A system and method for evaluating foam performance and soil remediation effectiveness for in-situ soil leaching processes

Abstract

The application provides a system and method for evaluating foam performance and soil remediation effect of an in-situ soil leaching process. The system comprises a foam generating unit, a remediation effect testing unit and a foam measuring unit. The method comprises: mixing a solution and a foaming gas in a pipeline and then making the mixture enter a foam generating device to form foam; making the foam enter a soil extractor, and making the foam pass through contaminated soil to leach the soil, determining the residual concentration of pollutants in the soil after leaching by the foam, and then evaluating the soil remediation effect; and making the foam enter a foam volume measuring device to evaluate the foamability and stability of the foam. The system and method of the application can evaluate the foamability, stability and soil remediation effect of the foam, and have the advantages of simple operation, sensitive response, high efficiency and the like.

Description

Technical Field

[0001] The present invention relates to a foam performance and soil remediation effect evaluation system and method for an in-situ soil leaching process, belonging to the technical field of foam soil remediation. Background Art

[0002] Given the current state of contaminated soil, a variety of remediation technologies have been established. Among them, surfactant foam extraction has proven to be a novel and effective method, garnering widespread attention in recent years. Foam-enhanced remediation technology combines the solubilization capacity of surfactants with vapor-phase extraction processes to achieve simple and efficient in-situ remediation of contaminated sites.

[0003] At present, the surfactant foam extraction process has made great progress in the field of remediation engineering technology. CN102371268A discloses a surfactant foam flushing technology for the remediation of polychlorinated biphenyl contaminated soil. The technology uses surfactants and nitrogen to produce ectopic foam, and flushes the soil medium by pressurized injection. CN108655169A provides a soil remediation system and remediation method based on colloidal microfoam. The method uses a high-speed mixer to prepare colloidal microfoam, which is injected into the soil contaminated area through a vertical injection well, and the foam eluent and pollutant gas are extracted by a vertical extraction well. CN208712512U discloses a system for the remediation of organic contaminated soil by surfactant foam-assisted persulfate oxidation. By setting up a chemical treatment system, a foam generation system and a recovery and treatment system above the ground, efficient and deep degradation of organic pollutants is achieved. CN111346909A discloses an in-situ remediation method for petroleum hydrocarbon contaminated soil based on foam enhancement. The foam is prepared by Tween 80, water, catechol and ferrous sulfate, and is injected into the soil in combination with sodium percarbonate.

[0004] Combined with the above summary, it can be found that although scholars have done a lot of research on the practical engineering application of foam remediation technology, there are few methods and devices for evaluating the performance of foam used for soil leaching and the soil remediation effect. The flow of foam through porous contaminated soil media is a complex phenomenon, which includes the formation of initial foam, foam rupture, capillary pressure effect and foam crossflow effect. The transmission of stable foam occurs in the porous channel in the form of plug flow. If the foam ruptures during the transmission process, the ruptured foam will move in the form of liquid and gas. At this time, the liquid can be transmitted radially (laterally) along the pores of the soil medium, producing a diffusion-like effect. Highly stable foam can maintain greater airflow resistance in the soil matrix, thereby avoiding gas infiltration and crossflow. Therefore, before actual engineering application, it is necessary to quickly evaluate the foaming properties, stability and specific soil leaching remediation effect of the foam.

[0005] The current method for evaluating the performance of foam is mainly the Waring Blender method. The method is to place a surfactant solution in a container, generate foam by using a high-speed blender, and then measure the foaming property and stability. The method has the advantages of short measurement time and easy operation, but due to the instability of the foam structure, the generated foam is difficult to be stably transferred, and thus the repair effect evaluation of the specific soil cannot be performed. At the same time, the method cannot accurately control the air addition amount during the foam generation process. In addition, since the Waring Blender method must mix all components of the foaming liquid in the container before foaming, when evaluating the foam stability and foaming property of the foam cooperated with the oxidation injection, the oxidant is easy to react with the surfactant in the liquid phase, causing adverse effects. In general, although the Waring Blender method is a reliable method for evaluating the stability of foam, it is difficult to be applied to the comprehensive performance evaluation of the foam used in the soil leaching process. SUMMARY

[0006] To solve the above technical problems, the purpose of the present application is to provide a system and method for evaluating the performance of foam and the soil repair effect in the in-situ soil leaching process. The system and method of the present application can evaluate the foaming property, stability of the foam and the soil repair effect, and have the advantages of simple operation, sensitive response, fast and efficient, etc.

[0007] To achieve the above purpose, the first aspect of the present application provides a system for evaluating the performance of foam and the soil repair effect in the in-situ soil leaching process, comprising a foam generating unit, a repair effect testing unit and a foam measuring unit.

[0008] The foam generating unit comprises a surfactant solution storage tank, a surfactant solution valve, a surfactant solution flow metering pump, a solution delivery pipeline, a gas valve, a gas flow metering pump, a gas delivery pipeline, a foam generating device and a foam output pipeline.

[0009] The repair effect testing unit comprises a first foam valve, a soil extractor, a pressure control device, a foam settler and a centrifugal pump.

[0010] The foam measuring unit comprises a second foam valve and a foam volume measuring device.

[0011] The foam generating device is in communication with the solution delivery pipeline, the gas delivery pipeline and the foam output pipeline. The solution delivery pipeline is in communication with the surfactant solution storage tank through the surfactant solution valve and the surfactant solution flow metering pump. The gas delivery pipeline is provided with the gas valve and the gas flow metering pump.

[0012] The foam output pipeline is connected to the soil extractor through the first foam valve. The soil extractor is filled with contaminated soil. The soil extractor is connected to the foam settler. The pressure control device is provided on the top of the foam settler. The foam settler is connected to the centrifugal pump.

[0013] The foam output pipeline is communicated with the foam volume measuring device through the second foam valve.

[0014] In the above system, preferably, the foam generating unit further comprises: a modifier solution storage tank, a modifier solution valve and a modifier solution flow metering pump; the solution delivery pipeline is connected to the modifier solution storage tank through the modifier solution valve and the modifier solution flow metering pump.

[0015] In the above system, preferably, the foam generating unit further comprises: an oxidant solution storage tank, an oxidant solution valve and an oxidant solution flow metering pump; the solution delivery pipeline is connected to the oxidant solution storage tank through the oxidant solution valve and the oxidant solution flow metering pump.

[0016] In the above system, preferably, the surfactant solution storage tank includes a plurality of surfactant solution storage tanks connected in parallel, for storing surfactant solutions of different types and / or concentrations.

