A chemical remediation agent for remediating TNT-contaminated soil, its preparation method and application

Abstract

This invention discloses a chemical remediation agent for remediating TNT-contaminated soil, its preparation method, and its application. The chemical remediation agent comprises an oxidant, an activator, and an auxiliary agent. The oxidant is hydrogen peroxide, the activator is bicarbonate, and the auxiliary agent is glycerol or a biosurfactant. The preparation method of the chemical remediation agent is as follows: the oxidant is diluted with water to obtain a diluted oxidant solution; the auxiliary agent and the activator are added sequentially to the diluted oxidant solution to obtain the chemical remediation agent. The chemical remediation agent provided by this invention is suitable for TNT-contaminated soil with a TNT concentration ≥1000 mg / kg, achieving a TNT removal rate ≥80% in the soil. Furthermore, this chemical remediation agent is environmentally friendly and will not cause secondary pollution to the soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil environment treatment, in particular to a chemical remediation agent for repairing TNT contaminated soil and a preparation method and application thereof. BACKGROUND

[0002] During the first and second world war, great progress has been made in the research of explosives. In recent years, explosives are widely used in military, mining, construction, high-energy metallurgy and other industries. The use of explosives, while solving the convenience, also has a huge hidden danger. In the process of manufacturing, using and destroying explosives, it leads to soil and water pollution. TNT is the most commonly used nitrobenzene explosive, and the soil pollution of TNT has adverse effects on humans, plants and microorganisms. Long-term exposure to TNT contaminated environment, in addition to the potential mutagenic and carcinogenic effects on human body, can also cause skin irritation, liver dysfunction, cataract and anemia, etc.; TNT has toxic effects on terrestrial plants, affects plant germination, reduces plant biomass, and causes abnormal plant growth.

[0003] Because nitrobenzene has high toxicity and is difficult to be biodegraded, conventional soil treatment methods are difficult to completely remove TNT in soil. At present, the repair methods of TNT contaminated soil include physical and chemical methods, microbial methods, plant methods, etc., such as pyrolysis, chemical oxidation, microbial inoculants, etc. Among them, the cost of pyrolysis method is relatively high, and it has great damage to soil structure and function; the time period of biological degradation is relatively long, and high concentration of TNT in soil can easily deactivate the degrading organisms, so it can be seen that the biological degradation method is difficult to be applied to high concentration of TNT contaminated soil.

[0004] In the chemical oxidation method, Fenton reagent composed of hydrogen peroxide and divalent iron ions is used based on the Fenton principle. In the redox process, hydroxyl radicals (·OH) generated by Fenton reagent can degrade the refractory organic pollutants in soil into non-toxic or less harmful substances. For example, a method for oxidizing nitrobenzene in soil in 201810654068.X uses ferrous sulfate and hydrogen peroxide as oxidants, combined with citric acid-sodium citrate buffer, and the removal rate of nitrobenzene in soil can reach 92.5%. However, when using Fenton principle to degrade nitrobenzene pollutants in soil, Fenton reagent is easy to decompose, the reaction is rapid, and a large amount of gas and heat is easy to produce, which leads to pollution transfer instead of pollution removal of part of volatile and semi-volatile organic pollutants, causing safety hazards to the construction site and the surrounding environment, and the utilization rate of active oxygen is not high. When using persulfate as an oxidant to oxidize organic pollutants, single persulfate cannot achieve good oxidation degradation effect when treating high-concentration organic pollutant-containing contaminated soil, and generally needs to be combined with an activator to better degrade organic pollutants in soil. The organic contaminated soil chemical oxidation remediation agent and use method in 202011227119.7 uses sodium persulfate as an oxidant to treat soil, and the reaction product sulfate will remain in the soil, causing secondary pollution to the soil. When using potassium permanganate as an oxidant to treat organic pollutants in soil, potassium permanganate is easy to have side reactions with other organic matters in soil, and the degradation effect is not good.

