Soil and underground water cooperative treatment method

Abstract

The invention relates to the technical field of soil and groundwater pollution treatment and remediation, and discloses a soil and groundwater cooperative treatment method which comprises the steps that polluted soil is treated in a thermal desorption mode, a composite agent is injected into a polluted groundwater layer at the thermal desorption waste heat temperature, and the composite agent contains persulfate and an alkaline oxidizing agent. According to the soil and underground water cooperative treatment method provided by the invention, a combined technology of thermal desorption and chemical injection treatment is adopted, pollutants are efficiently oxidized and decomposed, and standard treatment of organic chlorine polluted soil and underground water is realized. According to the technical scheme, the energy consumption is low, the treatment operation is simple, the efficiency is high, the control is easy, and a very good treatment effect is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil and groundwater pollution remediation, in particular to a method for the cooperative treatment of soil and groundwater. BACKGROUND

[0002] The remediation methods for organochlorine-contaminated soil mainly include physical remediation, chemical remediation and biological remediation.

[0003] The physical remediation methods include cement kiln co-processing, thermal desorption (or thermal stripping), safe landfill and leaching. Although such methods are widely used, they generally have the disadvantages of high equipment requirements, complex process flow, high energy consumption, high remediation cost and site limitations, and the physical and chemical properties of the soil after remediation are often changed, which often requires other methods for cooperative treatment.

[0004] The chemical remediation method mainly involves adding strong oxidizing agents to organochlorine pesticide-contaminated soil to remove pollutants in the soil through oxidation. However, the chemical stability of chlorinated organic compounds, especially high-boiling organic compounds containing benzene rings, is relatively strong, and general oxidizing agents cannot achieve ideal treatment results.

[0005] The biological remediation method mainly includes biological composting remediation, which adopts artificial strengthening measures such as adding livestock manure, nutrients and ventilation to promote the degradation of microorganisms in the contaminated soil to organic pollutants. This method often requires a long remediation time, generally more than six months.

[0006] In summary, the existing domestic organic contaminated soil remediation technology generally has the problems of extensive soil treatment, low treatment efficiency, high treatment energy consumption, and the need for improvement of tail gas and groundwater purification technology. Under this background, the overall remediation method for organochlorine-contaminated sites needs to consider simplifying the treatment equipment, reducing energy consumption and saving remediation costs.

[0007] CN106694540A discloses a method for remediation of organochlorine pesticide-contaminated soil using a remediation agent with chemical reduction performance and slow-release carbon source biomass to remediate organochlorine pesticide-contaminated soil through a combination of periodic anaerobic fermentation chemical reduction dechlorination and aerobic biodegradation. This method requires a long remediation time, which takes several days or even months, and does not involve the treatment of related site groundwater.

[0008] CN 111842461 A discloses an in-situ thermal leaching soil remediation system, including a leaching solution injection well. Leaching solution from a storage tank is injected into the leaching solution injection well via an injection device. The temperature of the leaching solution is between 80 and 90°C, which can promote the vaporization and volatilization of some low-boiling-point organic pollutants and accelerate the dissolution rate of pollutants and leaching agents, thereby reducing the remediation period. After the leaching solution reacts with the contaminated soil, the leaching solution containing pollutants, groundwater, and soil gas are extracted from the original contaminated site through a leaching solution extraction well, achieving efficient removal of pollutants. This method combines in-situ leaching and in-situ thermal desorption technologies, but it is only suitable for soil remediation of low-boiling-point organic pollutants.

[0009] CN 110510793 A discloses a system and method for the coordinated treatment of groundwater and soil. The treatment system includes a filtration unit and a soil remediation unit connected in sequence. The soil remediation unit includes a first mixing device, a stripping device, a second mixing device, and a solid-liquid separation device connected in sequence. Conveying devices are independently provided between the first mixing device and the stripping device, between the stripping device and the second mixing device, and between the second mixing device and the solid-liquid separation device. This method achieves the coordinated treatment of groundwater and soil, but requires complex equipment, has a long processing flow, and high treatment costs.

[0010] Existing technologies involve the remediation of soil containing organic pollutants, but they do not address in-situ remediation of soil containing organochlorine pollutants or in-situ treatment of groundwater. Furthermore, these technologies suffer from problems such as long process flow, complex operation, and high operating costs. Summary of the Invention

[0011] The purpose of this invention is to overcome the problems of long process flow, complex operation and high operating cost in the existing technology, and to provide a method for the co-treatment of soil and groundwater. The method of this invention can efficiently decompose chlorine-containing pollutants, with low energy consumption, high treatment efficiency and the effect of achieving simultaneous compliance of contaminated soil and groundwater.

