JP2002326081A - Method for making contaminated soil harmless - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an economical and efficient treating method which reduces the concentration of remaining fluorine and heavy metal in treated waste water and the elution value of fluorine and heavy metal of insolubilized soil to the environmental standard value or less by performing the collective treatment, as it is in the soil and without performing solid-liquid separation beforehand in the soil slurry, with respect to the soil and the soil slurry which are contaminated by fluorine and heavy metal. SOLUTION: A mineral acid is added as need to the soil and the soil slurry which are contaminated by fluorine and heavy metal, thereby, the pH is adjusted within a range of 2-4, aluminium or iron of 0.1-5.0 g/kg or aluminium salt or iron salt of 0.1-5.0 g/L is added and stirred, thereafter, alkali is added, the pH is adjusted within a range of 3-10 and, thereby, hydroxide is generated. Fluorine and heavy metal is subsumed and accompanied by the hydroxide which is generated and the insolubilized soil is produced. On the other hand, the slurry is subjected to the solid-liquid separation and is separated into deposit and treated waste water. This method for making contaminated soil harmless makes it possible to concurrently reduce the elution value of fluorine and heavy metal in the insolubilized soil and the concentration of remaining fluorine and heavy metal in the treated waste water to the environmental standard value or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for detoxifying soil contaminated with fluorine or a fluorine compound (both are collectively referred to as fluorine), and more particularly to a method for contaminating soil with fluorine or fluorine and heavy metals. The treated soil or soil slurry is subjected to batch treatment to obtain insolubilized soil having a low elution value of fluorine or fluorine and heavy metal (referred to as insolubilized soil) and treated wastewater having a low concentration of residual fluorine or residual fluorine and heavy metal ( And wastewater treatment).

[0002]

2. Description of the Related Art In recent years, for example, when constructing an apartment on a site where a factory located in an urban area has been relocated, attention has been paid to the problem of soil contamination due to harmful substances accumulated in the soil for many years. It has become necessary to take measures to purify the soil in accordance with the "Soil Environmental Standards", but no soil environmental standards exist for fluorine. But,
Regarding "Additional items of environmental standards related to soil pollution", which was consulted by the Secretary of the Environment Agency to the Central Environment Council in July 1999, the Central Environment Council Soil Agrochemicals Subcommittee on December 26, 2000 The proposal was finalized and submitted to the Commissioner for the Environment Agency. Among them, fluorine is mentioned as an additional item of the soil environmental standard, and the Environment Agency will carry out necessary procedures such as revision of the notification of the Environment Agency based on this report. Therefore, in the near future, fluorine will be added as a soil environmental standard. As described above, the method of purifying fluorine-contaminated soil is a new item, so there are no cases of purification, and the development of a purification method is extremely urgent.
In addition, it is expected that there is a large amount of complex contamination of fluorine and heavy metals, and a method for simultaneously rendering both harmless is desired. There have been methods to remediate heavy metal contaminated soil, including chemical treatment followed by containment and solidification with concrete, and physical measures include the removal of contaminated surface soil to a certain depth. There is a known method of soiling and then soil that is not contaminated.
There is no known method for repairing soil contaminated with fluorine.

[0003]

SUMMARY OF THE INVENTION The present invention reduces the elution value of fluorine or fluorine and heavy metals from soil or soil slurry contaminated with fluorine or fluorine and heavy metals to an environmental standard value or less. Proposes an economical treatment method in which batch treatment is carried out without solid-liquid separation in advance and solid-liquid separation is carried out at the end to reduce residual fluorine or the concentration of residual fluorine and heavy metals in treated wastewater.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, as a method of purifying soil contaminated with fluorine or fluorine and heavy metals, a metal salt is added, The insolubilization of fluorine and heavy metals in soil by entraining and coprecipitating fluorine or fluorine and heavy metals with metal hydroxides, and simultaneously reducing the concentration of residual fluorine or residual fluorine and heavy metals in treated wastewater for soil slurries And developed an economical and efficient treatment method.

