CN111100647A

CN111100647A - Oxygen-containing anionic heavy metal contaminated soil stabilization remediation agent and soil remediation method

Info

Publication number: CN111100647A
Application number: CN201911128357.7A
Authority: CN
Inventors: 魏勇红; 喻海彬; 黄放; 李少雄; 江湛如; 袁本琦
Original assignee: Hunan Kinglv Environmental Protection Co ltd
Current assignee: Hunan Kinglv Environmental Protection Co ltd
Priority date: 2019-11-18
Filing date: 2019-11-18
Publication date: 2020-05-05
Anticipated expiration: 2039-11-18
Also published as: CN111100647B

Abstract

The embodiment of the invention provides an oxygen anion type heavy metal polluted soil stabilization remediation agent and a soil remediation method, the remediation agent can rapidly, efficiently and permanently stabilize oxygen anion type heavy metals in soil through multiple ways such as oxidation reduction, adsorption and chemical precipitation, and compared with a remediation agent which is only stabilized by an iron-based material, the remediation agent has a better stabilization effect and is not easy to rebound.

Description

Oxygen-containing anionic heavy metal contaminated soil stabilization remediation agent and soil remediation method

Technical Field

The invention belongs to the technical field of soil remediation, and particularly relates to an oxygen-containing anionic heavy metal contaminated soil stabilization remediation agent and a soil remediation method.

Background

Soil is a vital natural resource for guaranteeing sustainable development and is also an important object for ecological and environmental protection.

The common heavy metal pollution elements comprise cadmium, lead, mercury, arsenic, hexavalent chromium, nickel and the like, wherein the cadmium, lead, nickel and other elementsThe migration in soil is mainly in the form of positive charged cations, the migration capability of heavy metals of this type is generally stronger under acidic conditions, and the activity thereof is gradually reduced with the increase of pH value. Therefore, the treatment of the heavy metal contaminated soil is usually a repair treatment by adding an alkaline oxide to increase the pH value of the soil and forming a negatively charged hydroxide colloid to adsorb the negatively charged hydroxide colloid. However, the migration of heavy metals in soil is mainly based on the form of oxygen-containing anions, such as arsenic, antimony, selenium, hexavalent chromium, vanadium, molybdenum, tungsten and other elements. For example arsenic is often H in conventional environments₂AsO₄ ^-、HAsO₄ ^2-、H₂AsO₃ ^-Etc.; antimony is often Sb (OH)^6-、Sb(OH)^4-Etc.; hexavalent chromium is often Cr₂O₇ ^2-、CrO₄ ^2-Exists in the form of (1); tungsten under near neutral and alkaline conditions is often referred to as WO₄ ^2-、HWO₄ ^2-Etc.; molybdenum is often MoO under near neutral and alkaline conditions₄ ^2-Exists in the form of (1); selenium is often SeO₄ ^2-Exists in the form of (1); vanadium mainly expressed as VO₃ ^-Exist in the form of (1). Because the soil is negatively charged, the adsorption capacity of the negatively charged metal is weaker, so that the heavy metal has stronger migration capacity in the environment and larger influence on the environment. Especially when the heavy metals coexist with cationic heavy metals such as lead, zinc, cadmium and the like, the two types of heavy metals are difficult to be simultaneously stabilized to reach the standard.

At present, the commonly used agents for stabilizing and repairing heavy metals containing oxygen anions are mainly iron-based materials, such as reduced iron powder, nano zero-valent iron, ferrous sulfate, ferric trichloride, red mud, ferrihydrite and the like. The material can form iron minerals such as ferrihydrite, goethite and the like after being added into soil, and the mineral components have good adsorption effect on oxygen-containing anionic heavy metals. However, the repairing effect of the iron-based material for repairing the oxygen-containing anion type heavy metal contaminated soil is gradually reduced along with the oxidation of the compound formed by the iron-based material, and even a rebound phenomenon occurs, so that the long-term effect of the repairing effect cannot be ensured.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a stabilizing and repairing agent and a soil repairing method for the soil polluted by the heavy metal containing the oxygen anion type, the repairing agent can rapidly, efficiently and permanently stabilize the heavy metal containing the oxygen anion type in the soil through various ways such as oxidation reduction, adsorption, chemical precipitation and the like, and compared with a repairing agent which is only stabilized by an iron-based material, the stabilizing effect is better and the soil repairing method is not easy to rebound.

