CN114345914B

CN114345914B - Ectopic remediation method for organophosphorus pesticide and VOCs (volatile organic compounds) composite contaminated soil

Info

Publication number: CN114345914B
Application number: CN202111652048.7A
Authority: CN
Inventors: 李鸿炫; 张晓斌; 刘鹏; 康绍果; 籍龙杰; 郭楠; 杨乐巍; 杜娇皓; 高月昆; 杨云杰; 邹鹏
Original assignee: BCEG Environmental Remediation Co Ltd
Current assignee: BCEG Environmental Remediation Co Ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2023-02-24
Anticipated expiration: 2041-12-30
Also published as: CN114345914A

Abstract

The invention belongs to the technical field of soil remediation, and particularly relates to an ectopic remediation method for soil compositely polluted by organophosphorus pesticides and VOCs. The method adopts a staged mode to remove VOCs and organophosphorus pesticides in the soil, has the characteristics of small dosage of quicklime and an oxidizing agent, low energy consumption, thorough restoration and green sustainability. Specifically, the method removes part of VOCs pollutants through normal temperature desorption, removes part of organophosphorus pesticides through alkaline hydrolysis reaction, and saves the using amount of oxidizing agents. Aiming at the remediation work of the organophosphorus pesticide and VOCs composite contaminated soil, the method reduces the remediation cost and reduces the sulfate concentration in the remediated field. The quicklime used in the invention has three functions of promoting normal-temperature desorption, promoting alkaline hydrolysis reaction and activating sodium persulfate, and makes full use of the effects of the quicklime in each stage.

Description

Ectopic remediation method for organophosphorus pesticide and VOCs (volatile organic compounds) composite contaminated soil

Technical Field

The invention belongs to the technical field of soil remediation, and particularly relates to an ectopic remediation method for soil compositely polluted by organophosphorus pesticides and VOCs.

Background

The organophosphorus pesticide is widely used in agriculture as a broad-spectrum pesticide herbicide, and has the advantages of rapid development due to the advantages of rich varieties, low price, easy biodegradation and the like, and certain problems of 'running, overflowing, dripping, leaking' and the like exist in the production or storage process of the organophosphorus pesticide due to historical limitations, so that certain pollution is caused to soil and underground water. It is reported that the sites are not only polluted by the organophosphorus pesticides, but also polluted by the organophosphorus pesticides and Volatile Organic Compounds (VOCs) in a combined manner, so that the sites polluted by the organophosphorus pesticides are more difficult to treat. Many organophosphorus pesticide contaminated sites are mostly located in new urban centers, have high land development value and urgently need to be repaired and treated. Therefore, the development of a quick, efficient and economic remediation technology for remedying the soil polluted by the organophosphorus pesticides and the VOCs is urgently needed.

At present, documents and patent reports about the remediation technology of the soil polluted by the organophosphorus pesticides and the VOCs are not found, and only some relevant reports about the remediation technology of the soil polluted by the organophosphorus pesticides exist in China. The restoration technology aiming at the composite polluted site of the organophosphorus pesticide and the VOCs is mainly divided into three types, namely thermal desorption restoration, biological restoration and chemical oxidation restoration according to the process principle. The thermal desorption technology is a technology for separating pollutants from soil by increasing temperature, but the application range of the thermal desorption technology is limited by the defects of high energy consumption, poor economy and the like of the thermal desorption restoration technology. Bioremediation is a technology for removing organic pollutants from soil by utilizing the enrichment or degradation capability of microorganisms or plants, but the bioremediation technology is not suitable for the current situation of the demand of efficient site remediation due to the defects of long remediation period, unstable remediation effect and the like. Chemical oxidation restoration is a technology for removing organic pollutants by adding an oxidizing agent into soil, and compared with other technologies, the chemical oxidation restoration technology can degrade the organic pollutants more efficiently and quickly, but can lead to more sulfate residues in the soil when a large amount of activated persulfate is used for oxidation restoration, and has certain corrosivity on the steel structure of a building in a subsequent field.

