Method and device for treating soil heavy metal through in-situ soaking and leaching

Abstract

The invention relates to the technical field of soil heavy metal pollution treatment and remediation, and discloses a method and device for treating soil heavy metal through in-situ soaking and leaching, and the method comprises the following steps: arranging a system; pumping drainage and liquid filling: pumping drainage of soil moisture in the treatment area until the underground water level stably drops to a target depth; the repairing agent liquid medicine is poured till the ground is filled with the repairing agent liquid medicine; standing and soaking; sampling detection: extracting liquid from the soaked soil body, sampling to detect the heavy metal concentration, and judging whether heavy metal recovery is carried out or not according to a detection result; if not, returning to the step of standing and soaking; heavy metal recovery; washing the soil body with clear water to enable the residual quantity of the repairing agent to meet environmental requirements, and finishing treatment. According to the method, the underground water is pumped through the high-energy water pump, the remediation agent liquid is recharged and soaked, the heavy metal-containing liquid is circularly pumped and drained, and the remediation agent liquid is recharged to leach the contaminated soil, so that the heavy metals in the soil can be simply, conveniently, economically and efficiently removed.

Description

Technical Field

[0001] This invention relates to the field of soil heavy metal pollution control and remediation technology, specifically to a method and apparatus for in-situ soaking and leaching treatment of soil heavy metals. Background Technology

[0002] Remediation of heavy metal pollution in soil, especially for large-scale, deeply contaminated sites, is a major challenge in the fields of environmental protection and resource recycling. In-situ remediation technologies avoid large-scale excavation and soil transportation, and have the advantages of lower cost and less site disturbance. Among them, in-situ leaching and soaking technologies, which inject remediation agents into contaminated soil to desorb heavy metals from soil particles and remove them with the liquid, are effective remediation methods.

[0003] However, existing in-situ leaching technologies have significant drawbacks in practical engineering applications: First, for soils with good permeability, the injected remediation agent solution is prone to uncontrolled lateral and vertical migration and diffusion within the treatment area. This not only leads to a large loss of the remediation agent and a sharp increase in costs, but more seriously, it may carry the contaminated liquid (precious liquid) enriched with heavy metals to the surrounding clean soil and groundwater, causing secondary pollution and posing a high environmental risk. Second, existing technical systems mostly focus on pollutant removal as the sole objective, with the treatment process ending at the extraction and harmless disposal of the contaminated liquid. When the soil contains heavy metals with high economic value, this method directly results in the loss of precious metal resources, failing to achieve synergy between pollution control and resource recovery, resulting in low economic efficiency. Furthermore, for poorly permeable clayey soils, traditional gravity leaching is extremely inefficient and has a long remediation cycle.

[0004] Therefore, there is an urgent need to develop an improved in-situ soaking and rinsing treatment method and apparatus that can effectively constrain the migration of the chemical solution, prevent secondary pollution, integrate a resource recovery unit, and adapt to different permeable soils to improve treatment efficiency, thereby maximizing environmental and economic benefits. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the above-mentioned background technology and to propose a method and apparatus that is convenient to construct, simple to operate, can prevent the leakage of remediation fluid and precious liquid, and can quickly and effectively remove heavy metals from the soil while also recovering heavy metals.

[0006] The technical solution of this invention is: a method for in-situ soaking and leaching treatment of heavy metals in soil, comprising the following steps: The system deployment includes: constructing an isolation system around and at the bottom of the treatment area, as well as constructing a liquid injection system, a monitoring system, a pumping system, and a recovery system; The process of pumping and irrigating includes: starting the pumping system to continuously pump out soil moisture in the treatment area, monitoring the groundwater level through the monitoring system until it stabilizes at the target depth; then starting the irrigating system to irrigate the remediation agent solution to the ground surface. Static soaking includes: stopping the injection and allowing the soil to soak in the remediation agent solution; Sampling and testing include: extracting and testing the concentration of heavy metals from the soil, and determining whether to proceed with the heavy metal recovery step based on the test results; if not, return to the static soaking step. Heavy metal recovery includes: starting the pumping system to pump out the liquid in the soil pores as a precious liquid and send it to the recovery system for refining; after refining, the tail liquid is replenished with a remediation agent and then reinjected into the treatment area; repeating this step and controlling the circulation based on the detection of the pumped liquid and soil. Rinsing the soil with clean water ensures that the residual amount of remediation agent meets environmental requirements.

[0007] Preferably, the isolation system includes a sealing side wall surrounding the treatment area and a sealing bottom wall at the bottom of the treatment area. The sealing side wall is a steel sheet pile wall formed by continuous interlocking or a mud mixing pile wall formed by overlapping each other. The sealing bottom wall is a water-stopping structure formed by overlapping high-pressure jet grouting piles.

[0008] Preferably, the irrigation system includes a remedial agent solution tank, an irrigation pump, and an irrigation pipeline network laid on the ground of the treatment area for injecting the remedial agent solution into the soil; The irrigation network includes irrigation filter pipes laid longitudinally along the treatment area, and multiple irrigation filter pipes are arranged in rows at intervals along the transverse side of the treatment area. The irrigation network also includes an irrigation main pipe laid transversely along the treatment area to connect the entire row of irrigation filter pipes. The irrigation main pipe is connected to the outlet of the irrigation pump, and the inlet of the irrigation pump is connected to the repair agent solution pool.

[0009] Furthermore, the pumping system includes multiple water collection wells, a high-energy water pump, a pumping pipeline, and return liquid pool A and return liquid pool B, all located within the treatment area. Each water collection well is equipped with a wellpoint pipe structure, which is connected to the inlet of the high-energy water pump via the pumping pipeline. The outlet of the high-energy water pump is provided with a return pipeline leading to return liquid pool A. Return liquid pool A is connected to return liquid pool B via a first pumping pipeline, and return liquid pool B is connected to the repair agent liquid pool via a second pumping pipeline. The wellpoint pipe structure includes an outer pipe and a suction pipe installed inside the outer pipe. A filter pipe is installed at the lower end of the outer pipe to filter the incoming liquid. An ejector is also installed inside the outer pipe to spray the liquid upwards. The outlet of the ejector is connected to the bottom end of the suction pipe. The upper end of the suction pipe is connected to the inlet of a high-energy water pump via a pumping pipe. The annular space between the outer pipe and the well wall is filled from bottom to top with a medium-coarse sand layer and a clay layer. More preferably, the medium-coarse sand layer is filled to a height of 2-3 meters from the bottom of the well to the ground surface, and the clay layer is filled to a height from the top of the medium-coarse sand layer to the ground surface.

[0010] Furthermore, the outer tube is a PVC water pipe or an electrode tube; When the outer tube is an electrode tube, the system layout steps also include the construction of an electroosmosis system. The electroosmosis system includes a dedicated electroosmosis power supply device and electrode plates set in the treatment area. The electrode plates and electrode tubes in the treatment area are arranged in rows at horizontal intervals. Multiple rows of electrode plates and multiple rows of electrode tubes are arranged alternately at intervals along the longitudinal direction of the treatment area. All electrode tubes are electrically connected to the same pole of the dedicated electroosmosis power supply device, and all electrode plates are electrically connected to the other pole of the dedicated electroosmosis power supply device. The electroosmosis system also includes an electroosmosis pipe leading out from the pumping pipe, the other end of which is connected to the main irrigation pipe; electroosmosis control valves are provided on the electroosmosis pipe and between the electroosmosis pipe connection point on the pumping pipe and the high-energy water pump.