The stabilizing and repairing agent for the oxygen-containing anionic heavy metal contaminated soil comprises a solid powder agent A and a liquid agent B; the solid powder medicament A comprises the following preparation raw materials in parts by weight:

hydrotalcite-like compound: 10-30 parts of (A) a water-soluble polymer,

calcium bentonite: 40-60 parts of (A) a water-soluble polymer,

alumina: 5 to 15 parts of (A) a water-soluble polymer,

magnesium oxide: 5-15 parts of a solvent;

the liquid medicament B is a soluble zirconium salt solution.

The stabilizing and repairing agent for the oxygen-containing anionic heavy metal contaminated soil provided by the embodiment of the invention at least has the following beneficial effects:

the remediation agent contains hydrotalcite-like materials, zirconium salt and other materials, can rapidly, efficiently and permanently stabilize oxygen-containing anionic heavy metals in soil through multiple ways such as oxidation reduction, adsorption, chemical precipitation and the like, and compared with a remediation agent which is only stabilized by an iron-based material, the remediation agent provided by the embodiment of the invention has a better stabilization effect and is not easy to rebound.

Wherein the hydrotalcite-like compound is modified by nano zero-valent iron. The preparation method of the nano zero-valent iron modified hydrotalcite-like material comprises the following steps: mixing 100 mesh hydrotalcite powder with 0.02mol/L FeSO₄The solution is added into inert gas N according to the solid-liquid ratio of 1:5₂Was stirred for 15min under the protection of (1), and then the solid portion was separated by centrifugation. Then mixing and stirring the separated solid part and a deionized water-ethanol (1:1) solution at a solid-to-liquid ratio of 1:2.5, and simultaneously dripping 50ml of 0.2mol/L KBH at a speed of 0.5ml/s₄Solution in N₂Stirred for 1h under protection of (1). And then centrifuging, cleaning the solid part with deionized water to remove residual ethanol, centrifuging, placing the solid part into an oven for drying, and finally grinding to obtain the nano zero-valent iron modified hydrotalcite-like material.

According to some embodiments of the invention, the concentration of the soluble zirconium salt solution is 0.01 to 1.0 mol/L.

According to some embodiments of the invention, the soluble zirconium salt solution is at least one of a zirconium oxychloride solution, a zirconium sulfate solution, and a zirconium sulfate solution.

According to the soil remediation method of the second aspect of the embodiment of the invention, the soil remediation method using the oxygen-containing anion type heavy metal contaminated soil stabilization remediation agent comprises the following steps:

s1: crushing the polluted soil, and adjusting the water content of the polluted soil to a first water content;

s2: uniformly mixing the solid powder medicament A with the soil treated in the step S1;

s3: spraying the liquid agent B into the soil treated in the step S2 until the water content of the polluted soil reaches a second water content;

s4: and (4) covering the soil treated in the step (S3) with a film and then curing.

The repairing method provided by the embodiment of the invention has at least the following beneficial effects:

in the repairing method provided by the embodiment of the invention, the repairing agent zirconium salt is added in the form of aqueous solution, so that the defect that the zirconium salt is easy to absorb water and agglomerate and is not easy to mix with soil is effectively avoided, and the addition amount of the zirconium salt can be accurately controlled to reduce the cost.

The addition of the liquid medicament avoids the adjustment of the water content of the soil in the subsequent maintenance stage, and the workload is reduced.

According to some embodiments of the invention, in step S1, the particle size of the crushed soil is less than or equal to 3 cm.

According to some embodiments of the invention, in the step S1, the first water content is 25-30%.

Except for crushing the polluted soil and adjusting the water content of the polluted soil, impurities in the soil need to be removed, so that the repairing medicament can be more uniformly dispersed in the mixing process. After the step S1 is completed, a sampling self-check is required, and the purpose of the sampling self-check is to determine the concentration of the target pollutant in the contaminated soil to be treated and the basic properties of the soil, and to provide a basis for determining the addition amount of the subsequent remediation agent.

According to some embodiments of the present invention, in step S2, the solid powder A is added in an amount of 1 to 10%.