That is, the present invention firstly comprises adding at least one of an aluminum salt and an iron salt to fluorine-contaminated soil or soil slurry, and then adjusting the content of the aluminum or iron salt to a weakly acidic or alkaline range. Or a method for detoxifying contaminated soil, comprising insolubilizing the fluorine by generating at least one hydroxide of iron hydroxide; secondly, a method of contaminating soil contaminated with fluorine and heavy metals. At least one of aluminum salts or iron salts is added to the soil or soil slurry and then adjusted to a weakly acidic or alkaline range to remove at least one hydroxide of aluminum or iron hydroxide. Detoxification of contaminated soil, characterized by insolubilizing said fluorine and heavy metal by producing; third, fluorine or fluorine and heavy metal A step of adding a mineral acid to the soil or soil slurry contaminated with and adjusting the acid range to an acidic range, and then adding and mixing at least one of an aluminum salt or an iron salt, Then, an alkali is added to adjust the pH to a weakly acidic range or an alkaline range to generate at least one hydroxide of aluminum or iron hydroxide, thereby insolubilizing the fluorine or the fluorine and the heavy metal. And fourthly, adding a mineral acid to the soil or soil slurry contaminated with fluorine or with fluorine and heavy metals to adjust to an acidic region. A first step, and then a second step of adding and stirring at least one of an aluminum salt and an iron salt, and then adding an alkali to adjust to a weakly acidic range or an alkaline range. A third step of obtaining a coprecipitated slurry in which the fluorine or the fluorine and the heavy metal are coprecipitated with at least one hydroxide of the produced aluminum or iron, and further, the coprecipitated slurry is subjected to solid-liquid separation. And a fourth step of separating the wastewater into insolubilized soil and treated wastewater by a method of detoxifying contaminated soil;
The adjusted acidic region in the first step is adjusted to pH 2
4, the amount of the aluminum salt added in the second step is 0.1% with respect to the weight of the soil as aluminum.
To 5.0 g / kg or 0.1 to 5.0 g / L with respect to the volume of the soil slurry, and the amount of iron salt added is 0.1 to 5.0 g / kg with respect to the weight of the soil as iron. 0 g / k
g or 0.1-5.
0 g / L, and the adjusted weakly acidic or alkaline range in the third step is pH 3-10.
Or the method according to 4, wherein the mineral acid is at least one of sulfuric acid, nitric acid or hydrochloric acid, the aluminum salt is at least one of aluminum sulfate or polyaluminum chloride, and the iron salt is Is at least one of ferrous sulfate, ferrous chloride, ferric sulfate or ferric chloride, and the alkali is at least one of sodium hydroxide, slaked lime or calcium carbonate.
The method according to any of claims 3 to 5, which is a species;
7. The method according to any of claims 3 to 6, wherein the insolubilized soil is used as a backfill soil or a raw material for producing other substances;
Eighth, the contaminated soil or soil slurry is obtained from soft ground, and a cement agent is used in place of or together with at least one of the aluminum salt or the iron salt. 7. The method according to 3, 5, or 6, wherein soil improvement and insolubilization are performed by using the insolubilized soil obtained by the addition as backfill soil; ninth, the contaminated soil before the first step. The method according to any one of claims 3 to 8, wherein the soil or the soil slurry is previously washed and classified with water, an alkaline aqueous solution or an acidic aqueous solution; The method according to any one of the third to ninth methods, which is performed on site.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, soil or soil slurry contaminated with fluorine or fluorine and heavy metals is simultaneously treated to insolubilize fluorine or fluorine and heavy metals in soil, Is characterized by reducing the concentration of residual fluorine or fluorine and heavy metals in the treated wastewater after solid-liquid separation.

In carrying out the treatment method of the present invention, the acidic region in the first step preferably has a pH of 2 to 4. When the pH is higher than 4, the insolubilization treatment of the soil becomes insufficient, and when the pH is 2 or lower, the effect is saturated and the amount of alkali used in the third step increases. Here, in the case where the contaminated soil to be treated is made acidic by adding at least one of aluminum salt or iron salt and hydrolyzed, or when the soil is acidic from the beginning, the first step Is omitted.
The amount of the aluminum salt added in the second step is 0.1 to 5.0 g / kg or 0.1 to 5.0 as aluminum with respect to the weight of the soil or the volume of the soil slurry, respectively.
g / L is preferred. Furthermore, even within this range, 0.5 g /
kg or more or 0.5 g / L or more, preferably 1.0 g
/ Kg or more or 1.0 g / L or more is more preferable.
However, the effect is saturated at 5.0 g / kg or more or 5.0 g / L or more. Less than 0.1 g / kg or 0.1 g
If it is less than / L, both the insolubilization treatment of the soil and the reduction of the residual fluorine or the concentration of fluorine and heavy metals in the treated wastewater will be insufficient.

