A method for remediating high-concentration organic pollutants in soil

Abstract

This application relates to the field of environmental remediation, and discloses a method for remediating high-concentration organic pollutants in soil. The method comprises the following steps: First, inject a nano zero-valent iron (nZVI) suspension into the contaminated soil for chemical reduction treatment, and then add sodium persulfate for oxidation treatment to convert complex organic pollutants into biodegradable intermediate products; Then, introduce two-stage microbial communities in sequence. The first-stage microbial community is used to degrade alcohol and ketone intermediate products, and the second-stage microbial community is used to degrade organic acid intermediate products to achieve complete mineralization of the pollutants. This method can significantly improve the pollutant degradation rate and the final removal effect, and is applicable to various treatment scenarios of high-concentration organic pollutants, having strong adaptability and economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental remediation, and particularly to a method for remediating high-concentration organic pollutants in soil. Background Art

[0002] With the rapid development of industrialization and urbanization, the problem of organic pollutants in soil has become increasingly serious. Especially in the long-term production activities in the fields of petrochemical, chemical, and agriculture, a large number of toxic and harmful organic substances are released into the environment. These organic pollutants (such as polycyclic aromatic hydrocarbons, benzene compounds, petroleum hydrocarbons, pesticides, etc.) are highly stable and persistent, and can exist in soil for a long time, posing a serious threat to the ecological environment and human health. Therefore, how to efficiently remediate and purify polluted soil has become an important research topic in the field of environmental science and engineering.

[0003] Traditional soil remediation methods include two main means: chemical treatment and bioremediation. However, although a single chemical treatment method can rapidly degrade organic pollutants in soil, it is usually difficult to completely convert pollutants into harmless substances, and secondary pollutants are easily generated during the treatment process. In addition, due to the complex chemical properties of pollutants in soil, a single chemical oxidant shows low efficiency in treating some high-molecular-weight pollutants. On the other hand, bioremediation technology centered on microbial degradation has good effects in treating some low-concentration and biodegradable pollutants, but in the face of high-concentration pollutants or recalcitrant compounds, the microbial activity is limited, the degradation efficiency is significantly reduced, and it often takes a long time to achieve significant removal of pollutants. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for remediating high-concentration organic pollutants in soil, which can efficiently and thoroughly remove high-concentration organic pollutants in soil, and at the same time overcome the limitations of single chemical treatment or bioremediation methods in terms of degradation efficiency and pollutant mineralization.

[0005] To achieve the above object, the present invention is realized through the following technical solutions: A method for remediating high-concentration organic pollutants in soil, comprising the following steps:

[0006] S1. Inject a nano-zero-valent iron suspension into the soil for chemical treatment;

[0007] S2. After the nano-zero-valent iron treatment, add sodium persulfate for oxidation treatment;

[0008] S3. Introduce the first-stage microbial community into the chemically treated soil to promote the biodegradation of alcohol and ketone intermediate products;

[0009] S4. After the first-stage biodegradation is completed, introduce the second-stage microbial community to treat the organic acid intermediate products;

[0010] S5. Conduct post-treatment on the soil after the remediation is completed.

[0011] Preferably, the preparation steps of the nano zero-valent iron suspension include:

[0012] Disperse the nano zero-valent iron particles in deionized water to prepare a suspension with a concentration of 10 - 30 g / L;

[0013] Perform oscillation treatment on the suspension, with an ultrasonic frequency of 40 kHz and an oscillation time of 30 - 60 minutes;

[0014] During the preparation of the suspension, adjust the pH value of the suspension to 6 - 8.

[0015] Preferably, the average particle size of the nano zero-valent iron particles is 50 - 100 nm, and the purity is greater than 99%.

[0016] Preferably, the injection amount of the nano zero-valent iron is controlled at 1 - 5 L per cubic meter of soil, and the injection depth is 5 - 20 cm.

[0017] Preferably, the sodium persulfate oxidation treatment includes the following steps:

[0018] Dissolve sodium persulfate in deionized water to prepare a solution with a concentration of 5 - 15 g / L;

[0019] Apply the sodium persulfate solution evenly to the contaminated soil that has been treated with nano zero-valent iron, with an injection depth range of 5 - 20 cm and an injection amount controlled at 5 - 10 L per cubic meter of soil;

[0020] During the oxidation treatment, keep the soil humidity within the range of 15 - 20%, and stabilize the pH value of the soil at 6.5 - 7.5 by adding phosphate buffer solution.

[0021] Preferably, the first-stage microbial community includes Pseudomonas and Bacillus, and the concentration of its suspension is 10 6 -10 8 CFU / mL, and the addition amount is 10 - 20 L per cubic meter of soil.

[0022] Preferably, during the first-stage microbial degradation process, the soil humidity is maintained at 20 - 25%, and the incubation time is 7 - 14 days.

[0023] Preferably, the second-stage microbial community includes Thiobacillus and Actinomycetes, and the concentration of its suspension is 10 6 -10 8CFU / mL, and the addition amount is 10 - 20 L per cubic meter of soil.

[0024] Preferably, the culture temperature of the second-stage microorganisms is 28 - 32 °C, the culture time is 48 hours, and the incubation time is 7 - 14 days.

[0025] Preferably, the post-treatment includes physical stabilization and backfilling treatment of the soil.

[0026] The present invention provides a method for repairing high-concentration organic pollutants in soil. It has the following beneficial effects:

[0027] 1. Through the chemical treatment of nano zero-valent iron (nZVI) and sodium persulfate, the present invention effectively accelerates the initial degradation process of organic pollutants. After the reduction reaction between nano zero-valent iron and pollutants, further oxidation by sodium persulfate rapidly decomposes the pollutants into biodegradable intermediate products, thus significantly increasing the rate of the entire repair process and causing the pollutant concentration to drop significantly in a short time.