[0012] To achieve the above objectives, the present invention provides a method for the synergistic treatment of soil and groundwater, the method comprising: treating contaminated soil by thermal desorption, and injecting a composite agent into the contaminated groundwater layer at the residual heat temperature of thermal desorption, wherein the composite agent contains persulfate and an alkaline oxidant.

[0013] The method of this invention can efficiently decompose chlorine-containing pollutants, with low energy consumption, high treatment efficiency, and the effect of achieving simultaneous compliance of contaminated soil and groundwater. Detailed Implementation

[0014] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and explanatory and are not intended to limit the present application.

[0015] The present application provides a method for treating soil and groundwater, which comprises: treating contaminated soil by using thermal desorption, and injecting a composite agent into the contaminated groundwater layer at the thermal desorption residual heat temperature, wherein the composite agent contains persulfate and alkaline oxidant.

[0016] In the present application, injecting the composite agent into the contaminated groundwater layer at the thermal desorption residual heat temperature means that the composite agent can be injected simultaneously with the thermal desorption, or injected at or after the end of the thermal desorption when there is residual heat, as long as the temperature condition of the thermal desorption residual heat is met.

[0017] The method of the present application is particularly suitable for treating soil and groundwater on the ground surface, and the present application can simultaneously achieve in-situ remediation of soil and groundwater contaminated with chlorinated organic matter, and has the characteristics of low energy consumption, high treatment efficiency and good treatment effect.

[0018] In the present application, in order to achieve thermal desorption, a heater is generally provided on the contaminated soil, which is well known to those skilled in the art, and will not be described in detail herein.

[0019] In the present application, in order to achieve the injection of various agents, an agent injection system is generally provided on the contaminated soil, which is well known to those skilled in the art, and will not be described in detail herein.

[0020] Specifically, according to a specific embodiment, the heater and the agent injection system can be multiple, the heater is arranged in an array, and the injection system is arranged at the intermediate position surrounded by the heater. The agent injection system generally comprises a well body, a storage tank, an agent adding system and an extraction system.

[0021] In the present application, the specific addition method of the composite agent has no special requirement and is selected and determined according to the need, for example, it can be added at one time or in batches, and when added in batches, the intermittent time is for example 0.5-3h.

[0022] In the present application, the aforementioned method can achieve the purpose of the present application, and there is no special requirement for the amount of each substance in the composite agent, according to a preferred embodiment of the present application, the molar ratio of persulfate to alkaline oxidant is 0.1-5:1, for example, 0.5:1, 0.7:1, 1:1, 1.5:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, etc. The use of the aforementioned technical solution has the characteristics of high oxidation efficiency, small total agent dosage and small change in pH value of the contaminated groundwater.

[0023] According to a preferred embodiment of the present application, the molar ratio of the persulfate salt to the alkaline oxidant is 0.5-4:1.

[0024] In the present application, the composite agent can be a composite agent formed by the persulfate salt and the alkaline oxidant alone, or can be added in various forms such as an aqueous agent, an emulsifying agent, etc. In the present application, the composite agent is used in the form of an aqueous agent for the convenience of addition, and therefore an exemplary embodiment is that the composite agent is an aqueous agent formed by dissolving the persulfate salt and the alkaline oxidant in water.

[0025] In the present application, there is no special requirement for the form of addition of the persulfate salt and the alkaline oxidant, and the specific form is determined according to the working conditions. For example, the persulfate salt can be dissolved in water first and then the alkaline oxidant is added, or both of them can be dissolved in water at the same time, which are all applicable to the present application. There is no special requirement for the amount of water, and the target amount for forming a uniform solution can be used.

[0026] In the present application, the optional range of the persulfate salt is wide, and the following exemplary description is provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the persulfate salt is one or more of potassium monopersulfate composite salt (2KHSO5·KHSO4·K2SO4), potassium monopersulfate, potassium persulfate, ammonium monopersulfate, sodium monopersulfate, and calcium monopersulfate. In the embodiments of the present application, the advantages of the present application are illustrated by taking the persulfate salt as potassium monopersulfate composite salt, potassium monopersulfate, etc. The foregoing technical solution has the advantages of low toxicity, high efficiency, and low cost.