[0017] In the above system, preferably, the modifier solution storage tank includes a plurality of modifier solution storage tanks connected in parallel, for storing modifier solutions of different types and / or concentrations.

[0018] In the above system, preferably, the oxidant solution storage tank includes a plurality of oxidant solution storage tanks connected in parallel, for storing oxidant solutions of different types and / or concentrations.

[0019] In the above system, preferably, the surfactant solution flow metering pump is a peristaltic pump.

[0020] In the above system, preferably, the modifier solution flow metering pump is a peristaltic pump.

[0021] In the above system, preferably, the oxidant solution flow metering pump is a peristaltic pump.

[0022] In the above system, preferably, the interior of the foam generating device is filled with a mesh structure medium. Specifically, the mesh structure medium may include one or a combination of polypropylene fiber mesh, polyester fiber mesh, and polyimide fiber mesh, etc., preferably polyester fiber mesh.

[0023] In the above system, preferably, the effective filling diameter inside the foam generating device is 2 to 10 mm, more preferably 5 mm.

[0024] In the above system, preferably, the effective filling length inside the foam generating device is 5 to 50 mm, more preferably 20 mm.

[0025] In the above system, preferably, the repair effect testing unit further includes a check valve and a residual foam collector; the soil extractor and the foam settler are connected to the residual foam collector through pipelines respectively, and the check valve is provided on the pipeline connecting the soil extractor and the residual foam collector.

[0026] In the above system, preferably, the inner diameter of the soil extractor is 20-100 mm, more preferably 34 mm.

[0027] In the above system, preferably, the mass of the contaminated soil filled in the soil extractor is 4 to 20 g, more preferably 4 g.

[0028] In the above system, the filling height of the contaminated soil is related to the filling mass, and is preferably 5 to 25 mm, and more preferably 5 mm.

[0029] In the above system, the foam volume measuring device can be any container with a volume recording function, preferably a 500-1000 mL measuring cylinder or measuring cup, more preferably a 500 mL measuring cylinder or measuring cup.

[0030] In the above system, preferably, the inner diameter of the pipeline in the system is 1 to 10 mm, more preferably 5 mm.

[0031] A second aspect of the present invention provides a method for evaluating foam performance and soil remediation effects during an in-situ soil washing process. The method uses the above-mentioned system to evaluate foam performance and soil remediation effects during an in-situ soil washing process. The method comprises the following steps:

[0032] (1) Opening the surfactant solution valve to allow the surfactant solution to enter the solution delivery pipeline after being metered by the surfactant solution flow metering pump; opening the gas valve to allow the foaming gas to enter the gas delivery pipeline after being metered by the gas flow metering pump; the solution and foaming gas are mixed in the pipeline and then enter the foam generating device to form foam which is then delivered by the foam output pipeline;

[0033] (2) opening the first foam valve and closing the second foam valve to allow the foam to enter the soil extractor. Under the action of the extraction pressure formed by the negative pressure generated by the centrifugal pump, the foam is allowed to pass through the contaminated soil to leach the soil. At least a portion of the foam that has passed through the contaminated soil enters the foam settler under the negative pressure drive for gas-liquid separation. The separated gas is extracted by the centrifugal pump. The concentration of pollutants in the soil before remediation and the residual concentration of pollutants in the soil after foam leaching are measured, and the soil remediation effect is evaluated.

[0034] (3) Open the second foam valve and close the first foam valve to allow the foam to enter the foam volume measuring device; record the foam volume formed when the total amount of the solution in step (1) is 50 mL, and then evaluate the foaming property of the foam; record the time when the liquid precipitated at the bottom of the foam volume measuring device is 25 mL, and then evaluate the stability of the foam.

[0035] In the above method, preferably, step (1) further comprises: opening the modifier solution valve to allow the modifier solution to enter the solution delivery pipeline after being metered by the modifier solution flow metering pump.

[0036] In the above method, preferably, step (1) further comprises: opening the oxidant solution valve to allow the oxidant solution to enter the solution delivery pipeline after being metered by the oxidant solution flow metering pump.

[0037] In the present invention, the flow rates of the surfactant solution flow metering pump, the modifier solution flow metering pump and / or the oxidant solution flow metering pump can be set according to the specific test requirements and the ratio of the surfactant solution and the modifier solution and / or the oxidant solution to achieve mixing of the surfactant solution and the modifier solution and / or the oxidant solution.

[0038] In the above method, preferably, in step (1), the foaming gas includes one or a combination of carbon dioxide, air, nitrogen, helium and argon, etc., more preferably air.

[0039] In the above method, preferably, in step (1), the total flow rate of the solution is 5-30 mL / min, and the flow rate of the foaming gas is 400-1025 mL / min. The present invention controls the flow rates of the solution and the foaming gas, which is conducive to forming stable and homogeneous foam.

[0040] In the above method, preferably, in step (2), the extraction pressure is controlled by a pressure control device provided on the top of the foam settler so that the vacuum degree of the system is controlled at -0.002 to -0.008 kPa.

[0041] In the above method, preferably, step (2) further comprises: a portion of the foam that passes through the contaminated soil enters the residual foam collector through a check valve, and the liquid after gas-liquid separation in the foam settler enters the residual foam collector.

[0042] In the above method, preferably, in step (2), the soil remediation effect is evaluated by calculating the remediation efficiency according to formula (1) and then quantitatively evaluating the remediation effect:

[0043]

[0044] In formula (1), η is the remediation efficiency under a certain foam extraction time t, C0 is the concentration of pollutants in the soil before remediation, and C t is the residual concentration of pollutants in the soil measured after the foam extraction time is t. The remediation effect can be judged by comparing the η values ​​of different foam systems at the same time.

[0045] In the above method, preferably, in step (3), the foamability is evaluated by calculating the foaming coefficient according to formula (2) to quantitatively evaluate the foamability:

[0046]

[0047] In formula (2), is the foaming coefficient, V liquid The volume of liquid required to form foam, i.e. 50 mL, V foam is the volume of foam formed (mL). The value can be used to judge the quality of foaming.

[0048] In the above method, preferably, in step (3), the stability is evaluated by the time when 25 mL of liquid precipitated from the bottom (i.e., the foam half-life).