[0028] 2. The present invention adopts a multi-stage microbial community regulation strategy, introducing suitable microbial communities according to different intermediate products of pollutants to achieve efficient degradation of intermediate products. The first-stage microbial community degrades alcohol and ketone intermediate products, and the second-stage microbial community specifically conducts complete mineralization of organic acid intermediate products. This staged treatment method significantly improves the efficiency and effect of microbial remediation.

[0029] 4. Through the combined action of chemical and biological composite treatment, the present invention not only accelerates the initial degradation of pollutants during the repair process but also promotes the complete mineralization of intermediate products. The concentration of the final residual pollutants is extremely low, approaching complete removal, achieving the efficient conversion of pollutants from complex structures to simple harmless substances, ensuring the thoroughness and long-term stability of the repair.

[0030] 5. The synergistic effect of chemical treatment and bioremediation in the present invention greatly increases the degradation rate and efficiency of pollutants, shortening the repair time, which significantly reduces the treatment cost in practical applications. The high degradation efficiency means reduced energy consumption and labor input during the repair cycle, thus showing greater advantages in terms of economy and environmental sustainability. Description of the Drawings

[0031] Figure 1 It is a flowchart of the method of the present invention. Detailed Embodiments

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Please refer to the attached Figure 1 , the present invention provides a method for repairing high-concentration organic pollutants in soil, which degrades and removes organic pollutants in soil in stages and efficiently through the synergistic effect of chemical treatment and bioremediation. Each step and its action mechanism will be described in detail in this embodiment.

[0034] Step S1: Chemical treatment of nano-zero-valent iron suspension

[0035] 1. Preparation of nano-zero-valent iron suspension:

[0036] Disperse nano-zero-valent iron (nZVI) particles with an average particle size of 50 - 100 nm and a purity greater than 99% in deionized water to prepare a suspension with a concentration of 10 - 30 g / L. Treat this suspension with an ultrasonic device at an oscillation frequency of 40 kHz and an oscillation time of 30 - 60 minutes to ensure the uniform dispersion of nano-particles in the solution. Adjust the pH value of the suspension to 6 - 8 by adding an appropriate amount of pH regulator to improve the stability of nZVI particles and prevent agglomeration.

[0037] 2. Injection process of nano-zero-valent iron:

[0038] Use an injection system to inject the nZVI suspension into the contaminated soil. The injection volume is controlled at 1 - 5 L per cubic meter of soil, and the injection depth is 5 - 20 cm. After injection, mechanically mix the soil to ensure the uniform distribution of nZVI in the soil.

[0039] Nano-zero-valent iron undergoes redox reactions with organic pollutants in the soil, converting high-molecular-weight organic pollutants (such as polycyclic aromatic hydrocarbons, petroleum hydrocarbons, etc.) into low-molecular-weight intermediate products (such as alcohols, ketones, and organic acids), thereby reducing the toxicity of the pollutants and improving their biodegradability. This process effectively breaks the chemical bonds in the pollutant molecules, making them more easily treated in the subsequent bioremediation stage.

[0040] Step S2: Oxidation treatment of sodium persulfate

[0041] 1. Preparation and application of sodium persulfate solution:

[0042] Dissolve sodium persulfate in deionized water to prepare a solution with a concentration of 5 - 15 g / L. Apply the sodium persulfate solution to the contaminated soil that has been treated with nZVI by means of uniform spraying or injection. The injection depth is controlled at 5 - 20 cm, and the injection volume is 5 - 10 L per cubic meter of soil.

[0043] 2. Reaction condition control:

[0044] During the oxidation process, maintain the soil humidity at 15 - 20%, and stabilize the soil pH value at 6.5 - 7.5 by adding phosphate buffer solution. Set the reaction time to 24 - 48 hours to ensure that sodium persulfate can effectively oxidize the intermediate products in the soil.

[0045] Sodium persulfate decomposes in the soil to generate reactive sulfate radicals (SO4· - ), which have strong oxidizing properties and can further degrade intermediate products such as alcohols and ketone compounds formed during the nZVI treatment process, converting them into smaller organic acids. This process greatly improves the biodegradability of pollutants and provides suitable conditions for the subsequent bioremediation stage.

[0046] Step S3: Introduction and degradation of the first - stage microbial community

[0047] 1. Selection and cultivation of the microbial community:

[0048] Select Pseudomonas and Bacillus as the microbial community for the first stage, and adjust the suspension concentration to 10 6 -10 8 CFU / mL in the laboratory. Uniformly add the cultured microbial suspension to the chemically treated soil at a rate of 10 - 20 L per cubic meter of soil.

[0049] 2. Degradation condition control:

[0050] In this stage, maintain the soil humidity at 20 - 25%, and the incubation time is 7 - 14 days to ensure the growth and reproduction of microorganisms under optimal conditions.

[0051] The first - stage microorganisms use alcohols and ketones as carbon sources and decompose these intermediate products into simpler organic acids and carbon dioxide through their metabolic enzyme systems. This decomposition reaction reduces the complexity and toxicity of pollutants and lays the foundation for the treatment of the second - stage microorganisms.

[0052] Step S4: Introduction and degradation of the second - stage microbial community

[0053] 1. Selection and cultivation of the microbial community:

[0054] After the biodegradation in the first stage is completed, a second-stage microbial community, including Thiobacillus and Actinomycetes, is introduced. The concentration of its suspension is maintained at 10 6 -10 8 CFU / mL and injected into the soil at a rate of 10 - 20 L per cubic meter of soil.

[0055] 2. Control of degradation conditions:

[0056] The culture temperature of the second-stage microorganisms is controlled at 28 - 32 °C, the culture time is 48 hours, and the incubation time is 7 - 14 days to ensure that the microorganisms decompose the intermediate organic acid products under the optimal metabolic conditions.

