JP6485513B1 - Heavy metal pollution control material and heavy metal pollution control method using the pollution control material - Google Patents

Abstract

The present invention is capable of insolubilizing heavy metals and the like in soil, solidifying the soil to improve strength, suppressing re-mudging, and maintaining the pH of the improved soil in a neutral region. Provide anti-pollution materials for heavy metals, etc., and heavy metal pollution control methods using the countermeasure materials. The anti-contamination material such as heavy metal of the present invention comprises dolomite compound, ferrous sulfate and a polymer material as essential components, and 55 to 55 of dolomite compound in the total amount of dolomite compound and ferrous sulfate. 95% by mass, containing ferrous sulfate in a proportion of 5 to 45% by mass, and 0.1% to 10% by mass of the polymer material based on the total amount of the dolomite compound and ferrous sulfate It is contained in a proportion and 0.5 to 8% by mass of MgO is contained in the pollution control material such as heavy metal. It is. [Selection figure] None

Description

  The present invention relates to pollution control materials such as heavy metals and heavy metal pollution control methods using the above pollution control materials, in particular, insolubilize heavy metals and the like, improve the strength of the treated soil by solidification performance and suppress re-mudging, The present invention relates to a pollution control material for heavy metals such as heavy metals having a soil reforming performance capable of maintaining soil pH at a neutral level and a pollution control method for heavy metals using the pollution control materials.

Conventionally, insolubilizing materials such as heavy metals in soil include iron powder-based insolubilizing materials such as ferric chloride and ferrous sulfate, cement-based insolubilizing materials, magnesium oxide (MgO) -based insolubilizing materials, quicklime and gypsum systems, blast furnaces Soil solidifying materials such as slag materials are known.
Iron powder-based insolubilizing materials such as ferric chloride and ferrous sulfate have a problem that heavy metals that can be insolubilized are limited to arsenic and it is difficult to cope with complex contamination.

Cement-based solidified materials, MgO-based solidified materials, or soil solidified materials using quicklime or blast furnace slag-based materials have been proposed.
However, these conventional soil-solidifying materials are affected by cement, quicklime, etc., so that the pH of the soil after modification becomes 10 or more and the alkalinity becomes strong, and the pH of the insolubilized soil remains high for a long time. Strongly alkaline groundwater flows out to the surrounding environment due to rainfall, etc., which may affect vegetation. Moreover, since the heavy metal insolubilization ability is low, there is a problem that heavy metals that have not been eluted in the neutral region are eluted.

As a magnesium oxide (MgO) -based solidifying material, a solidified and insolubilized material obtained by adding an organic polymer flocculant and a plurality of insolubilizing aids to improve soil strength is proposed in Japanese Patent Application Laid-Open No. 2003-225640 (Patent Document 1). Has been.
Although such materials have excellent solidification / insolubilization properties, the pH is likely to be more alkaline than untreated soil, and as with cement-based solidification materials, there is a possibility of affecting the surrounding environment. There is a problem that it is restricted by the application range of soil.

In order to prevent soil pH from becoming alkaline, JP 2014-185300 A (Patent Document 2) is based on gypsum and blast furnace slag, and is added with magnesium oxide or aluminum sulfate so that the pH becomes neutral. A soil-solidifying material adjusted to the above has been proposed.
However, although the pH is maintained neutral, the use index of the improved soil is limited because the cone index of the improved soil is as low as about 200 to 400 kN / m ² . Moreover, in order to improve the corn index to 200 to 400 kN / m ^2, it is necessary to add 100 kg or more of solidifying material per 1 m ³ of soil, which is not appropriate in terms of increase in the amount of improved soil solidifying material and cost. The insolubilization performance of heavy metals is not described. In addition, since the gypsum-based solidified material is water-soluble, dihydrate gypsum, which is a hydrated product, has a problem that the soil is re-mud and the corn index decreases in an environment where it is exposed to moisture such as rainwater for a long time. is there.