The amount of iron salt added in the second step is 0.1 to 5.0 g / kg or 0.1 to 5.0 as iron with respect to the weight of the soil or the volume of the soil slurry, respectively.
g / L is preferred. More preferably 0.5 g / kg or more or 0.5 g / L or more, further preferably 1.0 g / kg or more.
kg or more or 1.0 g / L or more. However, 5.
At 0 g / kg or more or 5.0 g / L or more, the effect is saturated. If it is less than 0.1 g / kg or less than 0.1 g / L, both the soil insolubilization treatment and the reduction of the residual fluorine or the concentration of fluorine and heavy metals in the treated wastewater will be insufficient. In comparison between aluminum salt and iron salt, aluminum salt is more effective in insolubilizing fluorine and reducing residual fluorine in wastewater in terms of the amount added and economical, and it is desirable to select aluminum salt.

The pH of the weakly acidic region or alkaline region in the third step is preferably 3 to 10. The pH is more preferably in the range of 5 to 10, and even more preferably in the range of 6 to 8. If the pH is lower than 3 or higher than 10, the soil insolubilization treatment will be insufficient, and for soil slurry, the reduction of residual fluorine or the concentration of residual fluorine and heavy metals in the treated wastewater and the insolubilization treatment will be insufficient. Further, it is desirable that the soil is rendered harmless by setting it in a neutral range, specifically, in the range of pH 7 to 8.

From the viewpoints of reactivity, handling, cost and the like, the mineral acid is preferably at least one of sulfuric acid, nitric acid and hydrochloric acid. The aluminum salt is preferably at least one of aluminum sulfate and polyaluminum chloride, and the iron salt is preferably at least one of ferrous sulfate, ferrous chloride, ferric sulfate and ferric chloride. . As the alkali, at least one of sodium hydroxide, calcium carbonate and slaked lime is preferable.
The use of sodium hydroxide reduces the incorporation of reaction products from alkali into the soil, and the use of calcium carbonate or slaked lime enhances the coprecipitation of fluorine or fluorine and heavy metals during gypsum precipitation.

[0011] In the treatment method of the present invention, by fluorine or
Soil or soil slurry contaminated by fluorine and heavy metals
As described above, and add mineral acid as needed to
And then add a few of the aluminum or iron salts
At least one kind is added, alkali is further added, and
Fluorine or iron hydroxide flocs are formed
Or fluorine and heavy metals to these aluminum hydroxides.
Or by the inclusion included within or inside the iron hydroxide
By coprecipitation with fluorine or fluorine in the insolubilized soil
Heavy metal elution values and soil slurries
Simultaneously determine the concentration of residual fluorine or fluorine and heavy metals in water
It is to be reduced below the reference value. In particular, aluminum hydroxide
Solubility product as a feature of minium: [Al³⁺] [OH^-]^Three= 1.9
2 × 10 ⁻³²(30 ° C) and very low solubility
In addition, the gel-like substance at the time of hydration has strong adsorptivity
These characteristics are known in the processing method of the present invention.
Is considered to be working effectively. Like this
Or fluorine and heavy metals with aluminum hydroxide or water
Insoluble in a stable form entrained by co-precipitation with iron oxide
And liquefied soil.

In the following examples, arsenic and hexavalent chromium are mainly described as fluorine and heavy metals. However, for heavy metals such as lead, cadmium and mercury, as in arsenic and hexavalent chromium, the same applies to soil. It is insolubilized and the concentration of residual fluorine and heavy metals is reduced in the wastewater for treatment of soil slurry. The present invention will be described in more detail with reference to the following examples, but the technical scope of the present invention is not limited to the description of these examples.

[0013]

[Example 1] The treatment method of the present invention was applied to a fluorine-contaminated soil (hereinafter referred to as soil A) in an area A. The fluorine content of soil A (-2 mm) is 420 mg / kg, and the fluorine elution value is 2.1 mg / L. The insolubilized soil obtained by the treatment method of the present invention was subjected to a dissolution test according to the method shown in the notification of the Environment Agency No. 46 (August 23, 1991).