For example, there have been disclosed compositions and applications for treating soil contaminated with high concentrations of organophosphorus pesticides, which are capable of effectively degrading organophosphorus pesticides at high concentrations in field soil by activating sodium persulfate with an alkali to generate strongly oxidizing sulfate radicals and hydroxyl radicals. The method comprises the steps of simultaneously adding sodium hydroxide and sodium persulfate into the site polluted soil containing high-concentration organophosphorus pesticide, standing in an incubator and stirring once a day. However, the method mainly aims at the high-concentration organic phosphorus contaminated soil, and although the method has a certain repairing effect on the organic phosphorus pesticide and VOCs composite contaminated soil, the method cannot ensure that the complete repairing is qualified. In addition, the main agents of the method are sodium hydroxide and sodium persulfate, the principle of activating the sodium persulfate by alkali is utilized to restore the organophosphorus contaminated soil, the required dosage of the sodium hydroxide, the sodium persulfate and the like is large, the restoration cost is increased, the economy is relatively poor, and more sulfate is remained in the soil.

In conclusion, the development of the remediation technology for the soil compositely polluted by the organophosphorus pesticide and the VOCs has wide application prospect and great application value.

Disclosure of Invention

Therefore, the invention aims to overcome the defects that the prior art does not have a technology for restoring the soil compositely polluted by the organophosphorus pesticides and the VOCs, and a single chemical oxidation treatment agent has more usage amount and can leave more sulfate in the soil, and the like, thereby providing the ectopic restoring method suitable for the soil compositely polluted by the organophosphorus pesticides and the VOCs.

Therefore, the invention provides the following technical scheme:

the invention provides an ectopic remediation method for organophosphorus pesticide and VOCs (volatile organic compounds) composite contaminated soil, which comprises the following steps:

and (3) normal temperature desorption: fully mixing the soil to be treated with quicklime, turning and throwing after the soil is heated, and removing VOCs in the soil by turning and throwing; wherein the amount of the quicklime is 2 to 5 percent of the mass of the soil to be treated;

alkaline hydrolysis reaction: fully mixing the turned soil with water, maintaining for the first time to obtain slurry, and performing the first maintenance, wherein the organophosphorus pesticide in the soil is subjected to alkaline hydrolysis reaction during the first maintenance; wherein the amount of the water is 100-300% of the mass of the soil to be treated;

chemical oxidation: adding an oxidizing agent into the slurry to uniformly mix the soil and the oxidizing agent, and performing secondary maintenance, wherein during the secondary maintenance, the oxidizing agent and the pollutants remained in the soil are subjected to oxidation reaction to thoroughly mineralize the pollutants; wherein the dosage of the oxidation medicament is 0.5-5% of the mass of the soil to be treated.

Optionally, in the alkaline hydrolysis step, the mass ratio of the water to the soil to be treated is 100% -300%.

Optionally, the persulfate is at least one of sodium persulfate, potassium persulfate and ammonium persulfate.

Optionally, the turning time is 1h-3h.

Optionally, the primary curing time in the alkaline hydrolysis step is 12-48 h;

optionally, the primary maintenance condition is that the soil is in a uniform slurry state and is not layered.

Optionally, the secondary curing time in the alkaline hydrolysis step is 12-48 h;

optionally, the secondary maintenance condition is that the soil is in a uniform slurry state and is not layered.

Optionally, after the secondary maintenance, detecting the concentration of the pollutants in the soil, and if the concentration of the pollutants in the soil does not reach the target repairing value, repeating the chemical oxidation step until the repairing is qualified.

Optionally, the soil to be treated is subjected to screening pretreatment to remove coarse impurities. Coarse impurities with the particle size of more than 50mm can be removed, and the contaminated soil is homogenized.

Optionally, the soil to be treated is organic phosphorus pesticide and VOCs composite contaminated soil.

Specifically, the soil ectopic remediation method provided by the invention comprises the following specific steps:

(1) Clearing and transporting the polluted soil: and clearing and digging the polluted soil according to the soil pollution range, and excavating and transferring the cleared and dug soil to a repair workshop. During the excavation process, the support of the foundation pit needs to be paid attention to, and the safety of the excavation process is ensured.