[0005] Therefore, it is necessary to properly repair the TNT contaminated soil in an environmentally friendly manner. Developing a chemical remediation agent with low damage to soil function and structure, high active oxygen utilization rate, and non-toxic and harmless residues and its application method has good application potential in repairing explosive contaminated sites. SUMMARY

[0006] The beneficial effects of the present application are:

[0007] 1. The chemical remediation agent provided by the present application is suitable for repairing TNT contaminated soil, especially for soil with TNT concentration ≥1000mg / kg, and the removal rate of TNT in soil by the chemical remediation agent provided by the present application is ≥80%.

[0008] 2. The chemical remediation agent provided by the present application is weakly alkaline, and the oxidant H2O2 in it ionizes to generate -OOH can undergo a nucleophilic substitution reaction with TNT in the soil to generate nitrite and nitrophenol intermediates, achieving rapid elimination of TNT. Simultaneously, bicarbonate is activated by H₂O₂ to generate percarbonate. Percarbonate decomposes to produce superoxide anion radicals and carbonate radicals, which react with nitrite to generate highly reactive nitrite radicals. These radicals disrupt the benzene ring structure, facilitating the further decomposition of TNT and its recalcitrant benzene-containing intermediates into smaller organic molecules. In other words, the TNT degradation product nitrite can accelerate the further degradation of TNT and its intermediates.

[0009] Therefore, the chemical remediation agent of this invention exhibits autocatalytic activity in the degradation of TNT. Due to the weakly alkaline nature of the solution, the Fenton reaction of metal ions in the soil with H₂O₂ is inhibited, resulting in slow and ineffective decomposition of H₂O₂. Furthermore, the activated percarbonate, superoxide anion, carbonate radicals, and nitrite radicals exhibit strong reaction selectivity, leading to high utilization of reactive oxygen species. The activity of the remediation agent can typically be maintained for more than 48 hours. The auxiliary agents, such as glycerol or biosurfactants, can promote the dissolution of adsorbed TNT in the soil, increase contact with the oxidant, and facilitate the degradation reaction.

[0010] 3. When using the chemical remediation agent provided by this invention to treat TNT-contaminated soil, the remaining oxidant H2O2 after the reaction can decompose into water and oxygen at normal temperature and pressure, which does not pollute the soil. Moreover, the auxiliary agent glycerol or biosurfactant serves as a carbon source and is decomposed by microorganisms in the soil. Bicarbonate is a common component in soil, and the remaining bicarbonate after the reaction will not cause harm to the soil.

[0011] 4. The chemical repair agent preparation method provided by the present invention is simple in process, and the raw materials of the chemical repair agent are inexpensive and readily available, making it suitable for large-scale production. Detailed Implementation

[0012] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0013] As described in the background section, TNT is highly toxic and difficult to degrade. Microbial and phytochemical methods are not suitable for degrading contaminated soil with TNT concentrations ≥1000 mg / kg. Pyrolysis is costly and causes significant damage to soil structure and function. In oxidation methods, Fenton's reagent, composed of hydrogen peroxide and ferrous ions, is unstable and poses environmental safety hazards, and its utilization rate of reactive oxygen species is low. When persulfate is used as an oxidant, the resulting sulfate can cause secondary pollution to the soil. Based on this, the present invention proposes a chemical remediation agent for remediating TNT-contaminated soil, which can achieve a TNT degradation rate of over 80% in the soil without causing secondary pollution, and is safe and efficient.

[0014] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0015] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0016] Example 1

[0017] (1) Dilute a 14% hydrogen peroxide aqueous solution with water by 8 times to obtain an oxidant dilution, wherein the molar concentration of hydrogen peroxide in the oxidant dilution is 0.52 mol / L;

[0018] (2) Add glycerol to the oxidant dilution in step (1) and stir to mix evenly to obtain a mixture, wherein the mass ratio of glycerol to oxidant dilution in the mixture is 1.2:100;

[0019] (3) Add sodium bicarbonate solid to the mixture in step (2), stir and mix evenly to obtain the chemical repair agent, wherein the molar concentration ratio of sodium bicarbonate solid to hydrogen peroxide in the mixture is 1:15;

[0020] The resulting chemical remediation agent contained 1.6% hydrogen peroxide by volume and 1.1 wt% glycerol by weight.

