Soil heavy metal decrement simulation device and contaminated soil in-situ remediation method

Abstract

The invention discloses a soil heavy metal decrement simulation device and a polluted soil in-situ remediation method. The device comprises a simulation soil box, a ploughing stirrer, a water tank, a first water pump, a water treatment unit, a heavy metal tester, a sensor group and a controller, to-be-repaired soil is contained in the simulated soil box, the sensor set is used for collecting soil information, clean water in the water tank enters the simulated soil box through the first water pump to cover the soil, and the ploughing stirrer conducts multidirectional stirring on the soil to enable heavy metal to be dissolved out and enter the soil to cover water or eluent. Then the water enters a water treatment unit for heavy metal decrement treatment and solid-liquid separation, then the water enters a heavy metal tester for detecting the content of the treated heavy metal, and a controller implements linkage control based on real-time data to provide in-situ heavy metal decrement conditions; according to the method, the concepts of in-situ elution decrement and eluent recycling of soil heavy metal pollution are fused, the remediation efficiency is high, the heavy metal remediation cost is low, the remediation period is short, and the automatic efficient decrement effect is achieved.

Description

A soil heavy metal reduction simulation device and an in-situ remediation method for contaminated soil Technical Field

[0001] This invention relates to the field of soil remediation technology, and in particular to a soil heavy metal reduction simulation device and an in-situ remediation method for contaminated soil. Background Technology

[0002] Currently, the mainstream technologies for in-situ remediation of heavy metal pollution in farmland soil include agronomic management, phytoremediation, and chemical passivation.

[0003] Agronomic management measures control heavy metal pollution through water management, fertilizer regulation, replacement of low-accumulation varieties, adjustment of soil pH, and adjustment of planting structure. However, crop structure adjustment may affect farmers' income and food production security, and its application scope is also limited.

[0004] While phytoremediation has the advantages of being environmentally friendly and maintaining soil ecology, it heavily relies on hyperaccumulating plants. However, these plants typically have low biomass, slow growth, poor mechanization adaptability, and are difficult to treat in a harmless manner, resulting in a long remediation cycle that often lasts for ten to several decades. This makes it difficult to meet the needs of the agricultural production cycle, thus limiting its application in agricultural production practices. Furthermore, it is also difficult to implement effectively on mildly polluted soils.

[0005] Chemical passivation relies on reactions such as adsorption, precipitation, ion exchange, and redox to reduce the activity of heavy metals. Although it is effective quickly, it still faces significant challenges: on the one hand, the soil remediation effect may be affected by environmental conditions, and there is a risk of heavy metal re-dissolution, so its long-term stability needs to be continuously monitored; on the other hand, the remediation effect of this technology depends on multiple technical parameters, and there is currently a lack of precise and efficient methods for optimizing these parameters. In practical applications, it is often necessary to obtain the optimal parameters through repeated and extensive field experiments, which consumes a lot of manpower, material resources, and time.

[0006] In summary, there is an urgent need for an in-situ remediation method for heavy metal contaminated soil that reduces time and economic costs, has a short remediation cycle, poses no risk of secondary pollution, is efficient, economical, scalable, and does not damage soil fertility. Summary of the Invention

[0007] The purpose of this invention is to address the technical problems of high cost, long cycle, easy damage to the topsoil, risk of secondary pollution, and inefficient reduction of heavy metals in polluted farmland soil by providing a soil heavy metal reduction simulation device and an in-situ remediation method for polluted soil.

[0008] The objective of this invention is achieved through the following technical solution: Firstly, this invention provides a soil heavy metal reduction simulation device, as shown in Figure 1, comprising: a simulated soil tank 1 for storing soil to be remediated, wherein the simulated soil tank has a water inlet on its upper side and a drain outlet on its bottom and / or another side; a tillage mixer 2, horizontally movable and positioned above the interior of the simulated soil tank, for uniformly tilling and mixing the soil within the tank in multiple directions; a water tank 3 for storing clean water and soil cover water or eluent that has passed heavy metal analysis; a first water pump 4, whose suction inlet is connected to the water tank, for pumping the liquid from the water tank into the simulated soil tank; and a water treatment unit. 5. Connected to the drainage outlet of the simulated soil tank, it is used for heavy metal reduction remediation treatment of soil overlying water or eluent, and to separate solid soil; 6. Heavy metal analyzer, installed on the pipeline after the water treatment unit, is used for online detection of heavy metals in the soil overlying water or eluent after remediation treatment; 7. Sensor group, installed on the side of the simulated soil tank, is used to collect soil temperature, humidity and composition information and transmit it to controller 8; 8. Controller 8, based on the real-time data of sensor group 7, performs linkage control on the water supply of the first water pump 4 and the tillage mixer 2, so that the cleaning-mixing-remediation-solid-liquid separation-detection form a cycle process to provide in-situ soil heavy metal reduction conditions.

[0009] Specifically, the soil overlying water consists of clean water and a liquid containing heavy metals after the soil to be remediated has been tilled and stirred. The soil eluent consists of clean water with added eluent and a liquid containing eluent and heavy metals after the soil to be remediated has been stirred in a tillage mixer. The addition of eluent depends on the leaching rate of heavy metals in the specific soil to be remediated. If the leaching rate of heavy metals is greater than or equal to 90% of the bioavailability of heavy metals when only clean water is added, then no eluent needs to be added. If it is less than 90%, then an eluent needs to be added.

[0010] As a further improvement to the above scheme, a flow regulating valve or a first flow meter is provided on the water path flowing into the simulated soil tank to regulate the water inflow into the simulated soil tank.

