WO2023123431A1 - In-situ remediation method for organophosphorus pesticide-contaminated soil - Google Patents

Abstract

The present invention relates to the technical field of soil remediation, and provides an in-situ remediation method for organophosphorus pesticide-contaminated soil. The method comprises: first injecting an alkaline remediation agent into a contaminated region in situ to perform an alkaline hydrolysis treatment on the contaminated region, and injecting an oxidizing agent in situ after alkaline hydrolysis to oxidize the contaminated region. According to the method, an alkaline remediation agent plays a role in promoting the alkaline hydrolysis of an organophosphorus pesticide in an early stage and carrying out alkali activation on the oxidizing agent in the later stage, and fully uses the effectiveness of the alkaline remediation agent at each stage. According to the remediation mode of first adding the alkaline remediation agent and then adding the oxidizing agent proposed in the present invention, the dosage of the oxidizing agent can be reduced, the residual amount of related inorganic salt in the remedied soil is reduced, and the degree to which the related inorganic salt corrodes a steel structure of a building is reduced. In addition, the present method is an in-situ remediation method, contaminated soil does not need to be excavated and transferred during the remediation process, and the problem of odor diffusion during the remediation process is ameliorated.

Description

An in-situ remediation method for organophosphorus pesticide-contaminated soil technical field

The invention relates to the technical field of soil remediation, in particular to an in-situ remediation method for organophosphorus pesticide-contaminated soil.

Background technique

Organophosphorus pesticides are broad-spectrum insecticides and herbicides, which are widely used in agricultural production due to their advantages of rich variety, low price and easy degradation. During the production or storage of organophosphorus pesticides, there are usually certain phenomena such as "running, escaping, dripping, and leaking", which will cause certain pollution to soil and groundwater. After investigation, it was found that the soil of the organophosphorus pesticide plant that had been shut down for many years still had a relatively high concentration of organophosphorus pesticides and a relatively large odor.

The areas polluted by organophosphorus pesticides still have high development value and need to be rehabilitated. However, organophosphorus pesticide-contaminated areas have the characteristics of complex types of pollutants, high pollution concentrations, and severe odors, which make the restoration and treatment of organophosphorus pesticide-contaminated areas face greater difficulties.

At present, the remediation technologies for organophosphorus pesticide-contaminated areas can be mainly divided into thermal desorption remediation technology, biological remediation technology and chemical oxidation remediation technology according to the process principle. Thermal desorption remediation technology separates pollutants from contaminated soil by increasing the temperature, but thermal desorption remediation technology has disadvantages such as high energy consumption and poor economy. Bioremediation technology uses the enrichment or degradation ability of microorganisms or plants to remove organic pollutants from contaminated soil, but bioremediation technology has disadvantages such as long repair period and unstable repair effect. Chemical oxidation remediation technology oxidizes and removes organic pollutants from contaminated soil by adding oxidants to the soil. Compared with other remediation technologies, chemical oxidation remediation technology can efficiently and quickly degrade organophosphorus pesticides.

Chinese patent CN106753386A discloses a composition for treating soil polluted by high-concentration organophosphorus pesticides. Its active ingredients are sodium hydroxide and sodium persulfate. Sodium Hydroxide and Sodium Persulfate.

However, in the process of realizing the present invention, the inventors found that adding sodium hydroxide and sodium persulfate to the polluted soil at the same time has the problem of poor remediation effect and high residual sulfate in the remediation soil.

Contents of the invention

Therefore, the technical problem to be solved in the present invention is to overcome when sodium hydroxide and sodium persulfate are added in the polluted soil simultaneously in the prior art, the repairing effect that exists is relatively poor and the defective that sulfate residual amount is higher in the soil after repairing, Therefore, an in-situ remediation method for organophosphorus pesticide-contaminated soil is provided.

For this reason, the present invention provides an in-situ remediation method for organophosphorus pesticide-contaminated soil, the method comprising: injecting an alkaline remediation agent in situ into the polluted area containing organophosphorus pesticides, so as to carry out alkaline hydrolysis treatment on the polluted area ; Injecting an oxidizing agent in-situ into the polluted area after alkali hydrolysis treatment, so as to carry out oxidation treatment on the polluted area.

