JP2003159583A - Treatment method for heavy metal polluted soil or waste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recover an expensive chelating agent to reutilize the same, to certainly prevent the elution of heavy metals, to hold the elution of heavy metals to an environmental standard value or less over a long period of time, to reduce the amount of use of the expensive chelating agent and to obtain high heavy metal removing effect by a reduced use amount of the chelating agent, in a treatment method for heavy metal polluted soil or waster, removing heavy metals in soil or waste polluted with heavy metals by bringing a chelating agent solution into contact with the polluted soil or waste. <P>SOLUTION: The solution after the contact with the polluted soil or waste is recovered and the recovered solution is brought into contact with an H-type cation exchange resin to remove heavy metals in the solution to regenerate the chelating agent. After the solution subsequent to the contact with the polluted soil or waste is recovered, a polyvalent metal salt and/or a cementitious compound is added to the soil or waste to prevent the elution of residual heavy metals. The soil or waste is brought into contact with sulfite and/or hydrogen sulfite along with the chelating agent solution or prior to the contact with the chelating agent solution to accelerate the elution of heavy metals. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating heavy metal-contaminated soil or waste, which comprises contacting a soil or waste contaminated with heavy metal with a chelating agent solution to remove the heavy metal in the soil or waste.

[0002]

2. Description of the Related Art In recent years, soil pollution and waste pollution due to heavy metals such as lead and cadmium have been found in various places, mainly in the former sites of factories. Therefore, a method for cleaning soil and waste contaminated with heavy metals. The research about is being promoted.

Since heavy metals cannot be decomposed like organic substances, in order to treat heavy metal contaminated soil, the contaminated soil is excavated and brought to a disposal site, insoluble heavy metal salts are produced and insolubilized, contaminated soil. A solidifying agent such as cement is added to solidify the soil, or the soil is energized to generate heat to solidify into glass. However, since all of these methods leave heavy metals in the soil, they are unreliable in terms of long-term stability.

Therefore, an electroosmosis method has been proposed as a method for removing heavy metals from soil (Japanese Patent Laid-Open No. 6-2183).
No. 55, “Remedial method for contaminated soil on site”, Japanese Patent Laid-Open No. 5-
59716, "Method and apparatus for treating contaminated soil"). Further, a method has been proposed in which a chelating agent is used to elute and remove heavy metals from contaminated soil (Japanese Patent Application Laid-Open No. Hei 4 (1999) -411).
-263874, "Method for cleaning heavy metal contaminated soil",
Water, Air, and Soil Poll
, 45, 361 (1989)), ethylenediaminetetraacetic acid salt (EDTA), nitrilotriacetic acid salt (NT)
Chelating agents such as A) have been investigated.

[0005]

However, the electroosmosis method is not practical because it is inefficient and costs a lot of money, and the method using a chelating agent is sufficient if soil is not used at a relatively high concentration. It is not possible to elute heavy metals from, and the cost is still high.

Further, with the method using a chelating agent, residual heavy metals are eluted and it is difficult to maintain the amount of heavy metals eluted below the environmental standard value for a long period of time.

The present invention solves the above-mentioned conventional problems, and an object thereof is to bring a chelating agent solution into contact with soil or waste contaminated with heavy metals to remove heavy metals in the soil or waste. It is an object of the present invention to provide a method for recovering and reusing a chelating agent in a method for treating heavy metal-contaminated soil or waste to be removed.

Another object of the present invention is to provide a method for treating heavy metal-contaminated soil or waste, which comprises contacting a soil or waste contaminated with heavy metals with a chelating agent solution to remove heavy metals in the soil or waste. The object of the present invention is to provide a method for reliably preventing the elution of heavy metals and maintaining the elution amount of heavy metals at or below the environmental standard value for a long period of time.