[0011] As a further improvement to the above solution, a horizontal moving mechanism is provided above the top of the simulated soil box, and the tillage mixer is located at the moving end of the horizontal moving mechanism, so that the tillage mixer can move along the length of the simulated soil box.

[0012] As a further improvement to the above solution, the horizontal moving mechanism includes a horizontal driving device and a ball screw drivenly connected to the horizontal driving device, as well as a screw nut slidably disposed on the ball screw; the tillage mixer is disposed on the screw nut; preferably, the horizontal moving device includes a first motor and a synchronous belt assembly drivenly connected to the first motor, the synchronous belt assembly having a driven pulley disposed on the ball screw.

[0013] As a further improvement to the above solution, the tillage mixer includes a second motor, a mixing rod, and mixing blades distributed on the mixing rod. The mixing blades have a spiral or arc-shaped structure. The second motor is mounted on the lead screw nut. One end of the mixing rod is driven and connected to the power output end of the second motor, and the other end extends into the simulated soil box. The mixing blades on the mixing rod mix the soil in the simulated soil box.

[0014] As a further improvement to the above scheme, the water treatment unit includes a pretreatment chamber, a barrier material layer, a multi-stage wastewater remediation layer, and an effluent rectifier connected in sequence. The pretreatment chamber is used to uniformly disperse the incoming soil overburden or eluent. The barrier material layer is composed of adsorption or ion exchange materials, which are used to adsorb, complex, and precipitate heavy metals in the soil overburden or eluent to reduce their concentration. The multi-stage wastewater remediation layer employs reaction units arranged in series to deeply treat the soil overburden or eluent for heavy metal removal. Each reaction unit comprises two parts: one part uses physical / chemical precipitation / adsorption / ion exchange or biological adsorption / precipitation methods; the other part is an eluent layer. The effluent rectifier is used to stabilize the effluent flow rate at the outlet of the water treatment unit and transport it to the heavy metal analyzer.

[0015] As a further improvement to the above solution, the simulated soil box includes a box body with openings at both the top and bottom, a filter plate at the bottom opening of the box body, a funnel at the bottom of the filter plate, and a sealing cover at the top opening of the box body, the sealing cover being openable; the sealing cover is provided with a waist-shaped sliding groove to provide space for the horizontal movement of the tillage mixer; the bottom of the funnel has a drainage outlet.

[0016] As a further improvement to the above scheme, the sensor group includes several soil sensors, which are arranged from top to bottom on the side of the simulated soil box to detect soil information at each height layer inside the simulated soil box; each soil sensor is used to collect parameter information of the corresponding soil height layer in real time, including temperature, humidity, nitrogen, phosphorus and potassium content, as well as pH, EC and salinity values.

[0017] As a further improvement to the above solution, the device also includes a real-time soil leachate measurement unit for online monitoring of the soil leachate after infiltration by overlying water or eluent. The real-time soil leachate measurement unit includes a pre-filtration component, a second water pump, and / or a second flow meter connected in sequence. The pre-filtration component is used to perform solid-liquid pre-separation of the soil leachate to obtain pre-filtered soil leachate. The second water pump is used to transport the pre-filtered soil leachate to the second flow meter. The output end of the second flow meter is connected to the heavy metal analyzer for real-time detection of the heavy metal content in the soil leachate. The data from the real-time soil leachate measurement unit is further compared with the data from the ICP-MS analyzer to calibrate the accuracy of the heavy metal analyzer's detection results.

[0018] The real-time soil leachate measurement unit can also be used for leaching experiments: the tillage mixer above the simulated soil box is replaced with a sprayer, and the leachate from the simulated soil box is measured by the real-time measurement unit to monitor the amount of heavy metals lost through leaching in real time.

[0019] As a further improvement to the above scheme, the soil heavy metal reduction simulation device also includes a display unit, which is electrically connected to the controller and is used to display the changes in soil properties before and after tillage and mixing in real time, so as to directly reflect the impact of the reduction operation on soil properties in the form of data.

[0020] This device can be used to simulate heavy metal reduction in soils with different properties to form a database of optimal parameter schemes, serving the industrialization of the technology. The system can use the corresponding heavy metal reduction scheme according to the actual soil properties.

[0021] Secondly, the present invention also provides a method for in-situ remediation of heavy metal contaminated soil, the steps of which include: S1, using the soil heavy metal reduction simulation device as provided in the first aspect, injecting clean water into the simulated soil tank and driving a tillage mixer to tillage and mix the soil, combined with a water treatment unit to perform heavy metal reduction and remediation treatment and continuous detection by a heavy metal analyzer, to obtain optimal parameters such as irrigation water volume, tillage and mixing intensity, mixing times, tillage soil depth, tillage path, water circulation times, and whether and what type of elution agent needs to be added; S2, inputting the optimal parameters obtained in step S1 into an in-situ heavy metal reduction operation vehicle and a large tillage and mixing device, so that it performs in-situ tillage, irrigation, elution and heavy metal reduction operations in the target farmland according to the optimal parameters, thereby achieving the standard remediation of soil heavy metal content.

[0022] As a further improvement to the above scheme, in step S1, the process of obtaining the optimal parameters includes: clean water from the water tank is pumped by the first water pump and the flow rate is adjusted by the first flow meter to enter the simulated soil tank; the tillage mixer is started to stir the soil multiple times with a set intensity and depth to obtain soil surface water or eluent; the stirred soil surface water or eluent enters the water treatment unit through the drain at the bottom of the simulated soil tank for heavy metal removal and solid-liquid separation, and then enters the heavy metal analyzer for heavy metal concentration detection; if the detection value does not meet the standard, the liquid is returned to the water treatment unit and the heavy metal removal process is repeated until the detection value meets the standard before returning to the water tank to enter the next cycle.