The inventors of the present invention have found that when sodium hydroxide and sodium persulfate are added to the polluted soil simultaneously in the prior art, the reason for the poor remedial effect is that adding sodium hydroxide and sodium persulfate simultaneously, its main principle is through Alkali activates sodium persulfate and utilizes the activated sodium persulfate to oxidize organophosphorus pesticides, which is a chemical oxidation reaction and does not take into account the alkaline hydrolysis of organophosphorus pesticides. In addition, sodium hydroxide and sodium persulfate are added to the soil at the same time, causing a large amount of sodium hydroxide to be used to activate sodium persulfate, and a large amount of sodium hydroxide will be consumed in the activation process of sodium persulfate, resulting in the effect of sodium hydroxide on organic phosphorus. The alkaline hydrolysis effect of pesticides is not fully exerted, which affects the alkaline hydrolysis reaction of organophosphorus pesticides, resulting in poor overall restoration effect; the reason for the high residual sulfate in the soil after restoration is that the activation of sodium hydroxide in sodium persulfate During the process, a large amount of sodium persulfate is consumed, and soil remediation is mainly completed by the oxidation of sodium persulfate, so the amount of sodium persulfate is relatively high, resulting in a high amount of sulfate residue in the soil after remediation.

Based on the above findings, the inventors of the present invention creatively propose to inject an alkaline restoration agent into the polluted area first to carry out alkaline hydrolysis treatment on the polluted area, and then inject an oxidant after the alkaline hydrolysis treatment is completed to oxidize the polluted area. The alkaline repairing agent in the present invention can at least play the following two roles: (1) in the alkaline hydrolysis stage, utilize the alkaline environment provided by it to promote the alkaline hydrolysis reaction of organophosphorus pesticides; (2) in the oxidation stage, utilize its An alkaline environment is provided for alkaline activation of the oxidizing agent.

Through the method of the present invention, on the one hand, it is possible to give full play to the alkaline hydrolysis effect of the alkaline restoration agent on organophosphorus pesticides, and improve the overall restoration effect; The residual amount can reduce the corrosion degree of related inorganic salts to the steel structure of buildings. In addition, there is an alkaline environment in the soil of the polluted area after the alkali hydrolysis treatment by the alkaline repair agent, which can provide corresponding conditions for the alkali activation of the oxidant, that is, the method of the present invention can ensure that the alkaline repair agent fully exerts its alkali At the same time as the hydrolysis, it provides alkali activation conditions for the oxidant.

In addition, the method of the present invention is an in-situ remediation method, which does not require excavation and transportation of contaminated soil during the remediation process, which alleviates the problem of odor diffusion in the remediation process of high-concentration organophosphorus pesticides.

In the present invention, specifically, organophosphorus pesticides may include phorate, ethion, parathion, terbufos, chlormethion, demeton, malathion, dimethoate, trichlorfon and Dichlorvos and many other organophosphorus pesticides. Before injecting the alkaline repair agent into the polluted area containing organophosphorus pesticides, the polluted area can also be cleaned up to remove solids such as bricks (stones), steel bars, dust-proof nets, construction equipment, and underground pipelines in the polluted area. Sexual debris to improve the subsequent soil remediation effect.

According to the present invention, before injecting the alkaline remediation agent into the polluted area containing the organophosphorus pesticide, the method may further include: determining the initial content of the organophosphorus pesticide in the polluted area; based on the initial content, determining The amount of the alkaline repairing agent is such that relative to 1 mole part of the organophosphorus pesticide, the amount of the alkaline repairing agent is 1.0-2.0 mole parts, preferably 1.2-1.5 mole parts. Controlling the relative usage of the alkaline repairing agent and the organophosphorus pesticide within the above range can ensure that the alkaline repairing agent fully exerts its alkaline hydrolysis effect on the one hand, and on the other hand can ensure that the necessary alkaline environment is provided for the alkali activation of the oxidizing agent.