[0057] Thiobacillus and Actinomycetes can efficiently decompose organic acid compounds and completely mineralize them into harmless carbon dioxide and water. The microbial metabolic process in this stage is the final step of the entire remediation method, ensuring the complete removal of pollutants and achieving the complete remediation of contaminated soil.

[0058] Step S5: Post-treatment

[0059] 1. Physical stabilization and backfilling of soil:

[0060] After the bioremediation is completed, the soil is physically stabilized, including drying and screening, to remove unreacted chemicals and microbial residues. Subsequently, the treated soil is backfilled to its original location, and the site is tidied up and vegetation is restored to restore the original ecological function of the soil.

[0061] 2. On-site management and environmental monitoring:

[0062] The remediated soil is regularly monitored, including the detection of soil physical and chemical properties and the concentration of residual pollutants, to ensure the persistence of the remediation effect and the ecological safety of the soil.

[0063] The present invention combines the chemical reduction treatment of nano-zero-valent iron with the strong oxidation treatment of sodium persulfate, effectively reducing the toxicity of high-molecular-weight organic pollutants in the soil and converting them into biodegradable intermediate products. In addition, through the dynamic regulation of multi-stage microbial communities, the efficient decomposition and complete mineralization of the intermediate products are achieved. The creativity of the present invention lies in its unique chemical-biological composite remediation strategy, which solves the problems of low treatment efficiency and long time of traditional remediation methods for high-concentration organic pollutants, significantly improves the efficiency and integrity of soil remediation, and has good practical value and promotion prospects.

[0064] To better understand the present invention, the above method will be described in detail below with specific embodiments.

[0065] Example 1: Remediation of petroleum-contaminated soil

[0066] Pollutant type: The main pollutant in the soil is petroleum hydrocarbons, and the pollution concentration is 1000 mg / kg.

[0067] 1. nZVI chemical treatment:

[0068] The concentration of nano zero-valent iron is 20 g / L, the particle size is 50 nm, the injection volume is 3 L per cubic meter of soil, and the injection depth is 10 cm.

[0069] The suspension is treated by ultrasonic oscillation for 40 minutes, and the ultrasonic frequency is 40 kHz.

[0070] 2. Sodium persulfate oxidation treatment:

[0071] The concentration of sodium persulfate is 10 g / L, the injection volume is 7 L per cubic meter of soil, and the injection depth is 10 cm.

[0072] The soil humidity is maintained at 18%, the pH value is controlled at 7.0, and the reaction time is 48 hours.

[0073] 3. First-stage bioremediation:

[0074] Pseudomonas and Bacillus are selected, and the concentration of the microbial suspension is 10 7 CFU / mL, and the addition amount per cubic meter of soil is 15 L.

[0075] Incubation conditions: The soil humidity is 22%, the incubation time is 10 days, and the temperature is maintained at 22 °C.

[0076] 4. Second-stage bioremediation:

[0077] Rhodobacter and Actinomycetes are selected, and the concentration of the microbial suspension is 10 7 CFU / mL, and the addition amount per cubic meter of soil is 15 L.

[0078] Incubation conditions: The soil humidity is 24%, the incubation time is 14 days, and the temperature is maintained at 30 °C.

[0079] Remediation effect: After 24 days of remediation, the concentration of petroleum hydrocarbons in the soil is reduced to less than 5 mg / kg, meeting the national standard.

[0080] Example 2: Remediation of pesticide-contaminated soil

[0081] Pollutant type: The main pollutant in the soil is organophosphorus pesticides, and the pollution concentration is 1500 mg / kg.

[0082] 1. nZVI chemical treatment:

[0083] The concentration of nano zero-valent iron is 15 g / L, the particle size is 80 nm, the injection volume is 4 L per cubic meter of soil, and the injection depth is 12 cm.

[0084] The suspension is treated by ultrasonic oscillation for 30 minutes, and the ultrasonic frequency is 40 kHz.

[0085] 2. Persulfate oxidation treatment:

[0086] The concentration of persulfate is 12 g / L, the injection volume is 5 L per cubic meter of soil, and the injection depth is 12 cm.

[0087] The soil humidity is maintained at 20%, the pH value is controlled at 7.5, and the reaction time is 36 hours.

[0088] 3. First-stage bioremediation:

[0089] Pseudomonas is selected, and the concentration of the microbial suspension is 10 6 CFU / mL, and the addition amount per cubic meter of soil is 12 L.

[0090] Incubation conditions: The soil humidity is 23%, the incubation time is 7 days, and the temperature is maintained at 25 °C.

[0091] 4. Second-stage bioremediation:

[0092] Rhodobacter is selected, and the concentration of the microbial suspension is 10 8 CFU / mL, and the addition amount per cubic meter of soil is 18 L.

[0093] Incubation conditions: The soil humidity is 25%, the incubation time is 10 days, and the temperature is maintained at 28 °C.

[0094] Remediation effect: After 17 days of remediation, the concentration of organophosphorus pesticides in the soil is reduced to less than 3 mg / kg.

[0095] Example 3: Remediation of benzene-contaminated soil

[0096] Pollutant type: The main pollutant in the soil is benzene organic matter, and the pollution concentration is 2000 mg / kg.

[0097] 1. nZVI chemical treatment:

[0098] The concentration of nano zero-valent iron is 25 g / L, the particle size is 100 nm, the injection volume is 5 L per cubic meter of soil, and the injection depth is 15 cm.

[0099] The suspension is treated by ultrasonic oscillation for 60 minutes, and the ultrasonic frequency is 40 kHz.

[0100] 2. Persulfate oxidation treatment:

[0101] The concentration of sodium persulfate is 15 g / L, the injection volume is 6 L per cubic meter of soil, and the injection depth is 15 cm.

