Soil remediation eluent and soil remediation method

Abstract

The invention belongs to the technical field of soil pollution remediation, particularly provides an eluent capable of simultaneously removing polycyclic aromatic hydrocarbon and heavy metal pollutants in soil and a soil remediation method, and aims to solve the problems of low efficiency and high secondary pollution risk in combined contaminated soil remediation. And the eluent comprises the following components in percentage by mass: 2-15% of a surfactant, 1-20% of a chelating agent and the balance of deionized water. The eluent prepared by the invention has the performance of efficiently and synchronously removing polycyclic aromatic hydrocarbons (PAHs) and heavy metals, is high in removal efficiency and good in biological safety, and is suitable for polluted soil remediation of industrial and mining polluted sites and agricultural lands.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil pollution remediation, and specifically relates to a preparation and application technology of an eluent for removing polycyclic aromatic hydrocarbons and heavy metal composite pollutants in soil. Background Art

[0002] Soil is a complex system composed of solid, liquid, and gas phases. It is one of the most important natural resources required for crop growth and human survival, and plays an important role in protecting the environment and maintaining ecological balance. In recent years, with the development of industry and the advancement of urbanization, heavy metal pollutants (such as Pb, Cd, and Hg) generated by industrial activities such as metallurgy, electroplating, and chemical industry, and persistent organic pollutants (represented by polycyclic aromatic hydrocarbons (PAHs)) derived from the incomplete combustion of fossil fuels have shown significant combined pollution characteristics in the soil environment. This multi-media and multi-phase synergistic pollution system not only aggravates the environmental persistence and bioavailability of pollutants, but also poses a potential threat to human health through the biomagnification effect of the food chain. Therefore, the coexistence of polycyclic aromatic hydrocarbons (PAHs) and heavy metals has become a key issue that needs to be urgently addressed in the current field of environmental pollution control.

[0003] Polycyclic aromatic hydrocarbons (PAHs) are typical persistent organic pollutants. Their low water solubility and high hydrophobicity cause them to remain in the soil for a long time, and they are enriched through the food chain to produce carcinogenic and teratogenic effects. Heavy metals (such as Pb, Cd, and Cu) pose a serious threat to soil microbial communities and plant growth due to their non-degradability and biotoxicity. The combined pollution of the two not only exacerbates ecological risks, but also significantly increases the difficulty of remediation due to the interactions between pollutants (such as PAHs-heavy metal complexation and competitive adsorption). Although chemical leaching technology is widely used in contaminated soil remediation due to its high efficiency, traditional chemical leaching technology usually designs eluents for a single type of pollutant, which severely limits its applicability in complex pollution scenarios. In addition, existing compounding technologies mostly adopt simple mechanical mixing strategies, ignoring the molecular interaction mechanism between agents, resulting in poor environmental compatibility between the components of existing compound eluents and obvious charge competition, which reduces the effect of their synergistic effect. Summary of the Invention

[0004] To address the inability of existing soil composite contamination remediation technologies to efficiently and simultaneously remove polycyclic aromatic hydrocarbons (PAHs) and heavy metals from soil, the high cost of eluents, and the significant risk of secondary contamination, the present invention aims to provide an environmentally friendly and economically viable eluent for the simultaneous removal of PAHs and heavy metal contaminants from soil.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A soil remediation eluent comprises the following components, calculated by total mass percentage: 2-15% of a surfactant, wherein the surfactant is composed of any two or more of anionic surfactants, nonionic surfactants, biosurfactants, or amphoteric surfactants; 1-20% of a chelating agent, wherein the chelating agent is composed of a biodegradable aminopolycarboxylic acid chelating agent and a natural organic acid; and the balance is deionized water.