According to the present invention, before injecting the oxidizing agent into the contaminated area after alkaline hydrolysis treatment, the method may further include: determining the intermediate content of the organophosphorus pesticide in the polluted area after alkaline hydrolysis treatment; For the intermediate content, the amount of the oxidant is determined so that relative to 1 mole part of the organophosphorus pesticide, the amount of the oxidant is 1.0-3.0 mole parts, preferably 1.5-2.5 mole parts. Controlling the relative usage of oxidants and organophosphorus pesticides within the above range can ensure a good soil remediation effect on the one hand and avoid the introduction of a large amount of related inorganic salts due to excessive use of oxidants on the other hand.

The method for determining the organophosphorus pesticide content (initial content or intermediate content) in the polluted area can be a common detection method in the field, for example, it can be a detection method such as gas chromatography, liquid chromatography, spectroscopic analysis or enzyme-linked immunoassay.

According to the present invention, the alkaline repairing agent and the oxidant can be selected within a certain range, for example, the alkaline repairing agent can include at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide and ammonia water , preferably sodium hydroxide; the oxidizing agent may include persulfate, preferably sodium persulfate.

According to the present invention, the time of the alkaline hydrolysis treatment and the oxidation treatment can be selected within a certain range, for example, in the operation of carrying out alkaline hydrolysis treatment on the polluted area, the time of the alkali hydrolysis treatment can be 1 ~7 days; in the operation of performing oxidation treatment on the polluted area, the time for the oxidation treatment may be 3-14 days.

According to the present invention, when injecting the alkaline repairing agent into the polluted area containing organophosphorus pesticides, the high-pressure rotary spraying method can be used to inject the alkaline repairing agent solution into the polluted area through at least one injection hole, wherein the The injection pressure of the high-pressure rotary spraying method may be 25-30 MPa, and the mass concentration of the alkaline repairing agent in the alkaline repairing agent solution may be 10%-35%, preferably 15%-30%.

When injecting the oxidizing agent into the contaminated area after alkaline hydrolysis treatment, a high-pressure rotary spraying method can be used to inject the oxidant solution into the contaminated area after alkaline hydrolysis treatment through at least one injection hole, wherein the high-pressure rotary spraying The injection pressure of the spray method may be 25-30 MPa, and the concentration of the oxidant in the oxidant solution may be 100g/L-300g/L, preferably 120g/L-250g/L.

Within the above concentration range, the alkaline restoration agent solution and the oxidizing agent solution have suitable viscosity and good spray performance, and under the above concentration conditions, the usage amount of the alkaline restoration agent solution and the oxidizing agent solution is appropriate, which can effectively avoid the Problems with soil saturation due to excessive use of alkaline remedial solutions or oxidizer solutions.

According to the present invention, the alkaline restoration agent solution and the oxidant solution may share the same injection hole, and the distance between any two adjacent injection holes is 3m-5m. Wherein, the plurality of injection holes may be distributed in a grid shape, and the shape of the grid may be selected within a certain range, for example, it may be an equilateral triangle or a square.

According to the present invention, after determining that the oxidation treatment is completed, the method may further include: determining the real-time content of the organophosphorus pesticide in the polluted area after the oxidation treatment; determining the difference between the real-time content and the preset target content Relative size: when the real-time content is greater than the preset target content, repeat the method until the real-time content is less than or equal to the preset target content.

Fig. 1 schematically shows a flow chart of an in-situ remediation method for organophosphorus pesticide-contaminated soil according to an embodiment of the present invention. As shown in Fig. 1, the method includes the following operations:

(1) Site leveling, measurement and setting out: remove bricks (stones), steel bars, dust screens, construction equipment, underground pipelines and other sundries left in the polluted area. According to the distribution map of the inflection point of the site red line and the injection point of the high-pressure jet jetting, the borehole is positioned using RTK, and the center point of the borehole is calibrated with white ash.

(2) Equipment assembly and debugging: After the high-pressure rotary jet drilling rig enters the site, it will be assembled and debugged. In order to ensure the smooth progress of the construction, the air pressure during construction is 0.7MPa, the injection pressure of the agent is 25-30MPa, the pipeline passage is normal, and there is no air leakage at other connections.

(3) The first medicament injection: Use a high-pressure rotary jet drilling rig to evenly inject the prepared sodium hydroxide solution into the polluted area for alkaline hydrolysis reaction. The amount of medicament injected is determined according to the pollution degree of the polluted area. According to the solubility of sodium hydroxide and the viscosity of the solution, the mass concentration of sodium hydroxide in the sodium hydroxide solution is determined to be between 10% and 30%.