[0102] The soil moisture is maintained at 17%, the pH value is controlled at 6.8, and the reaction time is 48 hours.

[0103] 3. First-stage bioremediation:

[0104] Pseudomonas is selected, the concentration of the microbial suspension is 10 8 CFU / mL, and the addition amount per cubic meter of soil is 20 L.

[0105] Incubation conditions: The soil moisture is 20%, the incubation time is 14 days, and the temperature is maintained at 20°C.

[0106] 4. Second-stage bioremediation:

[0107] Actinomycetes are selected, the concentration of the microbial suspension is 10 8 CFU / mL, and the addition amount per cubic meter of soil is 12 L.

[0108] Incubation conditions: The soil moisture is 22%, the incubation time is 10 days, and the temperature is maintained at 28°C.

[0109] Remediation effect: After 24 days of remediation, the concentration of benzene pollutants in the soil is reduced to less than 7 mg / kg.

[0110] Example 4: Remediation of polycyclic aromatic hydrocarbon-contaminated soil

[0111] Pollutant type: The main pollutant in the soil is polycyclic aromatic hydrocarbons (PAHs), and the pollution concentration is 1800 mg / kg.

[0112] 1. nZVI chemical treatment:

[0113] The concentration of nano zero-valent iron is 20 g / L, the particle size is 60 nm, the injection volume is 4 L per cubic meter of soil, and the injection depth is 10 cm.

[0114] The suspension is treated by ultrasonic oscillation for 40 minutes, and the ultrasonic frequency is 40 kHz.

[0115] 2. Sodium persulfate oxidation treatment:

[0116] The concentration of sodium persulfate is 10 g / L, the injection volume is 6 L per cubic meter of soil, and the injection depth is 10 cm.

[0117] The soil moisture is maintained at 15%, the pH value is controlled at 6.5, and the reaction time is 48 hours.

[0118] 3. First-stage bioremediation:

[0119] Select Bacillus, with the concentration of the microbial suspension being 10 7 CFU / mL, and the addition amount per cubic meter of soil being 15 L.

[0120] Incubation conditions: soil humidity is 23%, incubation time is 10 days, and the temperature is maintained at 24 °C.

[0121] 4. Second-stage bioremediation:

[0122] Select Actinomycetes, with the concentration of the microbial suspension being 10 7 CFU / mL, and the addition amount per cubic meter of soil being 12 L.

[0123] Incubation conditions: soil humidity is 24%, incubation time is 14 days, and the temperature is maintained at 30 °C.

[0124] Remediation effect: After 28 days of remediation, the concentration of polycyclic aromatic hydrocarbons in the soil is reduced to less than 5 mg / kg. [[ID=2I]]

[0125] Example 5: Remediation of soil contaminated with chlorinated organic compounds

[0126] Pollutant type: The main pollutant in the soil is chlorinated organic compounds, with a pollution concentration of 1200 mg / kg.

[0127] 1. nZVI chemical treatment:

[0128] The concentration of nano zero-valent iron is 15 g / L, the particle size is 50 nm, the injection amount is 3 L per cubic meter of soil, and the injection depth is 8 cm.

[0129] The suspension is treated by ultrasonic oscillation for 30 minutes, and the ultrasonic frequency is 40 kHz.

[0130] 2. Sodium persulfate oxidation treatment:

[0131] The concentration of sodium persulfate is 10 g / L, the injection amount is 5 L per cubic meter of soil, and the injection depth is 8 cm. [[ID=4I]]

[0132] The soil humidity is maintained at 18%, the pH value is controlled at 7.0, and the reaction time is 36 hours.

[0133] 3. First-stage bioremediation:

[0134] Select Pseudomonas and Bacillus, with the concentration of the microbial suspension being 10 6 CFU / mL, and the addition amount per cubic meter of soil being 12 L.

[0135] Incubation conditions: soil humidity is 20%, incubation time is 7 days, and the temperature is maintained at 22 °C.

[0136] 4. Second-stage bioremediation:

[0137] Select Leimonas, and the concentration of the microbial suspension is 10 8 CFU / mL, and the addition amount per cubic meter of soil is 18 L.

[0138] Incubation conditions: soil humidity is 25%, incubation time is 12 days, and the temperature is maintained at 30 °C.

[0139] Remediation effect: After 19 days of remediation, the concentration of chlorinated organic compounds in the soil is reduced to less than 4 mg / kg.

[0140] To better highlight the technical advantages of the present invention, the above method will be described in detail below through comparative experiments in combination with specific examples.

[0141] Comparative experiment 1: Comparison of the treatment effect of nano zero-valent iron (nZVI)

[0142] Experimental materials: contaminated soil (the type of pollutant is petroleum hydrocarbons, and the concentration is about 1500 mg / kg), nano zero-valent iron (nZVI, average particle size 50 - 100 nm, purity > 99%), sodium persulfate, Pseudomonas and Bacillus microbial communities.

[0143] Experimental group (the present invention group):

[0144] S1: Use an nZVI suspension with a concentration of 20 g / L, the injection amount is 3 L per cubic meter of soil, and the injection depth is 10 cm.

[0145] Subsequent steps are carried out according to the method of the present invention: sodium persulfate oxidation treatment (S2), two-stage bioremediation (S3 and S4), and post-treatment (S5).

[0146] Control group 1 (nZVI-free group):

[0147] S1: Do not add the nZVI suspension and directly skip the chemical reduction treatment stage.

[0148] Subsequent treatment steps are the same as those of the experimental group: sodium persulfate oxidation treatment (S2), two-stage bioremediation (S3 and S4), and post-treatment (S5).

[0149] Experimental steps

[0150] 1. Soil sample preparation:

[0151] Collect contaminated soil samples in the polluted area, divide them into two groups, which are used for the experimental group and Control group 1 respectively. After homogenizing each group of samples, load them into experimental reactors of the same specification.