Another object of the present invention is to provide a method for treating heavy metal-contaminated soil or waste, which comprises contacting a soil or waste contaminated with heavy metal with a chelating agent solution to remove heavy metals in the soil or waste. It is an object of the present invention to provide a method for reducing the amount of expensive chelating agent used and obtaining a high heavy metal removing effect with a small amount of chelating agent used.

[0010]

A method for treating heavy metal-contaminated soil or waste according to claim 1, wherein a chelating agent solution is contacted with the soil or waste contaminated with heavy metal, and the heavy metal in the soil or waste is treated. In a method for treating heavy metal-contaminated soil or waste, the solution after contact with the soil or waste is collected, and the collected solution is contacted with an H-type cation exchange resin to collect heavy metal in the solution. It is characterized by doing.

Contact of a chelating agent solution that produces a stable water-soluble chelate with heavy metals with contaminated soil or waste,
Heavy metals such as lead, cadmium, and mercury existing in soil or waste can be dissolved in water as water-soluble and thereby most of heavy metals in soil or waste can be removed.

In the chelating agent solution that has come into contact with the heavy metal-contaminated soil or waste, calcium ion, magnesium ion, iron ion, which is a constituent of the soil or a component contained in the waste, other than the heavy metal ion to be removed, Many kinds of metal ions such as aluminum ions and manganese ions are dissolved as chelate compounds. Therefore, the ability of the chelating agent solution after contact with soil or waste material to dissolve heavy metal ions is greatly reduced, and even if it is directly contacted with new contaminated soil or waste material, the elution and removal effect of heavy metal ions is almost eliminated. I can't get it.

Therefore, in the method of claim 1, the chelating agent solution after contacting with the contaminated soil or waste is separated from the soil or waste and recovered, and then contacted with a cation exchange resin adjusted to H type. Then, the chelating agent can be recovered in the acid form by collecting the metal ions with the H-type cation exchange resin. The chelating agent recovered as the acid form can be reused by neutralizing with an alkali such as sodium hydroxide, and the amount of the chelating agent used is significantly reduced.

Further, it has been conventionally considered difficult to treat heavy metal wastewater in the presence of a chelating agent. By separating the chelating agent and the heavy metal ions in this manner, the heavy metal ion-containing material obtained at the time of regeneration of the ion exchange resin is contained. The recycled wastewater can be easily treated by applying ordinary neutralization / coagulation sedimentation method.

The method for treating heavy metal-contaminated soil or waste according to claim 2, wherein a chelating agent solution is contacted with the soil or waste contaminated with heavy metal to remove the heavy metal in the soil or waste. Alternatively, in the method for treating waste, the solution after contacting the soil or the waste is collected, and then the polyvalent metal salt and / or the cement-based compound is added to the soil or the waste.

As described above, when a chelating agent solution that forms a stable water-soluble chelate with heavy metals is brought into contact with contaminated soil or waste, heavy metals such as lead, cadmium and mercury existing in the soil or waste are soluble in water. Can be eluted into the water as water, which can remove most of the heavy metals in the soil or waste. However, in this way, when the metal containing the heavy metal in the soil or waste is eluted, the organic matter in the soil or the waste that is bound to the soil or the waste through the metal is easily eluted. As the organic substance is eluted, the slight amount of residual heavy metals bound to the organic substance is further eluted. Therefore, conventionally, it has been difficult to reliably prevent the elution of heavy metals from the soil or the waste after the treatment with the chelating agent.

Therefore, according to the method of claim 2, the polyvalent metal salt and / or the soil or the waste after the treatment with the chelating agent solution is added.
Alternatively, a cementitious compound is added. This makes it possible to reattach organic substances that have once been eluted through the added polyvalent metal salt and / or cementitious compound to soil or waste, reliably prevent the elution of heavy metals, and reduce the amount of elution to environmental standards. It is possible to maintain below the value.