[0023] By comparing and analyzing the irrigation amount, stirring intensity, number of stirrings, tillage depth, path trajectory, number of cycles, and heavy metal concentration in the supernatant or elution solution of the remediated soil in the cyclic experiment, the optimal combination of the above parameters was determined.

[0024] As a further improvement to the above scheme, in step S2, the heavy metal reduction operation vehicle irrigates with clean water according to the irrigation water volume and actual irrigation area determined in step S1, and the large-scale tillage and mixing equipment performs in-situ tillage according to the depth and path determined in step S1, so as to achieve a heavy metal leaching effect equivalent to the simulated conditions.

[0025] Because the present invention adopts the above technical solutions, the beneficial effects of this application are as follows: 1. The present invention provides a soil heavy metal reduction simulation device, which realizes a continuous cycle process of soil washing, mixing, remediation, separation and detection by constructing a system consisting of a simulated soil box, a tillage mixer, a water tank, a first water pump, a water treatment unit and a heavy metal analyzer. This structural combination enables the device to simulate in-situ remediation conditions, thereby obtaining heavy metal reduction parameters suitable for polluted farmland.

[0026] First, the mixing blades of the mobile tillage mixer extend into the simulated soil tank, allowing for multi-directional mixing of soil at different depths and in different areas. This enables heavy metals to more fully enter the solution phase, providing a more realistic in-situ simulation basis for subsequent remediation treatments. Compared to traditional static leaching methods, this structure more closely resembles the actual tillage conditions of farmland, which helps improve the accuracy of parameter derivation.

[0027] Secondly, the water tank, the first water pump, and the water treatment unit form a stable circulating water circuit, which allows the clean water to be reused repeatedly, reduces the amount of water used in the experiment, and makes the soil and the treatment liquid of the water treatment unit form a closed loop flow, which is convenient for simulating the response under different remediation intensities over a long period of time.

[0028] Furthermore, the tandem setup of the water treatment unit and the heavy metal analyzer enables real-time acquisition of changes in heavy metal content in soil overlying water or eluent under different treatment conditions. This facilitates rapid assessment of remediation effectiveness and optimization of key parameters such as stirring intensity and irrigation volume, thereby improving parameter optimization efficiency.

[0029] In addition, the data acquisition unit can obtain changes in soil temperature, humidity and composition. Based on this real-time data, the controller implements linkage control of the water pump and tillage mixer, enabling the device to automatically adjust its operating strategy under different soil conditions, making the obtained parameters more universal and reliable.

[0030] This invention achieves effective simulation of the in-situ heavy metal remediation process in soil through the synergistic effect of the equipment structure. It can systematically obtain optimized remediation parameters applicable to contaminated soil, which helps to reduce remediation costs, shorten the remediation cycle, and reduce disturbance to the topsoil. It provides an economical and scalable technical approach for the treatment of heavy metal contaminated soil.

[0031] 2. The present invention also provides a method for in-situ remediation of soil contaminated with heavy metals. By using a soil heavy metal reduction simulation device to obtain the key operating parameters required for in-situ remediation, and applying these parameters to the remediation operation of actual farmland, the in-situ heavy metal reduction process has become more targeted and controllable.

[0032] First, in step S1, the simulation device, through a continuous cycle of cleaning, tilling, remediation, solid-liquid separation, and online monitoring, can systematically evaluate the effects of different irrigation volumes, mixing intensities, tilling depths, and other factors on heavy metal desorption under controlled conditions, thereby obtaining an optimal parameter combination that better suits soil characteristics. Compared to relying on experience or single-factor experiments to determine operating conditions, this method can obtain more definitive and repeatable parameter data in a shorter time.

[0033] Secondly, the sensing, repair, and detection units set up in the simulation device enable parameter optimization to be based on objective data, which helps to eliminate uncertainties caused by differences in soil conditions and improves the applicability of the obtained parameters under different regional soil conditions.

[0034] Furthermore, in step S2, the parameters obtained through simulation optimization are directly imported into the actual heavy metal reduction operation vehicle and large-scale tillage and mixing equipment. This helps to reduce the trial and error process in actual operations, making the in-situ remediation process more efficient, and reducing unnecessary disturbances and resource input.

[0035] This invention, through the technical approach of "simulation optimization - in-situ execution", makes the operating conditions for in-situ soil heavy metal remediation more reasonable, which helps to improve remediation efficiency, reduce operating costs, and reduce the impact on the topsoil structure, providing an implementable technical solution for reducing heavy metals in polluted farmland. Attached Figure Description