[0049] The present invention provides a system and method for evaluating foam performance and soil remediation efficacy during in-situ soil leaching. Currently, the predominant foam performance evaluation method is the Waring-Blender method. Due to the instability of the foam structure, the foam produced by this method is difficult to stably transfer, making it incapable of evaluating the remediation efficacy of specific soils. Furthermore, this method cannot precisely control the amount of air added during the foam generation process. Furthermore, when evaluating the stability and foaming properties of foams injected during synergistic oxidation, the oxidant easily reacts with the surfactant in the liquid phase, resulting in adverse effects. The system and method of the present invention address the inability of conventional foam evaluation methods to effectively transfer and test soil leaching efficacy, enabling simultaneous evaluation of foam foamability, stability, and the remediation efficacy of specific soils. Furthermore, in addition to evaluating the performance and soil remediation efficacy of foams prepared using conventional surfactants, the system and method of the present invention can also evaluate the foamability, stability, and soil remediation efficacy of foams produced using the simultaneous addition of foam modifiers and oxidants. The system and method of the present invention offer excellent stability, generate stable and uniform foam, and have an adjustable gas-liquid flow ratio, meeting performance evaluation requirements. Furthermore, they are simple to operate, responsive, fast, and efficient.

[0050] In summary, the technical solution of the present invention has at least the following beneficial effects:

[0051] (1) It solves the problem that traditional foam evaluation methods cannot effectively transfer and test soil leaching effects;

[0052] (2) The gas and liquid flow rates can be precisely controlled during the evaluation process;

[0053] (3) It can simultaneously meet the evaluation requirements of foam foaming, stability and soil remediation effect;

[0054] (4) In addition to evaluating the performance of surfactant-prepared foams and the soil remediation effect, the foaming properties, stability, and remediation effect of foam modifiers, oxidants, etc. added simultaneously can also be evaluated. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A schematic structural diagram of a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process provided in a specific embodiment of the present invention.

[0056] Figure 2 It is the foam volume formed by the different surfactant solutions in Example 2 when the total amount of the solution is 50 mL.

[0057] Figure 3 The time when 25 mL of liquid is precipitated from the bottom of the foam volume measuring device 302 by the different surfactant solutions in Example 2.

[0058] Figure 4 is the pollutant removal rate corresponding to different solution flow rates in Example 3.

[0059] Figure 5 is the pollutant removal rate corresponding to the filling mass of different contaminated soils in Example 4.

[0060] Figure 6 is the volume of foam formed under the conditions of different concentrations of modifier solution in Example 5.

[0061] Figure 7 It is the time when 25 mL of liquid is precipitated under the conditions of different concentrations of modifier solution in Example 5.

[0062] Figure 8 is the volume of foam formed under the conditions of different concentrations of modifier solution in Example 7.

[0063] Figure 9 It is the time when 25 mL of liquid is precipitated under the conditions of different concentrations of modifier solution in Example 7.

[0064] Figure 10 is the volume of foam formed under the conditions of different concentrations of oxidant solution in Example 9.

[0065] Figure 11 It is the time when 25 mL of liquid is precipitated under the conditions of different concentrations of oxidant solution in Example 9.

[0066] Figure 12 It is the pollutant removal rate in the soil after different remediation times in Example 10.

[0067] Description of the accompanying drawings: surfactant solution storage tank 101, surfactant solution valve 102, surfactant solution flow metering pump 103, solution delivery pipeline 104, gas valve 105, gas flow metering pump 106, gas delivery pipeline 107, foam generating device 108, foam output pipeline 109, modifier solution storage tank 110, modifier solution valve 111, modifier solution flow metering pump 112, oxidant solution storage tank 113, oxidant solution valve 114, oxidant solution flow metering pump 115;

[0068] a first foam valve 201, a soil extractor 202, a pressure control device 203, a foam settler 204, a centrifugal pump 205, a check valve 206, and a residual foam collector 207;

[0069] A second foam valve 301 and a foam volume measuring device 302 . DETAILED DESCRIPTION

[0070] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0071] Example 1

[0072] This embodiment provides a foam performance and soil remediation effect evaluation system for in-situ soil leaching process, the structure of which is as follows: Figure 1 As shown, the system includes: a foam generating unit, a repair effect testing unit and a foam measuring unit;

[0073] The foam generating unit includes a surfactant solution storage tank 101, a surfactant solution valve 102, a surfactant solution flow metering pump 103, a solution delivery pipeline 104, a gas valve 105, a gas flow metering pump 106, a gas delivery pipeline 107, a foam generating device 108, and a foam output pipeline 109.

[0074] The repair effect testing unit includes a first foam valve 201, a soil extractor 202, a pressure control device 203, a foam settler 204, a centrifugal pump 205, a check valve 206 and a residual foam collector 207;

[0075] The foam measuring unit includes a second foam valve 301 and a foam volume measuring device 302;

[0076] The foam generating device 108 is connected to the solution delivery pipeline 104, the gas delivery pipeline 107 and the foam output pipeline 109; the solution delivery pipeline 104 is connected to the surfactant solution storage tank 101 through the surfactant solution valve 102 and the surfactant solution flow metering pump 103; the gas delivery pipeline 107 is provided with a gas valve 105 and a gas flow metering pump 106;

[0077] The foam output pipeline 109 is connected to the soil extractor 202 through a first foam valve 201. The soil extractor 202 is filled with contaminated soil. The soil extractor 202 is connected to a foam settler 204. A pressure control device 203 is provided on the top of the foam settler 204. The foam settler 204 is connected to a centrifugal pump 205. The soil extractor 202 and the foam settler 204 are respectively connected to a residual foam collector 207 through pipelines. A check valve 206 is provided on the pipeline connecting the soil extractor 202 and the residual foam collector 207.

[0078] The foam output line 109 is connected to the foam volume measuring device 302 through the second foam valve 301 .

[0079] In this embodiment, the foam generating unit further includes: a modifier solution storage tank 110, a modifier solution valve 111 and a modifier solution flow metering pump 112; the solution delivery pipeline 104 is connected to the modifier solution storage tank 110 through the modifier solution valve 111 and the modifier solution flow metering pump 112.

[0080] In this embodiment, the foam generating unit further includes: an oxidant solution storage tank 113, an oxidant solution valve 114 and an oxidant solution flow metering pump 115; the solution delivery pipeline 104 is connected to the oxidant solution storage tank 113 through the oxidant solution valve 114 and the oxidant solution flow metering pump 115.

[0081] In this embodiment, the surfactant solution flow metering pump 103 , the modifier solution flow metering pump 112 , and the oxidant solution flow metering pump 115 are all peristaltic pumps.

[0082] In this embodiment, the interior of the foam generating device 108 is filled with a mesh structure medium, which is a polypropylene fiber mesh.

[0083] In this embodiment, the effective filling diameter inside the foam generating device 108 is 5 mm.

[0084] In this embodiment, the effective filling length inside the foam generating device 108 is 20 mm.

[0085] In this embodiment, the inner diameter of the soil extractor 202 is 34 mm.