[0011] Furthermore, the monitoring system includes a pore water pressure probe, a groundwater level well, and a soil moisture content probe installed within the treatment area; The recycling system includes a recycling pipeline connected in parallel with the return pipeline and recycling equipment installed on the recycling pipeline. Furthermore, the monitoring system includes pore water pressure probes and groundwater level wells to monitor the groundwater level in the treatment area during the pumping process. The monitoring system also includes soil moisture content probes to calculate the concentration C1 of the remediation agent solution used in the irrigation.

[0012] Furthermore, in the drainage and irrigation steps, the concentration C1 of the remediation agent solution used for irrigation is calculated based on the soil moisture content w1 measured on-site after drainage, combined with the soil specific gravity G, void ratio e, and the target baseline concentration C0 of the remediation agent solution obtained in the previous work. The calculation formula is C1=C0×(e / (e-w1×G)), where the soil moisture content w1 is measured by a soil moisture meter, and both C1 and C0 are in mol / L.

[0013] Furthermore, when the outer tube is an electrode tube, in the pumping and irrigating steps, the electro-osmosis system is activated simultaneously to assist in the pumping process while the pumping system is pumping out soil moisture. Specifically, this includes: Open the electroosmosis control valve on the pumping pipeline and close the electroosmosis control valve on the electroosmosis pipeline. Start the high-energy water pump to pump the water accumulated in the collection well to the return liquid pool A. At the same time, turn on the electroosmosis special power supply equipment to make the pore water in the soil seep into the collection well.

[0014] Furthermore, when the outer tube is an electrode tube, in the pumping and filling steps, the electroosmosis system is simultaneously activated to assist filling when the filling system irrigates the repair agent solution, specifically including: The electroosmosis control valve on the extraction pipeline is closed, and the electroosmosis control valve on the electroosmosis pipeline is opened. The injection pump is started to inject the repair agent solution from the chemical solution tank into the soil through the injection pipeline network. At the same time, the dedicated electroosmosis power supply equipment is turned on to allow the repair agent solution from the chemical solution tank to seep into the soil through the collection well.

[0015] Furthermore, when the outer tube is an electrode tube, in the heavy metal recovery step, the electroosmosis system is simultaneously activated to assist in the drainage process when pumping out the pore fluid in the soil, specifically including: The electroosmosis control valve on the pumping pipeline is opened and closed. The high-energy water pump is started to pump out the pore liquid in the soil as a precious liquid and send it to the recovery equipment. At the same time, the dedicated electroosmosis power supply is turned on to allow the pore water in the soil to seep into the collection well. The tail liquid extracted and discharged by the recovery equipment is returned to the return liquid pool A, pumped to the return liquid pool B to replenish the repair agent, and then returned to the chemical pool of the irrigation system. It continues to irrigate the treatment area through the irrigation pipeline network.

[0016] Preferably, the process of rinsing the soil with clean water specifically includes: pumping out accumulated water in the treatment area until the groundwater level stabilizes and drops to a preset level; and then rinsing the treatment area with clean water until the water level reaches the ground surface. Extract the liquid sample and determine whether the remediation agent content meets environmental requirements. If yes, the treatment ends; otherwise, simultaneously start the irrigation system to irrigate with clean water and the drainage system to extract the liquid until the remediation agent content in the soil sample meets environmental requirements.

[0017] The present invention also provides an apparatus for in-situ leaching and treatment of soil heavy metals according to any of the above-described methods, comprising an isolation system, a pumping system, an irrigation system, a recovery system, and a monitoring system. The isolation system is located around and at the bottom of the processing area to form an isolated reaction zone that is open at the top; The irrigation system includes a remedial agent solution tank, an irrigation pump, and an irrigation pipeline network laid on the ground of the treatment area for injecting the remedial agent solution into the soil. The irrigation system also includes a geotextile covering the surface of the treatment area and a sealing membrane located above the geotextile. The pumping system includes a water collection well, a high-energy water pump, a pumping pipeline, and return pools A and B, all located within the treatment area. The water collection well is equipped with a wellpoint pipe structure and is connected to the inlet of the high-energy water pump via the pumping pipeline. The outlet of the high-energy water pump is connected to the return pool A via a return pipeline. The return pool A is connected to the return pool B via a first pumping pipeline, and the return pool B is connected to the repair agent solution pool via a second pumping pipeline. The recycling system includes a recycling pipe connected in parallel with the return pipe and recycling equipment installed on the recycling pipe; The monitoring system includes a pore water pressure probe, a groundwater level well, and a soil moisture content probe installed within the treatment area.

[0018] The beneficial effects of this invention are: (1) The method of the present invention uses a high-energy water pump to drain the groundwater, recharge the remediation agent solution and soak it, and then circulates and pumps out the heavy metal-containing solution and recharges the remediation agent solution to rinse the contaminated soil. This method can remove heavy metals from the soil in a simple, economical and efficient way.

[0019] (2) The recycling system set in the method of the present invention can refine the liquid medicine (precious liquid) containing heavy metals, so as to realize the recycling and utilization of important metal resources.

[0020] (3) The present invention uses a method of treating heavy metals in soil by collecting water from wells, followed by recharge, soaking and leaching. This method can treat heavy metals in soils of various depths. For contaminated soils of different depths, corresponding rainwater well systems can be selected, with a maximum depth exceeding 100m.

[0021] (4) The method of the present invention treats heavy metals in soil by in-situ soaking and leaching, without the need to excavate and transport contaminated soil, and can treat heavy metals in very deep soil. Therefore, this method can be used for the treatment of precious metal tailings and has great value for the secondary development and utilization of precious metal tailings.

[0022] (5) The method of the present invention is also a simple, economical and efficient treatment method for groundwater pollution. By draining the groundwater and then refilling it with clean water, the groundwater pollution problem can be completely solved.

[0023] (6) The method of the present invention can treat various types of soil heavy metal pollution. For soil with good permeability, a general water collection well can be used to collect water by gravity; for soil with poor permeability, an electro-osmotic dewatering well can be used to accelerate the seepage of the remediation agent into the water collection well through the combined action of gravity and electro-osmotic force, thereby accelerating the leaching efficiency of the agent.

[0024] (7) The sealing film covering the ground prevents the evaporation of the repair agent, which reduces the consumption of the agent, lowers the cost of heavy metal repair projects, and prevents the agent from evaporating and polluting the surrounding air.

[0025] (8) The isolation system can keep the repair agent and the agent containing heavy metals within the range of the soil being treated, ensuring the soaking effect and preventing the loss of precious liquid; at the same time, the isolation system prevents the leakage of the agent and prevents the agent from polluting the surrounding soil.

