Application of organic contaminant in removal of active oxygen carrier oxidizer in soil

Abstract

To provide application of active oxygen carrier oxidizer in removal of organic contaminant in soil by which organic contaminant in soil can be efficiently removed, and secondary pollution is not caused.SOLUTION: Provided is application of active oxygen carrier oxidizer in removal of organic contaminant in soil, where the mass content of active oxygen in the active oxygen carrier oxidizer is 19 to 24%. A new-type active oxygen carrier is used as an oxidizer and applied to remediation of polluted soil. The oxidizer exhibits a powder state, and has high storage and conveyance safety. The active oxygen carrier is dissolved into water and can slowly release active substance, a utilization rate of the oxidizer is higher than that of peroxide, and remediation efficiency basically is not affected by the hydrogen ion concentration of environment. At the same time, efficient removal of soil organic contaminant can be achieved only by adding the oxidizer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention belongs to the technical field of soil purification, and specifically relates to the application of reactive oxygen species carrier oxidants in the removal of organic pollutants in soil.

Background Art

[0002] Soil is the largest "source", the largest "sink", and the largest "purifier" in environmental pollution. In the past few decades, China's industrialization and urbanization have been booming, and both industrialization and urbanization are inseparable from the huge demand for land. The main pollutants in soil are heavy metals and organic pollutants such as polycyclic aromatic hydrocarbons, total petroleum hydrocarbons, halogenated hydrocarbons, benzene derivatives, pesticides, and polychlorinated biphenyls. In China, polycyclic aromatic hydrocarbon pollution of sites is the most common, accounting for 54.9% of organic pollution sites. Polycyclic aromatic hydrocarbons have the characteristics of teratogenicity, carcinogenicity, and mutagenicity, are highly chemically stable, are difficult to be decomposed by biology, and may exist in soil for decades. The longer the pollution time, the more stubborn and difficult to remove polycyclic aromatic hydrocarbons are. Therefore, it is urgent to find a safe and efficient method to remove polycyclic aromatic hydrocarbons in the environment.

[0003] Chemical acidification repair has the advantages of high repair efficiency, short time, low cost, strong universality, etc. In-situ chemical oxidation injects oxidants and auxiliary reagents underground through injection wells, and through the actions of acid-base reactions, adsorption-desorption, dissolution, hydrolysis, ion exchange, precipitation, oxidation-reduction, etc., organic pollutants in soil or groundwater are decomposed into non-toxic or less dangerous substances. In-situ ex-situ chemical oxidation is convenient for construction. After safe treatment, a repair greenhouse is built on the site, the pollutants are excavated, put into an oxidation tank and stirred to react, and after the treated soil is maintained, it is backfilled. During in-situ chemical oxidation or in-situ ex-situ chemical oxidation repair, the selection of oxidants is important. Generally used oxidants include hydrogen peroxide, sodium persulfate, potassium permanganate, etc. Sodium persulfate and potassium permanganate are costly and at the same time are prone to cause secondary pollution. During the repair of persulfate, it causes soil acidification, leading to the elution of heavy metals and the migration of pollutants, and is prone to generate nitro group by-products. At the same time, the remaining persulfate causes corrosion of the building. After repair with potassium permanganate, precipitation of manganese dioxide is generated, the permeability of the soil decreases, the input and dispersion of the oxidant are hindered, and at the same time, the pollutants are wrapped, preventing the elution and oxidation of the pollutants.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In consideration of this, the object of the present invention is to provide the application of an active oxygen carrier oxidant in the removal of organic pollutants in soil, which can efficiently remove organic pollutants in soil and will not cause secondary pollution.

Means for Solving the Problems

[0005] To achieve the above object of the invention, the present invention provides the following technical solutions: The present invention provides the application of an active oxygen carrier oxidant in the removal of organic pollutants in soil, and the mass content of active oxygen in the active oxygen carrier oxidant is 19-24%.

[0006] Preferably, the active oxygen carrier oxidant contains potassium perborate.

[0007] Preferably, the usage ratio of the active oxygen carrier oxidant to the soil to be repaired is 0.04 - 4 mol: 1 kg.

[0008] Preferably, when the active oxygen carrier oxidant removes polycyclic aromatic hydrocarbons in the soil, it further contains a solution of an iron-based chelating agent, magnetite or pyrite.

[0009] Preferably, the iron-based chelating agent contains iron nitrilotriacetate, sodium iron ethylenediaminetetraacetate, iron ethylenediaminedisuccinate, iron oxalate, iron citrate or iron humate.

[0010] Preferably, the molar concentration of the solution of the iron-based chelating agent is 0.1 - 0.4 mol / L, and the molar ratio of the active oxygen carrier oxidant to the iron-based chelating agent is 10: 0.1 - 5.

