Method for repairing hexavalent chromium contaminated soil through combination of composite activator and electrodynamic force

Abstract

The invention discloses a method for repairing hexavalent chromium contaminated soil through combination of a composite activator and electrodynamic force, and belongs to the technical field of heavy metal contaminated soil repairing. Comprising the following steps: air-drying hexavalent chromium polluted soil, sieving to remove impurities, and mixing by using a drum mixer to obtain a uniform soil sample; the method comprises the following steps: filling a soil sample into a soil remediation tank, slowly adding a composite soil activator solution formed by mixing tartaric acid with the concentration of 0.1 mol / L and potassium chloride with the concentration of 0.04-0.06 mol / L into the soil until the soil is completely infiltrated, and performing electrokinetic remediation on the soil sample infiltrated with the composite soil activator solution until the remediation is finished. According to the method, the hexavalent chromium contaminated soil is remedied through combination of low-molecular organic acid and potassium chloride and electrokinetic remediation, the removal efficiency of hexavalent chromium is remarkably improved, the remedied soil can reach the national standard first-class land use screening value, damage to the soil structure and secondary pollution are avoided, meanwhile, the effect of improving alkaline soil is achieved, and the method is suitable for large-scale popularization and application. Good popularization and application prospects are realized.

Description

Technical Field

[0001] The invention relates to a method for repairing hexavalent chromium contaminated soil, and in particular to a method for repairing hexavalent chromium contaminated soil by using a composite activator in combination with electric power, and belongs to the technical field of heavy metal contaminated soil repair. Background Art

[0002] In recent years, with the rapid development of my country's social economy, the industrial structure has been continuously adjusted and upgraded, and the relocation of enterprises in industries such as chromium salt production, leather making, electroplating, metallurgy, and pigment manufacturing has accelerated, resulting in a large amount of chromium-contaminated soil. Chromium in chromium-contaminated soil usually exists in hexavalent and trivalent forms, among which hexavalent chromium has attracted much attention due to its carcinogenic toxicity, high activity, and easy migration, and has been listed as the first batch of toxic and hazardous soil substances that are subject to key control by the state.

[0003] At present, the commonly used remediation technologies for hexavalent chromium contaminated soil include chemical reduction, solidification and stabilization, chemical leaching, electric remediation, incineration disposal, etc. Among them, hexavalent chromium in the soil mainly exists in the form of oxygen-containing anions. When using electric technology to remediate hexavalent chromium contaminated soil, a DC electric field is added at both ends of the soil. The hexavalent chromium migrates to the anode end in the soil or is converted into a low-toxic form. The electric remediation technology has attracted more and more attention due to its advantages of completely removing pollutants, less secondary pollution, and convenient post-processing. However, the above-mentioned remediation methods still have the following problems: 1) For example, the Chinese invention patent with application publication number CN113182349A discloses a method for remediating chromium-contaminated soil using an electrokinetic coupled permeable reaction wall (EK-RPB). The method prepares PRB material and fills it into the permeable reaction wall of the device, fills chromium-contaminated soil into the soil chamber of the device, adds electrolyte to the cathode chamber and the anode chamber, and connects the electrodes to a DC power supply, thereby improving the removal efficiency of hexavalent chromium in the electrokinetic remediation. However, the PRB material prepared by the method requires raw materials such as magnesium nitrate, aluminum nitrate, and urea, which increases the remediation cost and may cause secondary pollution; 2) For example, the Chinese invention patent with application publication number CN109174951A discloses an electrodynamic remediation method for hexavalent chromium-contaminated soil. The hexavalent chromium in the soil is enriched in the anode tank through electromigration. Although the hexavalent chromium in the soil is removed after the remediation treatment, the concentration of soil pollutants after treatment by this method is high (78.6-282.7 mg / g), which is much higher than the screening value of the second category of land use in GB36600 (5.7 mg / g), and it is difficult to find an application scenario in reality; 3) For example, the Chinese invention patent with application publication number CN116871315A provides a system for remediating hexavalent chromium contaminated soil with a composite bacterial agent. The system combines electrodynamic remediation with microbial agent remediation to reduce hexavalent chromium in contaminated soil to trivalent chromium, thereby reducing the toxicity of chromium. However, this method requires the purchase of commercial microbial agents for cultivation, which is costly and complex to operate. In addition, the overall removal efficiency of hexavalent chromium does not reach 50%, which limits the promotion and application of this technology.