The purpose of step S2 is to preliminarily stabilize the contaminated soil.

According to some embodiments of the invention, in the step S3, the second water content is 35-50%.

In step S3, the concentration and the amount of addition of the liquid chemical B are determined based on the concentration and the water content of the target pollutant in the contaminated soil.

The purpose of step S3 is to secondarily stabilize the contaminated soil.

According to some embodiments of the invention, in step S4, the curing time is 7-10 days.

In step S4, the film used for the coating may be a rain-proof film, and a rain-proof plastic cloth is preferable.

According to some embodiments of the invention, after the step S4, the method further comprises sampling the contaminated soil, and if the content of the oxyanion heavy metal in the soil is not up to the standard, repeating the steps S2-S4.

In the embodiment of the invention, the action mechanism of the solid powder medicament A is as follows: the hydrotalcite-like material is anionic clay, has a special layered structure and physical and chemical properties, and has a strong adsorption effect on anions. The nanometer zero-valent iron has reducibility, can reduce oxygen-containing anion type heavy metal into a low-valent and difficult-to-migrate form, and can form ferrihydrite and other derived minerals with strong adsorption effect on the oxygen-containing anion type heavy metal. Therefore, the nano zero-valent iron modified hydrotalcite-like material has reducibility and strong oxygen-containing anion adsorption capacity, and can avoid the influence of agglomeration on the repair effect of the nano zero-valent iron in the use process. And substances such as calcium bentonite, magnesium oxide, aluminum oxide and the like can have good adsorption and stabilization effects on other cationic heavy metals such as cadmium, lead and the like coexisting in the polluted soil.

The mechanism of action of the liquid agent B: zirconium ion (Zr)⁴⁺) Can form stable insoluble compound with oxyanion, and can carry out deep stabilization treatment on residual oxyanion heavy metal which is not completely adsorbed and stabilized after primary stabilization treatment. Meanwhile, the method can also prevent the partial oxygen-containing anionic heavy metal from being released again due to the oxidation of the hydrated hydroxide of the iron, and ensure the long-acting property of the repairing medicament.

Drawings

FIG. 1 is a process flow diagram of example 2.

Detailed Description

The following are specific examples of the present invention, and the technical solutions of the present invention will be further described with reference to the examples, but the present invention is not limited to the examples.

Example 1

The embodiment provides an oxygen anion type heavy metal contaminated soil stabilization and remediation agent, which comprises a solid powder agent A and a liquid agent B; the solid powder medicament A comprises the following preparation raw materials in parts by weight:

hydrotalcite-like compound: 10-30 parts of calcium bentonite: 40-60 parts of alumina: 5-15 parts of magnesium oxide: 5-15 parts of a solvent;

the liquid medicament B is soluble zirconium salt solution.

Wherein the hydrotalcite-like compound is modified by nano zero-valent iron. The preparation method of the nano zero-valent iron modified hydrotalcite-like material comprises the following steps: mixing 100 mesh hydrotalcite powder with 0.02mol/L FeSO₄The solution is added into inert gas N according to the solid-liquid ratio of 1:5₂Under the protection of (1), stirring for 15min, and centrifugingThe solid fraction was removed. Then mixing and stirring the separated solid part and a deionized water-ethanol (1:1) solution at a solid-to-liquid ratio of 1:2.5, and simultaneously dripping 50ml of 0.2mol/L KBH at a speed of 0.5ml/s₄Solution in N₂Stirred for 1h under protection of (1). And then centrifuging, cleaning the solid part with deionized water to remove residual ethanol, centrifuging, placing the solid part into an oven for drying, and finally grinding to obtain the nano zero-valent iron modified hydrotalcite-like material.

The concentration of the soluble zirconium salt solution is 0.01-1.0 mol/L. The soluble zirconium salt solution is at least one of a zirconium oxychloride solution, a zirconium sulfate solution, and a zirconium oxysulfate solution.

Example 2

The present example provides a soil remediation method using the oxygen-containing anionic heavy metal contaminated soil stabilization remediation agent of example 1, the flow chart is shown in fig. 1, and the steps include:

In step S1, the grain size of the soil after crushing treatment is less than or equal to 3 cm. The first water content is 25-30%.

