Remediation agent and remediation method for chromium-contaminated soil

Abstract

The invention discloses a remediation agent for chromium-contaminated soil and a remediation method. The remediation agent comprises the following components: a reducing agent, a precipitator, wheat bran, an organic fertilizer, sludge and a mineral material, the reducing agent is one or any composition of more than two of a sulfenyl compound, hydrazine hydrate, ferrous sulfate, ferrous chloride, sodium hydrogen sulfite, sodium pyrosulfite, sodium thiosulfate, sodium sulfite and sodium hydrosulfite, and the precipitating agent is composed of a sulfenyl compound and phosphate. The sulfenyl compound is one or any composition of more than two of sodium sulfide, ammonium sulfide, sodium polysulfide, ferrous sulfide, potassium sulfide, potassium polysulfide and calcium sulfide, and the phosphate is one or any composition of more than two of monopotassium phosphate, monocalcium phosphate, phosphoric acid, diammonium hydrogen phosphate or disodium hydrogen phosphate. Through the physicochemical synergistic effect of reduction, precipitation and adsorption, the long-term stabilization effect on heavy metal ions and toxic organic pollutants in soil is greatly enhanced, and the soil remediation effect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation, and in particular to a remediation agent and a remediation method for chromium-contaminated soil. Background Art

[0002] Chromium is a silvery white, brittle and hard heavy metal. In recent years, with the development of industry, chromium and its compounds have been widely used as important raw materials in metallurgy, electroplating, leather making, paint, pigment, printing and dyeing, pharmaceutical and other industries. Chromium often exists in two stable valence states in natural soil-water systems: hexavalent chromium Cr(VI) and trivalent chromium Cr(III). Trivalent chromium salts can be hydrolyzed in neutral or weak alkaline solutions to produce chromium hydroxide that is insoluble in water and precipitates in the water body to form bottom mud. Therefore, trivalent chromium in nature is mainly adsorbed on solid substances and exists in sediments. Hexavalent chromium is mostly soluble in water, and the toxicity of chromium mainly comes from hexavalent chromium. Hexavalent chromium is a "trivalent" pollutant that has been confirmed by research. It is mainly in the form of CrO4 in soil and groundwater. 2- and HCrO 4- It exists in the form of chromium, is highly soluble, and is easy to migrate. It is identified as one of the most harmful pollutants in the environment and must be effectively controlled. At present, chemical reduction is mainly used for chromium pollution in soil: chemical reduction technology is to inject a reducing agent to react chemically with hexavalent chromium to reduce it to trivalent chromium with less toxicity. Commonly used reducing agents include zero-valent iron powder and ferrous sulfate. Zero-valent iron powder is usually ground into tiny particles, or even nano-particles, to better react with pollutants. Ferrous sulfate has a strong reducing property and can reduce hexavalent chromium to trivalent chromium, and by adjusting the pH value, it can generate a stable hydroxide precipitate. Although the existing chemical reduction technology can reduce hexavalent chromium to trivalent chromium, the repair effect is poor and the stability is low. In addition, due to the fast migration rate of hexavalent chromium in the soil, it has a great impact on the environment and human health. In addition, the repair cost of the existing chemical reduction technology is high, and the amount of the repair agent cannot be controlled, and a large amount of the repair agent is often required. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a repair agent and a repair method for chromium-contaminated soil with good repair effect, controllable agent dosage and stable effect.

[0004] The technical solution of the present invention is as follows:

[0005] A repair agent for chromium-contaminated soil, the components of which include a reducing agent, a precipitating agent, wheat bran, organic fertilizer, sludge and mineral materials, the reducing agent is one or a combination of two or more of a sulfide-based compound, hydrazine hydrate, ferrous sulfate, ferrous chloride, sodium bisulfite, sodium pyrosulfite, sodium thiosulfate, sodium sulfite and sodium dithionite, the precipitating agent is composed of a sulfide-based compound and a phosphate, the sulfide-based compound is one or a combination of two or more of sodium sulfide, ammonium sulfide, sodium polysulfide, ferrous sulfide, potassium sulfide, potassium polysulfide and calcium sulfide, and the phosphate is one or a combination of two or more of potassium dihydrogen phosphate, calcium dihydrogen phosphate, phosphoric acid, diammonium hydrogen phosphate or disodium hydrogen phosphate.