(2) Soil homogenization treatment: and (3) carrying out screening pretreatment on the polluted soil transferred to the closed workshop by using an ALLU screening hopper, removing coarse impurities with the particle size of more than 50mm, and ensuring the homogenization of the polluted soil.

(3) And (3) normal temperature desorption: and (3) adding about 2-5% of quicklime into the homogenized organic phosphorus pesticide and VOCs composite polluted soil, and fully mixing the polluted soil and the quicklime. And after fully mixing the soil and the quicklime, turning and throwing by using a machine, wherein the turning and throwing time is about 1-3 h approximately. In addition, the change condition of the soil temperature needs to be monitored in real time in the turning process, and the turning can be started when the soil temperature is increased to 40 ℃. VOCs in partial soil can be removed in the normal temperature desorption process.

(4) Alkaline hydrolysis reaction: desorbing the organophosphorus pesticide and VOCs polluted soil at normal temperature, and adding a proper amount of water into the soil, wherein the recommended soil-water ratio is 1:1-1: 3, mixing the soil into slurry, and maintaining for about 12-48 h. As quicklime is added into the soil in the normal-temperature desorption stage, the slurry soil is in an alkaline environment, and the alkaline hydrolysis of the organophosphorus pesticide is promoted. The alkaline hydrolysis reaction process can remove most of the organophosphorus pesticide in the soil.

(5) Chemical oxidation: granular sodium persulfate is added into the muddy soil, and the adding amount can be judged according to the concentration of the pollutants. And fully mixing the added sodium persulfate with the slurry soil, and maintaining for about 12-48 h. The chemical oxidation process can thoroughly mineralize residual organophosphorus pesticides and VOCs in the soil.

(6) Sampling and detecting: and (5) collecting the maintained soil for detection, and if the concentration of the pollutants in the soil does not reach the restoration target value, repeating the step (5) according to the concentration of the pollutants until the restoration is qualified.

Compared with other repair technologies, the method can effectively reduce the dosage of the oxidation medicament (persulfate), and overcomes the defect of high residual concentration of the sulfate after the conventional persulfate oxidation technology is used for repairing. In addition, the technology has the advantages of high repairing efficiency, thorough repairing, short repairing time and the like.

The technical scheme of the invention has the following advantages:

1. the invention provides an ectopic remediation method for organophosphorus pesticide and VOCs (volatile organic compounds) composite contaminated soil, which comprises the following steps: and (3) normal temperature desorption: mixing soil to be treated with quicklime, and turning over; wherein the amount of the quicklime is 2-5% of the mass of the soil to be treated; alkaline hydrolysis reaction: mixing the turned soil with water, and maintaining for one time to obtain slurry; chemical oxidation: adding an oxidizing agent into the slurry, mixing, and performing secondary maintenance; wherein the dosage of the oxidation medicament is 0.5-5% of the mass of the soil to be treated. The invention belongs to a combination technology, and adopts a staged mode to remove VOCs and organophosphorus pesticides in soil, and the invention has the characteristics of small dosage of quicklime and oxidizing agents, low energy consumption, thorough restoration and green sustainability. Specifically, most VOCs pollutants are removed through normal temperature desorption, and part of organophosphorus pesticide is removed through alkaline hydrolysis reaction, so that the using amount of an oxidizing agent is saved. Aiming at the remediation work of the organophosphorus pesticide and VOCs composite contaminated soil, the method reduces the remediation cost and reduces the sulfate concentration in the remediated field. The quicklime used in the invention has three functions, and the effectiveness of the quicklime in each stage is fully utilized. In the normal-temperature desorption stage, the effect of mixed heating of the quicklime and the soil is utilized, so that the normal-temperature desorption efficiency is improved, and the removal of VOCs in the composite contaminated soil is facilitated; in the alkaline hydrolysis reaction stage, an alkaline environment is provided for slurry-like soil, the alkaline hydrolysis of the organophosphorus pesticide is promoted, and the use amount of a subsequent oxidizing agent is reduced; in the chemical oxidation stage, an alkaline environment is provided for the added oxidizing agent, the oxidizing agent can be activated by alkali, and residual organophosphorus pesticides and VOCs can be thoroughly removed.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a flow chart of a soil ex-situ remediation method provided by the present invention;

FIG. 2 is a graph showing the change in concentration of contaminants during soil remediation according to example 1 of the present invention.