[0152] 2. Nano zero-valent iron treatment (only for the experimental group):

[0153] After preparing the nZVI suspension to a concentration of 20 g / L, it was treated with ultrasound for 40 minutes to ensure its uniform dispersion.

[0154] The suspension was injected into the soil of the experimental group, and the injection depth was controlled at 10 cm. Subsequently, it was stirred evenly to make the nZVI evenly distributed in the soil.

[0155] 3. Sodium persulfate oxidation treatment (S2):

[0156] Sodium persulfate solution with a concentration of 10 g / L was added to the two groups of soil respectively. The injection volume was 5 L per cubic meter of soil, and the injection depth was 10 cm.

[0157] The soil humidity was controlled at 18%, the pH value was stabilized at 7.0, and the reaction time was 48 hours.

[0158] 4. Two-stage bioremediation:

[0159] S3 (the first-stage microbial remediation): Pseudomonas and Bacillus were introduced into the two groups respectively. The concentration of the microbial suspension was 10 7 CFU / mL, and the addition amount per cubic meter of soil was 15 L. The incubation time was 10 days.

[0160] S4 (the second-stage microbial remediation): Subsequently, Thiobacillus and Actinomyces were introduced. The concentration of the suspension was 10 7 CFU / mL, and the addition amount per cubic meter of soil was 15 L. The incubation time was 14 days.

[0161] 5. Data collection:

[0162] The two groups of soil samples were sampled every 48 hours to analyze the concentration changes of organic pollutants and intermediates (such as alcohols, ketones, organic acids).

[0163] The experimental results are shown in the following table:

[0164]

[0165] From the data in the above table, it can be obtained that:

[0166] During the whole treatment process, the initial pollutant concentration in the experimental group decreased significantly faster than that in Comparative Example 1. On the 10th day, the pollutant concentration in the experimental group dropped to 100 mg / kg, while there was still a residue of 600 mg / kg in Comparative Example 1.

[0167] The experimental group generated more intermediates (alcohols, ketones, organic acids), while Comparative Example 1 generated fewer intermediates in the initial stage, resulting in the influence on the efficiency of subsequent microbial treatment.

[0168] By the 24th day, the final pollutant concentration in the experimental group dropped below 5 mg / kg, while the residual concentration in Comparative Example 1 remained at 50 mg / kg.

[0169] Mechanism of action of nano zero-valent iron (nZVI): nZVI reacts with organic pollutants through redox reactions, breaking the molecular structure of the pollutants and converting them into intermediate products that are more easily biodegradable. This process significantly accelerates the initial degradation rate of the pollutants and provides better conditions for subsequent chemical oxidation and biodegradation.

[0170] Advantages of the formation of intermediate products: Due to the generation of a large number of intermediate products (such as alcohols and ketones) during the nZVI treatment process, these intermediate products are more easily decomposed and utilized by the microorganisms subsequently introduced, thereby improving the bioremediation efficiency and forming a synergistic effect of chemical-biological combined remediation.

[0171] Limitations of Comparative Example 1: In the absence of nZVI in Comparative Example 1, the molecular structure of the pollutants remained intact, restricting the effectiveness of sodium persulfate and microorganisms, resulting in low pollutant degradation efficiency and insufficient formation of intermediate products, thus hindering the progress of the subsequent remediation stage.

[0172] The present invention significantly improves the initial degradation efficiency of pollutants by introducing nano zero-valent iron (nZVI) and promotes the formation of biodegradable intermediate products. These intermediate products make the subsequent bioremediation process more efficient and achieve the complete mineralization of pollutants.

[0173] Compared with traditional single chemical or biological treatment methods, the chemical-biological combined remediation strategy of the present invention shows significant advantages in the overall removal rate and degradation speed of pollutants, especially achieving significant degradation of high-concentration organic pollutants in the short term.

[0174] Comparative Experiment 2: Comparison of the effects of sodium persulfate oxidation treatment

[0175] Experimental materials: Contaminated soil (main pollutant is petroleum hydrocarbons, initial concentration is about 1500 mg / kg), nano zero-valent iron (nZVI, average particle size 50 - 100 nm, purity > 99%), sodium persulfate, and microbial communities of Pseudomonas and Bacillus.

[0176] Experimental group (the present invention group):

[0177] S1: First, use the nZVI suspension (20 g / L), with an injection volume of 3 L per cubic meter of soil and an injection depth of 10 cm.

[0178] S2: After the nZVI treatment, add a sodium persulfate solution with a concentration of 10 g / L and an injection volume of 5 L per cubic meter of soil.

[0179] Subsequent steps: two-stage bioremediation (S3 and S4) and post-treatment (S5).

[0180] Control Example 2 (sodium persulfate-free group):

[0181] S1: Similarly use nZVI suspension (20 g / L), injection volume is 3 L per cubic meter of soil, and injection depth is 10 cm.

[0182] Skip the sodium persulfate treatment in the S2 stage and do not add any oxidants.

[0183] Subsequent steps: two-stage bioremediation (S3 and S4) and post-treatment (S5).

[0184] Experimental procedure

[0185] 1. Soil sample preparation:

[0186] Collect contaminated soil samples, divide them into the experimental group and Control Example 2, and ensure that the two groups of samples have the same initial pollutant concentration and physical and chemical properties.

[0187] Each group of samples is evenly distributed in an independent reactor for subsequent treatment.

[0188] 2. Nano zero-valent iron treatment (S1):

[0189] Both groups inject nZVI suspension (20 g / L) under the same conditions, the injection depth is 10 cm, and stir evenly.

[0190] 3. Sodium persulfate oxidation treatment (S2, only for the experimental group):

[0191] Add sodium persulfate solution to the soil in the experimental group, with a concentration of 10 g / L and an injection volume of 5 L per cubic meter of soil.