[0004] In summary, the current electric remediation methods still have shortcomings and deficiencies such as low pollutant removal rate, long remediation time, high energy consumption, high cost, and complex operation, which limit the promotion and application of electric remediation technology. Compared with other heavy metals, hexavalent chromium has better electrical mobility. Therefore, how to further improve the electrical mobility of hexavalent chromium and enhance the electric technology to remediate hexavalent chromium contaminated soil is a remediation technology that is worth exploring and has good application prospects. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of low pollutant removal rate and long restoration time in the existing hexavalent chromium contaminated soil restoration, and provide a method for restoring hexavalent chromium contaminated soil by using a composite activator in combination with electric power. By adding a composite soil activator to the hexavalent chromium contaminated soil and combining it with electric power restoration, the exchangeable state of chromium is increased, thereby improving the migration and conversion efficiency of hexavalent chromium, improving the soil restoration effect, enhancing soil fertility, and thus improving the soil.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a method for remediating hexavalent chromium contaminated soil by using a composite activator combined with electric power, comprising the following steps: Step S1, preparing soil samples: The hexavalent chromium contaminated soil is air-dried, sieved to remove large particles of impurities, mixed with a drum mixer without destroying the soil particle structure to obtain a uniform soil sample, and the soil sample is placed at room temperature for use; Step S2: Filling the soil sample into the soil remediation tank: Take the prepared soil sample and fill it into a soil restoration tank made of organic glass, and keep the soil surface height in the tank consistent, wherein the volume of the soil restoration tank is greater than 20%~25% of the mass of the filled soil; Step S3, preparing a composite soil activator solution and infiltrating the soil sample: The composite soil activator solution is a mixture of tartaric acid with a concentration of 0.1 mol / L and potassium chloride with a concentration of 0.04-0.06 mol / L. The composite soil activator solution is slowly added to the soil until the soil is completely soaked. After the addition of the composite soil activator solution, it is left to stand for 24 hours to maintain the soil moisture content at 28%-31%. The relationship between the addition amount of the composite soil activator solution and the soil moisture content is: , where x is the volume of tartaric acid solution (in L ), y is the initial soil moisture content, z is the soil mass in the soil restoration tank (in kg ); Step S4: constructing cathode tank and anode tank for electric repair based on the soil repair tank: The cathode tank and the anode tank are respectively located on both sides of the soil remediation tank, and the two are separated by an anion exchange membrane and a cation exchange membrane respectively. Graphite electrode plates are inserted into the cathode tank and the anode tank, and are connected to a voltage and current controller through a wire. Deionized water is added to the anode tank, and citric acid is added to the cathode tank. The liquid level of the added liquid is high enough to submerge the graphite electrode plates in the cathode tank and the anode tank. Step S5, performing electrokinetic repair on the soil sample soaked with the composite soil activator solution: A 45V direct current is applied to the cathode tank and the anode tank, and the electric field strength is maintained at 1.5V / cm through a voltage and current controller to keep the circulation unobstructed and continuously powered on until the repair is completed.

[0007] Furthermore, in step S3, the flow rate of slowly adding the composite soil activator solution into the soil is 8.0-8.5 mL / min.

[0008] Furthermore, in step S4, the concentration of citric acid in the cathode cell is 0.1 mol / L, and the volume of the added water is the same as the volume of the citric acid.

[0009] Furthermore, in step S4, the soil remediation tank, cathode tank and anode tank are all made of organic glass with a thickness of 2 mm, and the anion exchange membrane and cation exchange membrane are both made of polystyrene.

[0010] Furthermore, in step S5, the continuous power-on operation time is 72 to 240 hours.

[0011] The beneficial effects of the present invention are: 1) In the present invention, low-molecular organic acid and potassium chloride are combined with electric remediation to remediate hexavalent chromium contaminated soil. When the hexavalent chromium content of the contaminated soil is 10-15 mg / kg and the voltage gradient is 1.5 V / cm, the hexavalent chromium removal rate reaches 84.96%-86.45% after the remediation, which significantly improves the removal efficiency of hexavalent chromium. The hexavalent chromium content of the soil after remediation is lower than the first-class land screening value of 3.0 mg / kg in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard" (GB36600-2018), which avoids structural damage and secondary pollution to the soil, and at the same time has the effect of improving alkaline soil, and has good prospects for promotion and application.