[0027] In the present application, the optional range of the alkaline oxidant is wide, and the following exemplary description is provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the alkaline oxidant is one or more of potassium ferrate, calcium peroxide, and magnesium peroxide. The foregoing technical solution has the advantages of high efficiency and low cost.

[0028] In the present application, there is no special requirement for the amount of the composite agent, and an exemplary embodiment is provided, but the scope of the present application is not limited thereto. According to a preferred embodiment of the present application, the addition amount of the persulfate salt is 0.1wt%-2wt% of the quality of the contaminated groundwater, for example, 0.3wt%, 0.5wt%, 0.8wt%, 1.1wt%, 1.4wt%, 1.7wt%, 1.9wt%, etc., preferably 0.5wt%-1.5wt%; and the addition amount of the alkaline oxidant is 0.05wt%-2wt% of the quality of the contaminated groundwater, for example, 0.15wt%, 0.35wt%, 0.55wt%, 0.75wt%, 1.15wt%, 1.55wt%, 1.75wt%, etc., preferably 0.1wt%-0.8wt%. The foregoing technical solution has the advantages of small amount and high economy.

[0029] In the present application, the treatment time of the composite agent is not particularly required, and is determined according to the operation temperature, for example, and can be 6-12 h. By using the above technical solution, the treatment time is short.

[0030] The above technical solutions can achieve the purpose of the present application. According to a preferred embodiment of the present application, the thermal desorption temperature is 50-500°C, for example, 70°C, 130°C, 150°C, 190°C, 220°C, 250°C, 270°C, 350°C, 420°C, 470°C, etc., and is preferably 100-300°C. By using the above technical solution, the equipment is simple and convenient to implement.

[0031] In the present application, the thermal desorption waste heat temperature can be selected in a wide range, and any thermal desorption waste heat temperature can achieve the purpose of the present application. The following is exemplary, but does not limit the scope of the present application. According to a preferred embodiment of the present application, the thermal desorption waste heat temperature is 40-150°C, for example, 55°C, 65°C, 75°C, 80°C, 85°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., and is preferably 50-90°C, and more preferably 80-90°C.

[0032] In the present application, the content of each substance in the contaminated groundwater is not particularly required. According to a preferred embodiment of the present application, the total organic carbon content in the contaminated groundwater is 50-1000 mg / L, and the chloride ion content is 1000-10000 mg / L. In the present application, the advantages of the present application are illustrated by using contaminated groundwater with a total organic carbon content of 180 mg / L and a chloride ion content of 6900 mg / L.

[0033] In the present application, the pH of the contaminated groundwater is not particularly required. According to a preferred embodiment of the present application, the pH of the contaminated groundwater is 5-9.

[0034] The present application is suitable for treating various contaminated soils. The following is exemplary, but does not limit the scope of the present application. According to a preferred embodiment of the present application, the contaminated soil is a soil contaminated with chlorine-containing organic matter.

[0035] In the present application, the chlorine-containing organic matter can be selected in a wide range. According to a preferred embodiment of the present application, the chlorine-containing organic matter includes one or more of chlorobenzene, o-nitrochlorobenzene, p-nitrochlorobenzene, m-nitrochlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, and 4-chloroaniline.

[0036] In the present application, the aforementioned technical solutions can achieve the purpose of the present application, according to a preferred embodiment of the present application, the pretreatment agent is injected into the contaminated groundwater layer before the injection of the composite agent to remove the chloride ions in the groundwater. The aforementioned technical solutions have the advantages of low processing cost and simple operation.

[0037] In the present application, the optional range of the pretreatment agent is wide, according to a preferred embodiment of the present application, the pretreatment agent is one or more of talc, mordenite, attapulgite and activated clay, and the advantages of the present application are illustrated by taking talc as the pretreatment agent in the examples.

[0038] In the present application, the form of the addition of the pretreatment agent has no special requirements, and is determined according to the working conditions, for example, in order to simplify the operation, it can be formed into a solution / fluid form and then injected into the groundwater layer by an injection device, and the amount of water has no special requirements, and generally the target amount for forming a uniform solution can be used.

[0039] In the present application, the amount of the pretreatment agent has no special requirements, according to a preferred embodiment of the present application, the amount of the pretreatment agent is 1wt%-10wt% of the amount of the groundwater, for example, 2wt%, 3wt%, 5wt%, 7wt%, 8wt%, 9wt% and the like.