[0026] (9) By pumping out the pesticide solution in the soil and re-irrigating with clean water through the pumping and irrigation system, the pesticide solution in the soil can be replaced and discharged more fully, thereby achieving a very ideal soil purification effect. Attached Figure Description

[0027] Figure 1 This is a flowchart of the in-situ soaking and leaching method for treating heavy metals in soil, as described in Example 1. Figure 2 This is a schematic diagram of the plan layout of the irrigation system in Example 1.

[0028] Figure 3 This is a schematic diagram of the layout of the pumping system (jet well point) and recovery system in Example 1.

[0029] Figure 4 This is a vertical schematic diagram of the pumping system (jet well point) and recovery system structure in Example 1.

[0030] Figure 5 for Figure 4 Enlarged view of point A in the middle.

[0031] Figure 6 This is a flowchart of the in-situ soaking and leaching method for treating heavy metals in soil, as shown in Example 2. Figure 7 This is a schematic diagram of the layout of the pumping system (electroosmotic well point) and the recovery system in Example 2.

[0032] Figure 8 This is a vertical schematic diagram of the pumping system (electroosmotic well point) and recovery system structure in Example 2 (in the state of pumping groundwater).

[0033] Figure 9 for Figure 8 Enlarged view of section B in the middle.

[0034] Figure 10 This is a schematic diagram of the plan layout of the electroosmotic well points in Example 2.

[0035] Figure 11 This is a vertical schematic diagram of the structure of the pumping system (electroosmotic well point) and recovery system in Example 2 (in the state of fluid injection).

[0036] Figure 12 This is a schematic diagram of the heavy metal recovery status of the pumping system (electroosmotic well point) and the recovery system in Example 2.

[0037] The components are: 1-treatment area, 2-collection well, 3-high-energy water pump, 4-liquid extraction pipe, 5-injection filter pipe, 6-injection main pipe, 7-injection pump, 8-PVC water pipe, 9-recovery equipment, 10-return tank A, 11-return tank B, 12-control valve, 13-repair agent solution tank, 14-sealing membrane, 15-geotextile, 16-sealing sidewall, 17-sealing bottom wall, 19-threaded connection and sealing, 20-four-way pipe, 21-clay layer, 2 2-Medium-coarse sand layer, 23-Pore water pressure probe, 24-Groundwater level well, 25-Soil moisture content probe, 26-Electrode tube, 27-Electrode plate, 28-Negative electrode, 29-Positive electrode, 30-Electroosmosis power supply, 31-Suction pipe, 32-Ejector, 33-Filter pipe, 34-Recovery pipe, 35-Return pipe, 36-First pumping pipeline, 37-Second pumping pipeline, 38-Connecting seat, 39-Electroosmosis control valve, 40-Electroosmosis pipeline. Detailed Implementation

[0038] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. The following specific embodiments will further describe the present invention in detail.

[0039] Example 1 like Figures 2-5 As shown in the figure, this embodiment provides an in-situ soaking and leaching device for treating heavy metals in soil, which is mainly composed of five parts: an isolation system, a pumping system, an irrigation system, a recovery system, and a monitoring system.

[0040] The isolation system forms the basis of in-situ soaking and rinsing. Its purpose is to enclose the treatment area 1 around its perimeter and bottom, forming an open-top isolated reaction zone to prevent the loss of chemical and precious solutions. The isolation system includes a sealing side wall 16 surrounding the treatment area 1 and a sealing bottom wall 17 located at the bottom of the area. The sealing side wall 16 is formed by continuous interlocking of steel sheet piles or by overlapping mud mixing piles; the sealing bottom wall 17 is constructed using a high-pressure jet grouting device.

[0041] The pumping system includes a collection well 2, a high-energy water pump 3, a pumping pipe 4, and a return liquid pool group, all located in the treatment area 1. The collection well 2 is equipped with a wellpoint pipe structure and is connected to the inlet of the high-energy water pump 3 via the pumping pipe 4. The high-energy water pump 3 and the return liquid pool group are both located on the side outside the treatment area 1. The return liquid pool group includes a return liquid pool A10 and a return liquid pool B11 arranged along the flow direction. A return pipe 35 is provided at the outlet of the high-energy water pump 3, leading to the return liquid pool A10.

[0042] The wellpoint pipe structure includes an outer pipe and a suction pipe 31 installed inside the outer pipe. A filter pipe 33 is installed at the lower end of the outer pipe to filter the incoming liquid. An ejector 32 is also installed inside the outer pipe to spray the liquid upwards. The outlet of the ejector 32 is connected to the bottom end of the suction pipe 31. The upper end of the suction pipe 31 is connected to the inlet of a high-energy water pump 3 via a pumping pipe 4. The ejector 32 and the high-energy water pump 3 maintain constant linkage during operation. Figure 5 As shown, the outer pipe is connected to the filter pipe 33 vertically. In some preferred embodiments, the outer pipe and the filter pipe 33 are connected by a connecting seat 38. The connecting seat 38 can be a shrink tube or other connecting pipe fittings. The filter pipe 33 can be a steel pipe with a closed lower end and filter holes evenly distributed on the entire side wall. In some preferred embodiments, the outer surface of the side wall is also wrapped with a filter screen to further increase the filtration efficiency.

[0043] The annular space between the outer pipe of the wellpoint pipe structure and the well wall of the collection well 2 is filled from bottom to top with a medium-coarse sand layer 22 and a clay layer 21. The medium-coarse sand layer 22 is filled to a height of 2-3m from the bottom of the well to the ground, and the clay layer 21 is filled to a height of 0.5-1.0m from the top of the medium-coarse sand layer 22 to the ground. The collection well 2 is located above the sealing bottom wall 17, with its bottom 0.5-1.0m away from the sealing bottom wall 17, to avoid damaging the sealing bottom wall 17 during drilling of the collection well 2.

[0044] Depending on the depth of the contaminated soil to be treated, different wellpoint dewatering systems can be selected: for contaminated soil depths less than 6m, lightweight wellpoint dewatering can be used; for contaminated soil depths of 6-20m, jet wellpoint dewatering can be used; for contaminated soil depths of 20-40m, tubular wellpoint dewatering can be used; and for contaminated soil depths greater than 40m, deep wellpoint dewatering can be used. This embodiment uses jet wellpoint dewatering based on the depth of the contaminated soil.

[0045] The outer pipe in the wellpoint pipe structure can be either a regular PVC water pipe (8) or an electrode pipe (26), depending on the permeability of the soil. For soils with good permeability (permeability coefficient k ≥ 0.1 m / d), gravity dewatering is used, with a regular PVC water pipe (8) as the outer pipe, allowing groundwater to flow to the collection well under gravity. This embodiment illustrates this approach. For soils with poor permeability (permeability coefficient k < 0.1 m / d), electroosmotic dewatering is used, with an electrode pipe (26) as the outer pipe and an accompanying electroosmotic system, allowing groundwater to flow to the collection well under the combined action of electroosmotic force and gravity.

[0046] The injection system includes a remedial agent solution tank 13 located on one side of the treatment area 1, an injection pump 7, and an injection pipeline network laid on the ground of the treatment area 1 for injecting the remedial agent solution into the soil. The return tank A10 in the pumping system is connected to the return tank B11 via the first pumping pipeline 36, and the return tank B11 is connected to the remedial agent solution tank 13 via the second pumping pipeline 37.