[0012] 2) In the present invention, the composite soil activator and electrokinetic remediation are combined, and the effect after remediation is higher than the hexavalent chromium removal rate of only using electrokinetic remediation or adding a single low-molecular organic acid or potassium chloride. Therefore, by controlling the solvent addition and remediation conditions between the composite soil activator and electrokinetic remediation, a good synergistic remediation effect is achieved.

[0013] 3) In addition to the synergistic repair effect, the composite soil activator of the present invention has tartaric acid as a low molecular weight organic acid, which is a natural secretion of plant roots and microorganisms. Adding it to the soil will not cause secondary pollution and can also avoid damaging the soil structure; potassium chloride, as a common agricultural fertilizer, can also be used as soil potassium fertilizer to enhance soil fertility without causing secondary pollution or damaging the soil structure; 4) The composite soil activator is added in the present invention, and the soil pH after the repair is lower than the original soil pH to a certain extent, and it can also have a certain improvement effect on alkaline soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram showing the effect of soil hexavalent chromium restoration at different locations measured in Example 1 of the present invention; Figure 2 This is a diagram showing the effect of soil hexavalent chromium restoration at different locations measured in Example 2 of the present invention; Figure 3 This is a diagram showing the hexavalent chromium remediation effect of soil at different locations measured in Example 3 of the present invention. DETAILED DESCRIPTION

[0015] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments.

[0016] The electric repair device used in the electric repair process in the following embodiments can use an existing or temporarily built experimental device, or can use, for example, a heavy metal contaminated soil repair device with authorization announcement number CN221453822U, which can meet the use scenario of the electric repair process. For specific parameter settings, please refer to the following embodiments.

[0017] Example 1: The present invention provides a method for repairing hexavalent chromium contaminated soil using a composite activator combined with electric power, comprising the following steps: Step S1, preparing a soil sample: taking 0.7072 g of potassium dichromate granules, adding 374 mL of deionized water, stirring and dissolving to obtain a potassium dichromate solution; adding 4.5 kg of clean soil into a drum mixer, starting the mixer, adding the potassium dichromate solution while stirring, stirring for 2 h until completely uniformly mixed, and standing in the dark for 4 days for use.

[0018] Step S2, filling the soil sample into the soil remediation tank: take the 4.5 kg soil sample prepared above, fill the soil sample into the soil remediation tank made of plexiglass, and keep the soil surface height in the tank consistent, the hexavalent chromium concentration in the contaminated soil sample is 13.1 mg / kg, and the volume of the soil remediation tank is greater than 20%~25% of the mass of the filled soil.

[0019] Step S3, preparing a composite soil activator solution and infiltrating the soil sample: Take 22.5135g of tartaric acid granules and 4.473g of potassium chloride granules respectively, add 1500mL of deionized water, stir and dissolve to obtain 0.1mol / L tartaric acid and 0.04mol / L potassium chloride solution, and mix to obtain a composite soil activator solution; The composite soil activator solution was slowly added to the soil at a flow rate of 8.3 mL / min until the soil was completely soaked. After the addition of the composite soil activator solution, the soil was allowed to stand for 24 hours to maintain a soil moisture content of 31%.

[0020] Step S4: constructing cathode tank and anode tank for electric repair based on the soil repair tank: The cathode tank and the anode tank are located on both sides of the soil remediation tank, and are separated by an anion exchange membrane and a cation exchange membrane respectively. Graphite electrode plates are inserted into the cathode tank and the anode tank, and are connected to a voltage and current controller through wires. 0.7L of deionized water is added to the anode tank, and 0.7L of citric acid with a concentration of 0.1mol / L is added to the cathode tank. The liquid levels of the added liquids are sufficient to submerge the graphite electrode plates in the cathode tank and the anode tank.

[0021] Step S5, performing electrokinetic repair on the soil sample soaked with the composite soil activator solution: A 45V direct current was applied to the cathode tank and the anode tank, and the electric field strength was maintained at 1.5V / cm through a voltage and current controller to keep the circulation smooth. The system was continuously powered on for 72 hours.

[0022] Turn off the power supply, divide the soil in the soil remediation tank from the anode to the cathode into 4 parts (A1~A4) at a distance of 15 cm each, measure the hexavalent chromium concentration respectively, and calculate the hexavalent chromium removal rate.

[0023] like Figure 1 As shown, the hexavalent chromium concentrations are: A1 is 3.0 mg / kg, A2 is 2.1 mg / kg, A3 is 1.0 mg / kg, A4 is 1.0 mg / kg, and the average concentration is 1.775 mg / kg; the average removal rate of hexavalent chromium is 86.45%; and the soil pH value after remediation is reduced from 9.51 to 7.81.