[0007] The preparation method of the soil remediation eluent comprises the following steps:

[0008] Step 1: Mix any two of anionic surfactants, nonionic surfactants, biosurfactants, or amphoteric surfactants in a mass ratio of 1:1 to 1:10 in a water bath at 40 to 50° C., and stir magnetically at 600 rpm for 20 minutes to fully mix and dissolve the mixture to form a transparent and stable micellar solution;

[0009] Step 2: Dissolve the biodegradable aminopolycarboxylic acid chelating agent and natural organic acid in deionized water preheated at 40-50°C in a mass ratio of 1:0.5-1:10, and promote the dissociation of the chelating agent by 40kHz ultrasound for 10 minutes. Subsequently, under a constant temperature of 30-35°C, the chelating agent solution is slowly added dropwise to the surfactant solution at a rate of 0.5mL / min according to its mass percentage in the soil remediation eluent. Simultaneously, high shear emulsification is performed at 8000rpm for 5-8 minutes to achieve instantaneous charge matching between the polar heads of the chelating agent and the surfactant to avoid micelle collapse caused by the chelating agent. Then, the mixture is adjusted to 500rpm and gently stirred for 12-15 minutes to maintain dynamic equilibrium to prevent micelle breakage caused by excessive shearing.

[0010] Step 3: After uniform mixing, deionized water is added to the mixed system obtained in step 2 to a total amount of 100%, the pH of the system is adjusted to neutral, and then the system is subjected to high-pressure homogenization (150 bar) cycle treatment 3 times to effectively overcome the coordination bond between soil organic matter and heavy metals and eliminate microscopic phase separation, thereby obtaining the soil remediation eluent.

[0011] Preferably, the surfactant is prepared by compounding any two of anionic surfactants, nonionic surfactants, biosurfactants or amphoteric surfactants in a mass ratio of 1:1 to 1:10.

[0012] Further preferably, the anionic surfactant is one or more of sodium α-olefin sulfonate (AOS), methyl fatty acid ester sulfonate (MES), sodium fatty alcohol polyoxyethylene ether sulfate (AES), sodium dodecylbenzene sulfonate (LAS), sodium lauryl sulfate (SDS), sodium lauryl polyether sulfate (SLES), sodium cocoyl glutamate, and alkyl polyoxyethylene ether phosphate. Even more preferably, the anionic surfactant is one or more of methyl fatty acid ester sulfonate (MES), sodium fatty alcohol polyoxyethylene ether sulfate (AES), and sodium cocoyl glutamate.

[0013] Further preferably, the nonionic surfactant is one or more of polyoxyethylene sorbitan fatty acid ester (Tween-80), alkyl glycoside (APG), fatty alcohol polyoxyethylene ether (AEO series), C13 isopropyl alcohol amide, sorbitol ester (Span), polyoxyethylene stearate (such as PEG-40 stearate), coconut oil diethanolamide (6501), polyoxyethylene glyceride (PEO), polyoxyethylene glyceride (Brij series), Pluronic F127, and saponin. Even more preferably, the nonionic surfactant is one or more of polyoxyethylene sorbitan fatty acid ester (Tween-80), alkyl glycoside (APG), fatty alcohol polyoxyethylene ether (AEO series), sorbitol ester (Span), coconut oil diethanolamide (6501), polyoxyethylene glyceride (Brij series), and saponin.

[0014] Further preferably, the biosurfactant is one or more of rhamnolipids, sophorolipids, trehalolipids, mannolipids, erythritol esters, lipopeptides and lipoproteins.

[0015] Further preferably, the amphoteric surfactant is one or more of cocamidopropyl betaine (CAPB), sodium oliveoamphoacetate, lauryl dimethyl betaine (BS-12), amphoteric imidazoline acetate, and lecithin.

[0016] Preferably, the chelating agent is a compound of a biodegradable aminopolycarboxylic acid chelating agent and a natural organic acid in a mass ratio of 1:0.5 to 1:10.

[0017] Further preferably, the biodegradable aminopolycarboxylic acid chelating agent is one or more of tetrasodium N-diacetate (GLDA), ethylenediamine disuccinic acid (EDDS), tetrasodium iminodisuccinate (IDS), tetrasodium aspartate (ASDA), methylglycine diacetic acid (MGDA), iminodisuccinic acid (IDHA), tetrasodium 3-hydroxy-2,2'-iminodisuccinate (HIDS), and AILT-105.