In the past, when modifying soil strength, such as improving the strength of heavy metal contaminated soil, an insolubilizing material and a solidifying material were added separately, but a material capable of expressing the solidifying performance and insolubilizing performance with a single material is expected. In addition, there is a growing need for materials in which the pH of the improved soil is in a neutral region in order to suppress the influence on the surrounding environment.
In recent years, the modified soil may be landfilled on the shores of lakes, shores, etc., and it has a re-mudging suppression function even when it comes in contact with moisture so that heavy equipment can run stably after landfill. Needs are growing.

As a pH-neutral solidified insolubilizing material, Japanese Patent No. 5748015 (Patent Document 3) proposes a pH-neutral solidifying insolubilized material combining light-burned MgO, aluminum sulfate, and ferrous sulfate. No. 5315096 (Patent Document 4) proposes a pH neutral solidified insolubilized material containing calcined gypsum (hemihydrate gypsum), an aluminum compound, a calcium component and / or a magnesium component.
However, the solidified and insolubilized material disclosed in Patent Document 3 has good pH neutrality maintenance ability, insolubilization performance, and improved corn index improvement of the modified soil, but there is a risk of re-mudging.
Further, the solidified and insolubilized material disclosed in Patent Document 4 is excellent in pH neutrality maintaining ability and insolubilized performance, but since the gypsum is the base like the pH neutralized solidified material, the cone index of the improved soil can be increased even if the amount added is increased. Is about 200 kN / m ² and there is a risk of re-mudging in the long term.
Therefore, there is a problem that the conventional solidified and insolubilized material is restricted by the application range of the improved soil.

JP 2003-225640 A JP 2014-185300 A Japanese Patent No. 5748015 Japanese Patent No. 5315096

  The object of the present invention is to solve the above-mentioned problems, insolubilize heavy metals and the like in the soil, has both solidification performance and re-mudging suppression function to improve and improve the strength of the treated soil, An object of the present invention is to provide a pollution control material such as heavy metal capable of maintaining the performance of maintaining pH neutral.

  Another object of the present invention is to apply the above-mentioned anti-pollution material for heavy metals to the soil contaminated with heavy metals to insolubilize heavy metals, etc., and to improve strength and suppress re-mudification by solidifying the treated soil. It is to provide a heavy metal pollution control method using heavy metal pollution control materials that demonstrate the soil modification performance.

  This invention discovered that the said subject can be solved by including the specific material as an essential content material by a specific compounding ratio, etc., and came to this invention.

(1) The pollution control material such as heavy metal of the present invention contains dolomite compound, ferrous sulfate and polymer material as essential components, and 55 to 95 of dolomite compound in the total amount of dolomite compound and ferrous sulfate. % By mass and ferrous sulfate in a proportion of 5 to 45% by mass, and the polymer material in a proportion of 0.1 to 10% by mass with respect to the total amount of the dolomite compound and ferrous sulfate And a heavy metal contamination countermeasure material containing 0.5 to 8% by mass of MgO.

(2) In the pollution control material for heavy metals and the like of (1) above, the pollution control material for heavy metals and the like is in a powder form.

(3) In the pollution control material such as heavy metal of (1) or (2) above, CaMg (CO ₃ ) ₂ , MgO, and CaCO ₃ are essential components of the dolomite compound, and at least one dolomite compound is used. It is characterized by that.

Furthermore, heavy metals pollution abatement material (1), the polymeric material is an organic polymeric flocculant and / or thickener, wherein the organic polymer flocculant is polyacrylamide, polyacrylic acid ester, polyamidine, poly It is at least one selected from the group consisting of sodium acrylate, polyethylene oxide, and sodium acrylate-acrylamide copolymer, and the thickener is selected from a cellulose-based thickener, a polyamide-based thickener, and a polyvinyl alcohol-based thickener. It is at least one selected from the group consisting of:

( 4 ) The heavy metal pollution control method of the present invention is a heavy metal pollution control method characterized by using any of the above (1) to ( 3 ) heavy metal pollution control materials mixed with soil.
( 5 ) The above-mentioned ( 4 ) heavy metal pollution control method is characterized in that the pH of the soil to which the heavy metal pollution control material is added is neutral (5.8 to 8.6).