[0047] The layout of the irrigation pipeline network is as follows: Figure 2 As shown, Figure 2 The treatment area 1 is divided into two sections: left-right and right-right (length direction) and up-down (width direction). The irrigation network includes irrigation filter pipes 5 and irrigation main pipes 6. Irrigation filter pipes 5 are laid longitudinally along the treatment area 1, with multiple pipes arranged in rows at intervals along the transverse direction. The longitudinal ends of each filter pipe 5 are near the longitudinal edge of the treatment area 1, and the entire row of filter pipes extends to the surface of the entire treatment area 1. Each filter pipe 5 has irrigation holes on its periphery, allowing the entire site to be infused with the remedial agent. The irrigation main pipe 6 is laid transversely along the treatment area 1, connecting the rows of filter pipes 5. The irrigation main pipe 6 is connected to the outlet of the irrigation pump 7, and the inlet of the pump 7 is connected to the remedial agent pool 13. In some preferred embodiments, the irrigation main pipe 6 is connected to each filter pipe 5 via a four-way pipe 20. Each of the four ends of the four-way pipe 20 is equipped with threaded connections and seals 19 to achieve a sealed connection between the pipes.

[0048] The irrigation main pipe 6 can be a single pipe or multiple pipes spaced longitudinally. In some preferred embodiments, when the longitudinal dimension of the treatment area 1 is large, setting multiple irrigation main pipes 6 can divide the large treatment area into multiple supply zones, thereby shortening the liquid delivery path, significantly reducing hydraulic losses, ensuring more balanced irrigation pressure and flow in each area, effectively avoiding uneven local irrigation, and improving the overall irrigation efficiency and operational stability of the system. In this embodiment, two irrigation main pipes 6 are spaced longitudinally. The inlets of all irrigation main pipes 6 converge and are connected to the outlet of the irrigation pump 7. When the irrigation pump 7 starts, the repair agent liquid in the repair agent liquid tank 13 is pumped by the irrigation pump 7 to all irrigation main pipes 6, and then the repair agent liquid is injected into the entire site through the irrigation filter pipe 5.

[0049] The injection system also includes a geotextile 15 covering the treatment area 1 and a sealing membrane 14 above the geotextile 15. Covering the ground with the sealing membrane prevents the evaporation of the remediation agent, which reduces the consumption of the agent, lowers the cost of heavy metal remediation projects, and prevents the agent from evaporating and polluting the surrounding air.

[0050] The recycling system includes a recycling pipe 34 connected in parallel with the return pipe 35 and a recycling device 9 installed on the recycling pipe 34. Control valves 12 are installed on the recycling pipe 34 and on the pipe section of the return pipe 35 connected in parallel with the recycling pipe 34, for controlling the flow of the pumped liquid from the outlet of the high-energy water pump 3 to the recycling device 9 or the return liquid pool A10.

[0051] The monitoring system includes a pore water pressure sensor 23, a groundwater level well 24, and a soil moisture content sensor 25, all installed within treatment area 1. The pore water pressure obtained from the pore water pressure sensor 23 and the measured groundwater level obtained from the groundwater level well 24 are used to monitor changes in the groundwater level during the pumping process. The measured soil moisture content obtained from the soil moisture content sensor 25 is used to calculate the concentration C1 of the injected remediation agent solution.

[0052] like Figure 1 As shown, the in-situ leaching method for treating heavy metals in soil according to the present invention is carried out using the above-mentioned apparatus according to the following steps. Before on-site construction, preparatory work must be completed: ① Conduct on-site investigation of the area to be treated to understand the distribution of soil layers, the physical and mechanical properties of the soil (especially permeability), and the types, contents, and forms of heavy metals in the soil.

[0053] ② Select an appropriate remediation agent based on the type and occurrence state of the heavy metal and the characteristics of this method. In this embodiment, the heavy metal to be treated is nickel (Ni), and the remediation agent is disodium EDTA.

[0054] ③ Through indoor batch testing, the target baseline concentration C0 of the repair agent solution and the proposed soaking time T0 were determined, and the heavy metal content P0 of the liquid extracted after soaking was analyzed and estimated.

[0055] S1, System Deployment (1) Construction isolation system 16. Sealed sidewalls constructed using sheet piles or mixing piles: The Larssen sheet pile wall system employs a self-sealing waterproofing system with a waterproofing grade of not less than P6, using a lock-type waterproofing structure. The sheet pile model is determined based on the thickness of the soil layer to be treated: (i) when the soil thickness is ≤8m, model SP-II is selected; (ii) when 8m ≤ soil thickness ≤12m, model SP-III is selected; (iii) when 12m ≤ soil thickness ≤18m, model SP-IV is selected. Sheet piles are driven to the required depth around the area of ​​the soil to be treated, according to relevant technical specifications.

[0056] Double-row interlocking mixing piles are used for sealing and water stoppage. Bentonite is used as the mixing material for the mud slurry, with a mud slurry specific gravity of 1.30~1.40 and a mud slurry mixing ratio of >35%. The permeability coefficient of the mud-mixed pile wall is ≤1×10⁻⁶. -5 cm / s. A four-spray, four-mix construction process was adopted, and mud-mixing piles were driven to the design requirements according to relevant specifications.

[0057] Construction of the sealing bottom wall 17: High-pressure jet grouting piles are used to form a sealing wall 2-3m below the bottom of the treatment area. The triple pipe construction process is adopted, with overlapping arrangement, pile spacing of 1.5-2.0m, overlap size of adjacent jet grouting piles ≥300mm, and actual pile length (i.e., vertical thickness of the wall) of 0.8-1.5m to ensure reliable bottom sealing.

[0058] (2) Construction exhaust system According to the design requirements, a drilling rig is used to pre-drill holes to 0.5~1.0m above the sealing bottom wall 17, with the hole diameter being 10~30mm larger than the outer diameter of the outer pipe, forming a water collection well 2; the filter pipe 33, the ejector 32, the suction pipe 31, and the outer pipe are connected to form an integral well point pipe structure; the assembled well point pipe structure is slowly lowered into the water collection well 2 using a crane, ensuring that the filter pipe 33 is completely located in the aquifer; the annular space between the outer pipe and the hole wall is filled with a layer of coarse sand 22, with the filling height from the bottom of the well to 2~3m above the ground, and the top is sealed with a layer of clay 21.

[0059] A pumping pipe 4 is laid on the ground. The pumping pipe 4 is connected to the suction pipe at the opening of all the water collection wells 2. The outlet of the pumping pipe 4 is led out of the site.

[0060] (3) Install monitoring system In treatment area 1, pore water pressure probes 23 and groundwater level wells 24 are installed as per design requirements to monitor changes in groundwater level when the pumping system is started and when the remediation agent is reinjected. Soil moisture content probes 25 are installed to monitor the moisture content of each soil layer after the groundwater level drops.

[0061] (4) Construction grouting system A liquid injection filter pipe 5 is laid on the ground. The liquid injection filter pipe 5 is connected to the liquid injection main pipe 6 through a four-way pipe 20. On the surface of the treatment area 1, a layer of woven geotextile 15 is first laid on top of the liquid injection filter pipe 5 and the liquid injection main pipe 6 to protect the sealing membrane, and then a sealing membrane 14 is covered on top. The liquid extraction pipe 4 and the liquid injection main pipe 6 pass through the sealing membrane 14.