(4) Monitoring and maintenance: Close the site for maintenance for about 3 days. During the maintenance process, take samples of the soil and groundwater in the polluted area to measure pH, and closely monitor the change of soil pH.

(5) The second chemical injection: the prepared sodium persulfate solution is evenly injected into the polluted area with a high-pressure rotary jet drilling machine, and the oxidation reaction is carried out. According to the solubility of sodium persulfate and the viscosity of the solution, the concentration of sodium persulfate solution is determined to be between 100g/L and 300g/L.

(6) Monitoring and maintenance: After the second injection, the site will be closed for maintenance for about 14 days. During the maintenance process, the soil and groundwater in the polluted area will be sampled to measure pH, and the changes in soil pH will be closely monitored.

(7) Inspection and acceptance: After the maintenance work is completed, soil sampling points will be arranged within the remediation range, and soil samples will be taken to test the effect of in-situ remediation. If the soil or groundwater level reaches the remediation target value, repeat steps (3) to (6) according to the pollution concentration until the remediation is qualified.

The technical solution of the present invention has the following advantages:

1. In the in-situ remediation method of organophosphorus pesticide-contaminated soil provided by the present invention, the alkaline remediation agent is injected into the polluted area earlier to carry out alkaline hydrolysis treatment to the polluted area, and after the alkaline hydrolysis treatment is completed, oxidant is injected to treat the polluted area. The area is oxidized. The alkaline restoration agent can play at least the following two functions: in the alkaline hydrolysis reaction stage, use the alkaline environment it provides to promote the alkaline hydrolysis reaction of organophosphorus pesticides; in the oxidation stage, use the alkaline environment it provides to activate the oxidant with alkali. Through this method, on the one hand, it can give full play to the alkali hydrolysis effect of the alkaline repair agent on organophosphorus pesticides, and improve the overall repair effect; on the other hand, it can reduce the amount of oxidant, thereby reducing the residual amount of related inorganic salts in the repaired soil. Reduce the corrosion degree of related inorganic salts to the steel structure of buildings.

2. The in-situ remediation method of organophosphorus pesticide-contaminated soil provided by the present invention does not need to clear and transport the contaminated soil during the remediation process of the in-situ remediation method, which alleviates the problem of odor diffusion in the remediation process of high-concentration organophosphorus pesticides question.

3. In the in-situ remediation method of organophosphorus pesticide-contaminated soil provided by the present invention, the usage amount of the alkaline remediation agent is suitable, and there is an alkaline environment in the soil of the polluted area after using it to carry out alkaline hydrolysis treatment, and the alkali that can be an oxidizing agent Activation provides corresponding conditions, that is, the method of the present invention can provide alkali activation conditions for the oxidant while ensuring that the alkali restoration agent fully exerts its alkali hydrolysis effect.

4. In the in-situ remediation method of organophosphorus pesticide-contaminated soil provided by the present invention, the amount of oxidant used is appropriate, which can ensure a good soil remediation effect on the one hand, and avoid the introduction of a large amount of related inorganic salts due to excessive use of oxidant on the other hand.

5. In the in-situ remediation method of organophosphorus pesticide-contaminated soil provided by the present invention, the alkaline remediation agent solution and oxidant solution used have suitable concentration and viscosity, and can effectively Avoid problems with soil saturation due to overuse of alkaline remediator solutions or oxidizer solutions.

Description of drawings

In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the specific implementation or description of the prior art. Obviously, the accompanying drawings in the following description The drawings show some implementations of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

Fig. 1 schematically shows a flow chart of an in-situ remediation method for organophosphorus pesticide-contaminated soil according to an embodiment of the present invention.

Detailed ways

The following examples are provided in order to further understand the present invention better, are not limited to the best implementation mode, and do not limit the content and protection scope of the present invention, anyone under the inspiration of the present invention or use the present invention Any product identical or similar to the present invention obtained by combining features of other prior art falls within the protection scope of the present invention.

If no specific experimental steps or conditions are indicated in the examples, it can be carried out according to the operation or conditions of the conventional experimental steps described in the literature in this field. The reagents or instruments used, whose manufacturers are not indicated, are all commercially available conventional reagent products.