[0011] Preferably, the preparation method of the iron nitrilotriacetate is mixing an iron sulfate solution with a chelating agent solution containing a nitrilotriacetic acid solution, a sodium ethylenediaminetetraacetate solution, an ethylenediaminedisuccinic acid solution, an oxalic acid solution, a citric acid solution or a humic acid solution, performing a chelation reaction to obtain a solution of an iron-based chelating agent.

[0012] Preferably, the molar concentration of the iron sulfate solution is 0.1 - 0.4 mol / L, and the molar concentration of the chelating agent solution is 0.1 - 0.4 mol / L.

[0013] Preferably, the temperature of the chelation reaction is 10 - 40 °C, and the time is 0.1 - 2 h.

[0014] The present invention further provides a method for repairing contaminated soil, which includes the step of spraying water for repair after mixing the active oxygen carrier oxidant and the soil to be repaired.

Advantages of the Invention

[0015] The present invention provides the application of an active oxygen carrier oxidant in the removal of organic pollutants in soil, and the mass content of active oxygen in the active oxygen carrier oxidant is 19-24%. The present invention uses a novel active oxygen carrier as an oxidant and applies it to the remediation of contaminated soil. The oxidant is in powder form and has high storage and transportation safety. The active oxygen carrier can dissolve in water and slowly release active substances. The utilization rate of the oxidant is higher than that of the same type of peroxide, and the repair efficiency is basically not affected by the hydrogen ion concentration of the environment. At the same time, efficient removal of soil organic pollutants can be achieved only by adding the oxidant. Compared with persulfate and permanganate, the active oxygen carrier does not produce oxidant residues, generates small side effects, and hardly causes secondary pollution to the environment.

[0016] Furthermore, the present invention further promotes the ability of the active oxygen carrier to remove pollutants by adding chelated iron.

Brief Description of the Drawings

[0017]

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Mode for Carrying Out the Invention

[0018] The present invention provides the application of an active oxygen carrier oxidant in the removal of organic pollutants in soil.

[0019] In the present invention, the particle size of the active oxygen carrier oxidant is preferably 1 to 20 μm, more preferably 1 μm. The mass content of active oxygen in the active oxygen carrier oxidant is preferably 19 to 24%, more preferably 20%. In the present invention, the organic pollutant is preferably a polycyclic aromatic hydrocarbon.

[0020] In the present invention, the active oxygen carrier oxidant is preferably potassium peroxoborate, and the preparation of the potassium peroxoborate is prepared according to CN201010153288.8.

[0021] In the present invention, the ratio of the usage amount of the active oxygen carrier oxidant to the soil to be repaired is preferably 0.04 to 4 mol: 1 kg, more preferably 0.1 to 1 mol: 1 kg.

[0022] In the present invention, when the active oxygen carrier oxidant removes polycyclic aromatic hydrocarbons in soil, it further contains a solution of an iron-based chelating agent, magnetite or pyrite.

[0023] In the present invention, the molar concentration of the solution of the iron-based chelating agent is preferably 0.1 to 0.4 mol / L, more preferably 0.4 mol / L.

[0024] In the present invention, the iron-based chelating agent preferably includes iron nitrilotriacetate, sodium iron ethylenediaminetetraacetate, iron ethylenediaminedisuccinate, iron oxalate, iron citrate or iron humate, and more preferably iron nitrilotriacetate.

[0025] In the present invention, the molar ratio of the potassium peroxoborate to the iron-based chelating agent is 10:0.1 to 5, more preferably 10:1.

[0026] In the present invention, the method for preparing the solution of the iron-based chelating agent is preferably Mixing an iron sulfate solution with a chelating agent solution containing a nitrilotriacetic acid solution, a sodium ethylenediaminetetraacetate solution, an ethylenediaminedisuccinic acid solution, an oxalic acid solution, a citric acid solution or a humic acid solution, performing a chelation reaction, and obtaining a solution of the iron-based chelating agent. In the present invention, the preparation of the nitrilotriacetic acid solution is preferably dissolving nitrilotriacetic acid powder in water, dropping an NaOH solution to adjust the pH to >12 to dissolve the nitrilotriacetic acid, and obtaining a nitrilotriacetic acid solution.

[0027] In the present invention, the molar concentration of the iron sulfate solution is preferably 0.1 to 0.4 mol / L, more preferably 0.4 mol / L. The mass concentration of the chelating agent solution is preferably 0.1 to 0.4 mol / L, more preferably 0.4 mol / L.

[0028] In the present invention, the temperature of the chelation reaction is preferably 25°C, and the time is preferably 10 min.

[0029] The present invention further provides a method for repairing contaminated soil, which includes a step of mixing an active oxygen carrier oxidant with the soil to be repaired, and then spraying water for repair.