[0062] (5) Install the recycling system and related pipelines A high-energy water pump 3 and an injection pump 7 are installed on one side outside the treatment site 1. A chemical solution tank 13, a return tank A10, and a return tank B11 are excavated. The outlet of the extraction pipe 4 is connected to the inlet of the high-energy water pump 3. A parallel recovery pipe 34 and a return pipe 35 are installed at the outlet of the high-energy water pump 3. A recovery device 9 is installed on the recovery pipe 34. Control valves 12 are installed near the parallel connection points of the return pipe 35 and the recovery pipe 35. The outlets of both the return pipe 35 and the recovery pipe 35 lead to the return tank A10. A first pumping pipe 36 is installed to connect the return tank A10 to the return tank B11, and a second pumping pipe 37 is installed to connect the return tank B11 to the chemical solution tank 13. The inlet of the injection pump 7 is connected to the chemical solution tank 13, and its outlet is connected to the injection main pipe 6.

[0063] S2, pumping and filling The pumping system is activated, using high-energy water pump 3 to extract water from the collection well 2 and discharge it into the return liquid tank A10 to lower the groundwater level in the treatment area 1 (at this time, control valve 12 on the recovery pipe 34 is closed, and control valve 12 on the return pipe 35 is open). Pumping continues, while the groundwater level is monitored using pore water pressure probe 23 and groundwater level pipe 24. Pumping is stopped when the groundwater level is observed to have stabilized at the target depth.

[0064] After pumping stops, the soil moisture content w1 is measured using a soil moisture meter 25. Combined with the soil's specific gravity G, void ratio e, and the target baseline concentration C0 of the remediation agent obtained from previous work, the required concentration C1 of the remediation agent to be injected into the soil for full filling is calculated: C1 = C0 × (e / (e-w1×G)). In this embodiment, C0 = 0.15 mol / L, G = 2.65, e = 1.20, w1 = 25%, C1 = 0.15 × (1.20 / (1.20-25%×2.65)) = 0.335 mol / L. Specific gravity G refers to the ratio of the material's density to the density of standard water.

[0065] A repair agent solution with a concentration of C1 is prepared in the chemical solution tank 13. The irrigation system is started, and the irrigation pump 7 draws the repair agent solution from the chemical solution tank 13 and irrigates the surface of the treatment area 1 through the irrigation main pipe 6 and the irrigation filter pipe 5. The water level change during the irrigation is observed using the pore water pressure probe 23 and the groundwater level pipe 24. Irrigation is stopped when the solution level reaches the surface of the treatment area 1.

[0066] S3, let it stand and soak Stop the infusion and begin static soaking. The initial soaking time is T0, which is 10 to 15 days.

[0067] S4. Sampling and Testing After the soil has been left to stand for a period of time until T0, the soil is sampled and the concentration of heavy metals in the liquid is tested. The sample is then tested to determine whether the concentration of heavy metals meets the preset range (in this embodiment, the preset range of heavy metal concentration is ≥P0, P0=200mg / L). If it does, the next step of heavy metal recovery is performed. Otherwise, step S3 of standing soaking is repeated for a period of time T1=5~8 days until the concentration of heavy metals detected by the sample meets the preset range.

[0068] S5, Heavy Metal Recycling After the heavy metal content of the drainage solution is sampled and tested to meet the preset requirements, the removal and recovery of heavy metals in the soil are achieved through the organic combination and cyclical operation of the drainage system, the refining system, and the re-injection system.

[0069] Switch control valve 12 (i.e., control valve 12 on the recovery pipeline 34 is open, and control valve 12 on the return pipeline 35 is closed), start high-energy water pump 3 to pump the heavy metal-containing liquid (precious liquid) from the collection well to the recovery equipment 9, and adsorb, enrich and refine the precious liquid to obtain high-grade heavy metal products; the liquid discharged from the recovery system is then transported back to the return liquid pool B11, and an appropriate amount of remediation agent is added to make the liquid concentration reach concentration C0, and then pumped back to the liquid pool 13, and continued to be irrigated into the soil of the treatment area 1 through the irrigation system. The process of circulating and draining precious liquid, recovering heavy metal products, and refilling the remediation agent solution is based on the detection and control of the drained liquid and soil. Specifically, the circulation continues until the following two requirements are met simultaneously: (1) the grade of the extracted precious liquid is no longer sufficient to effectively extract heavy metal products, specifically the grade of the precious liquid (nickel concentration) < 30 mg / L, and (2) the heavy metal content in the soil has reached the relevant requirements of the relevant environmental protection regulations, specifically the soil heavy metal content (nickel content) < 60 mg / kg.

[0070] S6, Soil washing solution After the pumping, recovery, and reinjection processes in step S5 have met the predetermined requirements, the injection system is shut down, and control valve 12 is switched to connect the return pipe 35 to the return liquid pool A10. The pumping system is then started, and the liquid from the collection well 2 is pumped to the return liquid pool A10 via the high-energy water pump 7 until the groundwater level is observed to have stabilized at the target depth through the pore water pressure probe 23 and the groundwater level pipe 24, at which point pumping is stopped.

[0071] Start the irrigation system, replace the chemical tank 13 with clean water, start the irrigation pump 7, and spray clean water onto the ground of the treatment area 1 through the irrigation main pipe 6 and the irrigation filter pipe 5. Continue the irrigation process until the groundwater overflows onto the ground, then shut down the irrigation system.

[0072] The soil remediation agent content is sampled and tested to see if it meets environmental requirements (i.e., residual remediation agent concentration < 20 mg / kg). If not, the pumping and irrigation systems are started simultaneously. The simultaneous start-up operation is as follows: control valve 12 on the recovery pipe 34 is closed, control valve 12 on the return pipe 35 is opened, irrigation pump 7 is started to irrigate with clean water, and high-energy water pump 3 is started to pump out the liquid in the soil until the sampling results meet the environmental requirements of < 20 mg / kg.

[0073] Example 2 like Figures 7-10 As shown, this embodiment provides an apparatus for in-situ soaking and leaching treatment of heavy metals in soil. Except that the outer pipe of the pumping system adopts an electrode tube 26 and the entire apparatus also includes an electroosmosis system, the rest is basically the same as that in Embodiment 1.

[0074] When the outer tube is an electrode tube 26, the electroosmosis system includes a dedicated electroosmosis power supply device 30 and electrode plates 27 installed in the treatment area 1. The electrode plates 27 and electrode tubes 26 are arranged laterally in rows within the treatment area 1, with multiple rows of electrode plates 27 and multiple rows of electrode tubes 26 arranged alternately along the longitudinal direction of the treatment area 1. As needed, all electrode tubes 26 are connected to one of the positive or negative terminals of the dedicated electroosmosis power supply device 30, and all electrode plates 27 are electrically connected to the other terminal of the dedicated electroosmosis power supply device 30. In this embodiment, the electrode plates 27 and electrode tubes 26 are commonly used components in the field of electroosmosis. The electrode tubes 26 have no openings in their walls and copper wires are embedded axially inside. Copper wires are arranged along the length of the electrode plates 27.