Each polluted area involved in the embodiment of the present invention is located in a pesticide factory in Tianjin, and the types and concentrations of organophosphorus pesticides in each polluted area are shown in Table 1. The organophosphorus pesticide concentration involved in the examples of the present invention refers to the weight of the organophosphorus pesticide contained in every kilogram of polluted soil.

Table 1 Types and concentrations of organophosphorus pesticides in each polluted area

polluted area	Types of organophosphorus pesticides	Organophosphorus pesticide concentration, mg/kg
Contaminated area A	Phorate, ethion	280.23, 125.63
Contaminated area B	Phorate	32.69
Contaminated area C	parathion	764.57

Example 1

Use the following method to repair the contaminated area A:

(1) Use a high-pressure rotary jet drilling rig to inject an alkaline repair agent (sodium hydroxide) solution into the contaminated area A to carry out alkaline hydrolysis treatment on the contaminated area A. The injection pressure of the high-pressure rotary jet drilling rig is 30MPa, and the injection holes are positive Triangular grid distribution, the distance between any two adjacent injection holes is 3m;

Wherein, the alkaline repairing agent is a sodium hydroxide solution with a mass concentration of 30%, and the amount of the alkaline repairing agent solution is such that the amount of sodium hydroxide is 1.5 molar parts relative to 1 molar part of the organophosphorus pesticide;

(2) After 3 days of alkaline hydrolysis treatment, the intermediate concentrations of phorate and ethion in the contaminated area A were detected to be 56.96mg/kg and 7.24mg/kg respectively. Based on the intermediate concentrations, the impact of alkaline hydrolysis treatment on contaminated area A was calculated. The removal rates of phorate and ethion in medium were 79.8% and 94.2% respectively;

(3) Through the injection hole in the step (1), utilize a high-pressure jet jet drilling machine to inject an oxidizing agent (sodium persulfate) solution into the polluted area A after alkali hydrolysis treatment, to carry out oxidation treatment to the polluted area A, and the high-pressure jet jet drilling machine The injection pressure is 30MPa;

Wherein, the concentration of sodium persulfate in the oxidizing agent (sodium persulfate) solution is 200g/L, and the addition of the oxidizing agent solution makes relative to the organophosphorus pesticide of 1 molar part, the consumption of sodium persulfate is 1.5 molar parts;

(4) After 7 days of oxidation treatment, the concentrations of phorate and ethion in the polluted area A were detected to be 16.53mg/kg and 1.29mg/kg respectively. The removal rates of phosphorus and ethion were 70.9% and 82.2% respectively.

After testing, the content of sulfate in the soil is 756mg/kg, and the corrosion level to concrete buildings is weak. By calculation, the total removal rates of phorate and ethion in the polluted area A by the method of this embodiment are 94.1% and 98.9%, respectively.

Example 2

Use the following method to repair the contaminated area B:

(1) Use a high-pressure rotary jet drilling rig to inject an alkaline repair agent (sodium hydroxide) solution into the contaminated area B to carry out alkaline hydrolysis treatment on the contaminated area B. The injection pressure of the high-pressure rotary jet drilling rig is 25 MPa, and the injection holes are positive Triangular grid distribution, the distance between any two adjacent injection holes is 3m;

Wherein, the mass concentration of sodium hydroxide in the alkaline repairing agent solution is 35%, and the addition amount of the alkaline repairing agent solution makes relative to 1 mole part of phorate, the consumption of sodium hydroxide is 1.0 mole part;

(2) After one day of alkaline hydrolysis treatment, the intermediate concentration of methylone phosphorus in the polluted area B was detected to be 11.64mg/kg. Based on the intermediate concentration, the restoration rate of the organophosphorus pesticide-contaminated soil in the polluted area B by the alkaline hydrolysis treatment was calculated. 64.4%;

(3) Through the injection hole in the step (1), utilize a high-pressure rotary jet drilling machine to inject an oxidizing agent (sodium persulfate) solution into the polluted area B after alkali hydrolysis treatment, to carry out oxidation treatment to the polluted area B, and the high-pressure rotary jet drilling machine The injection pressure is 25MPa;

Wherein, the concentration of sodium persulfate in the oxidizing agent (sodium persulfate) solution is 100g/L, and the adding of oxidizing agent solution makes relative to the phorate of 1 molar part, the consumption of sodium persulfate is 2 molar parts;

(4) After 14 days of oxidation treatment, the real-time concentration of methophos in the polluted area B was detected to be 4.61 mg/kg. Based on this real-time concentration, the repair rate of the organophosphorus pesticide-contaminated soil in the polluted area B by the oxidation treatment was calculated to be 60.4%. .