[0024] Example 2: The present invention provides a method for remediating hexavalent chromium contaminated soil using a composite activator combined with electric power, comprising the following steps: Step S1, preparing a soil sample: taking 0.7072 g of potassium dichromate granules, adding 374 mL of deionized water, stirring and dissolving to obtain a potassium dichromate solution; adding 4.5 kg of clean soil into a drum mixer, starting the mixer, adding the potassium dichromate solution while stirring, stirring for 2 h until completely uniformly mixed, and standing in the dark for 4 days for use.

[0025] Step S2, filling the soil sample into the soil remediation tank: take the 4.5 kg soil sample prepared above, fill the soil sample into the soil remediation tank made of plexiglass, and keep the soil surface height in the tank consistent, the hexavalent chromium concentration in the contaminated soil sample is 13.1 mg / kg, and the volume of the soil remediation tank is greater than 20%~25% of the mass of the filled soil.

[0026] Step S3, preparing a composite soil activator solution and infiltrating the soil sample: Take 22.5135g of tartaric acid granules and 5.5913g of potassium chloride granules respectively, add 1500mL of deionized water, stir and dissolve to obtain 0.1mol / L tartaric acid and 0.05mol / L potassium chloride solution, and mix to obtain a composite soil activator solution; The composite soil activator solution was slowly added to the soil at a flow rate of 8.3 mL / min until the soil was completely soaked. After the addition of the composite soil activator solution, the soil was allowed to stand for 24 hours to maintain a soil moisture content of 31%.

[0027] Step S4: constructing cathode tank and anode tank for electric repair based on the soil repair tank: The cathode tank and the anode tank are located on both sides of the soil remediation tank, and are separated by an anion exchange membrane and a cation exchange membrane respectively. Graphite electrode plates are inserted into the cathode tank and the anode tank, and are connected to a voltage and current controller through wires. 0.7L of deionized water is added to the anode tank, and 0.7L of citric acid with a concentration of 0.1mol / L is added to the cathode tank. The liquid levels of the added liquids are sufficient to submerge the graphite electrode plates in the cathode tank and the anode tank.

[0028] Step S5, performing electrokinetic repair on the soil sample soaked with the composite soil activator solution: A 45V direct current was applied to the cathode tank and the anode tank, and the electric field strength was maintained at 1.5V / cm through a voltage and current controller to keep the circulation smooth. The system was continuously powered on for 72 hours.

[0029] Turn off the power supply, divide the soil in the soil remediation tank from the anode to the cathode into 4 parts (A1~A4) at a distance of 15 cm each, measure the hexavalent chromium concentration respectively, and calculate the hexavalent chromium removal rate.

[0030] like Figure 2 As shown, the hexavalent chromium concentrations are: A1 is 2.4 mg / kg, A2 is 2.2 mg / kg, A3 is 1.7 mg / kg, A4 is 1.58 mg / kg, and the average concentration is 1.97 mg / kg; the average removal rate of hexavalent chromium is 84.96%; and the soil pH value after remediation is reduced from 9.51 to 7.73.

[0031] Example 3: The present invention provides a method for repairing hexavalent chromium contaminated soil using a composite activator combined with electric power, comprising the following steps: Step S1, preparing a soil sample: taking 0.7072 g of potassium dichromate granules, adding 374 mL of deionized water, stirring and dissolving to obtain a potassium dichromate solution; adding 4.5 kg of clean soil into a drum mixer, starting the mixer, adding the potassium dichromate solution while stirring, stirring for 2 h until completely uniformly mixed, and standing in the dark for 4 days for use.

[0032] Step S2, filling the soil sample into the soil remediation tank: take the 4.5 kg soil sample prepared above, fill the soil sample into the soil remediation tank made of plexiglass, and keep the soil surface height in the tank consistent, the hexavalent chromium concentration in the contaminated soil sample is 13.1 mg / kg, and the volume of the soil remediation tank is greater than 20%~25% of the mass of the filled soil.

[0033] Step S3, preparing a composite soil activator solution and infiltrating the soil sample: Take 22.5135g of tartaric acid granules and 6.7095g of potassium chloride granules respectively, add 1500mL of deionized water, stir and dissolve to obtain 0.1mol / L tartaric acid and 0.06mol / L potassium chloride solution, and mix to obtain a composite soil activator solution; The composite soil activator solution was slowly added to the soil at a flow rate of 8.3 mL / min until the soil was completely soaked. After the addition of the composite soil activator solution, the soil was allowed to stand for 24 hours to maintain a soil moisture content of 31%.