The anti-pollution material for heavy metals and the like and the construction method for anti-pollution of heavy metals using the anti-corrosion material of the present invention can effectively insolubilize heavy metals etc. in the soil, and it is said that strength improvement by solidification of treated soil and re-mudging suppression While having the soil modification | reformation performance, the pH of the treated soil processed using the pollution control materials, such as heavy metals by this invention, can be kept neutral.
Therefore, in the past, insolubilized treated soil became alkaline, and strong alkaline groundwater flowed out to the surrounding environment due to rainfall, etc., and there was concern about the impact on vegetation. According to the above, since the pH of the improved soil is neutral, it is possible to cope with the site where the conventional insolubilizing material cannot be applied, and the application range of soil treatment contaminated with heavy metals can be expanded.
In addition, since re-mudging due to moisture from the outside can be suppressed, landfill treatment on the lake shore or coast can be made possible.
In particular, if the amount of lead, arsenic, and fluorine that are abundant in naturally contaminated soil is slightly above the soil elution standard, the effect of insolubilization and soil improvement performance can be achieved with a small addition amount. .

The present invention is illustrated by the following preferred examples, but is not limited thereto.
The pollution control material such as heavy metal of the present invention contains dolomite compound, ferrous sulfate and polymer material as essential components, and 55 to 95% by mass of dolomite compound in the total amount of dolomite compound and ferrous sulfate, Ferrous sulfate is contained in a proportion of 5 to 45% by mass, and the polymer material is contained in a proportion of 0.1 to 10% by mass with respect to the total amount of the dolomite compound and ferrous sulfate. And it is a pollution control material, such as a heavy metal, which contains 0.5-8 mass% of MgO in a pollution control material, such as a heavy metal.

  Preferably, the pollution control material such as heavy metal of the present invention is in a powder form. By being in powder form, handling and workability at the construction site becomes easier, and when mixed with soil, it can react quickly with moisture in the soil, adsorbing heavy metals etc. Can be insolubilized. Furthermore, ferrous sulfate, a dolomite compound, and a polymer material can be solidified by contacting and reacting with moisture in the soil, and the soil can be efficiently modified.

  Here, heavy metals and the like mean heavy metals and halogens, and heavy metals include, for example, one or more of manganese, chromium, copper, cadmium, mercury, selenium, lead, arsenic, cadmium, etc. In addition, a simple heavy metal and a compound thereof can be exemplified, and examples of the halogen include a simple substance such as fluorine and chlorine and a compound thereof. In addition to these, boron simple substance and compounds thereof contained in the second type specific harmful substances stipulated in the Soil Contamination Countermeasures Law can be exemplified, but they are not limited to these heavy metals and halogens.

  In the present invention, as an essential content material in pollution control materials such as heavy metals, dolomite compounds, ferrous sulfate and polymer materials are contained, and by setting each content to an amount within the above range, heavy metals etc. The above-mentioned, which can effectively insolubilize, improve the strength of the improved soil (improvement of solidification performance) and suppress soil re-mudging, and keep the pH of the improved soil neutral. It is possible to play the effects simultaneously.

The dolomite compound used for the pollution control material such as heavy metal of the present invention contains CaMg (CO ₃ ) ₂ , MgO and CaCO ₃ as essential components. Examples of the dolomite compound containing the above components include semi-baked dolomite mainly composed of MgO, CaCO ₃ , CaMg (CO ₃ ) ₂ , dolomite mainly composed of CaMg (CO ₃ ) ₂ , and the like. Those containing semi-baked dolomite and dolomite are preferred.
As the dolomite, any commercially available dolomite can be used, and the production area is not limited.
In addition, any half-baked dolomite that can be obtained in the market and semi-baked dolomite obtained by firing any dolomite available in the market can be used. It doesn't matter.
Semi-baked dolomite is not obtained by baking dolomite until the decomposition reaction shown in the following formula is completely completed, and contains MgO, CaCO ₃ , CaMg (CO ₃ ) ₂ as essential components.