The method for treating heavy metal-contaminated soil or waste according to claim 3 is a method for contacting a soil or waste contaminated with heavy metal with a chelating agent solution to remove the heavy metal in the soil or waste. Alternatively, in the method for treating waste, the soil or waste may be treated with sulfite and / or prior to contact with the chelating agent solution or prior to contact with the chelating agent solution.
Alternatively, it is characterized by being brought into contact with bisulfite.

Metals in soil or waste, mainly iron, manganese, etc., are reduced to a low oxidation state by contact with sulfite and / or bisulfite, and the bond with soil or waste is weakened and eluted. It will be easier.

Therefore, according to the method of claim 3, before the contact with the chelating agent solution or before the contact with the chelating agent solution,
Contacting the soil or waste with sulfite and / or bisulfite. As a result, heavy metals bound to iron or manganese oxide in soil or waste are in a state of being easily eluted, compared with the case where treatment is performed only with a chelating agent solution.
Heavy metals such as iron and cadmium can be efficiently made water-soluble and eluted from soil or waste.
As a result, the treatment time with the chelating agent solution can be shortened and the amount of chelating agent used can be reduced.

The chelating agent used in the present invention is L-
Selected from the group consisting of aspartic acid-N, N-diacetic acid, glutamic acid diacetic acid, hydroxyethyliminodiacetic acid, carboxymethyloxysuccinic acid, 3-hydroxy-2,2'-iminodisuccinic acid, polyaspartic acid and salts thereof. It is preferable that it is one kind or two or more kinds.

L-aspartic acid-N, N-diacetic acid, glutamic acid diacetic acid, hydroxyethyliminodiacetic acid, carboxymethyloxysuccinic acid, 3-hydroxy-2,
2′-iminodisuccinic acid and polyaspartic acid each have a carboxyl group and / or an amino group in the molecule, and due to the carboxyl group and / or the amino group, heavy metals such as lead, cadmium, and mercury in soil or wastes. It produces stable water-soluble chelates with ions. Due to this chelating action, when an aqueous solution of these substances is brought into contact with soil or waste contaminated with heavy metals, heavy metal ions can be efficiently eluted from the contaminated soil or waste. Therefore, the heavy metal can be efficiently removed from the soil or the waste by separating and recovering the chelating agent solution after contacting the contaminated soil or the waste from the soil or the waste.

Moreover, since all of these substances are biodegradable and decomposed even if they remain in the soil after the treatment, their influence on the environment is extremely small. In addition, after the treatment, a trace amount of the treatment agent (both the treatment agent that produces a heavy metal ion and a chelate and the treatment agent that does not produce a chelate) that could not be completely recovered is biodegraded, so that the heavy metal ion and the chelate are chelated. It is also possible to prevent the generation of heavy metal and chelate and re-elute heavy metals that remain in trace amounts in the soil. Therefore,
It is possible to prevent secondary pollution such as heavy metal pollution of groundwater caused by a trace amount residual treatment agent.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

First, the chelating agent solution used in the present invention will be described.

In the present invention, the chelating agent is
A substance having a carboxy group and / or an amino group in the molecule and forming a stable water-soluble chelate with a heavy metal is preferable.
For example, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), citric acid, L-aspartic acid-
Examples thereof include N, N-diacetic acid salt (ASDA), and particularly L-aspartic acid-N, N-diacetic acid, glutamic acid diacetic acid, hydroxyethyliminodiacetic acid, carboxymethyloxysuccinic acid, 3-hydroxy- 2,2'-iminodisuccinic acid, polyaspartic acid and salts thereof,
For example, one or two of alkali metal salts such as potassium salt and sodium salt and alkaline earth metal salts such as calcium salt.
It is preferable to use one or more species, and an aqueous solution of these chelating agents is generally used as the chelating agent solution. If the concentration of the chelating agent in the aqueous solution is too low, the elution effect of heavy metals will not be sufficient, and if it is too high, the cost of the drug will rise, so the solid concentration is 0.01 to 10% by weight,
It is particularly preferably 0.1 to 3% by weight.