[0075] The electroosmosis system also includes an electroosmosis pipe 40 extending from the extraction pipe 4, with the other end of the electroosmosis pipe 40 connected to the irrigation network. Electroosmosis control valves 39 are installed on both the electroosmosis pipe 40 and downstream of the connection point on the extraction pipe 4, which can be used to control the flow of the pumped liquid from the extraction pipe 4 to the high-energy water pump 3 or the irrigation network. In this embodiment, the other end of the electroosmosis pipe 40 is connected between the confluence of all irrigation main pipes 6 and the outlet of the irrigation pump 7.

[0076] Electrode tubes 26 and electrode plates 27 are arranged in processing area 1 as follows: Figure 10 As shown, each electrode plate 27 is arranged laterally along the processing area 1 in the width direction. In some preferred embodiments, the interval between two adjacent electrode plates 27 in each row of electrode plates 27 is less than the interval between two adjacent electrode plates 27 in each row of electrode tubes 26. Multiple rows of electrode plates 27 and multiple rows of electrode tubes 26 are arranged alternately at equal intervals along the longitudinal direction of the processing area 1. More preferably, twice the interval between two adjacent electrode plates 27 in each row of electrode plates 27 is equal to the interval between two adjacent electrode tubes 26 in each row of electrode tubes 26.

[0077] like Figure 6 As shown, the in-situ immersion and leaching method for treating heavy metals in soil according to the present invention is carried out using the above-mentioned apparatus according to the following steps. Before on-site construction, the preparatory work is completed in accordance with Example 1. Similarly, the heavy metal to be treated is nickel, and the remediation agent is disodium EDTA.

[0078] S1, System Deployment (1) Construction isolation system, refer to Example 1 (2) Construction drainage system and electroosmosis system According to the design requirements, a pre-drilling machine is used to drill holes 0.5-1.0m above the sealing bottom wall 17, with the hole diameter being 10-30mm larger than the outer diameter of the outer pipe, forming a water collection well 2. The filter pipe 33, ejector 32, suction pipe 31, and outer pipe (electrode pipe 26) are connected to form an integral well point pipe structure. A crane is used to slowly lower the assembled well point pipe structure into the water collection well 2, ensuring that the filter pipe 33 is completely located in the aquifer. The annular space between the outer pipe and the borehole wall is filled with coarse sand 22, with the filling height from the bottom of the well to 2-3m above the ground, and the top is sealed with clay 21. According to the design requirements, electrode plates 27 are installed around the electrode pipe 26 using a plate inserter.

[0079] A liquid extraction pipe 4 is laid on the ground. The liquid extraction pipe 4 is connected to the suction pipe at the opening of all the water collection wells 2, and the outlet of the liquid extraction pipe 4 is led out of the site. All the electrode tubes 26 are electrically connected together with wires and led out of the site; all the electrode plates 27 are electrically connected together with wires and led out of the site.

[0080] (3) Install a monitoring system; (4) Install a construction grouting system (refer to Example 1). (5) Install recycling equipment and related pipelines A high-energy water pump 3 and an injection pump 7 are installed on one side outside the treatment site 1. A chemical solution tank 13, a return tank A10, and a return tank B11 are excavated. The outlet of the extraction pipe 4 is connected to the inlet of the high-energy water pump 3. A parallel recovery pipe 34 and a return pipe 35 are installed at the outlet of the high-energy water pump 3. A recovery device 9 is installed on the recovery pipe 34. Control valves 12 are installed near the parallel connection points of the return pipe 35 and the recovery pipe 34. The outlets of both the return pipe 35 and the recovery pipe 34 lead to the return tank A10. A first pumping pipe 36 is installed to connect the return tank A10 to the return tank B11, and a second pumping pipe 37 is installed to connect the return tank B11 to the chemical solution tank 13. The inlet of the injection pump 7 is connected to the chemical solution tank 13, and the inlet of the injection main pipe 6 merges with and connects to the outlet of the injection pump 7.

[0081] An electroosmosis pipe 40 is installed near the high-energy water pump 3 on the extraction pipe 4. Electroosmosis control valves 39 are installed on the electroosmosis pipe 40 and downstream of the connection point of the electroosmosis pipe 40 on the extraction pipe 4. A dedicated electroosmosis power supply device 30 is installed on one side outside the treatment site 1. All electrode tubes 26 and all electrode plates 27 are electrically connected to the two poles of the dedicated electroosmosis power supply device 30.

[0082] S2, pumping and filling like Figure 8 As shown, the pumping system is activated, using high-energy water pump 3 to extract water from the collection well 2 and discharge it into the return liquid pool A10 to lower the groundwater level in the treatment area 1. Simultaneously, the electroosmosis power supply 30 (10-60V) is turned on, with the positive terminal connected to electrode plate 27 and the negative terminal connected to electrode tube 26. This, combined with gravity and electroosmotic force, accelerates the seepage of pore water into the collection well 2. The electroosmosis control valve 39 on the pumping pipe 4 is opened, and the electroosmosis control valve 39 on the electroosmosis pipe 40 is closed. The control valve 12 on the recovery pipe 34 is closed, and the control valve 12 on the return pipe 35 is opened, pumping the water from the collection well 2 into the return liquid pool A10. Pumping continues in the collection well 2, while the groundwater level is monitored using the pore water pressure probe 23 and the groundwater level pipe 24. Pumping stops when the groundwater level has stabilized at the target depth.

[0083] After pumping is stopped, the water content w1 of soil layers at different depths is measured using soil moisture meter 25. Combined with the soil specific gravity G, void ratio e obtained from previous work, and the target baseline concentration C0 of the proposed remediation agent solution, the concentration of the remediation agent solution to be injected into the soil is calculated as C1 = C0 × (e / (e-w1 × G)). The remediation agent solution is prepared in solution tank 13, with a remediation agent concentration of C1.

[0084] like Figure 11As shown, the irrigation system is started, and the irrigation pump 7 extracts the repair agent solution from the chemical solution pool 13. The repair agent solution is then sprayed onto the surface of the treatment area 1 through the irrigation main pipe 6 and the irrigation filter pipe 5. At the same time, the electroosmosis control valve 39 is switched (the electroosmosis control valve 39 on the extraction pipe 4 is closed, and the electroosmosis control valve 39 on the electroosmosis pipe 40 is open), while the control valve 12 remains unchanged (the control valve 12 on the recovery pipe 34 is closed, and the control valve 12 on the return pipe 35 is open). The repair agent solution is injected into the collection well 2 through the well point pipe structure. The connection electrodes of the electrode plate 27, electrode pipe 26 and electroosmosis power supply 30 are switched, i.e., the negative electrode is connected to the electrode plate 27 and the positive electrode is connected to the electrode pipe 26. The electroosmosis power supply 30 is turned on, and the electroosmotic force accelerates the seepage of the repair agent solution into the soil through the collection well 2.