The processing method of the present invention was performed according to the flow shown in FIG. First, 50g of 100g of soil (15% moisture)
In a 0 mL container, a predetermined amount of polyaluminum chloride (0.3 g / kg, 0.6 g / kg as aluminum)
And ferric sulfate (three levels of 0.85 g / kg, 1.7 g / kg and 3.4 g / kg as iron) and mixed and stirred with a stirring rod. It was confirmed that the pH was brought to pH 3 by bringing the pH test paper into contact with the moisture adhering to the soil (in the case of pH 3 or more, a 10% aqueous sulfuric acid solution was dropped to pH 3). Next, calcium carbonate was added and mixed and stirred for 3 minutes to adjust the pH to 7 to obtain an insolubilized soil. FIG. 2 shows the results of subjecting this to a fluorine elution test according to the method disclosed in the Environment Agency Notification No. 46 (August 23, 1991).

As is apparent from FIG. 2, the fluorine elution value decreased with an increase in the amount of the aluminum salt or iron salt added. Further, it can be seen that the aluminum salt has a higher effect of reducing the fluorine elution value than the iron salt.

From the above results, in the case of soil A, the fluorine elution value could be reduced by the addition of an iron salt, but the addition of an aluminum salt was more effective, and at least 1.0 g / kg of aluminum was added. It can be seen that the fluorine elution value can be reduced to the environmental standard value (0.8 mg / L) or less by adding the aluminum salt.

Example 2 A soil, fluorine, hexavalent chromium, and arsenic-contaminated soil (hereinafter referred to as soil B) in a district B was treated in the same manner as in Example 1 with the addition of an aluminum salt. The level of the amount of aluminum salt added was 1.2 and 2.4 g / kg as aluminum. Soil B
(−2 mm) is 426 mg / k of fluorine.
g, hexavalent chromium 984 mg / kg and arsenic 2 mg / kg. The elution value of each contaminant was 3.5 mg / L of fluorine, 0.04 mg / L of hexavalent chromium, and 0.022 mg / L of arsenic. Table 1 shows the test results.

[0018]

[Table 1]

From the results shown in Table 1, with respect to soil B, the amount of aluminum salt added was at least 1.
At 2 g / kg, the fluorine elution value could be reduced below the reference value. At this time, the elution values of other heavy metals were 0.001 mg / L for arsenic and 0.02 m for hexavalent chromium.
g / L 2, which was sufficiently low.

Example 3 The treatment method of the present invention was performed on a slurry containing contaminated soil in the C area (hereinafter referred to as soil C). The fluorine content of soil C (-150 μm) is 72
0 mg / kg and the fluorine elution value is 1.5 mg / L. The fluorine concentration in the slurry containing the soil C was 2.7 mg.
/ L. The dissolution test was performed on the insolubilized soil obtained by the treatment method of the present invention in the same manner as in Examples 1 and 2.

The processing method of the present invention was performed according to the flow shown in FIG. First, 500 mL of slurry containing soil C (slurry concentration 50 g / 500 mL) was put into a 1000 mL container, and a 10% aqueous sulfuric acid solution was added dropwise while stirring with a stirrer until the pH of the slurry became 3. Next, a predetermined amount of aluminum chloride (0.1 g / L as aluminum, 0.1.
3 g of 5 g / L and 1.0 g / L) or ferric sulfate (0.1 g / L, 0.5 g / L and 1.0 g as iron)
g / L) and stirring was continued for 10 minutes. Next, a 10% slaked lime suspension is added to the mixture to a predetermined pH (pH 7, 8
After stirring for 10 minutes, a 0.1% aqueous solution of a polymer flocculant was appropriately added to form flocs. Subsequently, the agglomerated slurry was vacuum-filtered by Nutsche to separate into cake (insolubilized soil) and filtrate (processed wastewater). The residual fluorine concentration of the treated wastewater is shown in FIG. 4A for the aluminum salt and FIG. 4B for the iron salt. Further, a fluorine elution test was performed on the obtained insolubilized soil, and the results are shown in FIG. 5A for the aluminum salt and FIG. 5B for the iron salt, respectively.

As is apparent from FIGS. 4a and 4b, the addition of aluminum salt or iron salt significantly reduces the residual fluorine concentration in the treated wastewater, and the effect is more remarkable as the pH becomes closer to 7.0. . Regarding the fluorine elution value of the insolubilized soil, as can be seen from FIGS. 5A and 5B, the fluorine elution value of the insolubilized soil is significantly reduced by the addition of the aluminum salt or the iron salt. In comparison between the aluminum salt and the iron salt, the aluminum salt was more effective in reducing the fluorine elution value and the residual fluorine concentration in both the insolubilized soil and the treated wastewater.

