New device for remediation of heavy metal contaminated soil by combining pre-acidification process with cathode buffer zone electrokinetics and construction method

Abstract

The application discloses a new device for pre-acidification process combined with cathode buffer zone electric dynamic remediation of heavy metal contaminated soil and a construction method, and belongs to the field of electric dynamic remediation of heavy metal contaminated soil. The device comprises a soil remediation chamber and a sewage treatment chamber. The soil remediation chamber is open at the top, is provided with an anode plate on one side, and is provided with a cathode plate on the opposite side. Filter paper is attached to the two sides of the anode plate and the cathode plate. The cathode plate is further provided with a cathode buffer chamber opposite the anode plate. The anode plate and the cathode plate are connected through wires, a power supply and a sensor. The soil remediation chamber is connected with the sewage treatment chamber on the side provided with the cathode plate, and a gap is formed between the soil remediation chamber and the sewage treatment chamber to allow liquid to flow from the soil remediation chamber into the sewage treatment chamber. The sewage treatment chamber is provided with adsorption material. The sewage treatment chamber is provided with a drainage hole and a drainage pipe at the bottom end. The method can effectively remove heavy metals in sewage and can avoid the possibility of secondary pollution of the environment caused by electric dynamic remediation of sewage.

Description

Technical Field

[0001] This invention relates to a novel device and construction method for electrodynamic remediation of heavy metal contaminated soil using a pre-acidification process combined with a cathode buffer zone, and belongs to the field of electrodynamic remediation of heavy metal contaminated soil. Background Technology

[0002] Heavy metal ions pose a significant threat to human health. Excessive intake can cause symptoms such as diarrhea, cirrhosis, and movement disorders in mild cases, and heavy metal poisoning or even cancer in severe cases, seriously endangering human health. As heavy metals accumulate in soil over time, they gradually transform into more difficult-to-treat forms, characterized by long natural degradation times, difficulty in treatment using conventional methods, and poor treatment effectiveness.

[0003] Electrodynamic remediation (EMR) is a commonly used method for treating heavy metal-contaminated soil. EMR refers to the process of removing inorganic or organic pollutants from soil in an acidic environment using a low-voltage direct current electric field. However, when using traditional EMR devices to treat heavy metal-contaminated soil, the water content in the central and cathode zones is high because water is discharged from the cathode zone. Therefore, EMR suffers from drawbacks such as poor treatment efficiency in the central and cathode zones, uneven removal rates across different areas of the soil, and the discharged wastewater containing significantly excessive levels of heavy metals, requiring further treatment before discharge.

[0004] Therefore, there is a need to provide a method for electro-remediation of heavy metal contaminated soil with good removal effect. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a novel device and construction method for electrokinetic remediation of heavy metal contaminated soil using a pre-acidification process combined with a cathode buffer zone. This invention enhances the electrokinetic remediation effect through a pre-acidification process, utilizes novel materials to fabricate the electrokinetic remediation device, and selects cathode buffer materials to achieve complete heavy metal removal from the entire device. It improves the heavy metal removal rate in the central and cathode zones during the electrokinetic remediation process, resulting in a more uniform removal rate across the soil after remediation. Furthermore, it allows for simultaneous treatment of wastewater discharge. This not only improves the overall removal rate of heavy metal ions but also avoids secondary pollution from electrokinetic remediation wastewater.

[0006] The first objective of this invention is to provide a pre-acidification process, wherein the pre-acidification process involves soaking heavy metal contaminated soil in a pre-acidification solution, wherein the pre-acidification solution is a citric acid solution.

[0007] In one embodiment of the present invention, the concentration of the citric acid solution is 0.05-0.3 mol / kg.

[0008] In one embodiment of the present invention, the volume ratio of the citric acid solution to the mass of the sludge is 100-200 mL : 3 kg.

[0009] In one embodiment of the present invention, the soaking time is 5-30 minutes.

[0010] The second objective of this invention is to provide a novel electrically powered remediation device for heavy metal contaminated soil, comprising a soil remediation chamber and a wastewater treatment chamber;

[0011] The soil remediation chamber has an opening at the top, with an anode plate on one side and a cathode plate on the opposite side; both sides of the anode and cathode plates are covered with filter paper; a cathode buffer chamber is also provided in the direction of the cathode plate opposite to the anode plate; the anode and cathode plates are connected by wires, power supply, and sensors.