Detailed Description

The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.

The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.

Example 1

The embodiment provides an ectopic remediation method for organophosphorus pesticide and VOCs (volatile organic compounds) composite contaminated soil, the treatment process is shown in FIG. 1, and the specific operation steps are as follows:

(2) Soil homogenization treatment: and (3) carrying out screening pretreatment on the polluted soil transferred to the closed workshop by using an ALLU screening hopper, removing coarse impurities with the particle size of more than 50mm, and ensuring the homogenization of the polluted soil. Through detection, the concentration of phorate in the soil is 1335.66mg/kg, and the concentration of toluene is 954.25mg/kg.

(3) And (3) normal temperature desorption: and (3) adding 5% of quicklime into the homogenized polluted soil, and fully mixing the polluted soil and the quicklime. And after fully mixing the soil and the quicklime, turning and throwing by using a machine, wherein the turning and throwing time is about 3 hours. Through detection, the concentration of phorate in the soil after turning and throwing is 1295.87mg/kg, and the concentration of toluene is 37.69 mg/kg.

(4) Alkaline hydrolysis reaction: adding a proper amount of water after desorption at normal temperature, fully stirring to ensure that the soil is in a slurry state, wherein the soil-water ratio is 1:1, and maintaining for about 1 d. Through detection, after alkaline hydrolysis reaction, the concentration of phorate in the soil is 67.81mg/kg, and the concentration of toluene is 26.94mg/kg.

(5) Chemical oxidation: adding granular sodium persulfate into the muddy soil, wherein the adding ratio of the sodium persulfate is 1.0%, fully mixing the added sodium persulfate with the muddy soil, and maintaining for about 1 d. Through detection, after the chemical oxidation reaction, the concentration of phorate in the soil is 9.58mg/kg, the concentration of toluene is 1.92 mg/kg, and the concentration of sulfate ions is 987mg/kg.

(6) And (4) analyzing results: fig. 2 is a graph of the concentration change of the pollutants in the soil remediation process of the embodiment, and it can be seen from the graph that most of the pollutants in the organic phosphorus pesticides (VOCs) (toluene) are removed by normal temperature desorption, part of the organic phosphorus pesticides (phorate) are removed by alkaline hydrolysis reaction, and the residual organic phosphorus pesticides and VOCs can be completely removed in the chemical oxidation stage. After the organophosphorus pesticide and the VOCs polluted soil in the embodiment is repaired, the concentration of phorate in the soil is 13mg/kg lower than the repair target value; the concentration of toluene in the soil is also lower than the restoration target value and is 830mg/kg; the repaired soil has low sulfate content and weak corrosivity to concrete buildings.

Example 2

(1) The project is a soil and underground water restoration project of Tianjin certain pesticide factory, and the target pollutants in the soil mainly comprise benzene, toluene, ethylbenzene, parathion, ethion, phorate, terbufos and the like.

(2) Clearing and transporting the polluted soil: and clearing and digging the polluted soil according to the soil pollution range, and excavating and transferring the cleared and dug soil to a repair workshop. In the process of clearing and digging, attention needs to be paid to the supporting of the foundation pit, and the safety of the clearing and digging process is guaranteed.

(3) Soil homogenization treatment: and (3) carrying out screening pretreatment on the polluted soil transferred to the closed workshop by using an ALLU screening hopper, removing coarse impurities with the particle size of more than 50mm, and ensuring the homogenization of the polluted soil. The original concentrations of each contaminant in the soil are shown in table 1.