[0040] In the present application, the conditions of the pretreatment have no special requirements, according to a preferred embodiment of the present application, the temperature of the pretreatment is 10-50℃.

[0041] In the present application, the time of the pretreatment has no special requirements, and is selected and determined according to the operation temperature, for example, it can be 1-3h. The aforementioned technical solutions have the advantage of short processing time.

[0042] In the present application, the aforementioned technical solutions can achieve the purpose of the present application, according to a preferred embodiment of the present application, after the treatment of the composite agent is completed, a post-treatment agent is added to further improve the removal rate of the pollutants.

[0043] In the present application, the optional range of the post-treatment agent is wide, according to a preferred embodiment of the present application, the post-treatment agent is activated carbon powder and / or biological agent.

[0044] In the present application, the form of the addition of the post-treatment agent has no special requirements, and is determined according to the working conditions, for example, in order to simplify the operation, it can be formed into a solution / fluid form and then injected into the groundwater layer by an injection device, and the amount of water has no special requirements, and generally the target amount for forming a uniform solution can be used.

[0045] In the present application, the amount of post-treatment agent added is not particularly limited, according to a preferred embodiment of the present application, the amount of post-treatment agent added is 0.1wt%-15wt% of the amount of groundwater, for example, 1.5wt%, 3.5wt%, 5.5wt%, 7.5wt%, 9.5wt%, 11.5wt%, 13.5wt% and the like.

[0046] According to a preferred embodiment of the present application, the amount of activated carbon powder added is 0.1wt%-5wt% of the amount of groundwater, for example, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% and the like.

[0047] According to a preferred embodiment of the present application, the amount of biological agent added is 0.1wt%-10wt% of the amount of groundwater, for example, 1.5wt%, 3.5wt%, 5.5wt%, 7.5wt%, 9.5wt% and the like.

[0048] In the present application, the optional range of biological agents is wide, the following is exemplary, but not limited to the scope of the present application, according to a preferred embodiment of the present application, the biological agent is selected from one or more of anaerobic biological agent, aerobic biological agent and inter-aerobic biological agent, the advantages of the present application are illustrated by taking the biological agent as an anaerobic biological agent in the examples.

[0049] In the present application, the composition of anaerobic biological agent is anaerobic bacteria, as long as the purpose of the present application can be achieved, the present application does not have special requirements for the type of anaerobic bacteria.

[0050] In the present application, the time of post-treatment is not particularly limited, and is determined according to the operating temperature, for example, it can be generally 2h-10 days. By using the foregoing technical solution, the advantage of short processing time is achieved.

[0051] The present application will be described in detail by the following examples.

[0052] In the present application, the measurement of total organic carbon (TOC) of contaminated groundwater sample adopts Shimadzu TOC-L CPH / CPN Total Organic Carbon Analyzer, and the measurement standard adopted is the national standard "Water Quality: Total Organic Carbon (TOC): Determination: Non-dispersive Infrared Absorption Method (GB 13193-1991)".

[0053] The organic contaminated soil with a depth of more than 4.5 m is treated by using the in-situ heat conduction desorption technology, the target remediation area is indirectly heated by a heating pipe, the temperature reaches a target value, the pollutants are desorbed from the soil and separated, the pollutant vapor is extracted to the ground surface by a gas phase extraction system, the reagent is configured into an aqueous solution in a storage tank, and the reagent is injected into the groundwater layer by a reagent injection system, and the groundwater sample is extracted after treatment for analysis, which is well known to those skilled in the art, and will not be described in detail herein. In the following examples, the groundwater remediation depth is 4.5 m, and the reagent is injected into the groundwater layer every 5 m 2 One well body 1 is constructed.

[0054] In the following examples, the total organic carbon content in the contaminated groundwater is 180 mg / L, the chloride ion content is 6900 mg / L, and the pH of the contaminated groundwater is 7.5.

[0055] In the following examples, the contaminated soil is a soil contaminated by chlorinated organic matter, and the chlorinated organic matter includes chlorobenzene, o-nitrochlorobenzene, p-nitrochlorobenzene, m-nitrochlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, and 4-chloroaniline.

[0056] In the following examples, the iodine value of the activated carbon powder used is 700 mg / g.

[0057] In the following examples, the total organic matter (TOC) removal rate = (total organic carbon content in contaminated groundwater - total organic carbon content in treated water sample) / total organic carbon content in contaminated groundwater * 100%.