In step S2, the amount of solid powder A added is 1 to 10%. The purpose of step S2 is to preliminarily stabilize the contaminated soil.

In step S3, the second water content is 35-50%. The concentration and the addition amount of the liquid agent B are determined according to the concentration and the water content of the target pollutant in the polluted soil. The purpose of step S3 is to secondarily stabilize the contaminated soil.

In step S4, the curing time is 7-10 days. The film used for the covering film may be a rain-proof film, and a rain-proof plastic cloth is preferable.

And (5) after the step S4, sampling and detecting the polluted soil, and repeating the steps S2-S4 if the content of the oxygen-containing anionic heavy metal in the soil does not reach the standard.

Example 3

In this example, contaminated soil was treated with the remediation agent of example 1 and the remediation method of example 2. The specific situation is as follows:

the polluted soil is taken from cold water river tin mines, and the main pollution factors are antimony and arsenic. Through detection and analysis, the basic properties of the contaminated soil are shown in table 1.

TABLE 1 basic Properties of contaminated soil

The method comprises the following steps:

(1) and (3) pretreating 1kg of the polluted soil, wherein the pretreatment comprises air drying, crushing and sieving, so that the particle size of the pretreated soil is less than or equal to 3cm, and the water content is kept at about 30%. Meanwhile, sampling analysis is carried out to detect the basic properties of the polluted soil (the detection results are shown in table 1).

(2) According to the basic properties of the polluted soil shown in the table 1, the adding mass of the solid powder medicament A is determined to be 5% of the soil to be repaired, the preparation concentration of the liquid medicament B is 0.1mol/L, and the adding amount is 200 ml. Wherein the solid powder medicament A comprises the following components in percentage by weight: 15 parts of hydrotalcite-like compound, 60 parts of calcium bentonite, 10 parts of magnesium oxide and 15 parts of aluminum oxide.

(3) According to the determined dosage of the medicament, 50g of the solid powder medicament A and 1kg of the pretreated polluted soil are uniformly mixed.

(4) And spraying a liquid medicament B into the soil subjected to the primary stabilization treatment for secondary stabilization treatment, wherein the concentration of the medicament B is 0.1mol/L, and the spraying amount is 200 ml. And after spraying, uniformly stirring the soil.

(5) And covering a layer of preservative film on the soil subjected to the secondary stabilization treatment to isolate the soil from the outside air, and placing the soil in a constant-temperature constant-humidity incubator for maintenance for 7 days.

The soil after curing was sampled, water leaching was performed with reference to "solid waste leaching toxicity leaching method horizontal oscillation method", and the leachate was examined, with the examination results shown in table 2.

Evaluation standard of repairing effect: the leaching concentration of the target pollutant in the repaired soil meets the III-class water standard in the surface water quality standard.

TABLE 2 Leaching concentration of As and Sb in soil after stabilization and restoration

Parameter(s)	pH	Leaching concentration (mg/L) of As	Leaching concentration (mg/L) of Sb
				Soil after restoration	7.37	0.0011	0.0036
Surface water III	6-9	0.05	0.005

According to the detection results in the table 2, the remediation agent and the remediation method have good remediation effects on the heavy metal contaminated soil containing arsenic and antimony, and can effectively stabilize arsenic and antimony in the soil to achieve the soil remediation standard.

Example 4

the contaminated soil is obtained from the contaminated soil of a certain smeltery in Cili county, and the main contamination factors are arsenic, manganese and nickel. The basic properties of the contaminated soil are shown in table 3.

TABLE 3 basic Properties of the contaminated soil

The method for stabilizing and repairing the polluted soil comprises the following steps:

and (3) pretreating the polluted soil, including air drying, crushing, sieving, removing impurities and the like. The grain diameter of the pretreated soil is less than or equal to 3cm, and the water content is kept at about 30 percent.

And (3) taking 500g of the pretreated polluted soil, and uniformly mixing the solid powder medicament A with the pretreated polluted soil, wherein the addition amount of the solid powder medicament is 3% of the mass of the polluted soil to be treated. Wherein, the solid powder medicament A comprises the following components in percentage by weight: 10 parts of hydrotalcite-like compound, 60 parts of calcium bentonite, 15 parts of magnesium oxide and 15 parts of aluminum oxide.