[0086] In this embodiment, the mass of the contaminated soil filled in the soil extractor 202 is 4 g, and the filling height of the contaminated soil is 5 mm.

[0087] In this embodiment, the foam volume measuring device 302 is a 1000 mL measuring cup.

[0088] In this embodiment, the inner diameter of the pipeline in the system is 2 mm.

[0089] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the above-mentioned system to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0090] The surfactant solution used in this embodiment is: 500 mL of 4 g / L α-olefin sulfonate sodium (AOS) solution, stored in the surfactant solution storage tank 101. The foaming gas used is: high-purity nitrogen (≥99.999%).

[0091] The method of this embodiment includes the following steps:

[0092] (1) The surfactant solution, the optionally adopted modifier solution and the optionally adopted oxidant solution can be stored in their respective storage tanks, respectively. The surfactant solution valve 102 is opened, and the modifier solution valve 111 and the oxidant solution valve 114 are closed, so that the surfactant solution is metered by the surfactant solution flow metering pump 103 and then enters the solution delivery pipeline 104, and the flow rate of the surfactant solution flow metering pump 103 is set to 5 to 30 mL / min; the gas valve 105 is opened, so that the foaming gas is metered by the gas flow metering pump 106 and then enters the gas delivery pipeline 107, and the flow rate of the gas flow metering pump 106 is set to 400 to 1000 mL / min; the solution and the foaming gas are mixed in the pipeline and then enter the foam generating device 108 to form a stable and homogeneous foam which is then delivered by the foam output pipeline;

[0093] (2) Open the first foam valve 201 and close the second foam valve 301 to allow the foam to enter the soil extractor 202. Under the action of the extraction pressure formed by the negative pressure generated by the centrifugal pump 205, the foam passes through the contaminated soil to leach the soil. A portion of the foam that passes through the contaminated soil enters the residual foam collector 207 through the check valve 206, and another portion of the foam that passes through the contaminated soil enters the foam settler 204 under the drive of the negative pressure for gas-liquid separation. The extraction pressure is controlled by the pressure control device 203 provided on the top of the foam settler 204 to control the vacuum degree of the system at -0.002 to -0.008 kPa. The gas separated from the gas and liquid is extracted by the centrifugal pump 205, and the liquid separated from the gas and liquid enters the residual foam collector 207. The concentration of pollutants in the soil before remediation and the residual concentration of pollutants in the soil after foam leaching are measured, and the soil remediation effect is evaluated.

[0094] (3) Open the second foam valve 301 and close the first foam valve 201 to allow the foam to enter the foam volume measuring device 302; record the foam volume formed when the total amount of the solution in step (1) is 50 mL, and then evaluate the foaming property of the foam; record the time when the liquid precipitated at the bottom of the foam volume measuring device 302 is 25 mL, and then evaluate the stability of the foam.

[0095] In this embodiment, the amount of foam produced per minute is recorded as the foam preparation flow rate, and the optimal stable gas-liquid flow ratio for producing uniform and stable foam and the corresponding foam preparation flow rate are recorded, as shown in Table 1.

[0096] Table 1 Optimal stable gas-liquid flow ratio for producing uniform stable foam and the corresponding foam preparation flow

[0097] Solution flow rate (mL / min) Foaming gas flow rate (mL / min) Foam preparation flow rate (mL / min) 2.5 No optimal flow Preparation failure 5.0 409.7 108 7.5 499.3 122 10.0 542.8 132 12.5 622.1 155 15.0 640.0 176 17.5 778.4 190 20.0 799.4 210 22.5 855.0 233 25.0 907.9 260 27.5 946.3 287 30.0 1025.0 310 32.5 No optimal flow Preparation failure

[0098] It can be seen from Table 1 that the flow rate range of the solution and the foaming gas given in the present invention is conducive to the formation of stable and homogeneous foam, while it is difficult to prepare foam when the flow rate is not within the range controlled by the present invention.

[0099] Example 2

[0100] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is basically the same as that of Example 1, except that: the mesh structure medium filled inside the foam generating device 108 is a polyimide fiber mesh, the effective filling diameter inside the foam generating device 108 is 10 mm, and the effective filling length is 50 mm; the foam volume measuring device 302 is a 500 mL graduated cylinder; and the inner diameter of the pipeline in the system is 10 mm.

[0101] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0102] The surfactant solutions used in this example include: 100 mL of a 3 g / L sodium α-olefin sulfonate (AOS) solution, 100 mL of a 3 g / L sodium dodecylbenzenesulfonate (SDBS) solution, 100 mL of a 3 g / L sodium dodecyl sulfate (SDS) solution, 100 mL of a 3 g / L Triton X-100 (TX-100) solution, 100 mL of a 3 g / L polyoxyethylene lauryl ether (Brij 35) solution, 100 mL of a 3 g / L Tween 20 solution, and 100 mL of a 3 g / L Tween 80 solution, each stored in a surfactant solution storage tank 101. A valve can be used to switch between surfactant solution storage tanks 101 containing different surfactant solutions for each evaluation. The foaming gas used is high-purity argon (≥99.999%).

[0103] The method is basically the same as that of Example 1, except that the flow rate of the surfactant solution flow metering pump 103 is set to 15 mL / min, and the flow rate of the gas flow metering pump 106 is set to 600 mL / min. The foam volume (i.e., foaming amount) formed by different surfactant solutions when the total solution volume is 50 mL is as follows: Figure 2 The time (i.e., the precipitation time) for different surfactant solutions to precipitate 25 mL of liquid at the bottom of the foam volume measuring device 302 is shown in FIG. Figure 3 shown.

[0104] The foaming coefficient of each foam system was calculated according to formula (2) to quantitatively evaluate the foaming property:

[0105]

[0106] In formula (2), is the foaming coefficient, V liquid The volume of liquid required to form foam, i.e. 50 mL, V foam is the volume of foam formed (mL).

[0107] The results are shown in Table 2.

[0108] Table 2

[0109]

[0110] Depend on Figure 2 , Table 2 and Figure 3 It can be seen that the method and system of the present invention can accurately evaluate the foamability and stability of foam.

[0111] Example 3

[0112] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is basically the same as that of Example 1, except that: the mesh structure medium filled inside the foam generating device 108 is a polyester fiber mesh, the effective filling diameter inside the foam generating device 108 is 5 mm, and the effective filling length is 20 mm; the foam volume measuring device 302 is a 500 mL graduated cylinder; the inner diameter of the pipeline in the system is 5 mm; the effective volume of the foam settler 204 is 3 L; and the effective volume of the residual foam collector 207 is 5 L.