[0058] Example 1

[0059] 10 kg of talcum powder is mixed with 50 kg of water (1 m 3 of groundwater), and the reagent is injected into the groundwater layer by an injection device, and the treatment is carried out for 2 hours at 15℃.

[0060] The contaminated soil is treated by using the thermal desorption method, and the thermal desorption temperature is 250℃; 10 kg of monopersulfate potassium composite salt is dissolved in 50 kg of water, and the mixture is stirred and mixed until completely dissolved (the reagent amount is 1 m 3 of groundwater), and 5 kg of potassium ferrate is added and stirred and mixed until dissolved. The reagent in the storage tank is injected into the groundwater layer by an injection device in two times with an interval of 1 hour, and the reagent is activated to 80℃ by using the residual heat of thermal desorption. After treatment for 2 hours, the groundwater sample is extracted, and the pH is detected to be 7.2.

[0061] 5 kg of activated carbon powder is mixed with 25 kg of water (1 m 3 of groundwater), and the reagent is injected into the groundwater layer by an injection device, and the groundwater sample is extracted after 2 hours, and the total organic matter (TOC) removal rate is 95%.

[0062] Example 2

[0063] 10 kg of talc powder is mixed with 50 kg of water (1 m 3 of groundwater), and the mixture is injected into the groundwater layer by an injection device, and is treated at 25°C for 2 hours.

[0064] The contaminated soil is treated by thermal desorption at a temperature of 200°C. 10 kg of potassium peroxymonosulfate and 3 kg of calcium peroxide are dissolved in 50 kg of water, and the mixture is stirred until completely dissolved (the amount of the agent is 1 m 3 of groundwater). The agent in the storage tank is injected into the groundwater layer by an injection device, and the agent is activated to 80°C by the residual heat of thermal desorption. After 2 hours of treatment, a groundwater sample is extracted, and the pH is detected to be 7.3.

[0065] 15 kg of anaerobic bacteria is mixed with 50 kg of water (1 m 3 of groundwater), and the mixture is injected into the groundwater layer by an injection device. After 10 days, a groundwater sample is extracted, and the removal rate of total organic matter (TOC) is 88%.

[0066] Example 3

[0067] 10 kg of talc powder is mixed with 50 kg of water (1 m 3 of groundwater), and the mixture is injected into the groundwater layer by an injection device, and is treated at 25°C for 2 hours.

[0068] The contaminated soil is treated by thermal desorption at a temperature of 150°C. 10 kg of potassium peroxymonosulfate composite salt is dissolved in 50 kg of water, and the mixture is stirred until completely dissolved (the amount of the agent is 1 m 3 of groundwater). Then, 1 kg of potassium ferrate is added, and the mixture is stirred until completely dissolved. The agent in the storage tank is injected into the groundwater layer by an injection device in two times with an interval of 1 hour, and the agent is activated to 50°C by the residual heat of thermal desorption. After 2 hours of treatment, a groundwater sample is extracted, and the pH is detected to be 6.5, and the removal rate of total organic matter (TOC) is 66%.

[0069] Example 4

[0070] The contaminated soil is treated by thermal desorption at a temperature of 200°C. 10 kg of potassium peroxymonosulfate composite salt and 10 kg of calcium peroxide are dissolved in 50 kg of water, and the mixture is stirred until completely dissolved (the amount of the agent is 1 m 3 of groundwater). The agent in the storage tank is injected into the groundwater layer by an injection device, and the agent is activated to 90°C by the residual heat of thermal desorption. After 4 hours of treatment, a groundwater sample is extracted, and the pH is detected to be 7.4, and the removal rate of total organic matter (TOC) is 50%.

[0071] Example 5

[0072] The amount of potassium ferrate was 0.7 kg, and after the treatment, the groundwater sample was extracted, and the pH was 3, and the total organic matter (TOC) removal rate was 80%.

[0073] Example 6

[0074] The amount of potassium ferrate was 0.7 kg, and after the treatment, the groundwater sample was extracted, and the pH was 3, and the total organic matter (TOC) removal rate was 80%.

[0075] Example 7

[0076] The amount of potassium ferrate was 0.7 kg, and after the treatment, the groundwater sample was extracted, and the pH was 3, and the total organic matter (TOC) removal rate was 80%.

[0077] Example 8

[0078] The amount of potassium ferrate was 0.7 kg, and after the treatment, the groundwater sample was extracted, and the pH was 3, and the total organic matter (TOC) removal rate was 80%.