[0006] Furthermore, the mass percentage of each component is 5-25% of reducing agent, 25-55% of sulfur-based compound, 1-5% of phosphate, 6-12% of wheat bran, 5-10% of organic fertilizer, 4-8% of sludge, and 5-10% of mineral material.

[0007] Furthermore, the sludge is activated sludge from a municipal sewage plant.

[0008] A method for remediating chromium-contaminated soil comprises the following steps:

[0009] (1) Setting up detection holes and injection wells on the contaminated soil to be treated;

[0010] (2) Sampling through the detection hole to detect the total content of hexavalent chromium in the contaminated soil to be treated;

[0011] (3) Calculate the amount of repair agent required based on the total content of hexavalent chromium;

[0012] (4) a liquid remediation agent is obtained by mixing the reducing agent, precipitating agent, wheat bran, organic fertilizer, sludge and mineral materials, and then injected into the contaminated soil to be treated through an injection well according to the required amount, so that the remediation agent fully penetrates into the entire area of ​​the contaminated soil to be treated, and the contaminated soil is repaired, and at the same time, water is evenly sprayed on the contaminated soil to be treated through a spray system;

[0013] (5) Covering the surface of the contaminated soil to be treated with moisturizing materials for sealing and maintenance;

[0014] (6) After a period of sealed maintenance, samples are taken through the detection holes to detect the content of hexavalent chromium in the contaminated soil to be treated to see whether the remediation goal has been achieved;

[0015] (7) If the restoration target is not reached, repeat steps (1) to (6) until the restoration target is reached.

[0016] In step (2), the total content of hexavalent chromium is inferred from the mass of the sample and the content of hexavalent chromium in the sample by the mass of the entire contaminated soil to be treated.

[0017] In step (3), the ratio of the total content of hexavalent chromium to the repair agent is 10:1.

[0018] In step (4), the water content of the contaminated soil to be treated must be no less than 20%.

[0019] In step (5), the moisturizing material is a high-density polyethylene anti-seepage membrane.

[0020] In step (6), the curing time is not less than 5 days.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] The components of the repair agent provided by the present invention include a reducing agent, a sulfur-based compound, a phosphate, wheat bran, an organic fertilizer, sludge and a mineral material; wherein the reducing agent is one or a combination of two or more of the sulfur-based compound, hydrazine hydrate, ferrous sulfate, ferrous chloride, sodium bisulfite, sodium pyrosulfite, sodium thiosulfate, sodium sulfite and sodium dithionite, which can fully reduce the hexavalent chromium in the soil to trivalent chromium, greatly reduce the toxicity of the soil, and reduce its risk to the environment; the sulfur-based compound and the phosphate can combine with the heavy metal ions in the soil to produce sulfide precipitation and phosphate precipitation, and reduce the migration risk of heavy metal ions; the addition of wheat bran and organic fertilizer can improve the fertility of the soil and effectively restore the soil function; the activated sludge contains a complex microbial system, which can utilize the carbon source in the soil and the organic components such as the added organic fertilizer to achieve the reduction and adsorption of heavy metal chromium, and the mineral material has a strong adsorption characteristic, which can effectively reduce the leaching of heavy metal ions and toxic organic matter, thereby achieving the dual stabilization of physical and chemical properties, and reducing the leaching of heavy metal ions and toxic organic matter to the greatest extent. The present invention greatly enhances the long-term stabilization effect of heavy metal ions and toxic organic pollutants in the soil through the physical and chemical synergistic effects of reduction, precipitation and adsorption, has a good soil remediation effect, and has a good early application period. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] In order to illustrate the technical solution of the present invention, a specific embodiment is provided below for illustration.