[0113] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0114] The surfactant solution used in this example is: 2000mL of 4g / L α-olefin sulfonate sodium (AOS) solution, stored in surfactant solution storage tank 101. The foaming gas used is: air. The contaminated soil of this example was prepared by the following steps: based on natural soil, the phenanthrene contaminated soil used in the experiment was prepared; 1kg of pre-treated (screening out stones and branches with a particle size greater than 0.9mm and drying at 60°C for 24h) soil sample was weighed into a stainless steel tray, 500mL of 0.2g / L phenanthrene-dichloromethane solution was added thereto, and then stirred until mixed evenly, and placed in a fume hood to air dry and age for 3 weeks for use; after the aging was completed, the actual phenanthrene contamination concentration in the contaminated soil was measured to be 66.42mg / kg.

[0115] This method is basically the same as Example 1, except that the flow rate of the surfactant solution flow metering pump 103 is set to 5-15 mL / min, and the flow rate of the gas flow metering pump 106 is set to 500-640 mL / min. The residual concentration of pollutants in the soil after foam leaching is measured to obtain the residual concentration of pollutants in the soil under different solution flow rates and remediation times (i.e., extraction times). The pollutant removal rate (i.e., remediation efficiency) is calculated according to formula (1) to quantitatively evaluate the remediation effect: The soil remediation effect is evaluated by calculating the remediation efficiency according to formula (1) to quantitatively evaluate the remediation effect:

[0116]

[0117] In formula (1), η is the remediation efficiency under a certain foam extraction time t, C0 is the concentration of pollutants in the soil before remediation, and C t is the residual concentration of pollutants in the soil measured after foam extraction time t. Figure 4 shown.

[0118] Depend on Figure 4 It can be seen that the method and system of the present invention can accurately evaluate the leaching and remediation effect of a specific soil.

[0119] Example 4

[0120] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is basically the same as that of Example 1, except that: the mesh structure medium filled inside the foam generating device 108 is a polyester fiber mesh, the effective filling diameter inside the foam generating device 108 is 5 mm, and the effective filling length is 20 mm; the foam volume measuring device 302 is a 500 mL graduated cylinder; the inner diameter of the pipeline in the system is 5 mm; the effective volume of the foam settler 204 is 3 L; the effective volume of the residual foam collector 207 is 5 L; the mass of the contaminated soil filled in the soil extractor 202 is 4 to 20 g, and the filling height of the contaminated soil is related to the filling mass and is 5 to 25 mm.

[0121] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0122] The surfactant solution used in this example is: 2000mL of sodium dodecylbenzenesulfonate (SDBS) solution with a concentration of 4g / L, stored in surfactant solution storage tank 101. The foaming gas used is: air. The contaminated soil of this example was prepared by the following steps: based on natural soil, the phenanthrene-contaminated soil used in the experiment was prepared; 1kg of pre-treated soil sample (screened out stones and branches with a particle size greater than 0.9mm and dried at 60°C for 24h) was weighed into a stainless steel tray, 500mL of phenanthrene-dichloromethane solution with a concentration of 0.2g / L was added thereto, and then stirred until mixed uniformly, and placed in a fume hood to air-dry and age for 3 weeks for use; after the aging period, the actual phenanthrene contamination concentration in the contaminated soil was measured to be 66.42mg / kg.

[0123] This method is basically the same as Example 1, except that the flow rate of the surfactant solution flow metering pump 103 is set to 10 mL / min, and the flow rate of the gas flow metering pump 106 is set to 550 mL / min. The residual concentration of pollutants in the soil corresponding to the filling mass of different contaminated soils after 10 minutes of extraction is measured, and the pollutant removal rate (i.e., remediation efficiency) is calculated. The results are shown in Figure 2. Figure 5 shown.

[0124] Depend on Figure 5 It can be seen that the filling mass of the contaminated soil of the present invention can be controlled within a range of 4 to 20 g. The evaluation system and method of the present invention can accurately evaluate the soil remediation effect for different contaminated soil filling masses.

[0125] Example 5

[0126] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is basically the same as that of Example 1, except that: the mesh structure medium filled inside the foam generating device 108 is a polyester fiber mesh, the effective filling diameter inside the foam generating device 108 is 5 mm, and the effective filling length is 20 mm; the foam volume measuring device 302 is a 500 mL graduated cylinder; and the inner diameter of the pipeline in the system is 5 mm.

[0127] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0128] The surfactant solution used in this example is 1000 mL of an 8 g / L sodium dodecyl sulfate (SDS) solution, stored in surfactant solution storage tank 101. This example also uses a modifier solution (a homogeneous liquid phase solution): 100 mL of a series of xanthan gum solutions with a concentration gradient of 0.2 to 1.8 g / L, stored in modifier solution storage tank 110. A valve can be used to switch between modifier solution storage tanks 110 containing modifier solutions of varying concentrations for each evaluation. The foaming gas used is high-purity helium (≥99.999%).

[0129] The method of this embodiment includes the following steps:

[0130] (1) The surfactant solution and the modifier solution are stored in their respective storage tanks, the surfactant solution valve 102 and the modifier solution valve 111 are opened, and the oxidant solution valve 114 is closed. The surfactant solution is metered by the surfactant solution flow metering pump 103 and then enters the solution delivery pipeline 104. The flow rate of the surfactant solution flow metering pump 103 is set to 7.5 mL / min. The modifier solution is metered by the modifier solution flow metering pump 112 and then enters the solution delivery pipeline 104. The modifier solution flow metering pump 112 is set to 1 The flow rate of 12 is 7.5 mL / min, and the concentration of xanthan gum in the solution in the solution delivery pipeline 104 is adjusted to 0.1 to 0.9 g / L by mixing the surfactant solution with the modifier solution of different concentrations; the gas valve 105 is opened to allow the foaming gas to enter the gas delivery pipeline 107 after being measured by the gas flow metering pump 106, and the flow rate of the gas flow metering pump 106 is set to 600 mL / min; the solution and the foaming gas are mixed in the pipeline and then enter the foam generating device 108 to form a stable and homogeneous foam, which is then delivered by the foam output pipeline;

[0131] (2) Open the first foam valve 201 and close the second foam valve 301 to allow the foam to enter the soil extractor 202. Under the action of the extraction pressure formed by the negative pressure generated by the centrifugal pump 205, the foam passes through the contaminated soil to leach the soil. A portion of the foam that passes through the contaminated soil enters the residual foam collector 207 through the check valve 206, and another portion of the foam that passes through the contaminated soil enters the foam settler 204 under the drive of the negative pressure for gas-liquid separation. The extraction pressure is controlled by the pressure control device 203 provided on the top of the foam settler 204 to control the vacuum degree of the system at -0.002 to -0.008 kPa. The gas separated from the gas and liquid is extracted by the centrifugal pump 205, and the liquid separated from the gas and liquid enters the residual foam collector 207. The concentration of pollutants in the soil before remediation and the residual concentration of pollutants in the soil after foam leaching are measured, and the soil remediation effect is evaluated.