[0021] Example 2

[0022] (1) Dilute a 10% hydrogen peroxide aqueous solution with water by 5 times to obtain an oxidant dilution, wherein the molar concentration of hydrogen peroxide in the oxidant dilution is 0.088 mol / L;

[0023] (2) Add polysorbate 80 to the oxidant dilution in step (1), stir to mix evenly, and obtain a mixture, wherein the mass ratio of polysorbate 80 to oxidant dilution in the mixture is 0.1:100;

[0024] (3) Add sodium bicarbonate solid to the mixture in step (2) to obtain the chemical repair agent, wherein the molar concentration ratio of sodium bicarbonate solid to hydrogen peroxide in the mixture is 1:10.

[0025] The resulting chemical remediation agent contained 0.3% hydrogen peroxide by volume and 0.1 wt% polysorbate 80 by weight.

[0026] Example 3

[0027] (1) Dilute a 30% hydrogen peroxide aqueous solution with water by 10 times to obtain an oxidant dilution, wherein the molar concentration of hydrogen peroxide in the oxidant dilution is 0.88 mol / L;

[0028] (2) Add rhamnolipin to the oxidant dilution in step (1), stir to mix evenly, and obtain a mixture, wherein the mass ratio of rhamnolipin to oxidant dilution in the mixture is 2:100;

[0029] (3) Add sodium bicarbonate solid to the mixture in step (2), stir and mix evenly to obtain the chemical repair agent, wherein the molar concentration ratio of sodium bicarbonate solid to hydrogen peroxide in the mixture is 1:20.

[0030] The resulting chemical remediation agent contained 3.0% hydrogen peroxide by volume and 2 wt% rhamnolipid by weight.

[0031] Comparative Example 1: Chemical Remediation Agent Prepared Using Hydrogen Peroxide as a Raw Material

[0032] A chemical remediation agent is obtained by diluting a 14% hydrogen peroxide aqueous solution with water eight times.

[0033] The chemical remediation agent contains a hydrogen peroxide molar concentration of 0.52 mol / L.

[0034] Comparative Example 2: Chemical Remediation Agent Prepared Using Hydrogen Peroxide and Sodium Bicarbonate as Raw Materials

[0035] (1) Dilute a 14% hydrogen peroxide aqueous solution with water by 8 times to obtain an oxidant dilution, wherein the molar concentration of hydrogen peroxide in the oxidant dilution is 0.52 mol / L;

[0036] (2) Add sodium bicarbonate solid to the oxidant dilution in step (1), stir and mix evenly to obtain the chemical repair agent;

[0037] The molar ratio of sodium bicarbonate solid to hydrogen peroxide in the mixture is 1:15.

[0038] Comparative Example 3: Chemical Repair Agent Prepared Using Hydrogen Peroxide and Glycerin as Raw Materials

[0039] (1) Dilute a 14% hydrogen peroxide aqueous solution with water by 8 times to obtain an oxidant dilution, wherein the molar concentration of hydrogen peroxide in the oxidant dilution is 0.52 mol / L;

[0040] (2) Add glycerin to the oxidant dilution in step (1) and stir to mix evenly to obtain the chemical repair agent.

[0041] Experimental Example 1: The Remediation Effect of Chemical Remediation Agents on TNT-Contaminated Soil

[0042] The chemical remediation agent prepared in Example 1 and the chemical remediation agents prepared in Comparative Examples 1 to 3 were used to remediate soil contaminated with high concentrations of TNT. The degradation rate of TNT in the soil by each group of chemical remediation agents was measured, and the results are shown in Table 1.

[0043] The specific detection method is as follows: (1) The initial TNT concentration in the TNT-contaminated soil of the experimental group was tested by ultrasonic-assisted acetonitrile extraction-high performance liquid chromatography. The specific method is as follows: weigh the dry soil sample, add acetonitrile for ultrasonic extraction, separate and filter the extract, analyze the TNT content in the filtrate with liquid chromatography, and use the external standard method to quantify TNT.