[0025] Example 1

[0026] This embodiment provides a repair agent for chromium-contaminated soil, and its components include a reducing agent, a precipitating agent, wheat bran, an organic fertilizer, sludge and a mineral material. Among them, the reducing agent is one or more of a sulfur-based compound, hydrazine hydrate, ferrous sulfate, ferrous chloride, sodium bisulfite, sodium pyrosulfite, sodium thiosulfate, sodium sulfite, and sodium dithionite; the precipitating agent is composed of a sulfur-based compound and a phosphate, the sulfur-based compound is one or more of a sodium sulfide, ammonium sulfide, sodium polysulfide, ferrous sulfide, potassium sulfide, potassium polysulfide, and calcium sulfide, and the phosphate is one or more of a potassium dihydrogen phosphate, calcium dihydrogen phosphate, phosphoric acid, diammonium hydrogen phosphate or disodium hydrogen phosphate; the particle size of the wheat bran is less than or equal to 2 mm; the particle size of the organic fertilizer is less than or equal to 1 mm; and the sludge is activated sludge from a municipal sewage plant.

[0027] In this embodiment, the mass percentage of each component is 5% of reducing agent, 25% of sulfur-based compound, 1% of phosphate, 6% of wheat bran, 5% of organic fertilizer, 4% of sludge, and 5% of mineral material.

[0028] The repair method includes the following steps:

[0029] (1) Setting up detection holes and injection wells on the contaminated soil to be treated;

[0030] (2) sampling through the detection hole to detect the total content of hexavalent chromium in the contaminated soil to be treated, and specifically inferring the total content of hexavalent chromium from the overall mass of the contaminated soil to be treated based on the mass of the sample and the content of hexavalent chromium in the sample;

[0031] (3) The amount of repair agent required is calculated based on the total content of hexavalent chromium. The ratio of the total content of hexavalent chromium to the repair agent is 10:1. This can avoid the waste of repair agent caused by excessive use of the repair agent and achieve the effect of controllable agent.

[0032] (4) a liquid remediation agent is obtained by mixing the reducing agent, precipitating agent, wheat bran, organic fertilizer, sludge and mineral materials, and then injected into the contaminated soil to be treated through an injection well according to the required amount, so that the remediation agent fully penetrates into the entire area of ​​the contaminated soil to be treated, and the contaminated soil is repaired. At the same time, water is evenly sprayed on the contaminated soil to be treated through a spray system, so that the water content of the contaminated soil to be treated is not less than 20%;

[0033] (5) Covering the surface of the contaminated soil to be treated with a moisturizing material for sealing and curing. The moisturizing material may be a high-density polyethylene anti-seepage membrane;

[0034] (6) Sealing and curing for no less than 5 days to ensure that the agent in the soil reacts fully with the chromium pollutants. After sealing and curing, sampling is performed through the detection hole to detect the content of hexavalent chromium in the contaminated soil to be treated to see whether the remediation goal has been achieved;

[0035] (7) If the repair target is not reached, repeat steps (1) to (6) until the repair target is reached. Note: This step is generally not reached because the required amount of repair agent has been calculated in step (3). This step is to avoid mistakes.

[0036] Example 2

[0037] This embodiment provides a repair agent for chromium-contaminated soil, and its components include a reducing agent, a precipitating agent, wheat bran, an organic fertilizer, sludge and a mineral material. Among them, the reducing agent is one or more of a sulfur-based compound, hydrazine hydrate, ferrous sulfate, ferrous chloride, sodium bisulfite, sodium pyrosulfite, sodium thiosulfate, sodium sulfite, and sodium dithionite; the precipitating agent is composed of a sulfur-based compound and a phosphate, the sulfur-based compound is one or more of a sodium sulfide, ammonium sulfide, sodium polysulfide, ferrous sulfide, potassium sulfide, potassium polysulfide, and calcium sulfide, and the phosphate is one or more of a potassium dihydrogen phosphate, calcium dihydrogen phosphate, phosphoric acid, diammonium hydrogen phosphate or disodium hydrogen phosphate; the particle size of the wheat bran is less than or equal to 2 mm; the particle size of the organic fertilizer is less than or equal to 1 mm; and the sludge is activated sludge from a municipal sewage plant.