[0036] Figure 1 is a schematic diagram of the principle of a soil heavy metal reduction simulation device disclosed in this invention; Figure 2 is a schematic diagram of the principle of the real-time measurement unit for soil overlying water or eluent disclosed in this invention; Figure 3 is a front view of a soil heavy metal reduction simulation device disclosed in this invention; Figure 4 is a side view of a soil heavy metal reduction simulation device disclosed in this invention; Figure 5 is a CC cross-sectional view of Figure 4; Figure 6 is a three-dimensional schematic diagram 1 of a soil heavy metal reduction simulation device (with cabinet door removed) disclosed in this invention; Figure 7 is a three-dimensional schematic diagram 2 of a soil heavy metal reduction simulation device (with cabinet door removed) disclosed in this invention; Figure 8 is a partial enlarged view along line I of Figure 7. Figure 9 is a three-dimensional schematic diagram of a soil heavy metal reduction simulation device (with cabinet door removed) disclosed in this invention; reference numerals: 1, simulated soil box; 1-1, box body; 1-2, filter plate; 1-3, funnel component; 1-4, sealing cover; 1-5, waist-shaped chute; 2, tillage mixer; 3, water tank; 4, first water pump; 5, water treatment unit; 6, heavy metal analyzer; 7, sensor group; 8, controller; 9, horizontal moving mechanism; 10, first flow meter; 11, real-time soil leachate measurement unit; 11-1, pre-filtration component; 11-2, second water pump; 11-3, second flow meter; 11-4, ICP-MS detector. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0039] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0040] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0041] Example 1: Referring to the schematic diagram and different views in Figures 1-9, this invention provides a soil heavy metal reduction simulation device, including a simulated soil box 1, a tillage mixer 2, a water tank 3, a first water pump 4, a water treatment unit 5, a heavy metal analyzer 6, a sensor group 7, and a controller 8. By performing controllable cleaning, tillage, remediation, solid-liquid separation, and online detection operations on the soil, the optimal parameters for in-situ heavy metal reduction in the soil are obtained, providing experimental basis for determining in-situ operation parameters.

[0042] In this embodiment, the soil heavy metal reduction simulation device is shown in Figure 1, and also includes a frame. The simulated soil tank 1 is set on the left side of the frame via a base, and the water tank 3 and water treatment unit 5 are respectively set on the right side of the frame. Specifically, the simulated soil tank 1 is used to store the soil to be remediated. A water inlet is provided on the upper part of its inner side to allow cleaning water to enter the soil layer. A drain outlet is provided on the bottom and / or the other side to drain the water or elution solution on the soil after stirring. In this embodiment, there are 3 drain outlets. There is one drain outlet at the bottom of the simulated soil tank 1 and two drain outlets from top to bottom on the other side of the simulated soil tank 1.

[0043] The tillage mixer 2 can move horizontally and is located above the interior of the simulated soil box. It tills and mixes the soil through multi-directional rotation or reciprocating motion to simulate the mechanical tillage process in actual farmland.

[0044] Water tank 3 is used to store the clean water required for the experiment, and at the same time collect the soil supernatant or eluent that has passed the heavy metal test.

[0045] The suction port of the first water pump 4 is connected to the water tank 3. By controlling the start and stop of the water pump, clean water enters the simulated soil tank 1 at a set flow rate.

[0046] Water treatment unit 5, connected to the drain outlet of simulated soil tank 1, receives soil overburden or eluent discharged from the simulated soil tank and treats the heavy metals in the soil overburden or eluent within this unit to reduce the heavy metal content. Treatment methods can include adsorption, complexation, precipitation, or other suitable water treatment technologies, depending on specific needs. The solid components are then separated through settling or filtration. Specifically, the soil overburden consists of clean water and the liquid containing heavy metals from the soil to be remediated after tilling and mixing. The soil eluent consists of clean water with added eluent and the liquid containing eluent and heavy metals from the soil to be remediated after tilling and mixing. The addition of eluent depends on the leaching rate of heavy metals in the specific soil to be remediated. If the heavy metal leaching rate is greater than or equal to 90% of the bioavailability of heavy metals when only clean water is added, no eluent is needed; otherwise, eluent is required.

[0047] Water overlying the remediated soil continues to flow into the heavy metal analyzer 6. Real-time monitoring of the remediation effect is achieved through online measurement of heavy metal content. The correlation between the monitoring results and simulated conditions provides data support for optimizing the washing volume, stirring intensity, and remediation method.

[0048] Sensor group 7, deployed inside simulated soil chamber 1, includes several sensors for monitoring changes in soil temperature, humidity, and composition. The data collected by sensor group 7 is transmitted to controller 8 in real time. Controller 8 then adjusts the water supply of the water pump and the operating status of the tillage mixer 2 in a coordinated manner, so that cleaning, mixing, repair, solid-liquid separation, and detection form a continuous cycle to provide in-situ conditions for reducing heavy metals in the soil.

[0049] Through the above structural arrangement and interactive control, the migration and reduction process of heavy metals under different cleaning intensities, tillage depths, stirring times, water circulation times and remediation conditions can be simulated in an experimental environment, which can provide quantifiable parameter basis for actual farmland in-situ remediation.

[0050] As a preferred embodiment, in order to accurately control the amount of water flowing into the simulated soil tank 1, a flow regulating valve or a first flow meter 10 can be installed on the water path flowing into the simulated soil tank 1 so as to adjust the amount of water according to experimental needs, thereby ensuring that the moisture conditions of the simulated soil are controllable and uniform.

[0051] As a preferred embodiment, in order to improve the uniformity of soil mixing and tillage, a horizontal moving mechanism 9 is set above the top of the simulated soil box 1, as shown in Figures 3 and 8. The tillage mixer 2 is installed at the moving end of the horizontal moving mechanism 9, so that it can move along the length of the simulated soil box 1 to achieve comprehensive soil mixing.

[0052] Preferably, the horizontal moving mechanism 9 includes a horizontal driving device and a ball screw connected to it. A screw nut is slidably provided on the ball screw. The tillage mixer 2 is fixed on the screw nut. The horizontal driving device drives the screw nut to move along the ball screw, thereby driving the tillage mixer 2 to move linearly above the soil box.

[0053] Furthermore, the horizontal drive device includes a first motor and a synchronous belt assembly connected to the first motor. The driven pulley of the synchronous belt assembly is mounted on a ball screw. The rotation of the first motor drives the synchronous belt to rotate, thereby driving the ball screw and screw nut to move the tillage mixer 2 along the length of the soil box, so as to achieve uniform tillage and mixing of the soil.