[0030] In the present invention, the temperature of the repair is preferably room temperature, and after the water spraying, the water content of the soil to be repaired is preferably 25 to 80%, more preferably 30 to 50%.

[0031] In the present invention, when the reagent for soil repair is only the active oxygen carrier oxidant, the soil suitable for repair is soil with a lower concentration of contaminants or a higher Fe element content.

[0032] In the present invention, when the reagent for soil remediation further contains a solution of an iron-based chelating agent, the remediation method is to mix potassium peroxoborate with the soil to be remediated, and then spray the solution of the iron-based chelating agent onto the surface of the soil to be remediated for remediation.

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0034] Example 1 Ferrous sulfate solution: 40 mmol of ferrous sulfate was dissolved in 100 mL of water to obtain a 0.4 mol / L ferrous sulfate solution. 40 mmol of nitrilotriacetic acid powder was dissolved in 100 mL of water, and an NaOH solution was added dropwise to adjust the pH to 13 to dissolve the nitrilotriacetic acid, obtaining a 0.4 mol / L nitrilotriacetic acid solution. 100 mL of a ferrous sulfate solution with a molar concentration of 0.4 mol / L was slowly poured into 100 mL of a nitrilotriacetic acid solution with a molar concentration of 0.4 mol / L, and mixed and stirred for 10 min to obtain a nitrilotriacetic acid chelated iron solution with a molar concentration of 0.2 mol / L. Into a 100 mL Erlenmeyer flask, 5 g of severely contaminated soil with polycyclic aromatic hydrocarbons (the concentration of pyrene was 98.2 mg / kg), 1.3 mmol of potassium peroxoborate, 0.65 mL of a nitrilotriacetic acid chelated iron solution with a concentration of 0.2 mol / L were added, and then 4.4 g of water was added, and stirred at room temperature (25 °C) for 24 h under the condition that the vibration speed of the shaker was 100 revolutions / min. By detection, the removal rate of pyrene reached 67.8%.

[0035] Example 2 The reaction was carried out in a sandbox. The sandbox (sized 40 cm * 20 cm * 25 cm) contains, as shown in Figure 7a, from bottom to top, an aquifer (3 cm thick), a clay layer (15 cm thick), and heavily contaminated soil with polycyclic aromatic hydrocarbons (3 cm thick, 3 kg in total). 0.39 mol of potassium borate peroxide was added to the heavily contaminated soil with polycyclic aromatic hydrocarbons (as contaminants contained in the heavily contaminated soil with polycyclic aromatic hydrocarbons, the concentration of naphthalene was 61.88 mg / kg, the concentration of phenanthrene was 98.02 mg / kg, the concentration of pyrene was 101.08 mg / kg, and the total PAHs content was 261 mg / kg). It was placed in an open-air environment under room temperature conditions and reacted for 20 days by natural precipitation. By detection, the naphthalene concentration in the soil decreased by 92.5%, the phenanthrene concentration decreased by 98.7%, the pyrene concentration decreased by 81.0%, the total PAHs concentration decreased from 261 mg / kg to 11 mg / kg, and the removal rate reached 95.8%.

[0036] Example 3 In a 100 mL Erlenmeyer flask, 5 g of heavily contaminated soil with polycyclic aromatic hydrocarbons (the concentration of naphthalene, a contaminant contained in the heavily contaminated soil with polycyclic aromatic hydrocarbons, was 61.88 mg / kg, the concentration of phenanthrene was 98.02 mg / kg, and the concentration of pyrene was 101.08 mg / kg), and 0.67 mmol of potassium borate peroxide were added. Then 5 g of water was added, and it was stirred at room temperature for 24 h under the condition that the vibration speed of the shaker was 100 revolutions per minute. By detection, the removal rates of naphthalene, phenanthrene, and pyrene reached 71.2%, 64.2%, and 50.0% respectively.

[0037] Comparative Example 1 The difference from Example 3 is only that potassium borate peroxide was replaced with sodium percarbonate. By detection, the removal rates of naphthalene, phenanthrene, and pyrene reached 20.0%, 19.0%, and 10.0% respectively.

[0038] Comparative Example 2 The difference from Example 3 is only that potassium peroxoborate is replaced with calcium peroxide. By detection, the removal rates of naphthalene, phenanthrene and pyrene reached 23.0%, 15.1% and 11.6% respectively.

[0039] Comparative Example 3 The difference from Example 3 is only that potassium peroxoborate is replaced with hydrogen peroxide. By detection, the removal rates of naphthalene, phenanthrene and pyrene reached 19.4%, 10.9% and 8.6% respectively.

[0040] Comparative Example 4 The difference from Example 1 is only that potassium peroxoborate is replaced with sodium percarbonate. By detection, the removal rate of pyrene was 6.4%.

[0041] Comparative Example 5 The difference from Example 1 is only that potassium peroxoborate is replaced with calcium peroxide. By detection, the removal rate of pyrene was 36.7%.