[0038] In this embodiment, the mass percentage of each component is 10% of reducing agent, 35% of sulfur-based compound, 2% of phosphate, 8% of wheat bran, 6% of organic fertilizer, 5% of sludge, and 6% of mineral material.

[0039] The repair method includes the following steps:

[0040] (1) Setting up detection holes and injection wells on the contaminated soil to be treated;

[0041] (2) sampling through the detection hole to detect the total content of hexavalent chromium in the contaminated soil to be treated, and specifically inferring the total content of hexavalent chromium from the overall mass of the contaminated soil to be treated based on the mass of the sample and the content of hexavalent chromium in the sample;

[0042] (3) The amount of repair agent required is calculated based on the total content of hexavalent chromium. The ratio of the total content of hexavalent chromium to the repair agent is 10:1. This can avoid the waste of repair agent caused by excessive use of the repair agent and achieve the effect of controllable agent.

[0043] (4) a liquid remediation agent is obtained by mixing the reducing agent, precipitating agent, wheat bran, organic fertilizer, sludge and mineral materials, and then injected into the contaminated soil to be treated through an injection well according to the required amount, so that the remediation agent fully penetrates into the entire area of ​​the contaminated soil to be treated, and the contaminated soil is repaired. At the same time, water is evenly sprayed on the contaminated soil to be treated through a spray system, so that the water content of the contaminated soil to be treated is not less than 20%;

[0044] (5) Covering the surface of the contaminated soil to be treated with a moisturizing material for sealing and curing. The moisturizing material may be a high-density polyethylene anti-seepage membrane;

[0045] (6) The sealed maintenance shall be carried out for no less than 5 days to ensure that the reagents in the soil react fully with the chromium pollutants. After the sealed maintenance, the content of hexavalent chromium in the contaminated soil to be treated shall be tested through the detection hole to see whether the remediation goal has been achieved;

[0046] (7) If the repair target is not reached, repeat steps (1) to (6) until the repair target is reached. Note: This step is generally not reached because the required amount of repair agent has been calculated in step (3). This step is to avoid mistakes.

[0047] Example 3

[0048] This embodiment provides a repair agent for chromium-contaminated soil, and its components include a reducing agent, a precipitating agent, wheat bran, an organic fertilizer, sludge and a mineral material. Among them, the reducing agent is one or more of a sulfur-based compound, hydrazine hydrate, ferrous sulfate, ferrous chloride, sodium bisulfite, sodium pyrosulfite, sodium thiosulfate, sodium sulfite, and sodium dithionite; the precipitating agent is composed of a sulfur-based compound and a phosphate, the sulfur-based compound is one or more of a sodium sulfide, ammonium sulfide, sodium polysulfide, ferrous sulfide, potassium sulfide, potassium polysulfide, and calcium sulfide, and the phosphate is one or more of a potassium dihydrogen phosphate, calcium dihydrogen phosphate, phosphoric acid, diammonium hydrogen phosphate or disodium hydrogen phosphate; the particle size of the wheat bran is less than or equal to 2 mm; the particle size of the organic fertilizer is less than or equal to 1 mm; and the sludge is activated sludge from a municipal sewage plant.

[0049] In this embodiment, the mass percentage of each component is 20% of reducing agent, 45% of sulfur-based compound, 4% of phosphate, 10% of wheat bran, 8% of organic fertilizer, 7% of sludge, and 8% of mineral material.

[0050] The repair method includes the following steps:

[0051] (1) Setting up detection holes and injection wells on the contaminated soil to be treated;

[0052] (2) sampling through the detection hole to detect the total content of hexavalent chromium in the contaminated soil to be treated, and specifically inferring the total content of hexavalent chromium from the overall mass of the contaminated soil to be treated based on the mass of the sample and the content of hexavalent chromium in the sample;

[0053] (3) The amount of repair agent required is calculated based on the total content of hexavalent chromium. The ratio of the total content of hexavalent chromium to the repair agent is 10:1. This can avoid the waste of repair agent caused by excessive use of the repair agent and achieve the effect of controllable agent.