[0012] The soil remediation chamber is connected to a wastewater treatment chamber on the side with the cathode plate. There is a gap between the soil remediation chamber and the wastewater treatment chamber to allow liquid to flow from the soil remediation chamber into the wastewater treatment chamber. The wastewater treatment chamber contains adsorbent material. The bottom of the wastewater treatment chamber is equipped with a drain hole and a drain pipe.

[0013] In one embodiment of the present invention, the soil remediation chamber and the wastewater treatment chamber are made of mesoporous silica material.

[0014] In one embodiment of the present invention, the anode plate is a graphene plate; the cathode plate is a graphene plate with holes, the holes being used to allow liquid to pass through the wastewater treatment chamber.

[0015] In one embodiment of the present invention, the cathode buffer chamber is a cube made of mesoporous silicon material plate, hollow inside for placing filling material, with an opening at the top and holes on the front and back sides.

[0016] In one embodiment of the present invention, the filling material, by mass fraction, comprises 40%-45% slag, 30%-35% activated carbon, 5%-10% charcoal ash, 8%-10% fly ash, and 10%-20% water.

[0017] In one embodiment of the present invention, the cathode buffer chamber occupies 20-30% of the total volume of the soil remediation chamber.

[0018] In one embodiment of the present invention, the filling material accounts for 80-90% of the total volume of the cathode buffer chamber.

[0019] In one embodiment of the present invention, the sensor includes a current sensor, a voltage sensor, and a temperature sensor, used to measure changes in current, voltage, and temperature during the electrorepair reaction process.

[0020] In one embodiment of the present invention, the adsorbent material is a magnetic porous nanocomposite material, which is placed at the bottom of the wastewater treatment chamber.

[0021] In one embodiment of the present invention, the preparation process of the magnetic porous nanocomposite material is as follows:

[0022] First, mix cotton fibers with a strong alkaline solution of 0.1M~1.0M at a ratio of 1g: 5~15mL and let stand for 5-10 minutes. Then, adjust the pH of the cotton fibers to 7 and dry them. Next, mix them with a nickel nitrate solution of 0.1M~1.0M at a ratio of 1g: 5~15mL and soak them for 12~24 hours. After soaking, remove them and dry them for later use.

[0023] The third objective of this invention is to provide a cathode buffer filling material. The raw material components and their mass percentages are as follows: slag 40%-45%, activated carbon 30%-35%, charcoal ash 5%-10%, fly ash 8%-10%, and water 10%-20%.

[0024] In one embodiment of the present invention, the cathode buffer chamber filling material needs to be pressed into a cuboid test block.

[0025] In one embodiment of the present invention, the slag has a specific surface area greater than 300 m². 2 / kg of fine slag.

[0026] In one embodiment of the present invention, the activated carbon is made from coconut shells and is in the form of black granules.

[0027] In one embodiment of the present invention, the charcoal ash is the waste residue produced by burning wood or wood products, and its particle size ranges from 100 to 200 mesh.

[0028] In one embodiment of the present invention, the fly ash has a fineness of 100-200 mesh.

[0029] In one embodiment of the present invention, the water is deionized water.

[0030] In one embodiment of the present invention, the test block has a length of 8-10 cm, a width of 2-5 cm, a height of 10-15 cm, and a permeability coefficient of 1.2 × 10⁻⁶. -6 ~ 6×10 -5 .

[0031] A fourth objective of this invention is to provide a method for remediating heavy metal contaminated soil based on a novel electro-hydraulic remediation device. The method utilizes the aforementioned electro-hydraulic remediation device and includes the following steps:

[0032] S1. Pour the contaminated soil into the soil remediation chamber, then vibrate it thoroughly to make the soil uniform and remove air bubbles;

[0033] S2. Pour the citric acid solution into the soil remediation chamber, stir to make the soil uniform and remove air bubbles, and then let it stand for a period of time.

[0034] S3. Turn on the power to start the electric repair. After the repair is completed, open the drainage mechanism to discharge the electrolytic wastewater and reuse the treated soil sample.

[0035] In one embodiment of the present invention, the concentration of the citric acid solution in step S2 is 0.05-0.3 mol / kg.

[0036] In one embodiment of the present invention, the volume ratio of the citric acid solution to the mass of the sludge in step S2 is 100~200 mL : 3 kg.

[0037] In one embodiment of the present invention, the settling time in step S2 is 5-30 min.

[0038] In one embodiment of the present invention, the voltage for electric repair in step S3 is 25~30 V, the current is 2~3 A, and the repair time is 20~30 h.