In the present invention, the method for bringing such an aqueous solution of a chelating agent into contact with heavy metal-contaminated soil or waste is not particularly limited, but the following method can be adopted, for example. First, identify the contaminated part of the soil, surround this part with an impermeable wall such as sheet pile, and drill an injection well and a pumping well. Inject the aqueous solution of the chelating agent from the injection well,
Contact the contaminated soil with an aqueous solution of a chelating agent, then
Pumping water from the pumping well to collect water in which heavy metals are eluted. The polluted contaminated soil or waste is put in a washing tank together with the aqueous solution of the chelating agent and stirred. After that, solid-liquid separation is performed to separate purified soil or waste and water in which heavy metals are eluted, and the purified soil is backfilled. Dispose of waste by landfill.

In the method of claim 1, the chelating agent aqueous solution recovered by contacting with soil or waste by the above method or the like is passed through an H-type cation exchange resin packed column to be contacted. The metal ions are adsorbed (collected) on the H-type cation exchange resin to be removed. Since the aqueous solution of the chelating agent after being brought into contact with the H-type cation exchange resin is in an acid form, it is regenerated by adding alkali such as sodium hydroxide to neutralize the pH to about 5.0 to 9.0. .

The regenerated aqueous chelating agent solution has sufficient removal of metal ions and exhibits the same heavy metal elution effect as before soil or waste treatment. Therefore, this is repeatedly reused for treatment of heavy metal-contaminated soil or waste. can do.

In the method of claim 2, a polyvalent metal salt and / or a polyvalent metal salt is added to the soil or waste after the chelating agent aqueous solution is collected and separated by contacting with the soil or waste by the above method or the like. Add cementitious compound.

Specifically, in the above treatment, preferably, water is injected into the soil after recovering the chelating agent aqueous solution to wash it, and then an aqueous solution of a polyvalent metal salt is injected to remove residual heavy metals. Insolubilize. Alternatively, in the above treatment, the soil or waste after the treatment with the chelating agent aqueous solution and the solid-liquid separation is preferably washed with water, and then the polyvalent metal salt and / or the cement compound is added and stirred. Alternatively, an aqueous solution of a polyvalent metal salt may be sprayed on the soil or waste after the treatment.

As the polyvalent metal salt, salts such as chloride salts and sulfate salts of calcium, magnesium, iron and aluminum, or hydroxides and oxides thereof can be used.
Further, as the cement-based compound, cement, aluminosilicate or the like can be used. These polyvalent metal salts and cement compounds may be used alone or in combination.
You may use together more than one kind.

The amount of the polyvalent metal salt and / or the cement-based compound added may be such that the effect of preventing the elution of heavy metals can be obtained, and it depends on the type of the polyvalent metal salt or the cement-based compound used. If calcium chloride is added, it is 0.1-10 based on the weight of soil or waste.
Treat with powdered or aqueous solution of calcium chloride by weight. If it is lower than this concentration, the elution suppressing effect is lowered, and if it is higher than this concentration, the cost is increased and the waste is increased. When cement and polyiron sulfate are added together, the concentration of cement in the soil is 2 to 10% by weight, the concentration of polyiron sulfate is 3 to 15% by weight, and the pH of the eluate after addition is 8.
Adjust so that it is 0-10.5. Also in this case, if the addition amount is small, the elution suppressing effect decreases, and if the concentration is high, waste increases. Also, when the pH is out of the above range, the effect of suppressing elution decreases.

By adding a polyvalent metal salt and / or a cement-based compound to the soil or waste treated with the aqueous chelating agent solution in this manner, the elution of heavy metals from the soil or waste for a long period of time is performed. Can be reliably prevented.

In the method of claim 3, in treating the contaminated soil or waste by the above method or the like, the sulfite and / or the hydrogen sulfite, together with the chelating agent solution or prior to the contact with the chelating agent solution, Specifically, an aqueous solution of sulfite and / or bisulfite is brought into contact with soil or waste.