[0044] (2) Take 5g of TNT-contaminated soil, add 10mL of chemical remediation agent from each test group, mix evenly, react for 48h, drain the water and air dry, use ultrasound-assisted acetonitrile extraction-high performance liquid chromatography to detect the TNT concentration in the soil after reaction, and calculate the TNT degradation rate.

[0045] Table 1. Degradation rate (%) of TNT in soil by the chemical remediation agents prepared in Example 1 and Comparative Examples 1-3.

[0046]

[0047] As can be seen from the table above, the chemical remediation agent prepared by the present invention using hydrogen peroxide as an oxidant, sodium bicarbonate as an activator, and glycerol as an auxiliary agent can achieve a TNT degradation rate of 82.3% in soil. In contrast, when hydrogen peroxide is used alone to treat TNT-contaminated soil, the TNT degradation rate is only 16.5%; when hydrogen peroxide and sodium bicarbonate are used to treat TNT-contaminated soil, the TNT degradation rate is 58.8%; and when hydrogen peroxide and glycerol are used to treat TNT-contaminated soil, the TNT degradation rate is 29.1%.

[0048] Therefore, this application utilizes a combination of hydrogen peroxide and sodium bicarbonate, with glycerol or a biosurfactant as an adjuvant. This not only makes it suitable for soils with TNT concentrations ≥1000 mg / kg but also ensures a TNT reduction rate >80%. Hydrogen peroxide, acting as an oxidant, undergoes a nucleophilic reaction with TNT in the soil, leading to rapid TNT degradation. Simultaneously, bicarbonate, acting as an activator, reacts with hydrogen peroxide to generate percarbonate ions, which further decompose to generate nitrite radicals. These nitrite radicals can disrupt the benzene ring structure in TNT, facilitating further degradation into smaller molecules. Glycerol or a biosurfactant, as an adjuvant, promotes the dissolution of adsorbed TNT in the soil, increases the contact area between TNT and the oxidant, and accelerates the degradation reaction.

[0049] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. Use of a chemical remediation agent for remediating TNT-contaminated soil, characterized in that, The chemical repair agent is composed of an oxidizing agent, an activating agent and an auxiliary agent, the oxidizing agent is hydrogen peroxide, the activating agent is bicarbonate, and the auxiliary agent is glycerol or a biosurfactant, the biosurfactant is polysorbate 80 and / or rhamnolipid; The specific steps for repairing the TNT-contaminated soil by using the chemical repair agent are as follows: The chemical repair agent is mixed with the TNT-contaminated soil at a mass ratio of 5-10:1, and then the mixture is uniformly mixed and reacted for 12-48 hours.

2. Use according to claim 1, wherein In the chemical repair agent, the volume concentration of the oxidizing agent is 0.3%-3%, the weight percentage of the auxiliary agent is 0.1%-2%, and the molar concentration ratio of the activating agent to the oxidizing agent is 1:(10-20).

3. The use according to claim 1, wherein the compound is ###0002### The chemical repair agent is prepared by the following method: (1) The oxidizing agent is diluted with water at a dilution ratio of 5-10 times to obtain an oxidizing agent dilution solution; (2) The auxiliary agent is added to the oxidizing agent dilution solution and uniformly mixed to obtain a mixed solution; (3) The activating agent is added to the mixed solution and uniformly mixed to obtain the chemical repair agent.

4. Use according to claim 3, wherein the compound is ###0002### In step (1), the molar concentration of the oxidizing agent in the oxidizing agent dilution solution is 0.088-0.88 mol / L. In step (2), the mass ratio of the auxiliary agent to the oxidizing agent dilution solution is (0.1-2):

100.

6. The use according to claim 3, wherein the compound is ###0002### In step (3), the molar concentration ratio of the activating agent to the oxidizing agent in the mixed solution is 1:(10-20).

7. The use according to claim 1, wherein The concentration of TNT in the TNT-contaminated soil is ≥1000 mg / kg.

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