[0018] More preferably, the natural organic acid is one or more of citric acid, tartaric acid, malic acid, oxalic acid, succinic acid, tannic acid, chlorogenic acid, succinic acid, and humic acid.

[0019] A soil remediation method of the present invention, using the aforementioned soil remediation eluent, specifically comprises the following steps:

[0020] (1) Pretreatment of contaminated soil: Remove stones and plant debris from the contaminated soil and mechanically crush it to a particle size of ≤2 mm;

[0021] (2) Leaching and remediation of contaminated soil: The pretreated contaminated soil is placed in a leaching reaction device, and then an eluent is added. The soil is leached and shaken for a period of time to promote the renewal of the micelle-pollutant interface; then centrifugation is performed, and the soil is allowed to stand for stratification to obtain the remediated soil fraction;

[0022] (3) Recycling of eluent: The eluent is recycled after acidification, filtration and adsorption treatment.

[0023] Preferably, the solid-liquid ratio between the contaminated soil and the eluent is 1:5 to 1:20.

[0024] Preferably, the elution time is 12 to 30 hours.

[0025] Preferably, the elution temperature is 25-50°C.

[0026] The soil remediation eluent and soil remediation method of the present invention are applicable to the field of remediation of composite contaminated soil in industrial and mining contaminated sites and agricultural land.

[0027] Compared with the prior art, the advantages of the eluent disclosed in the present invention for removing polycyclic aromatic hydrocarbons and heavy metal pollutants in soil are:

[0028] (1) The soil remediation eluent provided by the present invention achieves pollutant removal through the synergistic effect of biodegradable surfactants and natural chelating agents, and has simple formula components and excellent environmental compatibility. Among them, anionic surfactants, nonionic surfactants, biosurfactants and amphoteric surfactants are compounded according to the specific formula ratio of the present invention, which significantly improves the solubilization ability of polycyclic aromatic hydrocarbons. The biodegradable aminopolycarboxylic acid chelating agent and natural organic acid are compounded according to the formula ratio of the present invention, which can exert the synergistic effect of the two and achieve the chelation and desorption of heavy metals. At the same time, the surfactant and chelating agent compound system breaks through the limitation of traditional single eluents that only target a certain type of pollutants, and uses molecular synergy to achieve the simultaneous removal of polycyclic aromatic hydrocarbons solubilization and heavy metal chelation, with removal rates reaching 75% to 90% and 60% to 85% respectively.

[0029] (2) The soil remediation eluent provided by the present invention only requires physical compounding during its preparation process, without the need for high temperature, high pressure or complex chemical reaction conditions. No organic solvents, waste acid or by-products are produced throughout the process. The raw materials are all degradable materials with a biodegradation rate of ≥80%. The chelating agent residue (such as IDS ≤ 0.08 mg / kg) is far lower than the agricultural land standard, significantly reducing the ecotoxicity risk (LC50 = 120 mg / L), while taking into account both high efficiency and safety.

[0030] (3) The soil remediation method provided by the present invention is simple to operate. It only requires optimizing the solid-liquid ratio under oscillation mode and treating for 12 to 30 hours to complete soil remediation. The entire process does not require complex equipment or high-energy consumption steps, and the eluate can be recycled 3 to 5 times after acidification and filtration. The removal effect of polycyclic aromatic hydrocarbons and heavy metals can still be maintained at more than 80% of the effect of the first use. There is no secondary pollution throughout the process, the amount of eluent used is reduced by 65% ​​to 80%, and the treatment time is shortened by 30% to 40%, greatly improving the remediation efficiency and economy. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used in the present invention have the same meanings as those generally understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the present invention. The present description and examples are intended to be illustrative only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] Example 1

[0037] (1) Composition, content and preparation of soil remediation eluent

[0038] In terms of mass percentage, it is composed of the following components:

[0039] A. Surfactant: anionic surfactant fatty acid methyl ester sulfonate (MES) and nonionic surfactant fatty alcohol polyoxyethylene ether (AEO-9) are mixed in a ratio of 1:1, with a total concentration of 15%;

[0040] B. Chelating agent: Tetrasodium glutamate N,N-diacetate (GLDA) and citric acid in a ratio of 1:4, total concentration 1%;

[0041] C. Deionized water: add to 100%.

