. In the last stage, a through-hole is located at the bottom of the housing, with its outer end connected to valve 13, forming the outlet of the microplastic filtration subsystem. The adjacent stages in the series structure... In the microplastic filtration device, the bottom of the housing of the previous stage microplastic filtration device is provided with at least one output port, and the same number of input ports are provided at the top of the housing of the next stage microplastic filtration device. Each output port at the bottom of the housing of the previous stage microplastic filtration device is connected to the corresponding input ports at the top of the housing of the next stage microplastic filtration device via a series of valves in a pipeline. From the first stage microplastic filtration device to the last stage microplastic filtration device, the filtration diameter of the end filter screens in each stage microplastic filtration device decreases sequentially. Each end filter screen is used to filter and extract microplastic particles of the corresponding filtration diameter from the liquid to be treated. The input port of the microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem and passes it sequentially through the end filter screens in the housing of each stage microplastic filtration device, where each end filter screen filters and extracts the microplastic particles of the corresponding filtration diameter from the liquid to be treated.

8. The system for recovering microplastics at the water-sediment interface according to claim 7, wherein: In each stage of the microplastic filtration device, a through hole is provided on the side of the housing at a preset height position corresponding to the end filter screen. The outer end of the through hole is connected to valve 10 and valve 11 respectively. The end of valve 11 facing away from the housing is used to connect to the plastic desorption liquid, and the end of valve 10 facing away from the housing is used to connect to the protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane. Each stage of the microplastic filtration device has an exhaust hole on the top surface of the housing, and the outer end of each exhaust hole is connected to valve 8 to form the exhaust port of each housing. In each stage of the microplastic filtration device, a through hole is provided on the side of the housing at a preset height position corresponding to the end filter screen. The outer end of the through hole is connected to the end cap respectively.

9. The control method of claim 8, wherein the control method is based on the slurry interface microplastic recovery system of claim 8. With valves three, four, and five, as well as valves eight, end caps, ten, and eleven in each level of the microplastic filtration device, all closed, the front-end suction subsystem sucks up mud and water from the target location, and after passing through the mud and water mixing subsystem, mud and water filtration subsystem, and plastic filtration subsystem in sequence, the control method includes a microplastic recovery method. For each level of the microplastic filtration device, the following steps are performed to extract microplastic particles of the corresponding filtration diameter in each level of the microplastic filtration device. Step A. For the microplastic filter device, close the valves connected to each inlet at the top of the housing and each outlet at the bottom, and then proceed to Step B; Step B. For the microplastic filtration device, open valve eleven connected to the housing to deliver plastic desorption liquid into the housing; at the same time, open valve ten connected to the housing to introduce a protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane into the housing, and open valve eight connected to the housing for exhausting the housing. Turn on the electronically controlled ultrasonic oscillator; Then proceed to step C; Step C. After the plastic desorption liquid has submerged the end filter screen in the tank, stop the delivery of the plastic desorption liquid and close valve eleven. Continue to deliver the protective gas and run the electrically controlled ultrasonic oscillator. After the preset delay time, stop the delivery of the protective gas and close valve ten. Then proceed to step D. Step D. For the microplastic filtration device, open the end cap connected to the housing, use the extraction device to connect the pipeline through the end cap to the housing, draw up the plastic desorption liquid in the housing, and then extract the microplastic particles in the plastic desorption liquid that meet the corresponding microplastic particle diameter.

10. The control method of claim 8, wherein the control method is based on the slurry interface microplastic recovery system of claim 8. Based on the fact that valves three, four, five, and valves eight, end caps, ten, and eleven in each level of microplastic filtration device are all closed, the front-end suction subsystem sucks up the mud and water at the target location and transports it to the mud and water filtration subsystem via the mud and water mixing subsystem. The control method for the mud and water filtration subsystem to the plastic filtration subsystem is executed according to the following steps. Step i. The mud-water filtration subsystem receives the mud-water to be treated from the mud-water mixing subsystem, filters out mud impurities from the mud-water to be treated, obtains the liquid to be treated, and delivers it to the microplastic filtration subsystem. The microplastic filtration subsystem receives the liquid to be treated from the mud and water filtration subsystem, filters the microplastic particles in the liquid to be treated by the microplastic filtration subsystem, discharges the remaining liquid, and then proceeds to step ii; Step ii. Close valve 2 connected to the tank in the mud-water mixing subsystem, and close valve 6 connected to the filter chamber in the mud-water filtration subsystem, then proceed to step iii; Step iii. For the mud and water filtration subsystem, turn on the electrically controlled heating and drying device in the filter chamber, dry the mud and impurities attached to the intermediate filter screens of each stage in the filter chamber for the preset time, then turn off the electrically controlled heating and drying device, and then proceed to step iv. Step iv. For the mud-water filtration subsystem, open valve five connected to the filtration chamber to deliver plastic desorption liquid into the filtration chamber; at the same time, open valve four connected to the filtration chamber to introduce a protective gas that does not chemically react with the plastic desorption liquid, plastic particles, and filter membrane into the filtration chamber, and turn on the electrically controlled ultrasonic oscillator in the filtration chamber, and open valve three connected to the filtration chamber for venting the filtration chamber; then proceed to step v. Step v. Keep the electrically controlled ultrasonic oscillator running. After the plastic desorption liquid has submerged the central filter screen at the highest position in the filter chamber, stop the delivery of the plastic desorption liquid and close valve five. Continue to deliver the protective gas for the preset delay time, then stop the delivery of the protective gas and close valve four. Then proceed to step vi. Step vi. For the mud-water filtration subsystem, open valve six connected to the filtration chamber. The plastic desorption liquid in the filtration chamber passes through the intermediate filter screens of each stage inside the filtration chamber from top to bottom, filtering out mud impurities in the plastic desorption liquid with a diameter larger than that of microplastic particles, obtaining the liquid to be treated, and then transporting it to the microplastic filtration subsystem through the output port of the mud-water filtration subsystem, and then proceeding to step vii. Step vii. The microplastic filtration subsystem receives the liquid to be treated from the mud-water filtration subsystem, filters the microplastic particles in the liquid to be treated by the microplastic filtration subsystem, discharges the remaining liquid, and then proceeds to step viii; Step viii. Determine whether the operations in steps ii to vii have reached the preset number of cycles. If yes, end the filtration operation that sequentially passes through the mud-water mixing subsystem, mud-water filtration subsystem, and plastic filtration subsystem; otherwise, return to step ii.

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