[0054] (4) a liquid remediation agent is obtained by mixing the reducing agent, precipitating agent, wheat bran, organic fertilizer, sludge and mineral materials, and then injected into the contaminated soil to be treated through an injection well according to the required amount, so that the remediation agent fully penetrates into the entire area of ​​the contaminated soil to be treated, and the contaminated soil is repaired. At the same time, water is evenly sprayed on the contaminated soil to be treated through a spray system, so that the water content of the contaminated soil to be treated is not less than 20%;

[0055] (5) Covering the surface of the contaminated soil to be treated with a moisturizing material for sealing and curing. The moisturizing material may be a high-density polyethylene anti-seepage membrane;

[0056] (6) The sealed curing shall be carried out for no less than 5 days to ensure that the reagents in the soil react fully with the chromium pollutants. After the sealed curing, the content of hexavalent chromium in the contaminated soil to be treated shall be tested through the detection hole to see whether the remediation goal has been achieved;

[0057] (7) If the repair target is not reached, repeat steps (1) to (6) until the repair target is reached. Note: This step is generally not reached because the required amount of repair agent has been calculated in step (3). This step is to avoid mistakes.

[0058] Example 4

[0059] This embodiment provides a repair agent for chromium-contaminated soil, and its components include a reducing agent, a precipitating agent, wheat bran, an organic fertilizer, sludge and a mineral material. Among them, the reducing agent is one or more of a sulfur-based compound, hydrazine hydrate, ferrous sulfate, ferrous chloride, sodium bisulfite, sodium pyrosulfite, sodium thiosulfate, sodium sulfite, and sodium dithionite; the precipitating agent is composed of a sulfur-based compound and a phosphate, the sulfur-based compound is one or more of a sodium sulfide, ammonium sulfide, sodium polysulfide, ferrous sulfide, potassium sulfide, potassium polysulfide, and calcium sulfide, and the phosphate is one or more of a potassium dihydrogen phosphate, calcium dihydrogen phosphate, phosphoric acid, diammonium hydrogen phosphate or disodium hydrogen phosphate; the particle size of the wheat bran is less than or equal to 2 mm; the particle size of the organic fertilizer is less than or equal to 1 mm; and the sludge is activated sludge from a municipal sewage plant.

[0060] In this embodiment, the mass percentage of each component is 25% of reducing agent, 55% of sulfur-based compound, 5% of phosphate, 12% of wheat bran, 10% of organic fertilizer, 8% of sludge, and 10% of mineral material.

[0061] The repair method includes the following steps:

[0062] (1) Setting up detection holes and injection wells on the contaminated soil to be treated;

[0063] (2) sampling through the detection hole to detect the total content of hexavalent chromium in the contaminated soil to be treated, and specifically inferring the total content of hexavalent chromium from the overall mass of the contaminated soil to be treated based on the mass of the sample and the content of hexavalent chromium in the sample;

[0064] (3) The amount of repair agent required is calculated based on the total content of hexavalent chromium. The ratio of the total content of hexavalent chromium to the repair agent is 10:1. This can avoid the waste of repair agent caused by excessive use of the repair agent and achieve the effect of controllable agent.