[0042] The soil remediation eluent is prepared by mixing the anionic surfactant MES and the nonionic surfactant AEO-9 in a 1:1 ratio by mass, heating them appropriately, and magnetically stirring them to form a micellar solution. Simultaneously, the chelating agent GLDA and citric acid are dissolved in preheated deionized water in a 1:4 ratio, and ultrasonic treatment is used to promote dissolution. Subsequently, the chelating agent solution is slowly added dropwise to the surfactant system at a rate of 0.5 mL / min under a constant temperature of 35°C and high-speed emulsification at 8000 rpm. After complete addition, stirring is continued. When the mixed solution changes from a milky white viscous fluid to a translucent solution, stirring is switched to a low speed of 500 rpm until the solution becomes homogeneous and transparent without visible streaks or particles, thus achieving phase equilibrium. Finally, deionized water is added to the resulting mixed system to the desired total volume, and the pH is adjusted to maintain a neutral environment. Finally, a stable composite eluent is obtained by three cycles of high-pressure homogenization (150 bar). The preparation process requires strict control of the temperature gradient and mixing rate to ensure the synergistic effect of the micellar structure and chelation efficiency.

[0043] (2) Contaminated soil remediation test

[0044] S1. Soil Samples: Collect soil from a coking plant. Remove rocks and plant debris, air-dry the soil, pass it through a sieve with a large aperture, and place it in a brown wide-mouth bottle for later use.

[0045] S2. 1 g of the aforementioned soil sample was placed in a 250 mL round-bottom flask. 200 mL of a 1:1 hexane:acetone solution was added and Soxhlet extraction was performed for 4-6 hours. The sample was then concentrated by rotary evaporation and purified by silica gel chromatography. The PAH content was then determined using an HPLC instrument (Arc HPLC-2998-QDa, Waters). Another 0.1 g of the aforementioned soil sample was placed in a 50 mL beaker. 20 mL of aqua regia was added and dissolved by heating. The sample was then analyzed for heavy metal content using an ICP-OES instrument (ICPOES720, Agilent). The results are shown in Table 1.

[0046] S3. Take another 1 g of the aforementioned soil sample and place it in a 50 mL centrifuge tube. Add eluent at a ratio of soil:eluent = 1:10, and then shake at 25°C, 150 rpm for 12 h.

[0047] S4. After standing for 2 hours, centrifuge (6000r, 10min) to separate. After the supernatant was filtered through a 0.45μm filter membrane, the PAHs content in the sample was detected by HPLC and the heavy metal content was detected by ICP-OES. The test results are shown in Table 1.

[0048] S5. The eluate was acidified (pH = 2.5) and centrifuged to recover the GLDA-heavy metal complex with a recovery rate of ≥80%. The precipitate was filtered and concentrated on a rotary evaporator to obtain a regenerated chelating agent mother liquor, which was recycled three times. The effective chelating capacity retention rate was measured by ICP-MS and was ≥90%.

[0049] Example 2

[0050] (1) Composition, content and preparation of soil remediation eluent

[0051] In terms of mass percentage, it is composed of the following components:

[0052] A. Surfactant: Anionic surfactant methyl ester sulfonate (MES) and nonionic surfactant alkyl polyglycoside (APG) were mixed at a ratio of 1:5, with a total concentration of 13.5%;

[0053] B. Chelating agent: ethylenediamine disuccinic acid (EDDS) and tartaric acid at a ratio of 1:0.5, with a total concentration of 8%;

[0054] C. Deionized water: add to 100%.

[0055] The method for preparing the soil remediation eluent using the above formula is shown in Example 1.