The concentration of sulfite and / or bisulfite in the aqueous solution of sulfite and / or bisulfite is preferably 0.01 to 10% by weight, more preferably 0.05 to 1% by weight, in terms of solid content. . If it is lower than this concentration, the effect of promoting the elution of heavy metals by sulfite and / or hydrogen sulfite cannot be sufficiently obtained, and if it is higher, the cost becomes higher.

Further, the ratio of the aqueous solution of sulfite and / or bisulfite to the aqueous solution of chelating agent is such that in order to sufficiently obtain the effect of the combination thereof, chelating agent: sulfite and / or hydrogen sulfite = 1. : 0.1 to 2 (weight ratio)
It is preferable to set it as the range.

In the treatment of contaminated soil or waste, the soil or waste is contacted with an aqueous solution of sulfite and / or bisulfite and then with an aqueous solution of a chelating agent. The soil or waste is simultaneously contacted with the aqueous sulfite and / or bisulfite solution and the aqueous chelating agent solution. The soil or waste is contacted with the chelating agent aqueous solution and then with the sulfite and / or bisulfite aqueous solution, and then with the chelating agent aqueous solution. Any method may be used, and in the case of simultaneously contacting with the sulfite and / or hydrogen sulfite aqueous solution and the chelating agent aqueous solution, a chelating agent aqueous solution containing the sulfite and / or hydrogen sulfite may be used.

As the sulfite and / or bisulfite, there can be used sulfites such as sodium sulfite and potassium sulfite, and bisulfites such as sodium bisulfite and potassium bisulfite. They may be used alone or in combination of two or more.

In this way, by using sulfite and / or bisulfite together with the chelating agent, the elution rate of heavy metals is increased by the elution promoting effect of sulfite and / or bisulfite, and the treatment time is increased. The amount of the expensive chelating agent used can be shortened to reduce the amount.

[0041]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

Example 1 Lead-contaminated soil collected from the site of a battery manufacturer was air-dried,
The particles were sieved to a particle size of 2 mm or less. 50g of this soil sample
And 0.3 wt% (3000 mg / L) of a chelating agent (L-aspartic acid-N, N-diacetic acid.
It is abbreviated as "A". ) 500 mL of the aqueous solution was placed in a 1 L poly container with a lid and shaken at 200 rpm for 24 hours. After shaking, the mixture was centrifuged, and the supernatant was added to 0.
It was filtered through a 45 μm membrane filter (hereinafter, the obtained filtrate is referred to as “soil wash water”). When the Ca ion concentration, Mg ion concentration, and Pb ion concentration in this soil wash water were measured, they were 330 mg / L and 30 mg / L, respectively.
L, 45 mg / L, and pH was 7.5.

A glass column was filled with 10 mL of a strongly acidic cation exchange resin adjusted to H type with 1N hydrochloric acid, and first, pure water was passed through for washing. The soil wash water previously obtained was passed through this column under the condition of SV = 2 hr ⁻¹ , and the Ca ion concentration, Mg ion concentration, Pb ion concentration, ASDA concentration, and pH of the column outlet for each predetermined water flow amount. Was measured and the results are shown in Table 1.

[0044]

[Table 1]

As shown in Table 1, metal ions were not detected for a while after the start of water flow, and ASDA was approximately 3000 mg.
/ L was detected. Metal ions became to be detected between 280 and 320 mL of water flow rate, and it was estimated that the ion exchange capacity was exceeded at this point.

The solution having a water flow rate of up to 280 mL was recovered and
After neutralizing the pH to 6.5 with aOH, 28 g of the soil sample was added again, shaken under the same conditions as above, and the Pb concentration in the solution obtained by filtration was measured and found to be 48 mg / L,
It was confirmed that the heavy metal leaching performance equivalent to that at the initial stage was exhibited due to the regeneration of ASDA.