[0039] Beneficial effects

[0040] 1. Compared with traditional electrostatic remediation tests, this invention provides a pre-acidification process that acidifies the soil before electrostatic remediation and causes some target heavy metal ions to detach from the surface of soil particles, thereby enhancing the effect of electrostatic remediation tests and improving the heavy metal removal rate.

[0041] 2. Compared with traditional electric remediation devices, this invention sets up a cathode buffer zone in the cathode area, extending the cathode area backward and moving the soil originally located in the cathode area forward to the center. This improves the removal rate of soil in the center and cathode areas, thereby enhancing the overall removal rate of electric remediation. It also makes the removal rates more balanced across different areas, reducing the workload for subsequent applications.

[0042] 3. Compared with traditional electric remediation devices that discharge electric remediation wastewater first and then treat it separately, the cathode buffer material of this invention has a certain adsorption capacity, and a wastewater treatment chamber is set in the cathode area to treat the electric remediation wastewater during the electric remediation process, thus avoiding the possibility of secondary pollution to the environment by the electric remediation wastewater.

[0043] 4. Compared with traditional electric repair devices that rely solely on electric repair to remove heavy metals, this invention uses adsorption materials for construction, and the electric repair device itself can also adsorb heavy metal ions to a certain extent, thus achieving heavy metal removal through multiple pathways and improving the overall heavy metal removal rate. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0045] Figure 1 This is a plan view of an electric remediation device for a novel heavy metal contaminated soil according to the present invention.

[0046] Figure 2 This is a schematic diagram of the anode plate of the present invention.

[0047] Figure 3 This is a schematic diagram of the cathode plate of the present invention.

[0048] Figure 4 This is a plan view of the outer side wall of the wastewater treatment plant of the present invention.

[0049] Figure 5 This is a front and back plan view of the cathode buffer chamber of the present invention.

[0050] Figure 6 This is a perspective view of the cathode buffer chamber of the present invention.

[0051] Figure 7 This is a plan view of the connection between the upper surface and the side surface of the cathode buffer chamber of the present invention.

[0052] Figure 8 This is a graph showing the heavy metal removal rate in the pre-acidification combined electrokinetic remediation test using different cathode buffer chamber filling materials in Example 3 of the present invention.

[0053] Figure 9 This is a graph showing the heavy metal removal rate in the combined electrokinetic remediation test using different pre-acidification reagents in Example 4 of the present invention.

[0054] Figure 10 This is a graph showing the heavy metal removal rate of pre-acidification combined with electrokinetic remediation at different citric acid concentrations in Example 5 of the present invention.

[0055] Figure 11 This is a graph showing the heavy metal removal rates of the conventional electro-repair test and the pre-acidification electro-repair test in Example 6 of the present invention.

[0056] In the diagram: 1. Power supply; 2. Sensor; 3. Anode plate; 4. Soil remediation chamber; 5. Cathode buffer chamber; 6. Cathode plate; 7. Wastewater treatment chamber; 8. Adsorbent material; 9. Filter paper; 10. Drainage hole; 11. Drainage pipe; 12. Wire. Detailed Implementation

[0057] 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 some, not all, of the embodiments of the present invention. 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.

[0058] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "attachment," and "placement" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or both integrated; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0059] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0060] Example 1

[0061] This embodiment provides a novel electrically powered remediation device for heavy metal contaminated soil, including a soil remediation chamber 4 and a wastewater treatment chamber 7.

[0062] The soil remediation chamber 4 has an opening at the top, with an anode plate 3 on one side and a cathode plate 6 on the opposite side. Filter paper 9 is attached to both sides of the anode plate 3 and the cathode plate 6. A cathode buffer chamber 5 is also provided on the cathode plate 6 in the direction opposite to the anode plate 3. The anode plate 3 and the cathode plate 6 are connected to the power supply 1 and the sensor 2 through wires 12.

[0063] The soil remediation chamber 4 is connected to the sewage treatment chamber 7 on the side where the cathode plate 6 is located. There is a gap between the soil remediation chamber 4 and the sewage treatment chamber 7 to allow liquid to flow from the soil remediation chamber 4 into the sewage treatment chamber 7. The sewage treatment chamber 7 contains adsorbent material 8. The bottom of the sewage treatment chamber 7 is provided with a drain hole 10 and a drain pipe 11.