[0085] The water level changes during the injection of the chemical solution were observed using a pore water pressure probe 23 and a groundwater level pipe 24. When the chemical solution level reached the surface of the treatment area 1, the injection was stopped, and the injection pump 7 and the electroosmosis power supply 30 were turned off.

[0086] S3, let it stand and soak Stop the infusion and begin static soaking. The initial soaking time is T0, which is 10-15 days.

[0087] S4. Sampling and Testing After the soil has been left to stand for a period of time until T0, the soil is sampled and the concentration of heavy metals in the liquid is tested to determine whether it meets the preset requirements (in this embodiment, the heavy metal concentration requirement for the sampled liquid is ≥P0, P0=200mg / L). If yes, the next step of heavy metal recovery is carried out; if not, the process returns to S3 to continue standing and soaking. The soaking time is T1=5~8 days each time until the concentration of heavy metals detected by the sampled liquid meets the preset requirements.

[0088] S5, Heavy Metal Recycling After the heavy metal content of the drainage solution is sampled and tested to meet the preset requirements, the removal and recovery of heavy metals in the soil are achieved through the organic combination and cyclical operation of the drainage system, the refining system, and the re-injection system.

[0089] like Figure 12As shown, switch the electroosmosis control valve 39 (open the electroosmosis control valve 39 on the extraction pipe 4 and close the electroosmosis control valve 39 on the electroosmosis pipe 40); switch the connection electrodes of the electrode plate 27, electrode tube 26 and electroosmosis power supply 30, connect the positive electrode plate 27 and the negative electrode tube 26, turn on the electroosmosis power supply 30, and accelerate the seepage of the medicine in the pores into the collection well 2 by combining gravity and electroosmotic force; switch the control valve 12 (i.e., open the control valve 12 on the recovery pipe 34 and close the control valve 12 on the return pipe 35), start the high-energy water pump 3 to pump the medicine containing heavy metals (precious liquid) from the collection well 2 to the recovery equipment 9, and adsorb, enrich and refine the precious liquid to obtain high-grade heavy metal products; the liquid discharged from the recovery system is then transported back to the return liquid pool B11, and an appropriate amount of remediation agent is added to make the concentration of the medicine reach concentration C0, and then pumped back to the medicine pool 13, and the irrigation pump 7 is turned on to continue to irrigate the soil in the treatment area 1 through the irrigation pipeline network. Based on the detection and control cycle of the pumped liquid and soil, the specific process is as follows: the cycle continues until the following two preset requirements are met simultaneously: (1) the grade of the pumped liquid is no longer sufficient to effectively extract heavy metal products, i.e., the grade of the liquid (nickel concentration) is <30mg / L, and (2) the heavy metal content in the soil has reached the relevant requirements of the relevant environmental protection regulations, i.e., the heavy metal content in the soil is <60mg / kg.

[0090] S6, Soil leaching solution After the pumping, recovery, and reinjection processes in step S5 have met the predetermined requirements, the injection pump 7 is shut down, and the control valve 12 is switched (i.e., the control valve 12 on the recovery pipe 34 is closed, and the control valve 12 on the return pipe 35 is open), connecting the return pipe 35 to the return pool A10. The electroosmosis power supply 30 is turned on, keeping the positive electrode connected to the electrode plate 27 and the negative electrode connected to the electrode tube 26, and the state of the electroosmosis control valve 39 remains unchanged (the electroosmosis control valve 39 on the pumping pipe 4 is open, and the electroosmosis control valve 39 on the electroosmosis pipe 40 is closed). The pumping system is started, and the liquid from the collection well 2 is pumped to the return pool A10 by the high-energy water pump 3 until the groundwater level is observed to have stabilized and dropped to the target depth through the pore water pressure probe 23 and the groundwater level pipe 24, at which point pumping stops.

[0091] Switch the electroosmosis control valve 39 (close the electroosmosis control valve 39 on the pumping pipe 4, and open the electroosmosis control valve 39 on the electroosmosis pipe 40), keeping the control valve 12 unchanged, and recharge the collection well with clean water; switch the connection electrodes of the electrode plate 27, electrode tube 26, and electroosmosis power supply 30, connecting the negative terminal of the electroosmosis power supply 30 to the electrode plate 27 and the positive terminal to the electrode tube 26. Start the irrigation system, replace the chemical tank 13 with clean water, start the irrigation pump 7, and irrigate the ground of the treatment area 1 with clean water through the irrigation main pipe 6 and irrigation filter pipe 5; turn on the electroosmosis power supply 30, and let clean water seep into the soil 1 of the treatment area through the collection well 2. Continue the irrigation process until the groundwater overflows the ground, then shut down the irrigation system.

[0092] The soil remediation agent content is sampled and tested to see if it meets environmental requirements (i.e., residual remediation agent concentration < 20 mg / kg). If not, the pumping and irrigation systems are started simultaneously (i.e., the electroosmosis control valve 39 on the pumping pipe 4 is opened, the electroosmosis control valve 39 on the electroosmosis pipe 40 is closed, the control valve 12 on the recovery pipe 34 is closed, the control valve 12 on the return pipe 35 is opened, the positive terminal of the electroosmosis power supply 30 is connected to the electrode plate 27, the negative terminal is connected to the electrode tube 26, and the high-energy water pump 3, the irrigation pump 7, and the electroosmosis power supply 30 are started). Clean water is then pumped and drained until the sampling results meet environmental requirements.

Claims

1. A method for in-situ soaking and leaching treatment of heavy metals in soil, characterized in that, Includes the following steps: The system deployment includes: constructing an isolation system around and at the bottom of the treatment area (1), and constructing an injection system, a monitoring system, a pumping system and a recovery system; Pumping and irrigating include: starting the pumping system to continuously pump out soil moisture in the treatment area (1), monitoring the groundwater level through the monitoring system until it stabilizes at the target depth; then starting the irrigating system to irrigate the repair agent solution to the ground surface; Static soaking includes: stopping the injection and allowing the soil to soak in the remediation agent solution; Sampling and testing include: taking samples of the soaked soil to test the concentration of heavy metals, and determining whether to proceed with the heavy metal recovery step based on the test results; if not, returning to the static soaking step. Heavy metal recovery includes: starting the pumping system to pump out the liquid in the soil pores as a precious liquid and send it to the recovery system for refining; after refining, the tail liquid is replenished with a remediation agent and then reinjected into the treatment area; repeating this step and controlling the circulation based on the detection of the pumped liquid and soil. Rinsing the soil with clean water ensures that the residual amount of remediation agent meets environmental requirements.

2. The method for in-situ soaking and leaching treatment of heavy metals in soil as described in claim 1, characterized in that, The irrigation system includes a remedial agent solution tank (13), an irrigation pump (7), and an irrigation pipeline network laid on the ground of the treatment area (1) for injecting the remedial agent solution into the soil; The irrigation network includes irrigation filter pipes (5) laid longitudinally along the treatment area (1), and multiple irrigation filter pipes (5) are arranged in rows at intervals along the treatment area (1). The irrigation network also includes an irrigation main pipe (6) laid transversely along the treatment area (1) to connect the entire row of irrigation filter pipes (5). The irrigation main pipe (6) is connected to the outlet of the irrigation pump (7), and the inlet of the irrigation pump (7) is connected to the repair agent liquid pool (13).