COMPARATIVE EXAMPLE 1 In Example 1, the soil washing water was mixed with the soil sample again without being contacted with the ion exchange resin, and the mixture was shaken and filtered under the same conditions, and the Pb ion concentration in the solution was 53.
mg / L, and 53-45 = 8 in the second soil treatment
It was found that only mg / L of lead could be eluted.

Comparative Example 2 When the soil washing water obtained in the same manner as in Example 1 was passed through a Na-type strongly acidic cation exchange resin, ASDA was detected immediately after the start of passing water, but metal ions were also detected. , AS
It was not possible to reproduce the DA.

Examples 2 to 4 Lead-contaminated soil collected from the site of a battery manufacturer was air-dried,
The particles were sieved to a particle size of 2 mm or less. 50g of this soil sample
Then, 500 mL of a 0.37 wt% ASDA aqueous solution was placed in a 1 L poly container with a lid, and shaken at 200 rpm for 24 hours. After the shaking was completed, the mixture was centrifuged and the supernatant was filtered with a 0.45 μm filter, and the lead concentration was measured by ICP emission spectrometry.

As a result of measuring the lead content in the contaminated soil in advance, it was 500 mg / kg, and the elution effect of ASDA was
As a percentage (removal rate) of the elution rate to this value, the elution rate was 370 mg / kg and the removal rate was 74%.
Met. The pH of the ASDA aqueous solution was adjusted to 7.0 ± 0.5 in advance before mixing with the contaminated soil.

Next, pure water 5 was added to the soil after the ASDA treatment.
00 mL was added, and the mixture was further shaken under the condition of 200 rpm for 24 hours, and after the shaking was completed, it was subjected to a centrifuge for solid-liquid separation, and washed with water. The soil after the water washing was air dried. Hereinafter, this soil is referred to as "ASDA-treated soil".

3 g of this ASDA-treated soil was added to 30 mL of an aqueous calcium chloride solution having the concentration shown in Table 2 to obtain 200 r
It was shaken for 24 hours under the condition of pm. After the shaking was completed, the mixture was put into a centrifuge for solid-liquid separation. The solid-liquid separated soil was mixed with 30 mL of pure water, shaken at 200 rpm for 6 hours, and subjected to a centrifuge for solid-liquid separation.
After filtering through a 45 μm filter, the lead concentration was measured by ICP emission spectrometry, and the results are shown in Table 2.

Examples 5-8 ASDA treated soil 3 obtained by treating in the same manner as in Example 2
After the amount of cement shown in Table 2 (wt% to soil added) was added to g and stirred well, washing with pure water, solid-liquid separation, filtration of the supernatant, and ICP emission analysis were performed in the same manner as in Example 2. Then, the lead concentration was measured, and the results are shown in Table 2.

Examples 9 and 10 ASDA-treated soil 3 obtained by treating in the same manner as in Example 2
To g, 3% by weight of cement was added to the soil, and the mixture was stirred well, after which it was allowed to stand for 1 hour, and then the amount of polyiron sulfate as shown in Table 2 (weight% to soil added) was added and stirred well. The treated soil was washed with pure water, subjected to solid-liquid separation, filtered the supernatant and subjected to ICP emission analysis in the same manner as in Example 2 to measure the lead concentration, and the results are shown in Table 2.

Comparative Example 3 The ASDA-treated soil obtained by treating in the same manner as in Example 2 was washed with pure water, solid-liquid separated, and the supernatant was filtered in the same manner as in Example 2 without further treatment. ICP emission analysis was performed to measure the lead concentration, and the results are shown in Table 2.

[0056]

[Table 2]

From Table 2, by treating the soil after treatment with a chelating agent with calcium chloride or cement, or with cement and polyiron sulfate, the elution of lead was brought to an environmental standard value (0.01 mg / L or less). You can see that it can be suppressed.