After testing, the content of sulfate in the soil is 851mg/kg, and the corrosion level to concrete buildings is weak. It is calculated that the total removal rate of phorate in the polluted area A by the method of this embodiment is 85.9%.

Example 3

Use the following methods to repair the contaminated area C:

(1) Use a high-pressure rotary jet drilling rig to inject alkaline repair agent (sodium hydroxide) solution into the contaminated area C to carry out alkaline hydrolysis treatment on the contaminated area C. The injection pressure of the high-pressure rotary jet drilling rig is 30MPa, and the injection holes are positive Triangular grid distribution, the distance between any two adjacent injection holes is 5m;

Wherein, the mass concentration of sodium hydroxide in the alkaline repairing agent solution is 10%, and the addition amount of the alkaline repairing agent solution makes relative to 1 molar part of parathion, the consumption of sodium hydroxide is 2.0 molar parts;

(2) After 7 days of alkaline hydrolysis treatment, the intermediate concentration of ethion in the polluted area C was detected to be 219.72mg/kg. Based on the intermediate concentration, the restoration rate of the organophosphorus pesticide-contaminated soil in the polluted area C by the alkaline hydrolysis treatment was calculated. 71.3%;

(3) Through the injection hole in the step (1), utilize a high-pressure jet jet drilling machine to inject an oxidizing agent (sodium persulfate) solution into the contaminated area C after alkali hydrolysis treatment, to carry out oxidation treatment to the contaminated area C, and the high-pressure jet jet drilling machine The injection pressure is 30MPa;

Wherein, the concentration of sodium persulfate in the oxidizing agent (sodium persulfate) solution is 300g/L, and the adding of oxidizing agent solution makes relative to the ethion of 1 molar part, the consumption of sodium persulfate is 2.5 molar parts;

(4) After 14 days of oxidation treatment, the real-time concentration of ethion in the detected polluted area C was 98.31 mg/kg. Based on the real-time concentration, the remediation rate of the organophosphorus pesticide-contaminated soil in the polluted area C by oxidation treatment was calculated to be 55.2%. .

After testing, the content of sulfate in the soil is 932mg/kg, and the corrosion level to concrete buildings is weak. It is calculated that the total removal rate of parathion in the polluted area C by the method of this embodiment is 87.1%.

Example 4

The contaminated area A was repaired by the method of Example 1, except that the alkaline repair agent used in this example was calcium hydroxide. After calculation, the total removal rates of phorate and ethion in the polluted area A by alkaline hydrolysis treatment and oxidation treatment in this embodiment are 68.3% and 54.1% respectively;

Comparative example 1

Use the following method to repair the contaminated area A:

(1) Use a high-pressure rotary jet drilling rig to inject a repair agent (sodium hydroxide + sodium persulfate) solution into the contaminated area A to repair the contaminated area A. The injection pressure of the high-pressure rotary jet drilling machine is 30MPa, and the injection holes Distributed in a regular triangular grid, the distance between any two adjacent injection holes is 2.5m;

Wherein, the mass concentration of sodium hydroxide in the repairing agent solution is 32%, the concentration of sodium persulfate is 200g/L, the addition of repairing agent makes relative to the organophosphorus pesticide of 1 molar part, the consumption of sodium hydroxide is 1.5 molar parts , the consumption of sodium persulfate is 3.0 mole parts;

(2) After 21 days of remediation treatment, the intermediate concentrations of phorate and ethion in the contaminated area A were detected to be 126.38 mg/kg and 77.56 mg/kg respectively. The total removal rates of ethion were 54.9%, 38.3% respectively

Experimental example

(1) Experimental object and remediation target: In the contaminated soil used in this experimental example, the organophosphorus pesticide was phorate, and the initial concentration was 227.84mg/kg. The restoration target value of phorate is 13mg/kg.