[0064] The soil remediation chamber 4 and the wastewater treatment chamber 7 are made of mesoporous silica material; the soil remediation chamber 4 is 15cm long, 10cm wide, and 10cm high, with a wall thickness of 0.5cm; the wastewater treatment chamber 7 is 10cm long, 5cm wide, and 10cm high; the length, width, and height are measured from the inside.

[0065] Both the anode plate 3 and the cathode plate 6 are 10cm long, 8cm wide, and 0.5cm thick; the anode plate 3 is a graphene plate; the cathode plate 6 is a graphene plate with holes, the holes being rhomboid in shape, used to allow liquid to flow into the wastewater treatment chamber.

[0066] The cathode buffer chamber 5 is a cube made of mesoporous silicon material plate, with a length of 10cm, a width of 3cm, and a height of 10cm. The length, width, and height are measured from the outside. The interior of the cathode buffer chamber 5 is hollow for placing filling material. The length of the hollow part is 9.5cm, the width is 2.5cm, and the height is 9.5cm. The cathode buffer chamber 5 has an opening at the top and holes on the front and back sides.

[0067] The sensor 2 includes a current sensor, a voltage sensor, and a temperature sensor, used to measure changes in current, voltage, and temperature during the electrorepair reaction process.

[0068] The adsorbent material 8 is a magnetic porous nanocomposite material, placed at the bottom of the wastewater treatment chamber; the amount of adsorbent material can be adjusted by the user, and the height of the adsorbent material 8 should at least exceed the drainage hole 10; the magnetic porous nanocomposite material is prepared by first mixing cotton fiber with a strong alkaline solution (0.1M~1.0M) at a ratio of 1g:10mL and letting it stand for 5-10 minutes, then adjusting the pH of the cotton fiber to 7 and drying it, then mixing it with a certain concentration (0.1M~1.0M) of nickel nitrate solution at a ratio of 1g:10mL, soaking it for 24 hours, and then drying it for later use.

[0069] Example 2

[0070] A construction method for an electrokinetic remediation device based on a novel heavy metal contaminated soil remediation apparatus, the method employing the electrokinetic remediation device described in Example 1, and the method includes the following steps:

[0071] S1. The moisture content of Taihu Lake silt is reduced by drying, and then the dried silt is crushed into Taihu Lake silt particles with a particle size of less than 0.1 mm by a crusher.

[0072] S2. Prepare a 6000 mg / L copper sulfate pentahydrate solution;

[0073] S3. Prepare a 0.1 mol / kg citric acid solution;

[0074] S4. Add 2.8 kg of Taihu Lake silt particles to 1.4 L of the prepared copper sulfate pentahydrate solution and stir thoroughly to ensure uniform mixing of soil and water, thus preparing a 3000 mg / kg Cu ​​solution. 2+ Contaminated soil;

[0075] S5. Weigh out 42% slag, 30% activated carbon, 8% charcoal ash, 9% fly ash and 11% deionized water by mass percentage, mix them and press them into a rectangular mixed filling material (HHCL). Fill the hollow part inside the cathode buffer chamber with the prepared mixed filling material and then tightly attach the cathode buffer chamber to the cathode plate.

[0076] S6. The configured Cu 2+ The contaminated soil was poured into the soil remediation chamber in three stages. After each pour, the soil was thoroughly vibrated to ensure uniformity and remove air bubbles. After the final pour, the soil was repeatedly vibrated to ensure even mixing.

[0077] S7. Pour 150 mL of 0.1 mol / kg citric acid solution into the soil remediation chamber. After contact with the soil, stir for 1-3 minutes, repeatedly vibrate to make the soil uniform and remove air bubbles, and soak for 5-30 minutes.

[0078] S8. Turn on the power, set the voltage to 30V and the current to 3A to start the electric repair. After 24 hours of electric repair, turn off the power, open the drainage mechanism, and drain the wastewater from the electric repair to obtain the treated soil sample.

[0079] According to the "Water Environmental Quality Standard" (GB 3838-2002) and the "Industrial Wastewater Discharge Standard" (GB 8978-1996), the secondary discharge standard for Cu ion-contaminated water should meet the requirement of Cu ≤ 1 mg / L. The results of testing the wastewater from the electro-remediation process are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] It is evident that the electric wastewater treatment method of this invention meets the discharge standards.