3. The method for in-situ soaking and leaching treatment of heavy metals in soil as described in claim 2, characterized in that, The pumping system includes multiple water collection wells (2), a high-energy water pump (3), a pumping pipe (4), and return pools A (10) and B (11) located in the treatment area (1). Each water collection well (2) is equipped with a wellpoint pipe structure, and the wellpoint pipe structure is connected to the inlet of the high-energy water pump (3) via the pumping pipe (4). The outlet of the high-energy water pump (3) is provided with a return pipe (35) leading to the return pool A (10). The return pool A (10) is connected to the return pool B (11) via the first pumping pipe (36). The return pool B (11) is connected to the repair agent liquid pool (13) via the second pumping pipe (37). The well point pipe structure includes an outer pipe and a suction pipe (31) installed inside the outer pipe. A filter pipe (33) is installed at the lower end of the outer pipe to filter the incoming liquid. An ejector (32) is also installed inside the outer pipe to spray the liquid upward. The outlet of the ejector (32) is connected to the bottom end of the suction pipe (31). The upper end of the suction pipe (31) is connected to the inlet of the high-energy water pump (3) via a liquid pumping pipe (4). The annular space between the outer pipe and the well wall of the water collection well (2) is filled with a medium-coarse sand layer (22) and a clay layer (21) from bottom to top.

4. The method for in-situ soaking and leaching treatment of heavy metals in soil as described in claim 3, characterized in that, The outer tube is a PVC water pipe (8) or an electrode tube (26). When the outer tube is an electrode tube (26), the system layout steps also include the construction of an electroosmosis system. The electroosmosis system includes an electroosmosis dedicated power supply device (30) and an electrode plate (27) set in the treatment area (1). The electrode plate (27) and electrode tube (26) in the treatment area (1) are arranged horizontally at intervals in rows. Multiple rows of electrode plates (27) and multiple rows of electrode tubes (26) are arranged alternately along the longitudinal direction of the treatment area (1). All electrode tubes (26) are electrically connected to the same pole of the electroosmosis dedicated power supply device (30), and all electrode plates (27) are electrically connected to the other pole of the electroosmosis dedicated power supply device (30). The electroosmosis system also includes an electroosmosis pipe (40) led out from the pumping pipe (4), the other end of which is connected to the irrigation main pipe (6); an electroosmosis control valve (39) is provided on the electroosmosis pipe (40) and between the connection point of the electroosmosis pipe (40) on the pumping pipe (4) and the high-energy water pump (3).

5. The method for in-situ soaking and leaching treatment of heavy metals in soil as described in claim 4, characterized in that, The monitoring system includes a pore water pressure probe (23), a groundwater level well (24), and a soil moisture content probe (25) installed in the treatment area (1). The recycling system includes a recycling pipe (34) connected in parallel with the return pipe (35) and recycling equipment (9) installed on the recycling pipe (34).

6. The method for in-situ soaking and leaching treatment of heavy metals in soil as described in claim 4, characterized in that, When the outer tube is an electrode tube (26), in the pumping and irrigating steps, the electro-osmosis system is activated simultaneously to assist in pumping out soil moisture, specifically including: Open the electroosmosis control valve (39) on the pumping pipe (4) and close the electroosmosis control valve (39) on the electroosmosis pipe (40). Start the high-energy water pump (3) to pump the water accumulated in the collection well (2) into the return liquid pool A (10). At the same time, turn on the electroosmosis special power supply equipment (30) to make the pore water in the soil seep into the collection well (2).

7. The method for in-situ soaking and leaching treatment of heavy metals in soil as described in claim 4, characterized in that, When the outer tube is an electrode tube (26), in the pumping and irrigation steps, the electroosmosis system is activated simultaneously to assist irrigation when the irrigation system irrigates the repair agent solution, specifically including: The electroosmosis control valve (39) on the pumping pipe (4) is closed and the electroosmosis control valve (39) on the electroosmosis pipe (40) is opened. The injection pump (7) is started to inject the repair agent solution from the chemical tank (13) into the soil through the injection network. At the same time, the electroosmosis special power supply equipment (30) is turned on to allow the repair agent solution from the chemical tank (13) to seep into the soil through the collection well (2).

8. The method for in-situ soaking and leaching treatment of heavy metals in soil as described in claim 5, characterized in that, When the outer tube is an electrode tube (26), in the heavy metal recovery step, the electroosmosis system is activated simultaneously to assist in the drainage when pumping out the pore liquid in the soil, specifically including: Open the electroosmosis control valve (39) on the pumping pipe (4) and close the electroosmosis control valve (39) on the electroosmosis pipe (40). Start the high-energy water pump (3) to pump out the soil pore liquid as precious liquid and pump it to the recycling equipment (9). At the same time, turn on the electroosmosis special power supply (30) to make the pore water in the soil seep into the collection well (2). The tail liquid extracted and discharged by the recycling equipment (9) flows back to the return liquid pool A (10). After being pumped to the return liquid pool B (11) to replenish the repair agent, it returns to the chemical liquid pool (13) of the irrigation system and continues to irrigate the treatment area (1) through the irrigation pipeline network.

9. The method for in-situ soaking and leaching treatment of heavy metals in soil as described in claim 1, characterized in that, The process of rinsing the soil with clean water specifically includes: Pump out the water in the treatment area (1) until the groundwater level stabilizes and drops to the preset level; then pour clean water into the treatment area (1) until the water fills to the ground. The soil is sampled and the remediation agent content is determined to meet environmental requirements. If it does, the treatment ends; otherwise, the irrigation system is activated to irrigate with clean water and the drainage system is activated to pump out the remediation agent until the remediation agent content in the soil sample meets environmental requirements.

10. An apparatus for the method of in-situ leaching treatment of heavy metals in soil as described in any one of claims 1 to 9, characterized in that, This includes isolation systems, pumping systems, filling systems, recovery systems, and monitoring systems. The isolation system is located around and at the bottom of the processing area (1) to form an isolated reaction zone with an open top; The irrigation system includes a repair agent solution tank (13), an irrigation pump (7), and an irrigation pipeline laid on the ground of the treatment area (1) for injecting the repair agent solution into the soil. The irrigation system also includes a geotextile (15) covering the surface of the treatment area (1) and a sealing membrane (14) above the geotextile (15). The pumping system includes a water collection well (2), a high-energy water pump (3), a pumping pipe (4), and return pools A (10) and B (11) located in the treatment area (1). The water collection well (2) is equipped with a wellpoint pipe structure and is connected to the inlet of the high-energy water pump (3) via the pumping pipe (4). The outlet of the high-energy water pump (3) is provided with a return pipe (35) leading to the return pool A (10). The return pool A (10) is connected to the return pool B (11) via the first pumping pipe (36). The return pool B (11) is connected to the repair agent liquid pool (13) via the second pumping pipe (37). The recycling system includes a recycling pipe (34) connected in parallel with the return pipe (35) and a recycling device (9) installed on the recycling pipe (34); The monitoring system includes a pore water pressure probe (23), a groundwater level well (24), and a soil moisture content probe (25) installed in the treatment area (1).

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