[0192] Control the soil humidity at 18%, and use phosphate buffer solution to stabilize the pH value at 7.0, and the reaction time is 48 hours.

[0193] Control Example 2 skips this step.

[0194] 4. Two-stage bioremediation (S3 and S4):

[0195] S3: Introduce the first-stage microbial community (Pseudomonas and Bacillus) into both groups respectively, with a microbial concentration of 10 7 CFU / mL, the addition amount per cubic meter of soil is 15 L, and the incubation time is 10 days.

[0196] S4: Subsequently introduce the second-stage microbial community (Thiobacillus and Actinomycetes), with the same concentration of 10 7CFU / mL, the addition amount per cubic meter of soil is 15 L, and the incubation time is 14 days.

[0197] 5. Data collection:

[0198] Soil samples are collected every 48 hours to analyze the concentration changes of organic pollutants and their intermediate products (alcohols, ketones, organic acids).

[0199] The experimental results are shown in the following table:

[0200]

[0201] From the data in the above table, it can be obtained that:

[0202] Initial degradation efficiency: After adding sodium persulfate, the pollutant concentration in the experimental group decreased significantly. The concentration dropped to 900 mg / kg on the 2nd day, while that in Comparative Example 2 dropped to 1100 mg / kg, showing an obvious gap.

[0203] Generation of intermediate products: A large number of intermediate products (such as alcohols, ketones, organic acids) were generated during the oxidation treatment in the experimental group. These intermediate products reached 600 mg / kg on the 8th day, while that in Comparative Example 2 was only 300 mg / kg.

[0204] Comparison of final concentrations: The pollutant concentration in the experimental group dropped below 3 mg / kg on the 24th day, while 40 mg / kg still remained in Comparative Example 2.

[0205] Mechanism of action of sodium persulfate oxidation: Sodium persulfate decomposes in the soil to generate sulfate radicals (SO4· - ), and these radicals have extremely high oxidation ability. They can quickly destroy the molecular structure of organic pollutants and convert them into intermediate products with low molecular weights (such as alcohols, ketones, and organic acids). These intermediate products have high biodegradability.

[0206] Role of intermediate products: More intermediate products were generated in the experimental group, providing a good metabolic basis for subsequent microbial remediation. This enables microorganisms to more rapidly mineralize these degradation products in the subsequent stage, improving the overall remediation efficiency.

[0207] Limitations of Comparative Example 2: In the absence of sodium persulfate oxidation treatment, the degradation of pollutants in Comparative Example 2 relies on nano-zero-valent iron and microbial remediation. However, lacking the assistance of the oxidation treatment stage results in insufficient generation of intermediate products and a slow pollutant degradation rate.

[0208] The addition of sodium persulfate for oxidation treatment not only significantly accelerates the initial degradation rate of pollutants but also generates a large number of intermediates for further microbial degradation, thereby improving the efficiency of the bioremediation stage. Compared to traditional single chemical treatment or bioremediation methods, the chemical-biological composite remediation strategy of the present invention demonstrates a higher degradation rate, stronger removal capacity, and more thorough pollutant mineralization, significantly improving the overall performance of soil remediation.

[0209] Comparative experiment 3: Comparison of the effects of single microbial remediation and multi-stage microbial remediation

[0210] Experimental materials: contaminated soil (the main pollutant is polycyclic aromatic hydrocarbons, with an initial concentration of about 1800 mg / kg), nano-zero-valent iron (nZVI, average particle size 50-100 nm, purity >99%), sodium persulfate, Pseudomonas, Bacillus, Ralstonia and actinomycete microbial communities.

[0211] Experimental group (the present invention group):

[0212] S1 and S2: nZVI suspension (20 g / L) was first used, followed by sodium persulfate oxidation treatment (10 g / L) to ensure that an intermediate product was generated after chemical treatment.

[0213] S3: Introduce the first-stage microbial community (Pseudomonas and Bacillus) to degrade alcohol and ketone intermediates.

[0214] S4: The second stage microbial community (Rattella and Actinomycetes) is then introduced to degrade organic acid intermediates.

[0215] Comparative Example 3 (single microbial group):

[0216] The chemical treatments of steps S1 and S2 are also performed.

[0217] Direct introduction of a single microbial community (Pseudomonas) to treat pollutants and their intermediates at all degradation stages

[0218] Experimental procedures

[0219] 1. Soil Sample Preparation:

[0220] PAH-contaminated soil samples were collected from the contaminated area and evenly divided into two groups (experimental group and comparative example 3) to ensure that the physical and chemical properties of the samples were consistent.

[0221] The samples were evenly loaded into individual reactors for subsequent processing steps.

[0222] 2. Chemical treatment stage (S1 and S2):

[0223] Both groups of soils were subjected to nZVI treatment (20 g / L) and sodium persulfate oxidation treatment (10 g / L) successively under the same conditions. The reaction time was 48 hours, and the soil humidity was controlled at 18% and the pH value was stabilized at 7.0.

[0224] Ensure that chemical treatment generates intermediate products such as alcohols, ketones, and organic acids.

[0225] 3. Microbial remediation stage:

[0226] Experimental group (multi-stage microbial remediation):

[0227] S3: First, introduce the first-stage microbial community (Pseudomonas and Bacillus) at a concentration of 10 7 CFU / mL, with an addition of 15 L per cubic meter of soil, and an incubation time of 10 days.

[0228] S4: Subsequently, introduce the second-stage microbial community (Thiobacillus and Actinomycetes) at a concentration of 10 7 CFU / mL, with an addition of 15 L per cubic meter of soil, and an incubation time of 14 days.

[0229] Control group 3 (single microbial remediation):

[0230] Directly introduce a single microbial community (Pseudomonas) at a concentration of 10 7 CFU / mL, with an addition of 30 L per cubic meter of soil, and a single incubation time of 24 days.