From the above results, in the case of soil C, in order to keep the residual fluorine concentration of the treated wastewater and the fluorine elution value of the insolubilized soil at or below the environmental standard value (all at 0.8 mg / L), at least 0.1% of aluminum is used. It can be seen that the goal is achieved by adding 5 g / L aluminum salt and subsequently adjusting the pH to at least 7.0-9.0.

Example 4 The treatment method of the present invention was performed on a fluorine-contaminated soil in the D area (hereinafter referred to as soil D).
The soil D (-2 mm) was mixed with a cement agent to form soft ground. The fluorine content of soil D is 420m
g / kg, the fluorine elution value is 3.5 mg / L. In the same manner as described above, the insolubilized soil obtained by the treatment method of the present invention was subjected to a dissolution test according to the method shown in the notification of the Environment Agency No. 46 (August 23, 1991).

The processing method of the present invention was carried out according to the flow of FIG. 1 except that a predetermined amount of Portland cement was mixed. First, 500 mL of 100 g of soil (15% moisture)
, A predetermined amount of polyaluminum chloride (aluminum, 1.2 g / kg, 2.4 g / kg, two levels) was added, and the mixture was stirred with a stirring rod. The pH was adjusted to pH 3 or less by bringing the pH test paper into contact with moisture attached to the soil. Next, a predetermined amount of cement (Portland cement, two levels of 5, 10% by weight) was added, and the pH was adjusted to 7 with calcium carbonate. FIG. 6 shows the result of subjecting this to a fluorine elution test according to the official method.

As is apparent from FIG. 6, even when the cement alone was added without adding the aluminum salt, the fluorine elution value tended to decrease with an increase in the addition amount. It can be seen that the addition of an aluminum salt dramatically reduces the fluorine elution value. Further, when the cement agent was added, the fluorine elution value tended to be reduced as compared with the case of using the aluminum salt alone, and it is clear that the cement agent acts as an insolubilizing aid.

From the above results, in the case of soil D, in order to reduce the fluorine elution value to the environmental standard value (0.8 mg / L) or less, a condition in which only a cement agent is added at 10% or an aluminum salt is converted to aluminum by 1%. It can be seen that the target is achieved under the condition of adding 0.2 g / kg or more and cement at 5% or more. Further, by repeatedly using the insolubilized soil obtained by adding the cement agent as backfill soil, it is possible to improve the soft ground composed of soil D and to insolubilize fluorine.
Two processing goals are met simultaneously.

Example 5 The soil A described in Example 1 was washed and classified as a pretreatment, and then the method of the present invention was applied. In the same manner as described above, the insolubilized soil obtained by the treatment method of the present invention was subjected to a dissolution test according to the method shown in the notification of the Environment Agency No. 46 (August 23, 1991).

The processing method of the present invention was performed in accordance with the flow chart of FIG. 1 except that the cleaning and classification treatments were performed. Washing and classification were performed by the methods described below. 500 g of soil A and 1 L of water
(Slurry concentration: about 33%) and placed in a pot mill (internal volume: 4 L) having a diameter of 210 mm, sealed and rotated for 20 minutes at 56 rpm on a pot mill rotating table to perform a washing treatment. Subsequently, the slurry was meshed with openings of 10 mm, 2 mm, and 6 mm.
Classification was performed using a standard sieve of 00 μm, 150 μm, 75 μm, and 38 μm. Particle size classification 10mm ~ 2mm as classification product,
2 mm to 600 μm, 600 μm to 150 μm, 150
Six products of μm to 75 μm, 75 μm to 38 μm, and 38 μm or less were obtained. Table 2 shows the weight distribution ratio and fluorine elution value of each classified product.

[0030]

[Table 2]

From the results shown in Table 2, the soil A had a fluorine elution value of 2.1 mg / L at -2 mm. However, depending on the classification, the classification with relatively low fluorine elution value (+38 μm) and the high fluoride elution value (−38 μm) Classification). −38
μm is 9.9 wt% as a weight distribution ratio,
It is less than 1/0. It is conceivable that the treatment can be performed more economically by controlling the amount of drug added in each section.

+38 μ corresponding to about 90 wt% of the total soil amount
The method of the present invention was performed according to the flow of FIG. A dissolution test was performed on the obtained insolubilized soil. The test results are shown in FIG. From FIG. 7, it can be seen that the target can be achieved by adding at least 0.2 g / kg of aluminum salt as aluminum in order to make the fluorine elution value of this category equal to or less than the reference value.