(4) Normal temperature desorption: and adding 3% of quicklime into the homogenized polluted soil, and fully mixing the polluted soil and the quicklime. And (3) after fully mixing the soil and the quicklime, turning and throwing by using a machine, wherein the turning and throwing time is about 1 h. Through detection, the concentrations of benzene, toluene and ethylbenzene in the soil are obviously reduced, and the concentrations are shown in table 1.

(5) Alkaline hydrolysis reaction: adding a proper amount of water after desorption at normal temperature, fully stirring to ensure that the soil is in a slurry state, wherein the soil-water ratio is 1:3, and maintaining for about 2 days. Through detection, after alkaline hydrolysis reaction, the concentrations of parathion, ethion, phorate and terbufos in the soil are reduced by injection at first, and the concrete results are shown in table 1.

(6) Chemical oxidation: adding granular sodium persulfate into the muddy soil, wherein the adding ratio of the sodium persulfate is 3%, fully mixing the added sodium persulfate with the muddy soil, and maintaining for about 24 hours. Through detection, the contents of benzene, toluene, ethylbenzene, parathion, ethion, phorate, terbufos and other pollutants in the soil are obviously reduced, and the contents are shown in table 1.

TABLE 1

(7) And (4) analyzing results: after the organophosphorus pesticide and VOCs polluted soil in the embodiment is repaired, benzene, toluene, ethylbenzene, parathion, ethion, phorate and terbufos in the soil all reach the repair target value; the sulfate ion concentration of the restored soil is 2108mg/kg, the sulfate content is lower, and the corrosion grade of the restored soil to concrete buildings is weak.

Comparative example

At present, documents and patent reports aiming at the remediation technology of the soil compositely polluted by the organophosphorus pesticide and the VOCs are not available basically, and although the conventional chemical oxidation technology of alkali-activated sodium persulfate has a certain remediation effect on the soil compositely polluted by the organophosphorus pesticide and the VOCs, the dosage of remediation agents is large, the remediation efficiency is low, the content of sulfate in the soil after remediation is high, and the details are shown in the following examples.

(1) Pollution characteristics: the target pollutants in the soil in the comparative example were benzene and phorate, and the original concentrations were 116.70mg/kg and 227.84mg/kg, respectively. The repair target values of benzene and phorate are 0.65 mg/kg and 13mg/kg respectively.

(2) The repairing technology comprises the following steps: chemical oxidation technology.

(3) Repairing the medicament: hydrogen peroxide, sodium persulfate, sodium hydroxide.

(4) Experimental group setup:

TABLE 2

Remarking: in the formula of the common alkali-activated sodium persulfate medicament, the mass ratio of sodium persulfate to sodium hydroxide is 2:1. The mass ratio of the sodium persulfate to the sodium hydroxide in the experiment group E, the experiment group F and the experiment group G is the same, but the adding ratio of the sodium persulfate to the contaminated soil is gradually increased.

(5) Experimental implementation

And collecting the contaminated soil, uniformly mixing the contaminated soil, using the soil as experimental soil to determine the original concentration of the contaminants. Accurately weighing 1000g of soil to be tested in a reaction vessel, adding corresponding agents according to the experimental group setting in the table 2, and after the agents are added, adding 1000g of deionized water to ensure that the soil and the agents are uniformly mixed and the soil is in a slurry state. After the soil of each experimental group was evenly stirred and was kept stand for 3 days in a dark place, sampling test was carried out, and the specific results are shown in the following table:

TABLE 3

(6) Data analysis

(1) The experimental group A is a blank group, and benzene and phorate in soil are both slightly reduced and mainly caused by factors such as volatilization, adsorption, photolysis and the like.

(2) The experimental group B is a hydrogen peroxide single oxidation group, although benzene and phorate in the soil are obviously reduced, the benzene and phorate in the soil do not reach the remediation target value, and the remediation efficiency of the soil compositely polluted by the organophosphorus pesticide and the VOCs only through hydrogen peroxide is proved to be poor.

(3) The experimental group C is a sodium persulfate single oxidation group, benzene and phorate in the soil are remarkably reduced but do not reach the remediation target value, and the remediation efficiency of the soil compositely polluted by the organophosphorus pesticide and the VOCs by the sodium persulfate single oxidation is relatively poor.