[0065] (4) a liquid remediation agent is obtained by mixing the reducing agent, precipitating agent, wheat bran, organic fertilizer, sludge and mineral materials, and then injected into the contaminated soil to be treated through an injection well according to the required amount, so that the remediation agent fully penetrates into the entire area of ​​the contaminated soil to be treated, and the contaminated soil is repaired. At the same time, water is evenly sprayed on the contaminated soil to be treated through a spray system, so that the water content of the contaminated soil to be treated is not less than 20%;

[0066] (5) Covering the surface of the contaminated soil to be treated with a moisturizing material for sealing and curing. The moisturizing material may be a high-density polyethylene anti-seepage membrane;

[0067] (6) The sealed curing shall be carried out for no less than 5 days to ensure that the reagents in the soil react fully with the chromium pollutants. After the sealed curing, the content of hexavalent chromium in the contaminated soil to be treated shall be tested through the detection hole to see whether the remediation goal has been achieved;

[0068] (7) If the repair target is not reached, repeat steps (1) to (6) until the repair target is reached. Note: This step is generally not reached because the required amount of repair agent has been calculated in step (3). This step is to avoid mistakes.

[0069] The test results are as follows:

[0070]

[0071] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A remediation agent for chromium-contaminated soil, characterized in that: Its components include reducing agents, precipitating agents, wheat bran, organic fertilizers, sludge and mineral materials. The reducing agent is one or a combination of two or more of sulfur-based compounds, hydrazine hydrate, ferrous sulfate, ferrous chloride, sodium bisulfite, sodium pyrosulfite, sodium thiosulfate, sodium sulfite and sodium dithionite. The precipitating agent is composed of sulfur-based compounds and phosphates. The sulfur-based compound is one or a combination of two or more of sodium sulfide, ammonium sulfide, sodium polysulfide, ferrous sulfide, potassium sulfide, potassium polysulfide and calcium sulfide. The phosphate is one or a combination of two or more of potassium dihydrogen phosphate, calcium dihydrogen phosphate, phosphoric acid, diammonium hydrogen phosphate or disodium hydrogen phosphate.

2. The remediation agent for chromium-contaminated soil according to claim 1, characterized in that: The mass percentage of each component is 5-25% of reducing agent, 25-55% of sulfur-based compound, 1-5% of phosphate, 6-12% of wheat bran, 5-10% of organic fertilizer, 4-8% of sludge and 5-10% of mineral material.

3. A remediation agent for chromium-contaminated soil according to claim 1 or 2, characterized in that: The sludge is activated sludge from a municipal sewage plant.

4. A method for remediating chromium-contaminated soil, characterized in that: The following steps are involved: (1) Setting up detection holes and injection wells on the contaminated soil to be treated; (2) Sampling through the detection hole to detect the total content of hexavalent chromium in the contaminated soil to be treated; (3) Calculate the amount of repair agent required based on the total content of hexavalent chromium; (4) a liquid remediation agent is obtained by mixing the reducing agent, precipitating agent, wheat bran, organic fertilizer, sludge and mineral materials, and then injected into the contaminated soil to be treated through an injection well according to the required amount, so that the remediation agent fully penetrates into the entire area of ​​the contaminated soil to be treated, and the contaminated soil is repaired, and at the same time, water is evenly sprayed on the contaminated soil to be treated through a spray system; (5) Covering the surface of the contaminated soil to be treated with moisturizing materials for sealing and maintenance; (6) After a period of sealed maintenance, samples are taken through the detection holes to detect the content of hexavalent chromium in the contaminated soil to be treated to see whether the remediation goal has been achieved; (7) If the restoration target is not reached, repeat steps (1) to (6) until the restoration target is reached.

5. A method for remediating chromium-contaminated soil according to claim 4, characterized in that: In step (2), the total content of hexavalent chromium is inferred from the mass of the sample and the content of hexavalent chromium in the sample by the mass of the entire contaminated soil to be treated.

6. A method for remediating chromium-contaminated soil according to claim 4, characterized in that: In step (3), the ratio of the total content of hexavalent chromium to the repair agent is 10:

1.

7. A method for remediating chromium-contaminated soil according to claim 4, characterized in that: In step (4), the water content of the contaminated soil to be treated must be no less than 20%.

8. A method for remediating chromium-contaminated soil according to claim 4, characterized in that: In step (5), the moisturizing material is a high-density polyethylene anti-seepage membrane.

9. A method for remediating chromium-contaminated soil according to claim 4, characterized in that: In step (6), the curing time is not less than 5 days.

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