And spraying the liquid medicament B into the soil mixed with the solid powder medicament A, and uniformly stirring. Wherein the concentration of the liquid medicament B is 0.05mol/L, and the addition amount is 100 ml.

And (3) maintaining the stabilized polluted soil, and separating the soil from the outside by using a preservative film to prevent water evaporation and air oxidation. Wherein the curing time is 7 days.

The soil after curing was sampled, and leaching experiments were performed on the samples according to the "solid waste leaching toxicity leaching method horizontal oscillation method" (HJ557-2010), and the results of leachate detection are shown in table 4:

TABLE 4 detection results of soil leachate after stabilization treatment

Parameter(s)	pH	Arsenic (mg/L)	Manganese (mg/L)	Nickel (mg/L)
					Treated soil	8.28	0.0096	0.023	0.012
Surface water III	6-9	0.05	0.1	0.02

According to the detection results in table 4, the leaching values of various indexes in the contaminated soil repaired by the repairing agent and the repairing method in the embodiment of the invention meet the corresponding repairing requirements. The results show that the repair agent not only can stabilize arsenic containing oxygen anions, but also has good repair effect on cationic manganese and nickel.

Example 5

the contaminated soil is taken from Changsha chromium salt works, and the main pollution factor is hexavalent chromium. The basic properties of the contaminated soil are shown in table 5.

TABLE 5 basic Properties of contaminated soil

The polluted soil is repaired by adopting the repairing agent and the repairing method of the embodiment of the invention, and the repairing method comprises the following steps:

and (3) pretreating the polluted soil, wherein the pretreatment comprises air drying, crushing, sieving and impurity removal, so that the particle size of the pretreated polluted soil is less than or equal to 3cm, and the water content is kept at about 30%.

1000g of the pretreated contaminated soil is taken for a stabilization test, 70g of the solid powder medicament A is added into 1000g of the contaminated soil, and the mixture is uniformly mixed. Wherein, the solid powder medicament A comprises the following components in percentage by weight: 20 parts of hydrotalcite-like compound, 60 parts of calcium bentonite, 10 parts of magnesium oxide and 10 parts of aluminum oxide.

200ml of liquid agent B is sprinkled into the contaminated soil mixed with solid powder agent A, and the mixture is stirred and mixed uniformly. Wherein the concentration of the liquid medicament B is 0.1 mol/L.

And (3) placing the stabilized soil in a constant-temperature constant-humidity incubator for maintenance, and meanwhile, covering a preservative film to isolate the soil from the outside so as to prevent water evaporation and air oxidation. The curing time was 7 days.

And (4) sampling and analyzing the cured soil, and carrying out leaching experiments on the samples according to a solid waste leaching toxicity leaching method horizontal oscillation method (HJ 557-2010).

And (4) placing the residual soil after sampling in a fume hood for long-term experimental observation, spraying 200ml of deionized water into the soil every two weeks, and uniformly mixing. Samples were taken at 1 month, 2 months, 3 months, 6 months, and 1 year after completion of the maintenance and analyzed.

The results are shown in Table 6:

TABLE 6 soil leaching test results

According to the detection results in table 6, the remediation agent and the remediation method in the embodiment of the invention have a good effect on stabilizing hexavalent chromium in chromium-contaminated soil. After the soil is stabilized and repaired, the leaching concentration of hexavalent chromium in the soil is sharply reduced to reach a repairing target value below. Meanwhile, the long-acting experiment shows that the one-year tracking experiment shows that the pH value of the restored soil and the leaching concentration of hexavalent chromium are very stable, the corresponding restoration target is met, and the rebound phenomenon does not occur. Therefore, the repairing medicament in the embodiment of the invention has good long-term effectiveness.

Example 6

The polluted soil is taken from a certain newly-changed antimony smelting plant area, the main pollution factor is antimony, the polluted soil is alkaline, the pH value is 9.86, the total antimony content is 186mg/kg, and the water leaching concentration of the antimony is 1.25 mg/L.

And (3) pretreating the polluted soil, wherein the pretreatment comprises air drying, crushing, impurity removing and sieving, so that the particle size of the soil to be treated is less than or equal to 3cm, and the water content is kept at about 30%.