(4) The experimental group D is an independent alkaline hydrolysis group, the content of phorate in the soil is remarkably reduced, the remediation target value is reached, but the content of benzene in the soil is reduced a little and the remediation target value is not reached, and the fact that the independent alkaline hydrolysis is effective on the organophosphorus pesticide but basically ineffective on VOCs pollutants is proved.

(5) The experimental group E, F, G is an alkali-activated sodium persulfate group, benzene and phorate in soil are remarkably reduced but do not reach the remediation target value, and the remediation efficiency of the soil compositely polluted by the alkali-activated sodium persulfate and organophosphorus oxide pesticide and VOCs is proved to be poor.

(6) By comparing the experimental group E, F, G with the experimental group D, the content of the organophosphorus pesticide in the experimental group D is remarkably reduced compared with that of the experimental group E, F, G, and the repair efficiency of alkali-activated sodium persulfate is lower than that of single alkaline hydrolysis for repairing the organophosphorus pesticide.

(7) The content of sulfate radicals in the experimental group C, E, F, G is high, and the corrosion to concrete buildings is high. The sulfate radical content of the experimental group E is more than 2550mg/kg, and the corrosion grade to the concrete building is medium grade; the sulfate radical content of the experimental group C, F, G is higher than 4500mg/kg, and the corrosion grade of the experimental group for concrete buildings is strong. The method proves that the sulfate radical content of the soil compositely polluted by the organophosphorus pesticide and the VOCs through the single sodium persulfate oxidation and the single alkali-activated sodium persulfate oxidation is greatly increased.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.

Claims

1. An ectopic remediation method for organophosphorus pesticide and VOCs composite contaminated soil is characterized by comprising the following specific steps:

and (3) normal temperature desorption: mixing the soil to be treated with quicklime, and turning over; wherein the amount of the quicklime is 2-5% of the mass of the soil to be treated;

alkaline hydrolysis reaction: mixing the turned soil with water, and carrying out primary maintenance to obtain slurry, wherein the water is used in an amount of 100-300% of the mass of the soil to be treated;

chemical oxidation: adding an oxidizing agent into the slurry, mixing, and carrying out secondary maintenance; wherein the dosage of the oxidation medicament is 0.5-5% of the mass of the soil to be treated.

2. The ex-situ remediation method for soil compositely contaminated by organophosphorus pesticide and VOCs according to claim 1, wherein the oxidizing agent is persulfate.

3. The method for the ex-situ remediation of the soil compositely polluted by the organophosphorus pesticides and VOCs according to claim 2, wherein the persulfate is at least one of sodium persulfate, potassium persulfate and ammonium persulfate.

4. The method for the ex-situ remediation of the soil compositely polluted by the organophosphorus pesticide and the VOCs according to any one of claims 1 to 3, wherein the turning time is 1h to 3h.

5. The ex-situ remediation method for soil compositely contaminated by organophosphorus pesticide and VOCs according to claim 4, wherein soil to be treated is mixed with quicklime, and after the temperature of the soil is raised, the soil is turned over.

6. The ex-situ remediation method for soil compositely contaminated by organophosphorus pesticide and VOCs according to any one of claims 1 to 3, wherein the primary curing time in the alkaline hydrolysis reaction step is 12 to 48 hours.

7. The method for the ex-situ remediation of soil compositely polluted by organic phosphorus pesticide and VOCs according to any one of claims 1 to 3, wherein the secondary curing time in the alkaline hydrolysis reaction step is 12h to 48h.

8. The ex-situ remediation method for soil compositely contaminated by organophosphorus pesticide and VOCs according to claim 1, wherein after the secondary maintenance, the concentration of the pollutants in the soil is detected, and if the target remediation value is not reached, the chemical oxidation step is repeated until the remediation is qualified.

9. The method for restoring the soil polluted by the organophosphorus pesticide and VOCs in a combined manner in an ectopic mode according to any one of claims 1 to 3, wherein the soil to be treated is subjected to screening pretreatment.