[0083] Compared to traditional electroremediation devices, this invention incorporates a cathode buffer zone in the cathode area, extending the cathode region backward and shifting the soil originally located in the cathode area to the center. This improves the removal rate of soil in the cathode area, thereby enhancing the overall removal rate of electroremediation. Unlike traditional electroremediation devices that discharge wastewater first and then treat it separately, this invention features a wastewater treatment chamber in the cathode area, treating the wastewater simultaneously during the electroremediation process, thus avoiding the possibility of secondary pollution. Furthermore, unlike traditional electroremediation devices that solely rely on electroremediation to remove heavy metals, this invention utilizes adsorption materials in its construction. The electroremediation device itself can also adsorb heavy metal ions to a certain extent, achieving multi-pathway heavy metal removal and improving the overall heavy metal removal rate.

[0084] Example 3

[0085] Referring to the steps of Example 2, the effects of different filling materials in the cathode buffer chamber were compared, and Cu with the same contamination concentration was selected. 2+ Electrokinetic remediation tests were conducted on contaminated soil. The filling materials selected included slag, activated carbon, biochar, palm fiber, a mixture of materials, slag + biochar, and biochar + activated carbon, as detailed below:

[0086] Slag filling material (LZ): The slag was purchased from a steel plant in Wuxi City;

[0087] Activated carbon filler material (HT): Activated carbon purchased from Sinopharm Group;

[0088] Biochar filler material (ST): Biochar was purchased from Sinopharm Group;

[0089] Palm fiber filling material (ZL): Palm fiber was purchased from a company in Hainan Province;

[0090] Hybrid filler material (HHCL): prepared by mixing slag, activated carbon, charcoal ash, fly ash and deionized water, wherein the mass ratio of slag, activated carbon, charcoal ash, fly ash and deionized water is 0.42 : 0.3 : 0.08 : 0.09 : 0.11;

[0091] Slag + biochar filling material (L+S): It is made by mixing slag and biochar, wherein the mass ratio of slag to biochar is 1:1;

[0092] Biochar + Activated Carbon Filler Material (S+H): Prepared by mixing biochar and activated carbon, wherein the mass ratio of biochar to activated carbon is 1:1.

[0093] All of the above-mentioned filling materials fill the hollow part of the cathode buffer chamber, and in this embodiment, a control group (W) is set up, that is, no material is filled in the cathode buffer chamber.

[0094] The soil removal rate of each part after the electric repair was tested is as follows: Figure 8 As shown. From Figure 8 It can be observed that using LZ, HHCL, and L+S as cathode buffer filling materials all improved the removal rate in the central and cathode areas compared to the group without a cathode buffer (W), while the removal rate in the anode area showed little difference. Furthermore, compared to the group without a cathode buffer, the removal rates in all areas of the group with a cathode buffer were more uniform. This demonstrates that filling the cathode buffer with suitable materials can improve the removal rate in the central and cathode areas and make the soil removal rate more uniform across different areas. Moreover, after traditional electrokinetic remediation, Cu in the wastewater... 2+ The concentration was approximately 3000 mg / L, while the concentration of wastewater treated with appropriate materials by this device was less than 1000 mg / L, significantly reducing the concentration of wastewater in the electro-remediation process.

[0095] Example 4

[0096] Referring to the steps of Example 2, the effects of different pre-acidification reagents were compared. Pre-acidification solutions were prepared using citric acid, tartaric acid, oxalic acid, lactic acid, and tetrasodium glutamate diacetate (GLDA) as pre-acidification reagents, with a concentration of 0.1 mol / kg and the same dosage. HHCl was used as the cathode buffer filling material. A combined pre-acidification and electrokinetic remediation experiment was conducted, and the average removal rate of different pre-acidification reagents using electrokinetic remediation was measured as follows: Figure 9 As shown.

[0097] The results showed that, among different pre-acidification reagents, citric acid had the highest removal rate of heavy metals in all soil samples.

[0098] Example 5

[0099] Following the steps of Example 2, the effects of different concentrations of pre-acidification solutions were compared. Citric acid solutions of 0.05, 0.1, 0.15, and 0.2 mol / kg were selected as pre-acidification solutions, with the dosage remaining constant. The average removal rates of different concentrations of citric acid were measured as follows: Figure 10 As shown.