[0132] (3) Open the second foam valve 301 and close the first foam valve 201 to allow the foam to enter the foam volume measuring device 302; record the foam volume formed when the total amount of the solution in step (1) is 50 mL, and then evaluate the foaming property of the foam; record the time when the liquid precipitated at the bottom of the foam volume measuring device 302 is 25 mL, and then evaluate the stability of the foam.

[0133] Under the conditions of different concentrations of modifier solution, the foam volume (i.e. foaming amount) formed when the total solution volume is 50mL is as follows: Figure 6 Under different concentrations of modifier solution, the time when the liquid precipitated from the bottom of the foam volume measuring device 302 is 25 mL (i.e., the precipitation time) is shown as follows. Figure 7 shown.

[0134] Depend on Figure 6 and Figure 7 It can be seen that the method and system of the present invention can achieve the simultaneous addition of a liquid-phase homogeneous modifier solution, and thus can evaluate the foamability and stability of the foam during the simultaneous addition of the modifier.

[0135] Example 6

[0136] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is the same as that of Example 5, and the effective volume of the foam settler 204 is 3L, and the effective volume of the residual foam collector 207 is 5L.

[0137] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0138] The surfactant solution used in this example was 2000 mL of a 4 g / L sodium α-olefin sulfonate (AOS) solution, stored in surfactant solution storage tank 101. This example also used a modifier solution (liquid phase homogeneous solution): 1000 mL of a 0.2 g / L xanthan gum solution, stored in modifier solution storage tank 110. The foaming gas used was air. The contaminated soil in this example was prepared by the following steps: Phenanthrene-contaminated soil was prepared using natural soil as a base; 1 kg of pretreated soil sample (screened to remove rocks and debris with a particle size greater than 0.9 mm and dried at 60°C for 24 hours) was weighed into a stainless steel tray, 500 mL of a 0.2 g / L phenanthrene-dichloromethane solution was added, and the mixture was stirred until uniformly mixed. The mixture was then air-dried and aged in a fume hood for 3 weeks before use. After aging, the actual phenanthrene contamination concentration in the contaminated soil was measured to be 66.42 mg / kg.

[0139] This method is basically the same as Example 5, except that: the flow rate of the surfactant solution flow metering pump 103 is set to 5 mL / min, the flow rate of the modifier solution flow metering pump 112 is set to 5 mL / min, the surfactant solution and the modifier solution are mixed so that the xanthan gum concentration of the solution in the solution delivery pipeline 104 is 0.1 g / L, and the flow rate of the gas flow metering pump 106 is set to 550 mL / min.

[0140] The residual concentration of pollutants in the soil after different remediation times (i.e., extraction time) was measured. Since xanthan gum only affects the foam performance without changing the remediation effect, the results obtained in this example are consistent with those in the Figure 4 The results were similar when the flow rate of the solution was 10 mL / min.

[0141] As can be seen from this example, the method and system of the present invention can achieve the simultaneous addition of a uniform liquid phase modifier solution, and thus can evaluate the soil remediation effect during the simultaneous addition of foam and modifier.

[0142] Example 7

[0143] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is the same as that of Example 5.

[0144] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0145] The surfactant solution used in this embodiment is: 1000mL of 8g / L sodium α-olefin sulfonate (AOS) solution, stored in surfactant solution storage tank 101. This embodiment also uses a modifier solution (solid suspension): 100mL of talc powder dispersion solution with a concentration gradient of 2-14g / L, respectively stored in modifier solution storage tank 110. Each evaluation can be performed by switching the modifier solution storage tank 110 with different concentrations of modifier solution. The talc powder dispersion solution is prepared by weighing a certain amount of talc powder and placing it in water. Ultrasonic dispersion is performed using a probe-type ultrasonic device for 5 minutes at an ultrasonic power of 1200W. The foaming gas used is: high-purity carbon dioxide (≥99.999%).

[0146] This method is basically the same as Example 5, except that: the flow rate of the surfactant solution flow metering pump 103 is set to 7.5 mL / min, the flow rate of the modifier solution flow metering pump 112 is set to 7.5 mL / min, and the concentration of talcum powder in the solution in the solution delivery pipeline 104 is 1 to 7 g / L by mixing the surfactant solution with the modifier solution of different concentrations, and the flow rate of the gas flow metering pump 106 is set to 600 mL / min.

[0147] Under the conditions of different concentrations of modifier solution, the foam volume (i.e. foaming amount) formed when the total solution volume is 50mL is as follows: Figure 8 Under different concentrations of modifier solution, the time when the liquid precipitated from the bottom of the foam volume measuring device 302 is 25 mL (i.e., the precipitation time) is shown as follows. Figure 9 shown.

[0148] Depend on Figure 8 and Figure 9 It can be seen that the method and system of the present invention can realize the simultaneous addition of the modifier solution in the state of solid suspension, and thus can evaluate the foamability and stability of the foam during the simultaneous addition of the modifier.

[0149] Example 8

[0150] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is the same as that of Example 5, and the effective volume of the foam settler 204 is 3L, and the effective volume of the residual foam collector 207 is 5L.

[0151] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0152] The surfactant solution used in this embodiment is: 1000mL of 8g / L α-olefin sulfonate sodium (AOS) solution, stored in surfactant solution storage tank 101. This embodiment also uses a modifier solution (solid suspension): 1000mL of 4g / L talc dispersion solution, stored in modifier solution storage tank 110. The talc dispersion solution is prepared by weighing a certain amount of talc, placing it in water, and ultrasonically dispersing it using a probe-type ultrasonic device for 5 minutes at an ultrasonic power of 1200W. The foaming gas used is: air. The contaminated soil of this example was prepared by the following steps: phenanthrene-contaminated soil was prepared using natural soil as a base; 1 kg of pretreated soil sample (screened to remove rocks and debris with a particle size greater than 0.9 mm and dried at 60°C for 24 h) was weighed and placed in a stainless steel tray; 500 mL of a 0.2 g / L phenanthrene-dichloromethane solution was added to the sample, followed by stirring until uniformly mixed. The sample was then placed in a fume hood to air-dry and age for 3 weeks before use; after aging, the actual phenanthrene contamination concentration in the contaminated soil was measured to be 66.42 mg / kg.