[0056] (2) Contaminated soil remediation test was carried out with reference to Example 1. The difference from Example 1 was that the ratio of soil to eluent was 1:5, and the mixture was shaken at a constant temperature of 30° C. and 150 rpm for 16 h.

[0057] Example 3

[0058] (1) Composition, content and preparation of soil remediation eluent

[0059] In terms of mass percentage, it is composed of the following components:

[0060] A. Surfactant: Nonionic surfactant Tween-80 and amphoteric surfactant cocamidopropyl betaine (CAPB) were mixed in a ratio of 1:2, with a total concentration of 11.6%;

[0061] B. Chelating agent: Tetrasodium aspartate (ASDA) and humic acid in a ratio of 1:2, with a total concentration of 6%;

[0062] C. Deionized water: add to 100%.

[0063] The method for preparing the soil remediation eluent using the above formula is shown in Example 1.

[0064] (2) Contaminated soil remediation test was carried out with reference to Example 1. The difference from Example 1 was that the ratio of soil to eluent was 1:18, and the mixture was shaken at a constant temperature of 38°C and 150 rpm for 20 h.

[0065] Example 4

[0066] (1) Composition, content and preparation of soil remediation eluent

[0067] In terms of mass percentage, it is composed of the following components:

[0068] A. Surfactant: Nonionic surfactant Tween-80 and biosurfactant rhamnolipid are mixed at a ratio of 1:8, with a total concentration of 9%;

[0069] B. Chelating agent: Tetrasodium iminodisuccinate (IDS) and oxalic acid at a ratio of 1:10, total concentration 18%;

[0070] C. Deionized water: add to 100%.

[0071] The present invention provides a method for remediating soil contaminated by polycyclic aromatic hydrocarbons and heavy metals, and the specific steps are as follows:

[0072] The method for preparing the soil remediation eluent using the above formula is shown in Example 1.

[0073] (2) Contaminated soil remediation test was carried out with reference to Example 1. The difference from Example 1 was that the ratio of soil to eluent was 1:8, and the mixture was kept at 42° C. and 150 rpm for 24 h.

[0074] Table 1 shows the elution effect of the soil remediation eluent prepared by Examples 1 to 4 of the present invention on a contaminated soil sample collected from a coking plant.

[0075] Table 1 Removal results of polycyclic aromatic hydrocarbons and heavy metal elements by eluent

[0076]

[0077]

[0078] As can be seen from Table 1, after the eluents prepared in Examples 1 to 4 were used to elute the polycyclic aromatic hydrocarbons-heavy metal composite contaminated soil, the removal efficiencies of polycyclic aromatic hydrocarbons and heavy metals in each example after elution were 75% to 90% and 60% to 85%, respectively. This indicates that the eluent provided by the present invention can simultaneously remove polycyclic aromatic hydrocarbons-heavy metal composite pollution, and the reason is that the components play a synergistic role.

[0079] Example 5

[0080] (1) Composition, content and preparation of soil remediation eluent

[0081] In terms of mass percentage, it is composed of the following components:

[0082] A. Surfactant: anionic surfactant sodium cocoyl glutamate and nonionic surfactant AEO-9 are mixed at a ratio of 1:6, with a total concentration of 12.3%;

[0083] B. Chelating agent: methylglycine diacetic acid (MGDA) and citric acid in a ratio of 1:5, with a total concentration of 15.0%;

[0084] C. Deionized water: add to 100%.

[0085] The method for preparing the soil remediation eluent using the above formula is shown in Example 1.

[0086] (2) Contaminated soil remediation test

[0087] S1. Soil Sample: Collect soil from a chemical plant. Remove any rocks and plant debris, air-dry the soil, pass it through a sieve with a small aperture, and place it in a brown wide-mouth bottle for later use.

[0088] S2. Place 1 g of the aforementioned soil sample in a 250-mL round-bottom flask and add 200 mL of a 1:1 hexane:acetone solution for Soxhlet extraction for 4-6 h. The sample is then concentrated by rotary evaporation and purified by silica gel chromatography. The sample is then sampled and analyzed for PAHs content using an HPLC instrument (Arc HPLC-2998-QDa, Waters).