[0034] Step S4: constructing cathode tank and anode tank for electric repair based on the soil repair tank: The cathode tank and the anode tank are located on both sides of the soil remediation tank, and are separated by an anion exchange membrane and a cation exchange membrane respectively. Graphite electrode plates are inserted into the cathode tank and the anode tank, and are connected to a voltage and current controller through wires. 0.7L of deionized water is added to the anode tank, and 0.7L of citric acid with a concentration of 0.1mol / L is added to the cathode tank. The liquid levels of the added liquids are sufficient to submerge the graphite electrode plates in the cathode tank and the anode tank.

[0035] Step S5, performing electrokinetic repair on the soil sample soaked with the composite soil activator solution: A 45V direct current was applied to the cathode tank and the anode tank, and the electric field strength was maintained at 1.5V / cm through a voltage and current controller to keep the circulation smooth. The system was continuously powered on for 72 hours.

[0036] Turn off the power supply, divide the soil in the soil remediation tank from the anode to the cathode into 4 parts (A1~A4) at a distance of 15 cm each, measure the hexavalent chromium concentration respectively, and calculate the hexavalent chromium removal rate.

[0037] like Figure 3 As shown, the hexavalent chromium concentrations are: A1 is 3.0 mg / kg, A2 is 1.64 mg / kg, A3 is 1.7 mg / kg, A4 is 1.4 mg / kg, and the average concentration is 1.94 mg / kg; the average removal rate of hexavalent chromium is 85.19%; and the soil pH value after remediation is reduced from 9.51 to 7.46.

[0038] Comparative Example 1: The difference compared with Example 1 is that only 0.1 mol / L tartaric acid solution is added.

[0039] Turn off the power supply, divide the soil in the soil remediation tank from the anode to the cathode into 4 parts (A1~A4) at a distance of 15 cm each, measure the hexavalent chromium concentration respectively, and calculate the hexavalent chromium removal rate.

[0040] Hexavalent chromium concentration: A1 is 2.5 mg / kg, A2 is 2.0 mg / kg, A3 is 2.3 mg / kg, A4 is 2.4 mg / kg, and the average concentration is 2.3 mg / kg; the average removal rate of hexavalent chromium is 82.44%; after restoration, the soil pH value decreased from 9.51 to 8.07.

[0041] Comparative Example 2: The difference from Example 1 is that only 0.04 mol / L potassium chloride solution is added.

[0042] Turn off the power supply, divide the soil in the soil remediation tank from the anode to the cathode into 4 parts (A1~A4) at a distance of 15 cm each, measure the hexavalent chromium concentration respectively, and calculate the hexavalent chromium removal rate.

[0043] Hexavalent chromium concentration: A1 is 9.3 mg / kg, A2 is 2.4 mg / kg, A3 is 2.8 mg / kg, A4 is 1.4 mg / kg, and the average concentration is 3.975 mg / kg; the average removal rate of hexavalent chromium is 69.66%; after restoration, the soil pH value decreased from 9.51 to 9.43.

[0044] Comparative Example 3: The difference from Example 1 is that only electrokinetic remediation is used without adding the composite soil activator solution, and deionized water is used instead.

[0045] Turn off the power supply, divide the soil in the soil remediation tank from the anode to the cathode into 4 parts (A1~A4) at a distance of 15 cm each, measure the hexavalent chromium concentration respectively, and calculate the hexavalent chromium removal rate.

[0046] Hexavalent chromium concentration: A1 is 6.7 mg / kg, A2 is 4.4 mg / kg, A3 is 5.15 mg / kg, A4 is 3.14 mg / kg, and the average concentration is 4.848 mg / kg; the average removal rate of hexavalent chromium is 63.00%; after remediation, the soil pH value decreased from 9.51 to 9.46.

[0047] Table 1 below shows the hexavalent chromium contaminated soil remediation effect values ​​measured in Examples 1 to 3 and Comparative Examples 1 to 3.