[0153] This method is basically the same as Example 7, except that: the flow rate of the surfactant solution flow metering pump 103 is set to 5 mL / min, the flow rate of the modifier solution flow metering pump 112 is set to 5 mL / min, and the surfactant solution and the modifier solution are mixed so that the concentration of talcum powder in the solution in the solution delivery pipeline 104 is 2 g / L, and the flow rate of the gas flow metering pump 106 is set to 550 mL / min.

[0154] The residual concentration of pollutants in the soil after different repair time (i.e. extraction time) was measured. Since talcum powder only affects the foam performance without changing the repair effect, the results obtained in this example are consistent with those in the Figure 4 The results were similar when the flow rate of the solution was 10 mL / min.

[0155] As can be seen from this example, the method and system of the present invention can achieve the simultaneous addition of a modifier solution in a solid suspension state, and thus can evaluate the soil remediation effect during the simultaneous addition of foam and modifier.

[0156] Example 9

[0157] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is the same as that of Example 5.

[0158] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0159] The surfactant solution used in this example is 1000 mL of 8 g / L sodium α-olefin sulfonate (AOS) solution, stored in surfactant solution storage tank 101. This example also uses oxidant solutions: 100 mL of sodium persulfate solutions with concentration gradients ranging from 10 to 80 g / L, stored in oxidant solution storage tank 113. A valve can be used to switch between oxidant solution storage tanks 113 containing oxidant solutions of varying concentrations for each evaluation. The foaming gas used is high-purity nitrogen (≥99.999%).

[0160] The method of this embodiment includes the following steps:

[0161] (1) The surfactant solution and the oxidant solution are stored in their respective storage tanks. The surfactant solution valve 102 and the oxidant solution valve 114 are opened, and the modifier solution valve 111 is closed. The surfactant solution is metered by the surfactant solution flow metering pump 103 and then enters the solution delivery pipeline 104. The flow rate of the surfactant solution flow metering pump 103 is set to 7.5 mL / min. The oxidant solution is metered by the oxidant solution flow metering pump 115 and then enters the solution delivery pipeline 104. The oxidant solution flow metering pump 115 is set to The flow rate of 115 is 7.5 mL / min. By mixing the surfactant solution with oxidant solutions of different concentrations, the concentration of sodium persulfate in the solution in the solution delivery pipeline 104 is adjusted to 5-40 g / L. The gas valve 105 is opened to allow the foaming gas to enter the gas delivery pipeline 107 after being measured by the gas flow metering pump 106. The flow rate of the gas flow metering pump 106 is set to 600 mL / min. The solution and foaming gas are mixed in the pipeline and then enter the foam generating device 108 to form a stable and homogeneous foam, which is then delivered by the foam output pipeline.

[0162] (2) Open the first foam valve 201 and close the second foam valve 301 to allow the foam to enter the soil extractor 202. Under the action of the extraction pressure formed by the negative pressure generated by the centrifugal pump 205, the foam passes through the contaminated soil to leach the soil. A portion of the foam that passes through the contaminated soil enters the residual foam collector 207 through the check valve 206, and another portion of the foam that passes through the contaminated soil enters the foam settler 204 under the drive of the negative pressure for gas-liquid separation. The extraction pressure is controlled by the pressure control device 203 provided on the top of the foam settler 204 to control the vacuum degree of the system at -0.002 to -0.008 kPa. The gas separated from the gas and liquid is extracted by the centrifugal pump 205, and the liquid separated from the gas and liquid enters the residual foam collector 207. The concentration of pollutants in the soil before remediation and the residual concentration of pollutants in the soil after foam leaching are measured, and the soil remediation effect is evaluated.

[0163] (3) Open the second foam valve 301 and close the first foam valve 201 to allow the foam to enter the foam volume measuring device 302; record the foam volume formed when the total amount of the solution in step (1) is 50 mL, and then evaluate the foaming property of the foam; record the time when the liquid precipitated at the bottom of the foam volume measuring device 302 is 25 mL, and then evaluate the stability of the foam.

[0164] Under different concentrations of oxidant solution, the foam volume (i.e. foaming amount) formed when the total solution volume is 50mL is as follows: Figure 10 Under different concentrations of oxidant solution, the time when the liquid precipitated from the bottom of the foam volume measuring device 302 is 25 mL (i.e., the precipitation time) is shown as follows. Figure 11 shown.

[0165] Depend on Figure 10 and Figure 11 It can be seen that the method and system of the present invention can realize the simultaneous addition of the oxidant solution, and thus can evaluate the foamability and stability of the foam during the simultaneous addition of the oxidant.

[0166] Example 10

[0167] This embodiment provides a foam performance and soil remediation effect evaluation system for an in-situ soil leaching process. The structure of the system is the same as that of Example 5, and the effective volume of the foam settler 204 is 3L, and the effective volume of the residual foam collector 207 is 5L.

[0168] This embodiment also provides a method for evaluating the foam performance and soil remediation effect of an in-situ soil leaching process. The method uses the system of this embodiment to evaluate the foam performance and soil remediation effect of an in-situ soil leaching process.

[0169] The surfactant solution used in this example was 1000 mL of an 8 g / L sodium α-olefin sulfonate (AOS) solution, stored in surfactant solution storage tank 101. This example also used an oxidant solution: 100 mL of a 40 g / L sodium persulfate solution, stored in oxidant solution storage tank 113. The foaming gas used was air. The contaminated soil in this example was prepared by the following steps: Phenanthrene-contaminated soil was prepared using natural soil as a base; 1 kg of pretreated soil sample (screened to remove rocks and debris larger than 0.9 mm and dried at 60°C for 24 hours) was weighed into a stainless steel tray, 500 mL of a 0.2 g / L phenanthrene-dichloromethane solution was added, and the mixture was stirred until uniformly mixed. The mixture was then air-dried and aged in a fume hood for 3 weeks before use; after aging, the actual phenanthrene concentration in the contaminated soil was measured to be 66.42 mg / kg.

[0170] This method is basically the same as Example 9, except that: the flow rate of the surfactant solution flow metering pump 103 is set to 5 mL / min, the flow rate of the oxidant solution flow metering pump 115 is set to 5 mL / min, the surfactant solution and the oxidant solution are mixed so that the concentration of persulfate in the solution in the solution delivery pipeline 104 is 20 g / L, and the flow rate of the gas flow metering pump 106 is set to 550 mL / min.

[0171] The residual concentration of pollutants in the soil after different remediation times (i.e. extraction time) was measured, and the pollutant removal rate (i.e. remediation efficiency) was calculated. The results are as follows: Figure 12 shown.