[0089] Another 0.1 g of the aforementioned soil sample was placed in a 50 mL beaker, 20 mL of aqua regia was added and heated to dissolve, and then the sample was taken and the heavy metal content was determined by ICP-OES (ICPOES720, Agilent). The test results are shown in Table 2.

[0090] S3. Take another 1 g of the aforementioned soil sample and place it in a 50 mL centrifuge tube. Add eluent at a ratio of soil:eluent = 1:12, and then shake at 26°C, 150 rpm for 30 h.

[0091] S4. After standing for 2 hours, the mixture was centrifuged (6000 r, 10 min) and the supernatant was filtered through a 0.45 μm filter membrane. The PAHs content in the sample was detected by HPLC and the heavy metal content was detected by ICP-OES. The test results are shown in Table 2.

[0092] S5. The eluate was acidified (pH = 2.5) and centrifuged to recover the MGDA-heavy metal complex with a recovery rate of ≥80%. The precipitate was filtered and concentrated on a rotary evaporator to obtain a regenerated chelating agent mother liquor, which was recycled three times. The effective chelating capacity retention rate was measured by ICP-MS and was ≥90%.

[0093] Example 6

[0094] (1) Composition, content and preparation of soil remediation eluent

[0095] In terms of mass percentage, it is composed of the following components:

[0096] A. Surfactant: Anionic surfactant methyl ester sulfonate (MES) and biosurfactant sophorolipid were mixed at a ratio of 1:4, with a total concentration of 10.0%;

[0097] B. Chelating agent: tetrasodium 3-hydroxy-2,2'-iminodisuccinate (HIDS) and tannic acid at a ratio of 1:7, total concentration 3.0%;

[0098] C. Deionized water: add to 100%.

[0099] The method for preparing the soil remediation eluent using the above formula is shown in Example 1.

[0100] (2) Contaminated soil remediation test was carried out with reference to Example 5. The difference from Example 5 was that the ratio of soil to eluent was 1:20, and the mixture was shaken at a constant temperature of 50° C. and 150 rpm for 12 h.

[0101] Example 7

[0102] (1) Composition, content and preparation of soil remediation eluent

[0103] In terms of mass percentage, it is composed of the following components:

[0104] A. Surfactant: nonionic surfactant AEO-9 and amphoteric surfactant sodium oliveoamphoacetate are mixed at a ratio of 1:10, with a total concentration of 2.0%;

[0105] B. Chelating agent: ethylenediamine disuccinic acid (EDDS) and malic acid in a 1:1 ratio, with a total concentration of 20.0%;

[0106] C. Deionized water: add to 100%.

[0107] The method for preparing the soil remediation eluent using the above formula is shown in Example 1.

[0108] (2) Contaminated soil remediation test was carried out with reference to Example 5. The difference from Example 5 was that the ratio of soil to eluent was 1:15, and the mixture was shaken at a constant temperature of 28° C. and 150 rpm for 22 h.

[0109] Example 8

[0110] (1) Composition, content and preparation of soil remediation eluent

[0111] In terms of mass percentage, it is composed of the following components:

[0112] A. Surfactant: The amphoteric surfactant dodecyl dimethyl betaine and the biosurfactant rhamnolipid are mixed in a ratio of 1:3, with a total concentration of 6.5%;

[0113] B. Chelating agent: AILT-105 and oxalic acid are mixed at a ratio of 1:8, with a total concentration of 5.0%;

[0114] C. Deionized water: add to 100%.

[0115] The method for preparing the soil remediation eluent using the above formula is shown in Example 1.

[0116] (2) Contaminated soil remediation test was carried out with reference to Example 5. The difference from Example 5 was that the ratio of soil to eluent was 1:14, and the mixture was shaken at a constant temperature of 40°C and 150 rpm for 14 h.

[0117] Table 2 shows the elution effect of the soil remediation eluent prepared by Examples 5 to 8 of the present invention on the contaminated soil sample collected from a chemical plant.