[0054] This invention enables precise control of water volume in simulated soil chamber 1 and homogenization of soil tillage, thereby improving the repeatability and reliability of soil heavy metal reduction experiments.

[0055] In a preferred embodiment, to achieve uniform tillage and thorough mixing of the soil, the tillage mixer 2 includes a second motor, a mixing rod, and mixing blades distributed on the mixing rod. The mixing blades have a spiral or arc-shaped structure, which can effectively increase the soil mixing efficiency and improve the uniformity of the soil.

[0056] The second motor is mounted on the lead screw nut of the horizontal moving mechanism 9. One end of the stirring rod is driven and connected to the power output end of the second motor, and the other end extends into the simulated soil box 1. The soil in the soil box is stirred by the stirring blades on the stirring rod, thereby realizing the comprehensive tillage and mixing of the soil.

[0057] With the above structural design, the tillage mixer 2 can efficiently and evenly mix the soil while moving horizontally, solving the problem of uneven soil mixing in traditional fixed mixing methods and improving the controllability and reliability of the simulation experiment.

[0058] In a preferred embodiment, to achieve effective remediation of heavy metals in soil washing solution, the water treatment unit 5 includes a pretreatment chamber, a barrier material layer, a multi-stage wastewater remediation layer, and an effluent rectifier connected in sequence.

[0059] The pretreatment chamber is used to uniformly disperse the incoming soil overlying water or eluent, so that it can uniformly contact the remediation medium in the subsequent water treatment unit 5, avoiding the problem of insufficient local treatment.

[0060] The barrier material layer is composed of adsorption or ion exchange materials loaded in the cavity. These materials can adsorb or complex and fix heavy metals in the soil overlying water or eluent, thereby effectively removing heavy metals from the soil overlying water or eluent.

[0061] The multi-stage wastewater remediation layer employs reaction units arranged in series to further treat the soil eluent that has passed through the barrier material layer, thereby removing residual heavy metals and other pollutants from the overlying water or eluent. The reaction unit consists of two parts: one part uses physical / chemical precipitation / adsorption / ion exchange methods or biological adsorption / precipitation methods, such as using alkalis, sulfides, aluminum salts, iron salts, or microorganisms / algae cells, to further remove residual heavy metals and other pollutants from the overlying water or eluent; the other part is an eluent layer, selected based on the heavy metal leaching rate in the simulated soil tank. This layer is used to mix the eluent into the overlying water or eluent before transferring it to the simulated soil tank to enhance the heavy metal leaching rate of the contaminated soil in the overlying water or eluent.

[0062] The effluent rectifier is used to stabilize the effluent flow rate at the outlet of the water treatment unit and deliver it to the heavy metal analyzer 6 to ensure the accuracy and repeatability of the measurement.

[0063] With the above-described structure, the present invention can achieve graded adsorption and deep treatment of heavy metals in soil leachate, improve remediation efficiency, and enhance experimental controllability and data reliability.

[0064] As a preferred embodiment, in order to achieve controllable treatment and drainage management of the soil, as shown in Figure 5, the simulated soil box 1 includes a box body 1-1 with openings at both the top and bottom. A filter plate 1-2 is provided at the bottom opening of the box body 1-1 to support the soil and allow water to pass through. A funnel component 1-3 is provided below the filter plate 1-2 to collect the water that passes through and guide it to the drain outlet for discharge. The drain outlet is located at the bottom of the funnel component 1-3 to ensure smooth and controllable drainage.

[0065] The top opening of the housing 1-1 is equipped with an openable sealing cover 1-4 to prevent external impurities from entering the soil box and to maintain the sealing of the experimental environment. The sealing cover 1-4 is also equipped with a waist-shaped sliding groove 1-5 to provide space for the horizontal movement of the tillage mixer 2, so that the mixer can move along the length of the soil box without being obstructed by the top structure, thus achieving uniform tillage and mixing of the soil.

[0066] With the above-mentioned structural design, the present invention can achieve uniform soil tillage and effective drainage while maintaining controllable soil moisture conditions, thereby improving the repeatability and reliability of soil heavy metal simulation remediation experiments.

[0067] As a preferred embodiment, in order to realize real-time monitoring of the soil condition in the simulated soil box 1, the sensor group 7 includes several soil sensors, which are distributed from top to bottom along the side of the simulated soil box 1, covering the soil at each height layer in the simulated soil box.

[0068] Each soil sensor is used to collect real-time data on temperature, humidity, and nitrogen, phosphorus, and potassium content at its corresponding soil depth. It can also detect soil physicochemical indicators, including pH, electrical conductivity (EC), and salinity. Sensor group 7 provides real-time dynamic information on the soil at different depths, enabling precise monitoring of the soil remediation status. This provides data support for soil remediation and water management, improving the controllability and repeatability of experiments.

[0069] As a preferred embodiment, in order to realize real-time monitoring of soil leaching solution after soil overlying water or leaching solution infiltration, the device also includes a real-time soil leaching solution measurement unit 11, as shown in Figure 2, to monitor the amount of heavy metals lost through leaching in real time.

[0070] The real-time soil leachate measurement unit 11 includes a pre-filtration component 11-1, a second water pump 11-2, and a second flow meter 11-3 connected in sequence. The pre-filtration component 11-1 is used to perform solid-liquid pre-separation of the soil leachate to remove suspended particles and ensure the accuracy of subsequent measurements; the second water pump 11-2 is used to transport the pre-filtered soil leachate to the second flow meter 11-3; the output of the second flow meter 11-3 is connected to a heavy metal analyzer 6 for real-time detection of heavy metal content in the soil leachate.