Examples 11 to 13 Lead-contaminated soil collected from the site of a battery manufacturer was air-dried,
The particles were sieved to a particle size of 2 mm or less. 5 g of this soil sample (lead content of about 500 mg / kg) and 50 mL of an aqueous sodium hydrogen sulfite solution having the concentration shown in Table 3 were placed in a 100 mL plastic container with a lid and shaken at 200 rpm for 24 hours. After the shaking was completed, it was subjected to a centrifuge for solid-liquid separation.

To the soil obtained by solid-liquid separation, 50 mL of 0.37 wt% ASDA aqueous solution was added, and the mixture was further shaken at 200 rpm for 24 hours. The eluate was filtered through a 0.45 μm filter, the lead concentration in the filtrate was measured by ICP emission spectrometry, and the removal rate for the lead content in the contaminated soil was determined in the same manner as in Example 1, and the results are shown in Table 3. Indicated. In addition, AS
The pH of DA solution is 7.0 ± before mixing with contaminated soil.
Adjusted to 0.5.

Comparative Example 4 The lead removal rate was determined in the same manner as in Example 11 except that the treatment with the sodium bisulfite aqueous solution was not performed and only the treatment with the ASDA aqueous solution was performed, and the results are shown in Table 3.

[0061]

[Table 3]

From Table 3, it can be seen that the combined use of sodium hydrogen sulfite can enhance the heavy metal elution effect of the chelating agent.

[0063]

As described in detail above, according to the present invention, a chelating agent solution is brought into contact with soil or waste contaminated with heavy metals to remove heavy metals in the soil or waste, or with heavy metal-contaminated soil. The following effects can be obtained in the waste treatment method. According to the method of claim 1, an expensive chelating agent can be recovered and reused by treating the used chelating agent with the H-type cation exchange resin. The cost can be reduced significantly. According to the method of claim 2, by adding the polyvalent metal salt and / or the cement-based compound to the soil or the waste after the treatment with the chelating agent, the elution of the heavy metal is surely prevented and the elution amount of the heavy metal is increased. It can be maintained below the environmental standard value for a long time. According to the method of claim 3, by using a sulfite and / or bisulfite together with the chelating agent, the elution effect of the heavy metal by the chelating agent is enhanced, and the heavy metal removing effect is high with a short treatment time and a small amount of the chelating agent used. Can be obtained.

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Claims (4)

[Claims] 1. A method for treating heavy metal-contaminated soil or waste, which comprises contacting a chelating agent solution with heavy metal-contaminated soil or waste to remove heavy metals in the soil or waste, wherein the soil or waste is treated. The method for treating heavy metal-contaminated soil or waste, comprising collecting the solution after contacting with H-type cation exchange resin to collect the heavy metal in the solution. 2. A method for treating heavy metal-contaminated soil or waste, which comprises contacting a chelating agent solution with soil or waste contaminated with heavy metals to remove heavy metals in the soil or waste, wherein the soil or waste is treated. A method for treating heavy metal-contaminated soil or waste, which comprises adding a polyvalent metal salt and / or a cement-based compound to the soil or waste after recovering the solution after contact with the soil or waste. 3. A method for treating heavy metal-contaminated soil or waste, which comprises contacting a chelating agent solution with heavy metal-contaminated soil or waste to remove heavy metals in the soil or waste, together with the chelating agent solution. Or a method for treating heavy metal-contaminated soil or waste, which comprises contacting the soil or waste with sulfite and / or bisulfite prior to contact with the chelating agent solution. 4. The chelating agent according to claim 1, wherein the chelating agent is L-aspartic acid-N, N-diacetic acid, glutamic acid diacetic acid, hydroxyethyliminodiacetic acid, carboxymethyloxysuccinic acid, A method for treating heavy metal-contaminated soil or waste, comprising one or more selected from the group consisting of 3-hydroxy-2,2'-iminodisuccinic acid, polyaspartic acid and salts thereof.