[0118] Table 2 Removal results of polycyclic aromatic hydrocarbons and heavy metal elements by eluent

[0119]

[0120]

[0121] As can be seen from Table 2, after the eluents prepared in Examples 5 to 8 were used to elute the polycyclic aromatic hydrocarbons-heavy metal composite contaminated soil, the removal efficiencies of polycyclic aromatic hydrocarbons and heavy metals in each example after elution were 75% to 90% and 60% to 85%, respectively. This indicates that the eluent provided by the present invention can simultaneously remove polycyclic aromatic hydrocarbons-heavy metal composite pollution, and the reason is that the components play a synergistic role.

Claims

1. A soil remediation eluent for removing polycyclic aromatic hydrocarbons and heavy metal complex pollutants in soil, characterized in that: The eluent is composed of the following components in terms of mass percentage: 2-15% surfactant, wherein the surfactant is a mixture of any two of anionic surfactant, nonionic surfactant, biosurfactant or amphoteric surfactant in a mass ratio of 1:1-1:10; 1-20% of a chelating agent, wherein the chelating agent is a compound of a biodegradable aminopolycarboxylic acid chelating agent and a natural organic acid in a mass ratio of 1:0.5-1:10; The balance was deionized water.

2. The soil remediation eluent according to claim 1, characterized in that The anionic surfactant is one or more of sodium α-olefin sulfonate, fatty acid methyl ester sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium dodecylbenzene sulfonate, sodium lauryl sulfate, sodium lauryl polyether sulfate, sodium cocoyl glutamate, and alkyl polyoxyethylene ether phosphate.

3. The soil remediation eluent according to claim 1, characterized in that The nonionic surfactant is one or more of polyoxyethylene sorbitan fatty acid ester, alkyl glycoside, fatty alcohol polyoxyethylene ether, C13 isopropanolamide, sorbitol ester, polyoxyethylene stearate, coconut oil diethanolamide, polyoxyethylene glyceride, polyoxyethylene glyceride, Pluronic F127, and saponin.

4. The soil remediation eluent according to claim 1, characterized in that The biosurfactant is one or more of rhamnolipids, sophorolipids, trehalolipids, mannose erythritol esters, lipopeptides and lipoproteins.

5. The soil remediation eluent according to claim 1, characterized in that The amphoteric surfactant is one or more of cocamidopropyl betaine, sodium oliveoyl amphoacetate, lauryl dimethyl betaine, amphoteric imidazoline acetate, and lecithin.

6. The soil remediation eluent according to claim 1, characterized in that The biodegradable aminopolycarboxylic acid chelating agent is one or more of tetrasodium N-diacetate, ethylenediamine disuccinic acid, tetrasodium iminodisuccinate, tetrasodium aspartic acid, methylglycine diacetic acid, iminodisuccinic acid, tetrasodium 3-hydroxy-2,2'-iminodisuccinate, and AILT-105.

7. The soil remediation eluent according to claim 1, characterized in that The natural organic acid is one or more of citric acid, tartaric acid, malic acid, oxalic acid, tannic acid, chlorogenic acid, succinic acid, and humic acid.

8. A soil remediation method, characterized in that: The following steps are involved: (1) Pretreatment of contaminated soil: Remove stones and plant debris from the contaminated soil and mechanically crush it to a particle size of ≤2 mm; (2) Leaching and remediation of contaminated soil: Place the pretreated contaminated soil in a leaching reaction device, then add the eluent and leach and shake for a period of time; Then centrifuge and separate, let it stand and separate to obtain the repaired soil isolate; (3) Eluent recycling: The eluent is recycled after acidification, filtration, and adsorption treatment; The eluent is the soil remediation eluent according to any one of claims 1 to 7.

9. The soil remediation method according to claim 8, characterized in that: The solid-liquid ratio between the contaminated soil and the eluent is 1:5 to 1:

20.

10. The soil remediation method according to claim 8, characterized in that: In the leaching reaction device, the elution time is 12 to 30 hours, and the elution temperature is 25 to 50°C.

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