(2) Restoration technology: alkaline hydrolysis technology, chemical oxidation technology, alkali activated chemical oxidation technology, alkaline hydrolysis-oxidation synergistic technology.

(3) Restoration agents: sodium persulfate, sodium hydroxide.

(4) Experimental group settings: as shown in Table 2.

Table 2 Experimental group settings

Remarks: In the commonly used alkali-activated sodium persulfate formulation, the weight ratio of sodium persulfate to sodium hydroxide is 2:1; the dosage ratio of the dosage refers to the percentage of the dosage of the dosage in the total weight of the polluted soil.

(5) Experimental method:

Take the polluted soil, mix it uniformly and use it as the test soil for the experiment, and measure the original concentration of phorate. Each group accurately weighed 1000g of the test soil into the reaction container, added the medicament according to the medicament dosage ratio of each experimental group in Table 2, and then added 1000g of deionized water to ensure that the soil and the medicament were evenly mixed and the soil was muddy. After the soil of the experimental groups A, B, C, and D was evenly stirred, it was left standing in the dark for 3 days, and samples were taken to detect the concentration of phorate and the concentration of sulfate radicals in the soil (the weight of sulfate radicals per kilogram of soil). The soil of experimental group E was first added with 0.5% sodium hydroxide on the 0th day, and after uniform stirring, it was kept in the dark for 1 day, then 1.0% sodium persulfate was added, and it was kept in the dark for 2 days. Sampling and testing at the same time. The test results are shown in Table 3.

Table 3 Phorate concentration and sulfate radical concentration in the soil of each experimental group

Experimental group number

Phorate (mg/kg)

Sulfate (mg/kg)

A	217.79	460
B	178.22	4507
C	12.19	464
D.	88.05	4661
E.	3.16	1183

(6) Data analysis:

①Experimental group A is the blank group. After the experiment, phorate in the soil decreased slightly, which was mainly caused by factors such as volatilization, adsorption and photolysis.

②Experimental group B is the sodium persulfate chemical oxidation group. Although the phorate in the soil decreased significantly after the experiment, it did not reach the restoration target value, indicating that the efficiency of sodium persulfate alone in oxidizing organophosphorus pesticides is poor.

③Experimental group C is the sodium hydroxide alkaline hydrolysis group. After the experiment, the phorate content in the soil decreased significantly, reaching the restoration target value, indicating that sodium hydroxide alkaline hydrolysis alone is effective for organophosphorus pesticides.

④Experimental group D is the alkali-activated chemical oxidation group of alkali-activated sodium persulfate. Although the phorate in the soil decreased significantly after the experiment, it did not reach the restoration target value, indicating that the alkali-activated chemical oxidation technology of alkali-activated sodium persulfate has a great impact on The oxidation efficiency of organophosphorus pesticides is poor.

⑤Experimental group E is an alkaline hydrolysis-oxidation synergistic group, and the phorate in the soil has been significantly reduced, reaching the restoration target value, which is significantly lower than the experimental group C, indicating that the alkaline hydrolysis-oxidation synergistic technology can remove organophosphorus pesticides. better.

⑥By comparing the experimental group D and the experimental group E, the organophosphorus pesticide content in the experimental group E was much lower than that in the experimental group D after the experiment, indicating that for the restoration of organophosphorus pesticides, the restoration efficiency of alkali-activated sodium persulfate is lower than that of alkaline hydrolysis- Oxidative Synergistic Repair Efficiency.

⑦ The sulfate radical content in experimental group B and experimental group D is greater than 4500 mg/kg, and the corrosion level to concrete buildings is strong, indicating that the oxidation of organophosphorus pesticides by sodium persulfate alone and by alkali activation of sodium persulfate will cause Sulfate content increased significantly.

⑧The sulfate content in the experimental group E was less than 1200mg/kg, and the corrosion level to concrete buildings was weak, indicating that when the alkaline hydrolysis-oxidation synergistic technology repaired organophosphorus pesticide-contaminated soil, it would not lead to a significant increase in the sulfate content in the soil .