[0071] Furthermore, to improve the accuracy of the measurement results, the real-time soil leachate measurement unit 11 establishes a data correspondence with the measurement data of the ICP-MS detector 11-4, and achieves high-precision online monitoring by calibrating the detection results of the heavy metal analyzer 6.

[0072] With the above-mentioned settings, the present invention can realize real-time online measurement of soil overlying water or eluent and leaching solution, and ensure data reliability, providing an accurate basis for evaluating the effect of soil heavy metal remediation.

[0073] In a preferred embodiment, the soil heavy metal reduction simulation device further includes a display unit, which is electrically connected to the controller 8 and is used to display the changes in soil properties before and after tillage and mixing in real time, so as to obtain the impact of the reduction operation on soil properties.

[0074] Example 2: This invention also provides an in-situ remediation method for soil contaminated with heavy metals. First, using the soil heavy metal reduction simulation device provided in Example 1, the optimal operating parameters for achieving effective heavy metal reduction (such as the optimal combination of irrigation water volume, tillage and mixing intensity, mixing times, tillage depth, tillage path, water circulation times, and whether to add a washing agent) are systematically studied and obtained under laboratory or pilot-scale conditions. Subsequently, the above-mentioned optimal operating parameters are applied to the in-situ remediation operation in actual farmland. Through a heavy metal reduction operation vehicle equipped with a water pump, a water treatment unit 5, and a heavy metal detector, as well as large-scale tillage and mixing equipment, in-situ tillage, irrigation, washing, and on-site remediation are performed according to the optimal parameters to effectively reduce the heavy metal content in the soil and ultimately meet the soil environmental quality standards. This solves the problems of parameter setting relying on experience, unstable washing effects, and high on-site trial and error costs in the traditional in-situ remediation process. The specific implementation steps are as follows: Step S1, the steps and methods for determining the optimal parameters through simulation experiments are as follows: S11, filling soil and initial settings: fill the soil to be remediated into the simulation soil box 1, record the soil type, pollution level and initial heavy metal content to form an optimal parameter scheme database.

[0075] S12. Water Injection and Mixing Operation: Start the first water pump 4, and inject clean water from the water tank 3 into the simulated soil tank 1 after adjusting the flow rate through the first flow meter 10. The amount of water injected is determined according to the experimental design, usually covering a certain soil depth and ensuring sufficient soil wetting. At the same time, start the tillage mixer 2, and set the mixing intensity (e.g., speed, torque), mixing depth (e.g., 10cm~30cm), mixing times (e.g., 1~5 times), and tillage path (e.g., straight reciprocating, spiral, etc.) to mechanically till and mix the soil, so as to promote full contact between soil particles and water and improve the leaching efficiency of heavy metals.

[0076] S13. Liquid Treatment and Solid-Liquid Separation: After stirring, the resulting soil overlying water is discharged through the drain at the bottom of the simulated soil tank 1 and enters the water treatment unit 5. Depending on the actual situation, precipitants, complexing agents, adsorbents, or biological agents are selected to remove or stabilize heavy metal ions in the liquid. Solid particles are then separated from the supernatant using methods such as precipitation, filtration, or centrifugation. The treated soil overlying water further enters the heavy metal analyzer 6 to detect its heavy metal concentration (e.g., lead, cadmium, arsenic, chromium, mercury) or related indicators (e.g., conductivity, pH, organic matter content).

[0077] S14. Cycling and Parameter Adjustment: If the heavy metal analyzer 6 shows that the heavy metal concentration still does not meet the preset compliance limit (refer to relevant national or local soil environmental quality standards), the overlying water of the soil is returned to the water treatment unit 5 for further heavy metal removal treatment until the test results meet the standards. This process can be repeated multiple times. Each cycle records the irrigation water volume, tillage and mixing intensity, number of mixing times, tillage depth, tillage path, and whether an eluent (a complexing agent or eluent that does not affect soil function and has no pollution risk) and its type.

[0078] S15. Determination of Optimal Parameters: Based on the data from multiple cyclic experiments, by comparing the heavy metal removal efficiency, treatment stability, washing water reuse rate, and overall operating cost under different parameter combinations, the optimal parameter combination that can achieve efficient heavy metal reduction and is feasible to operate is selected, including but not limited to: optimal irrigation water volume, tillage and mixing intensity, number of mixing times, tillage soil depth, tillage path trajectory, number of water cycles, and whether and what type of eluent is added.

[0079] Through the above process, the effect of heavy metal elution can be quantitatively evaluated under experimental conditions, making parameter selection more scientific and reliable, reducing blind adjustments in actual field trials, and improving the repeatability and applicability of remediation parameters.

[0080] Step S2, In-situ Remediation Operation: After obtaining the optimal parameters in step S1, these parameters are applied to the in-situ remediation operation of actual contaminated farmland soil. Using a heavy metal reduction operation vehicle equipped with a water pump, water treatment unit 5 and heavy metal detector, as well as a large tillage and mixing equipment, in-situ tillage, irrigation, washing and on-site remediation are performed according to the optimal parameters obtained in the soil heavy metal reduction simulation device to achieve the same heavy metal reduction effect as the simulation device.

[0081] The heavy metal reduction operation vehicle used in this step is an integrated operation platform. In addition to basic irrigation and operation control functions, it is also specially equipped with the following key components: Water pump: used to pressurize the clean water in water tank 3 and deliver it to the irrigation system, injecting it into the surface of the tilled soil according to the set water volume, providing the necessary moisture conditions for the leaching of heavy metals; Water treatment unit 5: integrated on the operation vehicle, used to rapidly treat the heavy metal-containing liquid (i.e., wash water) leached from the soil on-site. It can use methods such as adsorption, precipitation, oxidation-reduction, or complexation to reduce the concentration of heavy metals in the wash water. The treated water meets the standards and can be reused or discharged in compliance with standards; Heavy metal detector: used to detect the heavy metal content in the soil surface water, wash water, or remediated soil in real time or periodically on-site, in order to evaluate the remediation effect and provide a basis for parameter adjustment.