[0231] 4. Data collection:

[0232] Samples of both groups were taken every 48 hours to analyze the pollutant concentration and the concentration changes of various intermediate products (alcohols, ketones, organic acids).

[0233] The experimental results are shown in the following table:

[0234]

[0235] From the data in the above table, it can be obtained that:

[0236] Advantages of multi-stage remediation in the initial stage: In the experimental group, the pollutant concentration decreased to 1200 mg / kg on the 2nd day, while in control group 3, it only decreased to 1400 mg / kg. The experimental group generated more intermediate products, indicating that the first-stage microbial community effectively promoted the generation and initial degradation of intermediate products.

[0237] Degradation efficiency of intermediate products: The experimental group successfully converted most alcohols and ketones into organic acids by day 10, and the concentration of intermediate products decreased rapidly during the subsequent second-stage degradation process. However, the lack of microorganisms specifically targeting organic acid degradation in Comparative Example 3 resulted in the retention of intermediate products and a slow decrease in pollutant concentration.

[0238] Final pollutant removal rate: The experimental group reduced the pollutant concentration to below 5 mg / kg on the 24th day, achieving a significant pollutant mineralization effect; the final concentration of comparative example 3 was still 600 mg / kg, indicating that the effect of single microbial remediation was significantly limited when faced with different types of intermediates.

[0239] The mechanism of action of the multi-stage microbial community: The experimental group used a staged microbial community. In the first stage, microorganisms (Pseudomonas and Bacillus) efficiently degraded the alcohol and ketone intermediates generated after chemical treatment, providing suitable substrates for the second stage. In the second stage, microorganisms (Rattella and Actinomycetes) thoroughly mineralized the organic acid intermediates, maximizing the pollutant degradation rate.

[0240] Limitations of a single microbial community: Since Comparative Example 3 uses a single microorganism (Pseudomonas), its degradation mechanism cannot effectively cover different types of intermediates, especially for organic acid intermediates, the degradation efficiency is significantly reduced, resulting in a significant reduction in the repair effect.

[0241] Synergistic effect of microbial communities: The multi-stage microbial communities in the experimental group achieved staged decomposition of pollutants through targeted degradation of intermediate products, greatly improving the final mineralization efficiency and effectively preventing the re-accumulation of organic pollutants in the soil.

[0242] The multi-stage microbial remediation strategy employed in this invention significantly improves pollutant degradation rates and ultimate mineralization. Compared to traditional single-microbial remediation approaches, this invention utilizes a precise microbial community regulation mechanism to rapidly decompose different types of intermediates under appropriate conditions, significantly improving pollutant removal efficiency and demonstrating its superiority in the treatment of a wide range of complex organic pollutants.

[0243] Comparative experiment 4: Comparison of the effects of single chemical or biological treatment and chemical-biological combined treatment

[0244] Experimental materials: contaminated soil (the main pollutant is benzene organic matter, with an initial concentration of about 2000 mg / kg), nano-zero-valent iron (nZVI, average particle size 50-100 nm, purity >99%), sodium persulfate, Pseudomonas, Bacillus, Ralstonia and actinomycete microbial communities.

[0245] Experimental group settings:

[0246] Experimental group (the group of the present invention):

[0247] Chemical treatment: Chemical treatment was carried out using nZVI suspension (20 g / L) and sodium persulfate (10 g / L).

[0248] Bioremediation: A multi-stage microbial community (Pseudomonas, Bacillus, Thiobacillus, and Actinomycetes) was introduced for bioremediation.

[0249] Control group 4 (single chemical treatment group):

[0250] Only chemical treatment was carried out using nZVI suspension (20 g / L) and sodium persulfate (10 g / L), without any bioremediation stage.

[0251] Control group 5 (single bioremediation group):

[0252] The chemical treatment stage was skipped, and a single microbial community (Pseudomonas) was directly introduced for bioremediation.

[0253] Experimental procedures

[0254] 1. Soil sample preparation:

[0255] Benzene organic matter contaminated soil samples were collected from the contaminated area and evenly divided into three groups (experimental group, control group 4, control group 5) to ensure that the pollutant concentrations and physicochemical properties of each group of samples were consistent.

[0256] 2. Chemical treatment stage (S1 and S2, applicable to the experimental group and control group 4):

[0257] nZVI treatment: The nZVI suspension (20 g / L) was injected into the soil at an injection rate of 4 L per cubic meter of soil and an injection depth of 10 cm.

[0258] Sodium persulfate treatment: After the nZVI treatment, the sodium persulfate solution (10 g / L) was injected at an injection rate of 5 L per cubic meter of soil, and the soil moisture was maintained at 18% and the pH value was stabilized at 7.0.

[0259] 3. Bioremediation stage:

[0260] Experimental group (multi-stage microbial remediation):

[0261] S3: The first-stage microbial community (Pseudomonas and Bacillus) was introduced with a microbial concentration of 10^7 CFU / mL, an addition amount of 15 L per cubic meter of soil, and an incubation time of 10 days.

[0262] S4: Subsequently, the second-stage microbial community (Thiobacillus and Actinomycetes) was introduced with a concentration of 10^7 CFU / mL, an addition amount of 15 L per cubic meter of soil, and an incubation time of 14 days.

[0263] Comparative Example 5 (Single Bioremediation Group):

[0264] Introduce a single microbial community (Pseudomonas) with a concentration of 10^7 CFU / mL, an addition amount of 30 L per cubic meter of soil, and a single incubation time of 24 days.

[0265] 4. Data collection:

[0266] Collect soil samples from the three groups every 48 hours and analyze the concentration changes of pollutants and various intermediate products (such as alcohols, ketones, organic acids).