The -38 μm section after the above-mentioned washing and classification treatment is generated as a slurry. At this time, the fluorine concentration in the slurry liquid was 1.2 mg / L, and the slurry concentration was about 10%. The method of the present invention was performed on the slurry according to the flow shown in FIG. However, the final pH was adjusted to 7.0. A dissolution test was performed on the obtained insolubilized soil. FIG. 8 shows the fluorine elution value of the insolubilized soil. FIG. 9 shows the residual fluorine concentration in the obtained treated wastewater. 8 and 9, in order to make the residual fluorine concentration of the treated wastewater and the fluorine elution value of the insolubilized soil both below the reference value, at least 0.2 g / L of aluminum (2.0 g / k in terms of soil amount) in order to make the values below the reference values.
It can be seen that the target is achieved by adding the aluminum salt of g).

Based on the above results, the soil A was washed and classified, and the low-fluorine-eluting section and the high-fluorine-eluting section were separated.
The processing goal was achieved with the addition of g / kg of aluminum salt. This addition amount is 62.0% smaller than the addition amount of the reagent as compared with 1.0 g / kg (Example 1) as a result of treating the soil A as it is by the flow of FIG. That is, the soil A could be economically and efficiently treated by applying the washing and classification steps as the pretreatment for implementing the present invention.

[0035]

As described above, by treating a soil or a soil slurry contaminated with fluorine or fluorine and heavy metals by the method of the present invention, the soil can be treated with fluorine or fluorine and heavy metals in an insolubilized soil. For soil slurries, the concentration of residual fluorine or heavy metal and fluorine in treated wastewater and the concentration of fluorine and the elution value of fluoride in insolubilized soil obtained as sediment, or the elution value of heavy metal and fluorine in soil slurries should be reduced below the environmental standard value at the same time. Is now possible. According to this method, it is possible to cope with relatively unwieldy soil excavated from the site in different forms of water such as soil or soil slurry. Thus, it is possible to economically and efficiently treat soil contaminated with fluorine or fluorine and heavy metals at low cost without requiring a large space. Further, there is an advantage that the present invention can be applied to sludge generated after treating fluorine-contaminated soil in a special wet treatment step.

At present, the shortage of the final disposal site for industrial waste is a problem. However, the treatment method of the present invention is a kind of soil washing method, and the insolubilized soil recovered by this method is chemically stable. Therefore, unlike the conventional soil treatment method, there is no need to confine or solidify concrete and dispose of it, and there is no need to dispose of soil and seek new soil, and the insolubilization obtained by the treatment of the present invention. The soil can be reused for various uses such as backfilling as soil meeting environmental standards, and the total treatment cost can be greatly reduced. Further, by repeatedly using the insolubilized soil obtained by adding the cement agent as backfill soil, the two treatment goals of improving the soft ground and insolubilizing fluorine are simultaneously satisfied.

Further, according to the treatment method of the present invention, the concentration of residual fluorine and heavy metals in the treated wastewater can also meet the environmental standard values, and the contaminated soil can be removed without additional wastewater treatment equipment. The treatment method of the present invention can be performed on site, and according to this, the cost of loading and unloading contaminated soil can be significantly reduced. In addition, there is no emission of smoke and the like other than the treated wastewater that satisfies the environmental standard value, and the occurrence of secondary pollution can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram showing a processing flow of low moisture soil by a processing method of the present invention in an example.

FIG. 2 is a graph showing the relationship between the amount of aluminum or iron added when soil A is treated with an aluminum salt addition system or an iron salt addition system and the fluorine elution value of the insolubilized soil.

FIG. 3 is a view showing a processing flow of a soil slurry by a processing method of the present invention in an example.

FIG. 4A is a graph showing the relationship between the pH when the slurry containing soil C is treated with the aluminum salt addition system, the amount of aluminum salt added, and the concentration of residual fluorine in the treated wastewater;
b is a graph showing the relationship between the pH, the amount of iron salt added, and the concentration of residual fluorine in the treated wastewater when the slurry containing soil C was treated with the iron salt addition system.