[0082] In addition, the work site is equipped with large-scale tillage and mixing equipment, which has adjustable depth and controllable path tillage function. It can tillage and mix the contaminated soil in situ according to the tillage depth, mixing intensity, path trajectory and mixing number determined in step S1, so as to ensure that the soil disturbance conditions are consistent with those in the simulation device.

[0083] The specific in-situ remediation operation process is as follows: Parameter input and equipment debugging: The optimal parameters obtained in step S1 (including irrigation water volume, tillage depth, mixing times, path trajectory, water circulation times, whether to add eluent and its type, etc.) are input into the heavy metal reduction operation vehicle and large tillage and mixing equipment through the vehicle control module or manual setting to complete the equipment parameter setting and function debugging.

[0084] In-situ tillage and irrigation: Within the contaminated target farmland area, large-scale tillage and mixing equipment is first used to till and mix the soil in situ according to a set depth and path, loosening the soil structure and fully exposing heavy metals. Subsequently, a heavy metal reduction operation vehicle uses its equipped water pumps and irrigation system to inject clean water into the tilled soil surface at the optimal irrigation volume, promoting the leaching and migration of heavy metals in the soil.

[0085] Washwater Treatment and Recycling: Washwater containing heavy metals generated during tillage and irrigation can be guided by equipment or collected naturally into water treatment unit 5 for rapid on-site treatment. This unit selects appropriate treatment processes (such as adding adsorbents, complexing agents, or adjusting pH) based on the type and concentration of heavy metals in the washwater to reduce the heavy metal content. The treated water can be reused (e.g., for irrigation) or discharged in compliance with standards, depending on the actual situation, to reduce water waste and the risk of secondary pollution.

[0086] On-site testing and effectiveness evaluation: During or after the remediation process, the heavy metal detector on the heavy metal reduction vehicle is used to conduct on-site testing of the heavy metal content in the soil or wash water of the remediation area to evaluate whether the remediation effect has achieved the expected goals. If the standards are not met, the operating parameters can be fine-tuned or supplementary remediation work can be carried out based on the test results.

[0087] Work Completion and Verification: After the remediation work is completed, soil samples from the remediation area can be collected and sent to the laboratory for further analysis to confirm whether the heavy metal content in the soil meets the relevant national or local soil environmental quality standards. If it does, the remediation work is complete; if it still exceeds the standards, targeted secondary remediation or optimization of operation parameters can be carried out.

[0088] This invention utilizes a soil heavy metal reduction simulation device to obtain key operational parameters required for in-situ remediation, and applies these parameters to actual farmland remediation operations, making the in-situ heavy metal reduction process more targeted and controllable.

[0089] First, in step S1, the simulation device, through a continuous cycle of cleaning, tilling, remediation, solid-liquid separation, and online monitoring, can systematically evaluate the effects of different irrigation volumes, mixing intensities, tilling depths, and other factors on heavy metal desorption under controlled conditions, thereby obtaining an optimal parameter combination that better suits soil characteristics. Compared to relying on experience or single-factor experiments to determine operating conditions, this method can obtain more definitive and repeatable parameter data in a shorter time.

[0090] Secondly, the sensing, repair, and detection units set up in the simulation device enable parameter optimization to be based on objective data, which helps to eliminate uncertainties caused by differences in soil conditions and improves the applicability of the obtained parameters under different regional soil conditions.

[0091] Furthermore, in step S2, the parameters obtained through simulation optimization are directly imported into the actual heavy metal reduction operation vehicle and large-scale tillage and mixing equipment. The water pump, water treatment unit 5, and heavy metal detector 6 integrated on the heavy metal reduction operation vehicle enable the in-situ remediation operation to not only have efficient mechanical operation capabilities, but also realize the integrated functions of water supply, on-site treatment of pollutants, and real-time monitoring of effects, which significantly improves the intelligence, precision, and environmental protection level of the remediation operation; it helps to reduce the trial and error links in actual operation, making the in-situ remediation process more efficient, and reducing unnecessary disturbances and resource input.

[0092] This invention, through the technical approach of "simulation optimization - in-situ execution", makes the operating conditions for in-situ soil heavy metal remediation more reasonable, which helps to improve remediation efficiency, reduce operating costs, and reduce the impact on the topsoil structure, providing an implementable technical solution for reducing heavy metals in polluted farmland.

[0093] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A soil heavy metal reduction simulation device, characterized in that, include: A simulated soil tank (1) is used to store the soil to be repaired. It has a water inlet on the upper side and a drain outlet on the bottom and / or the other side. A tillage mixer (2) is set above the simulated soil tank (1) and is used to tillage and mix the soil in the soil tank from multiple directions. A water tank (3) is used to store clean water and collect soil cover water or eluent that has passed the test by a heavy metal detector (6). The clean water is water without heavy metal pollution. The soil cover water is specifically the clean water and the liquid containing heavy metals after tillage and mixing of the soil to be repaired. The eluent is specifically the clean water with added eluent and the liquid containing eluent and heavy metals after mixing the soil to be repaired by the tillage mixer. A first water pump (4) is connected to the water tank (3). The water tank (3) is used to pump the liquid in the water tank (3) into the simulated soil tank (1); the water treatment unit (5) is connected to the drain of the simulated soil tank (1) and is used to reduce the heavy metal content of the soil supernatant or eluent; the heavy metal analyzer (6) is set on the pipeline after the water treatment unit (5) and is used to detect the heavy metal content of the soil supernatant or eluent after the reduction treatment online; the sensor group (7) is set in the simulated soil tank (1) and is used to collect soil temperature, humidity and composition information and transmit it to the controller (8); the controller (8) performs linkage control on the water supply of the first water pump (4) and the operation of the tillage mixer (2) based on the real-time data of the sensor group (7) to provide in-situ soil heavy metal reduction conditions.