2000g of the pretreated polluted soil is averagely divided into two parts which are respectively named as an experimental group and a control group. The experimental group adopts the repairing agent and the repairing method in the invention, and the control group adopts common iron-based materials (mixture of ferrous sulfate, reduced iron powder and calcium oxide) as the repairing agent.

And (3) mixing the remediation agent with the contaminated soil, and fully and uniformly stirring, wherein the addition amount of the solid powder agent A in the experimental group is 3%, and the use amount of the iron-based material remediation agent in the control group is 5%. Wherein, the solid powder medicament A comprises the following components in percentage by weight: 15 parts of hydrotalcite-like compound, 55 parts of calcium bentonite, 15 parts of magnesium oxide and 15 parts of aluminum oxide.

The liquid agent B was sprayed to the test group at a concentration of 0.5mol/L in an amount of 200ml, and stirred and mixed well.

200ml of deionized water was sprayed onto the control group, and the mixture was stirred and mixed well.

And the stabilized soil is maintained, and the soil is isolated from the outside by adopting a preservative film, so that air oxidation is avoided. The curing time was 7 days.

And (5) sampling and checking, wherein the samples are respectively taken after being maintained for 7 days, 1 month, 2 months, 3 months, 6 months and 1 year.

The extracted sample was subjected to water immersion treatment, and the leachate was analyzed and detected, with the detection results shown in table 7:

TABLE 7 soil water leaching solution test results

According to the detection results in table 7, the soil repaired by the repairing agent and the repairing method in the embodiment of the invention has a very stable pH value of about 7. Meanwhile, the leaching concentration of antimony in the soil is lower than a repair target value of 0.005mg/L, and the antimony is still stable after 1 year of tracking detection. In the control group, the pH value of the soil leachate increases with time. Meanwhile, the leaching concentration of antimony in the control group is always higher than the target repair value, and the repair does not reach the standard. Further, it was found by long-term follow-up examination that the leaching concentration of antimony in the control group suddenly increased to a large extent at the sixth month, and the repairing effect was deteriorated.

Therefore, compared with the conventional iron-based material, the remediation agent and the remediation method provided by the embodiment of the invention have better effect and long-term stability on remediation of the oxygen-containing anionic heavy metal contaminated soil.

The embodiments described above are exemplary and do not represent the full nature and scope of the invention. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An oxygen anion type heavy metal contaminated soil stabilization remediation agent is characterized by comprising a solid powder agent A and a liquid agent B; the solid powder medicament A comprises the following preparation raw materials in parts by weight:

hydrotalcite-like compound: 10-30 parts of (A) a water-soluble polymer,

calcium bentonite: 40-60 parts of (A) a water-soluble polymer,

alumina: 5 to 15 parts of (A) a water-soluble polymer,

magnesium oxide: 5-15 parts of a solvent;

the liquid medicament B is a soluble zirconium salt solution.

2. The stabilizing and repairing agent for oxygen-containing anionic heavy metal contaminated soil according to claim 1, wherein the concentration of the soluble zirconium salt solution is 0.01-1.0 mol/L.

3. The agent for stabilizing and remediating oxygen-containing anionic heavy metal contaminated soil according to claim 2, wherein the soluble zirconium salt solution is at least one of a zirconium oxychloride solution, a zirconium sulfate solution, and a zirconium sulfate solution.

4. A soil remediation method using the oxygen-containing anionic heavy metal contaminated soil stabilization remediation agent as claimed in any one of claims 1 to 3, characterized by comprising the steps of:

5. The soil remediation method of claim 4 wherein in step S1, the size of the crushed soil is 3cm or less.

6. The soil remediation method of claim 4, wherein in step S1, the first moisture content is 25% to 30%.

7. The soil remediation method of claim 4, wherein in step S2, the solid powder agent A is added in an amount of 1-10%.

8. The soil remediation method of claim 4, wherein in step S3, the second moisture content is 35% to 50%.

9. The soil remediation method of claim 4, wherein in step S4, the curing time is 7 to 10 days.

10. The soil remediation method of claim 4 further comprising, after step S4, sampling the contaminated soil and repeating steps S2-S4 if the content of oxyanion-type heavy metals in the soil is not within the predetermined range.