FIG. 5A is a graph showing the relationship between the pH, the amount of aluminum salt added, and the fluorine elution value of the insolubilized soil when the slurry containing soil C is treated with the aluminum salt addition system,
Is a graph showing the relationship between the pH, the amount of iron salt added, and the fluorine elution value of the insolubilized soil when the slurry containing soil C was treated with the iron salt addition system.

FIG. 6 is a graph showing the relationship between the amounts of aluminum salt and cement added and the fluorine elution value after the insolubilization treatment of soil D.

FIG. 7 is a graph showing the relationship between the amount of aluminum salt added and the fluorine elution value after insolubilizing the washed and classified product (+38 μm) of soil A.

FIG. 8 is a graph showing the relationship between the amount of aluminum salt added and the fluorine elution value after the insolubilizing treatment of the washed and classified slurry (-38 μm) of soil A.

FIG. 9 is a graph showing the relationship between the amount of aluminum salt added and the concentration of residual fluorine after the insolubilization treatment of the washed and classified slurry of soil A (-38 μm).

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Claims (10)

[Claims] At least one of an aluminum salt and an iron salt is added to a soil or a soil slurry contaminated with fluorine, and then adjusted to a weakly acidic range or an alkaline range to thereby control the aluminum or iron hydroxide. A method for detoxifying contaminated soil, comprising insolubilizing the fluorine by generating at least one hydroxide of the above. 2. Addition of at least one of aluminum salt and iron salt to soil or soil slurry contaminated with fluorine and heavy metal, and then adjusting the pH to a weakly acidic range or an alkaline range to hydroxylate aluminum or iron. A method for detoxifying contaminated soil, comprising insolubilizing the fluorine and heavy metal by generating at least one hydroxide of the substances. 3. A first step of adding a mineral acid to a soil or a soil slurry contaminated with fluorine or fluorine and heavy metals to adjust to an acidic range, and then at least one of an aluminum salt or an iron salt. A second step of adding and mixing, and then adding an alkali to adjust the pH to a weakly acidic range or an alkaline range to form at least one hydroxide of aluminum or iron hydroxide to thereby form the fluorine. Or a third step of insolubilizing the fluorine and heavy metal;
A method for detoxifying contaminated soil, comprising: 4. A first step of adding a mineral acid to a soil or a soil slurry contaminated with fluorine or fluorine and heavy metals to adjust to an acidic range, and then at least one of an aluminum salt and an iron salt. A second step of adding and stirring, and then adding alkali to a hydroxide or at least one of aluminum or iron produced by adjusting to a weakly acidic area or an alkaline area, to the fluorine or the fluorine and heavy metal. A contaminated soil, comprising: a third step of obtaining a coprecipitated slurry obtained by coprecipitating the above, and a fourth step of solid-liquid separation of the coprecipitated slurry to separate it into insolubilized soil and treated wastewater. Detoxification method. 5. The adjusted acidic range in the first step is pH 2-4, and the amount of aluminum salt added in the second step is 0.1-5.0 g as aluminum based on the weight of the soil. / Kg or 0.1 to 5.0 g / L based on the volume of the soil slurry, and the amount of iron salt added is 0.1 to 5.0 g / L based on the weight of the soil as iron.
0 g / kg or 0.1 to 5.0 g / L based on the volume of the soil slurry, and the adjusted weakly acidic or alkaline range in the third step is pH 3 to 10.
The method according to claim 3 or 4, wherein 6. The mineral acid is at least one of sulfuric acid, nitric acid or hydrochloric acid, the aluminum salt is at least one of aluminum sulfate or polyaluminum chloride, and the iron salt is ferrous sulfate. , Ferrous chloride,
The method according to any one of claims 3 to 5, wherein the alkali is at least one of ferric sulfate and ferric chloride, and the alkali is at least one of sodium hydroxide, slaked lime and calcium carbonate. . 7. The method according to claim 3, wherein the insolubilized soil is used as a raw material for producing backfill soil or other substances. 8. The cement according to claim 1, wherein said contaminated soil or soil slurry is obtained from soft ground, and is used in place of or together with at least one of said aluminum salts or iron salts. 7. The method according to claim 3, 5 or 6, wherein the soil improvement and insolubilization are performed by using the insolubilized soil obtained by adding as backfill soil. 9. The method according to claim 3, wherein the contaminated soil or soil slurry is previously washed and classified with water, an alkaline aqueous solution or an acidic aqueous solution before the first step. 10. The method according to claim 3, wherein each of the steps is performed at a site where the contaminated soil or soil slurry is generated.