[0079] Example 9

[0080] The amount of potassium ferrate was 0.7 kg, and after the treatment, the groundwater sample was extracted, and the pH was 3, and the total organic matter (TOC) removal rate was 80%.

[0081] Comparative Example 1

[0082] The difference from Example 1 is only that 10 kg of potassium monopersulfate compound salt was dissolved in 50 kg of water as a medicament (the amount of medicament was calculated as 1 m 3 of groundwater). The other steps and conditions were the same.

[0083] The groundwater sample was extracted, and the pH was 2.8, and the total organic matter (TOC) removal rate was 75%.

[0084] Comparative Example 2

[0085] The difference from Example 1 is only that 5 kg of potassium ferrate solution was dissolved in 50 kg of water as a medicament (the amount of medicament was calculated as 1 m 3 of groundwater). The other steps and conditions were the same.

[0086] The groundwater sample was extracted, and the pH was 11.5, and the total organic matter (TOC) removal rate was 30%.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that the administration is not at the thermal desorption afterheat temperature, but at room temperature 25°C, and the other steps and conditions are the same.

[0089] The groundwater sample was extracted, and the pH was 4.8, and the total organic matter (TOC) removal rate was 18%.

[0090] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that various technical features are combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A method for the co-treatment of soil and groundwater, characterized in that, The method comprises: The contaminated soil is treated by thermal desorption, and a composite agent is injected into the contaminated groundwater layer at the thermal desorption residual heat temperature, the composite agent containing persulfate and alkaline oxidant.

2. The method of claim 1, wherein, In the composite agent, the molar ratio of persulfate to alkaline oxidant is 0.1-5:1, preferably 0.5-4:1; and / or The composite agent is an aqueous agent formed by dissolving the persulfate and alkaline oxidant in water.

3. The method of claim 1 or 2, wherein, In the composite agent, The persulfate is one or more of monopersulfate potassium compound, potassium monopersulfate, potassium persulfate, ammonium monopersulfate, sodium monopersulfate and calcium monopersulfate; and / or The alkaline oxidant is one or more of potassium ferrate, calcium peroxide and magnesium peroxide.

4. The method according to any one of claims 1-3, wherein The addition amount of the persulfate is 0.1wt%-2wt% of the mass of the contaminated groundwater, preferably 0.5wt%-1.5wt%; and / or The addition amount of the alkaline oxidant is 0.05wt%-2wt% of the mass of the contaminated groundwater, preferably 0.1wt%-0.8wt%.

5. The method according to any one of claims 1-4, wherein The thermal desorption temperature for treating the contaminated soil by thermal desorption is 50-500℃, preferably 100-300℃; and / or The thermal desorption residual heat temperature is 40-150℃, preferably 50-90℃, more preferably 80-90℃.

6. The method according to any one of claims 1-5, wherein The contaminated soil is soil contaminated by chlorinated organic compounds; Preferably, the chlorinated organic compounds include one or more of chlorobenzene, o-nitrochlorobenzene, p-nitrochlorobenzene, m-nitrochlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene and 4-chloroaniline.

7. The method according to any one of claims 1-6, wherein The total organic carbon content in the contaminated groundwater is 50-1000mg / L, and the chloride ion content is 1000-10000mg / L; and / or The pH of the contaminated groundwater is 5-9.

8. The method of any of claims 1-7, wherein, Before the composite agent is injected, a pretreatment agent is injected into the contaminated groundwater layer for pretreatment to remove chloride ions in the groundwater; Preferably, the pretreatment agent is selected from one or more of talc, erionite, attapulgite and activated clay; and / or The addition amount of the pretreatment agent is 1wt%-10wt% of the mass of the groundwater; and / or The pretreatment temperature is 10-50℃.

9. The method of any of claims 1-8, wherein, The method further comprises: after the treatment of the composite agent is completed, a post-treatment agent is added for post-treatment. Preferably, The post-treatment agent is activated carbon powder and / or biological agent; and / or The addition amount of the post-treatment agent is 0.1wt%-15wt% of the mass of the groundwater.

10. The method according to claim 9, wherein The addition amount of the activated carbon powder is 0.1wt%-5wt% of the mass of the groundwater; and / or The addition amount of the biological agent is 0.1wt%-10wt% of the mass of the groundwater; and / or The biological agent is selected from one or more of anaerobic biological agent, aerobic biological agent and facultative biological agent.