[0048] Table 1 / Hexavalent chromium concentration after repair (mg / kg) Average removal rate of hexavalent chromium (%) Example 2 1.78 86.45 Example 3 1.97 84.96 Example 4 1.94 85.19 Comparative Example 1 2.30 82.44 Comparative Example 2 3.98 69.66 Comparative Example 3 4.12 63.00 The measurement results in Table 1 show that, using the method for repairing hexavalent chromium contaminated soil provided by the present invention, the chromium pollution removal rate exceeds 82% after 72 hours, among which Example 2 has the best effect.

[0049] Compared with Comparative Examples 1 to 3 in Table 1, Example 2 shows that the effect of selecting the composite activator in the present invention is better than selecting a single activator or not adding any activator and the electric repair effect alone, and the hexavalent chromium removal rate can be increased by 4 to 23%, which can significantly reduce the hexavalent chromium concentration after repair.

[0050] In the present invention, low molecular weight organic acid and potassium chloride are combined with electric remediation to remediate hexavalent chromium contaminated soil. When the hexavalent chromium content of the contaminated soil is 10-15 mg / kg and the voltage gradient is 1.5 V / cm, the hexavalent chromium removal rate reaches 84.96%-86.45% after the remediation, which significantly improves the removal efficiency of hexavalent chromium. The hexavalent chromium content of the soil after remediation is lower than the first category land screening value of 3.0 mg / kg in the "Soil Environmental Quality Construction Land Soil Pollution Risk Control Standard" (GB36600-2018), which avoids structural damage and secondary pollution to the soil, and at the same time has the effect of improving alkaline soil, and has good promotion and application prospects.

[0051] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for remediating hexavalent chromium contaminated soil using a composite activator combined with electric power, characterized in that: The following steps are involved: Step S1, preparing soil samples: The hexavalent chromium contaminated soil is air-dried, sieved to remove large particles of impurities, mixed with a drum mixer without destroying the soil particle structure to obtain a uniform soil sample, and the soil sample is placed at room temperature for use; Step S2: Filling the soil sample into the soil remediation tank: Take the prepared soil sample and fill it into a soil restoration tank made of organic glass, and keep the soil surface height in the tank consistent, wherein the volume of the soil restoration tank is greater than 20%~25% of the mass of the filled soil; Step S3, preparing a composite soil activator solution and infiltrating the soil sample: The composite soil activator solution is a mixture of 0.1 mol / L tartaric acid and 0.04-0.06 mol / L potassium chloride. The composite soil activator solution is slowly added to the soil until the soil is completely soaked. After the addition of the composite soil activator solution, it is left to stand for 24 hours to maintain the soil moisture content at 28%-31%. The relationship between the addition amount of composite soil activator solution and soil moisture content is: , where x is the volume of tartaric acid solution (in L ), y is the initial soil moisture content, z is the soil mass in the soil restoration tank (in kg ); Step S4: constructing cathode tank and anode tank for electric repair based on the soil repair tank: The cathode tank and the anode tank are respectively located on both sides of the soil remediation tank, and the two are separated by an anion exchange membrane and a cation exchange membrane respectively. Graphite electrode plates are inserted into the cathode tank and the anode tank, and are connected to a voltage and current controller through a wire. Deionized water is added to the anode tank, and citric acid is added to the cathode tank. The liquid level of the added liquid is high enough to submerge the graphite electrode plates in the cathode tank and the anode tank. Step S5, performing electrokinetic repair on the soil sample soaked with the composite soil activator solution: A 45V direct current is applied to the cathode tank and the anode tank, and the electric field strength is maintained at 1.5V / cm through a voltage and current controller to keep the circulation unobstructed and continuously powered on until the repair is completed.

2. The method for remediating hexavalent chromium contaminated soil by using a composite activator combined with electric power according to claim 1, characterized in that: In the step S3, the composite soil activator solution is slowly added to the soil at a flow rate of 8.0-8.5 mL / min.

3. The method for remediating hexavalent chromium contaminated soil by using a composite activator combined with electric power according to claim 1, characterized in that: In step S4, the concentration of citric acid in the cathode cell is 0.1 mol / L, and the volume of water added is the same as the volume of citric acid.

4. The method for remediating hexavalent chromium contaminated soil by using a composite activator combined with electric power according to claim 1, characterized in that: In step S4, the soil remediation tank, cathode tank and anode tank are all made of organic glass with a thickness of 2 mm, and the anion exchange membrane and cation exchange membrane are all made of polystyrene.

5. The method for remediating hexavalent chromium contaminated soil by using a composite activator combined with electric power according to claim 1, characterized in that: In step S5, the continuous power-on operation time is 72 to 240 hours.

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