[0172] Depend on Figure 12 It can be seen that the method and system of the present invention can achieve the simultaneous addition of oxidant solution, and thus can evaluate the soil remediation effect of the foam during the simultaneous addition of oxidant.

[0173] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A foam performance and soil remediation effect evaluation system for in-situ soil leaching, comprising: Foam generation unit, repair effect testing unit and foam measurement unit; The foam generating unit includes a surfactant solution storage tank, a surfactant solution valve, a surfactant solution flow metering pump, a solution delivery pipeline, a gas valve, a gas flow metering pump, a gas delivery pipeline, a foam generating device and a foam output pipeline; The repair effect testing unit includes a first foam valve, a soil extractor, a pressure control device, a foam settler and a centrifugal pump; The foam measuring unit includes a second foam valve and a foam volume measuring device; The foam generating device is connected to the solution delivery pipeline, the gas delivery pipeline and the foam output pipeline; the solution delivery pipeline is connected to the surfactant solution storage tank through the surfactant solution valve and the surfactant solution flow metering pump; the gas delivery pipeline is provided with the gas valve and the gas flow metering pump; The foam output pipeline is connected to the soil extractor through the first foam valve. The soil extractor is filled with contaminated soil. The soil extractor is connected to the foam settler. The pressure control device is provided on the top of the foam settler. The foam settler is connected to the centrifugal pump. The foam output pipeline is communicated with the foam volume measuring device through the second foam valve.

2. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1, wherein: The foam generating unit further comprises: a modifier solution storage tank, a modifier solution valve and a modifier solution flow metering pump; the solution delivery pipeline is connected to the modifier solution storage tank through the modifier solution valve and the modifier solution flow metering pump.

3. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1, wherein: The foam generating unit further comprises: an oxidant solution storage tank, an oxidant solution valve and an oxidant solution flow metering pump; the solution delivery pipeline is connected to the oxidant solution storage tank through the oxidant solution valve and the oxidant solution flow metering pump.

4. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1, wherein: The interior of the foam generating device is filled with a mesh structure medium.

5. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 4, wherein: The mesh structure medium includes one or a combination of polypropylene fiber net, polyester fiber net and polyimide fiber net.

6. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 4 or 5, wherein: The mesh structure medium is a polyester fiber mesh.

7. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1, wherein: The effective filling diameter inside the foam generating device is 2 to 10 mm.

8. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1 or 7, wherein: The effective filling length inside the foam generating device is 5 to 50 mm.

9. The foam performance and soil remediation effect evaluation system for in-situ soil washing process according to claim 1, wherein: The repair effect testing unit further includes a check valve and a residual foam collector; the soil extractor and the foam settler are connected to the residual foam collector through pipelines respectively, and the check valve is provided on the pipeline connecting the soil extractor and the residual foam collector.

10. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1, wherein: The inner diameter of the soil extractor is 20-100 mm.

11. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1, wherein: The mass of the contaminated soil filled in the soil extractor is 4-20 g.

12. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1 or 11, wherein: The filling height of the contaminated soil is 5 to 25 mm.

13. The foam performance and soil remediation effect evaluation system for in-situ soil leaching process according to claim 1, wherein: The foam volume measuring device is a 500-1000 mL measuring cylinder or measuring cup.

14. The foam performance and soil remediation effect evaluation system for in-situ soil washing process according to claim 1, wherein: The inner diameter of the pipeline in the system is 1~10mm.

15. A method for evaluating foam performance and soil remediation effect during an in-situ soil washing process, the method using the foam performance and soil remediation effect evaluation system for in-situ soil washing according to any one of claims 1 to 14 to evaluate the foam performance and soil remediation effect during an in-situ soil washing process, the method comprising the following steps: (1) Open the surfactant solution valve to allow the surfactant solution to enter the solution delivery pipeline after being metered by the surfactant solution flow metering pump; Open the gas valve to allow the foaming gas to enter the gas delivery pipeline after being measured by the gas flow metering pump; the solution and foaming gas are mixed in the pipeline and then enter the foam generating device to form foam which is then delivered through the foam output pipeline; (2) Open the first foam valve and close the second foam valve to allow the foam to enter the soil extractor. Under the action of the extraction pressure formed by the negative pressure generated by the centrifugal pump, the foam is allowed to pass through the contaminated soil to leach the soil. At least a portion of the foam that has passed through the contaminated soil enters the foam settler under the drive of the negative pressure to separate the gas and liquid. The separated gas is extracted by the centrifugal pump. The concentration of pollutants in the soil before remediation and the residual concentration of pollutants in the soil after foam leaching are measured, and the soil remediation effect is evaluated. (3) Open the second foam valve and close the first foam valve to allow the foam to enter the foam volume measuring device; record the foam volume formed when the total amount of the solution in step (1) is 50 mL, and then evaluate the foaming property of the foam; record the time when the liquid precipitated at the bottom of the foam volume measuring device is 25 mL, and then evaluate the stability of the foam.

16. The method for evaluating foam performance and soil remediation effect in an in-situ soil washing process according to claim 15, wherein: Step (1) further includes: opening the modifier solution valve to allow the modifier solution to enter the solution delivery pipeline after being metered by the modifier solution flow metering pump.

17. The method for evaluating foam performance and soil remediation effect in an in-situ soil washing process according to claim 15, wherein: Step (1) further includes: opening the oxidant solution valve to allow the oxidant solution to enter the solution delivery pipeline after being metered by the oxidant solution flow metering pump.

18. The method for evaluating foam performance and soil remediation effect in an in-situ soil washing process according to claim 15, wherein: In step (1), the foaming gas includes one or a combination of carbon dioxide, air, nitrogen, helium and argon.

19. The method for evaluating foam performance and soil remediation effect in an in-situ soil washing process according to claim 15 or 18, wherein: In step (1), the foaming gas is air.

20. The method for evaluating foam performance and soil remediation effect in an in-situ soil washing process according to claim 15, wherein: In step (1), the total flow rate of the solution is 5-30 mL / min, and the flow rate of the foaming gas is 400-1025 mL / min.

21. The method for evaluating foam performance and soil remediation effect in an in-situ soil washing process according to claim 15, wherein: In step (2), the extraction pressure is controlled by a pressure control device provided on the top of the foam settler so that the vacuum degree of the system is controlled at -0.002 to -0.008 kPa.

22. The method for evaluating foam performance and soil remediation effect in an in-situ soil washing process according to claim 15, wherein: Step (2) further includes: a portion of the foam that passes through the contaminated soil enters the residual foam collector through the check valve, and the liquid after gas-liquid separation in the foam settler enters the residual foam collector.

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