As can be seen from Examples 1 to 4, Comparative Example 1, and Experimental Example, in the method for repairing organophosphorus pesticide-contaminated soil provided by the present invention, the alkaline repairing agent is injected into the polluted area earlier to carry out alkaline hydrolysis treatment to it, After the alkaline hydrolysis treatment is completed, the oxidant is injected to oxidize the contaminated area, which can significantly improve the repair effect on organophosphorus pesticide-contaminated soil.

As can be seen from Table 3, the method for remediating organophosphorus pesticide-contaminated soil provided by the present invention can reduce the amount of oxidant, thereby reducing the residual amount of relevant inorganic salts in the soil after remediation, and reducing the corrosion of relevant inorganic salts to building steel structures degree.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (9)

1. An in-situ remediation method for organophosphorus pesticide-contaminated soil, characterized in that the method comprises:

   Injecting an alkaline remediation agent in-situ into the polluted area containing organophosphorus pesticides, so as to carry out alkaline hydrolysis treatment on the polluted area;

   Injecting an oxidizing agent in situ into the polluted area after alkaline hydrolysis treatment, so as to oxidize the polluted area.
2. The method according to claim 1, characterized in that, before injecting alkaline restoration agent into the polluted area containing organophosphorus pesticides, said method also comprises:

   determining the initial content of said organophosphorus pesticide in said contaminated area;

   Based on the initial content, the amount of the alkaline repairing agent is determined so that relative to 1 mole part of the organophosphorus pesticide, the amount of the alkaline repairing agent is 1.0-2.0 molar parts, preferably 1.2-1.5 molar parts.
3. The method according to claim 1, characterized in that, before injecting the oxidizing agent into the contaminated area after alkaline hydrolysis treatment, the method further comprises:

   determining the intermediate content of the organophosphorus pesticide in the polluted area after the alkaline hydrolysis treatment;

   Based on the intermediate content, the amount of the oxidizing agent is determined such that the amount of the oxidizing agent is 1.0-3.0 mole parts, preferably 1.5-2.5 mole parts relative to 1 mole part of the organophosphorus pesticide.
4. The method according to any one of claims 1 to 3, wherein the alkaline restoration agent comprises at least one of sodium hydroxide, potassium hydroxide, calcium hydroxide and ammonia water, preferably sodium hydroxide ;

   The oxidizing agent includes persulfate, preferably sodium persulfate.
5. The method according to any one of claims 1 to 3, characterized in that, in the operation of carrying out alkaline hydrolysis treatment on the contaminated area, the time of the alkaline hydrolysis treatment is 1 to 7 days;

   In the operation of performing oxidation treatment on the polluted area, the time for the oxidation treatment is 3-14 days.
6. The method according to any one of claims 1 to 3, wherein the injection of an alkaline restoration agent into the polluted area containing organophosphorus pesticides comprises:

   Using a high-pressure rotary spraying method, through at least one injection hole, inject an alkaline repairing agent solution into the contaminated area, wherein, the injection pressure of the high-pressure rotary spraying method is 25-30 MPa, and the alkaline repairing agent solution The mass concentration of the alkaline restoration agent is 10%-35%, preferably 15%-30%.
7. The method according to claim 6, wherein the injection of an oxidizing agent into the contaminated area after alkaline hydrolysis treatment comprises:

   Using a high-pressure rotary spraying method, through at least one injection hole, inject an oxidant solution into the contaminated area after alkali hydrolysis treatment, wherein, the injection pressure of the high-pressure rotary spraying method is 25 to 30 MPa, and the oxidant solution described The concentration of the oxidizing agent is 100g/L-300g/L, preferably 120g/L-250g/L.
8. The method according to claim 7, characterized in that the alkaline restoration agent solution and the oxidant solution share the same injection hole, and the distance between any two adjacent injection holes is 3m-5m.
9. The method according to claim 1, wherein after determining that the oxidation treatment is completed, the method further comprises:

   determining the real-time content of the organophosphorus pesticide in the polluted area after oxidation treatment;

   Determine the relative size of the real-time content and the preset target content;

   In the case that the real-time content is greater than the preset target content, repeat the method until the real-time content is less than or equal to the preset target content.

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