[0100] The results showed that with increasing citric acid concentration, the removal of heavy metals in various soil components initially increased and then decreased. 0.1 mol / kg citric acid significantly reduced the removal of Cu... 2+ The removal effect is best at citric acid. This is mainly because when the concentration of citric acid is low, the H+ produced by ionization in the solution... + Inability to fully utilize Cu on the soil surface 2+ It is "squeezed" into the aqueous solution. When the citric acid concentration is too high, the H+ in the solution... + When the concentration is too high, the concentration gradient between the soil and the aqueous solution is affected, and some Cu in the solution... 2+The solution will be re-adsorbed onto the soil surface due to the osmotic difference, which will inhibit the pre-acidification effect. Therefore, 0.1 mol / kg is the optimal concentration of the pre-acidification solution.

[0101] Example 6

[0102] Referring to the steps of Example 2, the remediation effects of the conventional electrokinetic remediation test and the pre-acidification electrokinetic remediation test were compared: citric acid was used as the pre-acidification reagent, and the dosage remained constant. The average removal rates of the conventional electrokinetic remediation test and the pre-acidification electrokinetic remediation test were measured as follows: Figure 11 As shown.

[0103] The results showed that the removal rate of all parts of the soil after pre-acidification electrostatic remediation treatment was increased by about 17% compared with traditional electrostatic remediation. This demonstrates that, compared with traditional electrostatic remediation tests, the pre-acidification process provided by this invention acidifies the soil before electrostatic remediation, enabling some target heavy metal ions to detach from the surface of soil particles, thereby enhancing the effect of electrostatic remediation tests and improving the heavy metal removal rate.

[0104] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for remediating heavy metal contaminated soil based on a novel electric remediation device, characterized in that, The remediation method for heavy metal contaminated soil uses an electrically powered remediation device. The device includes a soil remediation chamber and a wastewater treatment chamber; The soil remediation chamber has an opening at the top, with a graphene plate on one side and a perforated graphene plate on the opposite side; filter paper is attached to both sides of the anode and cathode plates; a cathode buffer chamber is also provided in the direction of the cathode plate relative to the anode plate; the anode and cathode plates are connected by wires, power supply and sensors. The cathode buffer chamber is a cube made of mesoporous silicon material plate, hollow inside for placing filling material, with an opening at the top and holes on the front and back sides. The soil remediation chamber is connected to a wastewater treatment chamber on the side with the cathode plate. There is a gap between the soil remediation chamber and the wastewater treatment chamber to allow liquid to flow from the soil remediation chamber into the wastewater treatment chamber. The wastewater treatment chamber contains adsorbent material. The bottom of the wastewater treatment chamber is equipped with a drain hole and a drain pipe. The filling material, by mass fraction, consists of 40%-45% slag, 30%-35% activated carbon, 5%-10% charcoal ash, 8%-10% fly ash, and 10%-20% water; the adsorbent material is a magnetic porous nanocomposite material. The method for remediating heavy metal contaminated soil includes the following steps: S1. Pour the contaminated soil into the soil remediation chamber, then vibrate it thoroughly to make the soil uniform and remove air bubbles; S2. Pour the citric acid solution into the soil remediation chamber, stir to make the soil uniform and remove air bubbles, and then let it stand for a period of time. S3. Turn on the power to start the electric repair. After the repair is completed, open the drainage mechanism to discharge the electrolytic wastewater and reuse the treated soil sample.

2. The method for remediating heavy metal contaminated soil according to claim 1, characterized in that, The preparation process of the magnetic porous nanocomposite material is as follows: First, cotton fibers are mixed with a strong alkaline solution with a concentration of 0.1M~1.0M at a ratio of 1g: 5~15mL and allowed to stand for 5-10 minutes. Then, the pH of the cotton fibers is adjusted to 7 and dried. Next, the cotton fibers are mixed with a nickel nitrate solution with a concentration of 0.1M~1.0M at a ratio of 1g: 5~15mL and soaked for 12~24 hours. After soaking, the cotton fibers are dried and ready for use.

3. The method for remediating heavy metal contaminated soil according to claim 1, characterized in that, The concentration of the citric acid solution in step S2 is 0.05-0.3 mol / kg.

4. The method for remediating heavy metal contaminated soil according to claim 1, characterized in that, The volume ratio of the citric acid solution to the mass of the sludge in step S2 is 100~200 mL : 3 kg.

5. The method for remediating heavy metal contaminated soil according to claim 1, characterized in that, The settling time mentioned in step S2 is 5-30 min.

6. The method for remediating heavy metal contaminated soil according to claim 1, characterized in that, In step S3, the voltage for electric repair is 25~30V, the current is 2~3A, and the repair time is 20~24h.

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