[0042] Comparative Example 6 The difference from Example 1 is only that potassium peroxoborate is replaced with hydrogen peroxide. By detection, the removal rate of pyrene was 10.7%.

[0043] Figure 1 is an SEM image of potassium peroxoborate. It can be seen from Figure 1 that potassium peroxoborate is a micron-level white solid powder.

[0044] Figure 2 is the Raman spectrum characterization of potassium peroxoborate. It can be seen from Figure 2 that the surface of potassium peroxoborate contains rich peroxide-containing functional groups, including dual-core cyclic potassium peroxoborate (B2(O2)2), symmetric and asymmetric B-O(OH) stretching, symmetric and asymmetric peroxide B-O(O2).

[0045] As shown in Figure 3, the present invention tested the release situation of hydrogen peroxide after 0.65 mmol of potassium borate peroxide was dissolved in 100 ml of water. As can be seen from Figure 3, after potassium borate peroxide was dissolved in water, hydrogen peroxide solution was slowly released within several hours.

[0046] Figure 4 shows the signal that appeared in the electron paramagnetic resonance spectrum (EPR, Bruker A200S-95 / 12, Germany) after the superoxide radical released by the dissolution of potassium borate peroxide in water was captured by DMPO. (Reaction conditions: The scanning widths of spin trapping were set to 100 G and 115.4 G respectively. In the test, the microwave power and microwave frequency were set to 15 mW and 9.85 GHz respectively.). As can be seen from Figure 4, the signal showed a typical DMPO-O2 .- signal. It indicates that potassium borate peroxide decomposes when dissolved in water to generate superoxide radicals.

[0047] Figure 5 shows the removal rates of polycyclic aromatic hydrocarbons in contaminated soil by potassium borate peroxide in Example 3 and Comparative Examples 1-3. As can be seen from Figure 5, the removal rate of polycyclic aromatic hydrocarbons in Example 3 is much higher than that in Comparative Examples 1-3.

[0048] Figure 6 shows the removal rates of polycyclic aromatic hydrocarbons in contaminated soil by potassium borate peroxide in Example 1 and Comparative Examples 4-6. As can be seen from Figure 6, the removal rate of polycyclic aromatic hydrocarbons in Example 1 is much higher than that in Comparative Examples 4-6.

[0049] Figure 7 is a diagram of the repair process and repair results of Example 2. As can be seen from Figure 7, the potassium borate peroxide provided by the present invention can have a good repair effect even under natural conditions.

[0050] The above are only the preferred embodiments of the present invention. For those skilled in the art, without departing from the principle of the present invention, multiple improvements and refinements can be made, and these improvements and refinements also belong to the protection scope of the present invention.

Claims

1. A method for repairing contaminated soil, comprising the steps of mixing an active oxygen carrier oxidant with the soil to be repaired and then spraying water for repair. A method for repairing contaminated soil, characterized by the above.

2. The mass content of active oxygen in the active oxygen carrier oxidant is 19-24%. The repair method according to Claim 1.

3. The active oxygen carrier oxidant contains potassium peroxoborate. The repair method according to Claim 1.

4. The ratio of the usage amount of the active oxygen carrier oxidant to the soil to be repaired is 0.04-4 mol: 1 kg. The repair method according to Claim 1.

5. When the active oxygen carrier oxidant removes polycyclic aromatic hydrocarbons in the soil, it further contains an iron-based chelating agent solution, magnetite or pyrite. The repair method according to Claim 1.

6. The iron-based chelating agent includes iron nitrilotriacetate chelate, sodium ethylenediaminetetraacetate iron chelate, iron ethylenediaminedisuccinate chelate, iron oxalate chelate, iron citrate chelate or iron humate chelate. The repair method according to Claim 1.

7. The molar concentration of the iron-based chelating agent solution is 0.1-0.4 mol / L, and the molar ratio of the active oxygen carrier oxidant to the iron-based chelating agent is 10: 0.1-5. The repair method according to Claim 1.

8. The preparation method of the iron-based chelating agent solution is as follows: Mix a ferrous sulfate solution with a chelating agent solution containing a nitrilotriacetic acid solution, a sodium ethylenediaminetetraacetate solution, an ethylenediaminedisuccinic acid solution, an oxalic acid solution, a citric acid solution or a humic acid solution, perform a chelation reaction, and obtain an iron-based chelating agent solution. The repair method according to Claim 1.

9. The molar concentration of the ferrous sulfate solution is 0.1-0.4 mol / L, and the molar concentration of the chelating agent solution is 0.1-0.4 mol / L. The repair method according to Claim 6.

10. The temperature of the chelation reaction is 10-40 °C, and the time is 0.1-2 h. The repair method according to Claim 6.

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