2. The soil heavy metal reduction simulation device according to claim 1, characterized in that, A flow regulating valve or a first flow meter (10) is provided on the water path flowing into the simulated soil tank (1) to regulate the amount of water entering the simulated soil tank.

3. A soil heavy metal reduction simulation device according to claim 1 or 2, characterized in that, A horizontal moving mechanism (9) is provided above the top of the simulated soil box (1), which is fixed to the tillage mixer (2) so that the tillage mixer (2) can move along the length of the simulated soil box (1).

4. The soil heavy metal reduction simulation device according to claim 3, characterized in that, The horizontal moving mechanism (9) includes a horizontal driving device, a ball screw, and a screw nut; the horizontal driving device is driven and connected to the ball screw, the ball screw is provided with a screw nut, and the tillage mixer (2) is mounted on the screw nut; the horizontal driving device includes a first motor and a synchronous belt assembly, the first motor is driven and connected to the synchronous belt assembly; the synchronous belt assembly is provided with a driven pulley, and the driven pulley is mounted on the ball screw.

5. The soil heavy metal reduction simulation device according to claim 1, characterized in that, The tillage mixer (2) includes a second motor, a mixing rod and mixing blades; the mixing blades are distributed on the mixing rod and the mixing blades are spiral or arc-shaped; the second motor is mounted on the screw nut, one end of the mixing rod is driven and connected to the power output end of the second motor, and the other end extends into the simulated soil box and mixes the soil in the simulated soil box (1) through the mixing blades.

6. The soil heavy metal reduction simulation device according to claim 1, characterized in that, The water treatment unit (5) includes a pretreatment chamber, a barrier material layer, a multi-stage wastewater remediation layer, and an effluent rectifier. The pretreatment chamber is used to uniformly disperse the incoming soil overburden or eluent. The barrier material layer is composed of adsorption or ion exchange materials loaded within the layer. The adsorption or ion exchange materials are used to remove heavy metals from the soil overburden or eluent. The multi-stage wastewater remediation layer uses reaction units arranged in series to perform deep treatment on the overburden or eluent. The effluent rectifier is used to stabilize the effluent flow rate of the water treatment unit (5) and transport it to the heavy metal analyzer (6).

7. The soil heavy metal reduction simulation device according to claim 1, characterized in that, The simulated soil box (1) includes a box body, a filter plate, a funnel component and a sealing cover; the box body has openings at both the top and bottom; the filter plate is located at the bottom opening of the box body; the funnel component is located at the bottom of the filter plate, and the bottom of the funnel component has a drainage outlet; the sealing cover is located at the top opening of the box body, and the sealing cover can be opened; the sealing cover has a waist-shaped sliding groove to provide space for the horizontal movement of the tillage mixer (2).

8. The soil heavy metal reduction simulation device according to claim 1, characterized in that, The sensor group (7) includes several soil sensors, which are set on the side of the simulated soil box (1) to detect soil information at different heights. The soil sensors are used to collect parameters of the corresponding soil heights in real time, including temperature, humidity, nitrogen, phosphorus and potassium content, as well as pH, EC and salinity.

9. The soil heavy metal reduction simulation device according to claim 1, characterized in that, The device includes a real-time soil leachate measurement unit (11) for monitoring the soil leachate after it has been infiltrated by soil overlying water or leaching solution. The real-time soil leachate measurement unit (11) includes a pre-filtration component, a second water pump, and a second flow meter. The pre-filtration component is used to perform solid-liquid pre-separation of the soil leachate. The second water pump is used to transport the pre-filtered soil leachate to the second flow meter. The output end of the second flow meter is connected to the heavy metal analyzer (6) for real-time detection of the heavy metal content in the soil leachate. The data from the real-time soil leachate measurement unit (11) is correlated with the data from the ICP-MS analyzer to calibrate the accuracy of the heavy metal analyzer's detection results. The real-time soil leachate measurement unit can also be used for leaching experiments: the tillage mixer above the soil box is replaced with a sprayer, and the leachate from the soil column is passed through the real-time soil leachate measurement unit (11) to monitor the amount of heavy metals lost through leaching in real time.

10. A method for in-situ remediation of soil contaminated with heavy metals, characterized in that, Includes the following steps: S1. Using the soil heavy metal reduction simulation device as described in any one of claims 1-9, clean water is injected into the simulated soil tank (1) and the tillage mixer (2) is driven to tillage and mix the soil. Combined with the continuous detection of the water treatment unit (5) and the heavy metal analyzer (6), the optimal parameters of irrigation water volume, tillage and mixing intensity, mixing times, tillage soil depth, tillage path, water circulation times, and whether or not to add elution agent and its type are obtained. S2. The optimal parameters obtained in step S1 are input into the in-situ heavy metal reduction operation vehicle and the large tillage and mixing equipment, so that in-situ tillage, irrigation, elution and heavy metal reduction operations are performed in the target farmland according to the optimal parameters, thereby achieving the standard remediation of soil heavy metals.

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