[0267] The experimental results are shown in the following table:

[0268]

[0269] From the data in the above table, it can be obtained that:

[0270] Initial degradation efficiency: In the first 4 days, the pollutant concentration in the experimental group rapidly decreased from 2000 mg / kg to 1200 mg / kg, while in Comparative Example 4 (single chemical treatment) it decreased to 1400 mg / kg, and in Comparative Example 5 (single bioremediation) it only decreased to 1800 mg / kg, indicating that the chemical-biological combined treatment showed faster efficiency in the initial degradation.

[0271] Generation and degradation of intermediate products: A large number of intermediate products (alcohols, ketones, organic acids) were generated in the experimental group after chemical treatment, and these intermediate products were rapidly degraded during the bioremediation stage. While fewer intermediate products were generated in Comparative Example 4, and in Comparative Example 5, almost no sufficient intermediate products were produced in the absence of chemical treatment.

[0272] Comparison of final concentrations: The experimental group reduced the pollutant concentration to below 3 mg / kg on the 24th day, while the pollutant concentration in Comparative Example 4 was still 500 mg / kg, and that in Comparative Example 5 was 900 mg / kg, showing the significant advantage of the chemical-biological combined treatment in the final pollutant removal rate.

[0273] Chemical-biological synergistic mechanism: In the group of the present invention, through the combined chemical treatment of nZVI and sodium persulfate, complex organic pollutants were first converted into more easily degradable intermediate products (such as alcohols, ketones, and organic acids), and these intermediate products created suitable conditions for subsequent microbial degradation.

[0274] Dynamic regulation of multi-stage microbial communities: The experimental group utilized a two-stage microbial remediation strategy to achieve efficient mineralization of different types of intermediate products. The first-stage microbial community targeted the degradation of alcohols and ketones, and the second-stage microbial community targeted the degradation of organic acids, achieving a synergistic degradation effect of staged treatment.

[0275] Limitations of a single treatment method: Although Comparative Example 4 (single chemical treatment) can initially degrade pollutants, the lack of continuous degradation by subsequent microbial action makes it difficult to completely mineralize the intermediate products. In Comparative Example 5 (single bioremediation), due to the lack of a chemical pretreatment stage, the complex molecular structure of pollutants is difficult to be directly degraded by microorganisms, resulting in low overall degradation efficiency.

[0276] The chemical-biological composite treatment method of the present invention is significantly superior to single chemical treatment and single bioremediation methods in treating high-concentration organic pollutants in soil. Through the synergistic action of chemistry and biology, the present invention achieves a higher degradation rate and complete mineralization of pollutants. Experimental data verify the high-efficiency conversion ability of the present invention for intermediate products during the multi-stage treatment process, demonstrating its strong technical advantages and practical application potential in the field of complex soil pollution remediation.

[0277] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for repairing high-concentration organic pollutants in soil, characterized in that, It includes the following steps: S1. Inject a nano zero-valent iron suspension into the soil for chemical treatment; S2. After the nano zero-valent iron treatment, add sodium persulfate for oxidation treatment; S3. Introduce the first-stage microbial community into the chemically treated soil to promote the biodegradation of alcohol and ketone intermediate products; S4. After the first-stage biodegradation is completed, introduce the second-stage microbial community to treat the organic acid intermediate products; S5. Conduct post-treatment on the soil after the remediation is completed; The first-stage microbial community includes Pseudomonas and Bacillus, and the suspension concentration thereof is 10 6 -10 8 CFU / mL, and the addition amount is 10 - 20 L per cubic meter of soil; The second-stage microbial community includes Thiobacillus and Actinomycetes, and the suspension concentration thereof is 10 6 -10 8 CFU / mL, and the addition amount is 10-20 L per cubic meter of soil.

2. The remediation method of high-concentration organic pollutants in soil according to claim 1, wherein The preparation steps of the nano zero-valent iron suspension include: Disperse the nano zero-valent iron particles in deionized water to prepare a suspension with a concentration of 10 - 30 g / L; Conduct an oscillation treatment on the suspension, with an ultrasonic frequency of 40 kHz and an oscillation time of 30 - 60 minutes; During the preparation of the suspension, adjust the pH value of the suspension to 6 - 8.

3. The remediation method of high-concentration organic pollutants in soil according to claim 2, characterized in that, The average particle size of the nano zero-valent iron particles is 50 - 100 nm, and the purity is greater than 99%.

4. A method for remediating high-concentration organic pollutants in soil according to claim 1, characterized in that, The injection amount of the nano zero-valent iron is controlled at 1 - 5 L per cubic meter of soil, and the injection depth is 5 - 20 cm.

5. A method for repairing high-concentration organic pollutants in soil according to claim 1, characterized in that, The sodium persulfate oxidation treatment includes the following steps: Dissolve sodium persulfate in deionized water to prepare a solution with a concentration of 5 - 15 g / L; Uniformly apply the sodium persulfate solution to the contaminated soil that has been treated with nano zero-valent iron, with an injection depth range of 5 - 20 cm and an injection amount controlled at 5 - 10 L per cubic meter of soil; During the oxidation treatment, keep the humidity of the soil within the range of 15 - 20% and stabilize the pH value of the soil at 6.5 - 7.5 by adding phosphate buffer solution.

6. The method for remediating high-concentration organic pollutants in soil according to claim 1, wherein, During the first-stage microbial degradation process, keep the humidity of the soil at 20 - 25% and the incubation time is 7 - 14 days.

7. A method for remediating high-concentration organic pollutants in soil according to claim 1, characterized in that, The culture temperature of the second-stage microorganisms is 28 - 32 °C, the culture time is 48 hours, and the incubation time is 7 - 14 days.

8. A method for repairing high-concentration organic pollutants in soil according to claim 1, characterized in that, The post-treatment includes physical stabilization and backfilling treatment of the soil.

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