Dolomite has a double salt structure in which the molar ratio of limestone CaCO ₃ and magnesite MgCO ₃ is 1: 1, and Ca ²⁺ ions and Mg ²⁺ ions are alternately layered across the CO ₃ ^2- group. In general, the MgCO ₃ ratio is 10 to 45% by mass. Dolomite is present in large amounts in Japan, and adsorbents such as heavy metals using dolomite are advantageous from the viewpoint of cost and environmental burden.

  Dolomite reacts with moisture in the soil and calcium and magnesium are eluted as ions. The eluted calcium reacts with the aluminum component in the soil to precipitate an ettringite-like hydrate, thereby binding the soil particles firmly to promote aggregation and obtaining soil solidification performance. Moreover, since dihydrate gypsum precipitates when the eluted calcium reacts with sulfate ions eluted from ferrous sulfate, the soil strength improvement performance is improved by reducing the water content ratio in the soil. Similarly, magnesium sulfate hexahydrate precipitates when the eluted magnesium reacts with sulfate ions eluted from ferrous sulfate, so the soil strength improvement performance is improved by reducing the moisture content in the soil. .

In order to develop soil solidification performance, dolomite having a CaMg (CO ₃ ) ₂ phase content of 50% by mass or more with a value obtained by analyzing the dolomite using the Rietveld method based on powder X-ray diffraction is preferably used. More preferred is dolomite with a CaMg (CO ₃ ) ₂ phase of 80% by mass or more.

  In addition, semi-calcined dolomite contributes to the insolubilization performance of heavy metals and the like, and has a low MgO content and a pH of 9 to 10 compared to MgO alone or lightly calcined dolomite. It can be used suitably for invention.

In particular, as the semi-fired dolomite, the content of residual CaMg (CO ₃ ) ₂ phase in the dolomite fired product analyzed using the Rietveld method by powder X-ray diffraction is 0.4 ≦ x ≦ 35.4 (mass) %) Can be suitably used.
CaMg contained in half burnt dolomite _{(CO 3) 2} phase was quantified, by using the semi-sintered dolomite CaMg _{(CO 3) 2} phases remaining amount within the above range, the composition according to the origin of the dolomite ore as a raw material Regardless of the difference between the two and the setting of the firing conditions such as the firing temperature, the dolomite can have the most excellent adsorption performance such as heavy metals.

As described above, dolomite is fired to exhibit a decomposition reaction represented by CaMg (CO ₃ ) ₂ → MgO + CaCO ₃ + CO ₂ . It is considered that pores are formed by the above thermal decomposition by firing of such dolomite and insolubilizing ability such as heavy metals is exhibited.
In the present invention, the residual amount of the dolomite phase (CaMg (CO ₃ ) ₂ phase) in the semi-fired dolomite obtained by firing dolomite is analyzed by the Rietveld method using powder X-ray diffraction, and the residual CaMg (CO ₃ ) ₂ phase is analyzed. Content of 0.4 ≦ x ≦ 35.4 (mass%), preferably 1.8 ≦ x ≦ 17.4 (mass%), and particularly preferably, heavy metals and the like are improved more favorably. It is possible to realize insolubilization.

For example, such a suitable semi-calcined dolomite has a residual CaMg (CO ₃ ) ₂ phase content in the calcined dolomite analyzed by the Rietveld method by powder X-ray diffraction, preferably 0.4 ≦ x ≦ 35. .4 (mass%), more preferably 1.8 ≦ x ≦ 17.4 (mass%).
The temperature at which dolomite is calcined is not particularly limited, and can be usually calcined at a temperature at which dolomite is calcined to produce semi-calcined dolomite, for example, 650-1000 ° C. If the residual CaMg (CO ₃ ) ₂ phase content is 0.4 ≦ x ≦ 35.4 (mass%), the baking time is not limited.

In addition, the dolomite compound contained in the pollution control material such as heavy metal of the invention is 55 to 95% by mass, preferably 70 to 95% by mass of the dolomite compound in the total amount of the total amount of the dolomite compound and ferrous sulfate. And containing ferrous sulfate in an amount of 5 to 45% by mass, preferably 5 to 30% by mass.
At such a ratio, the effect of the present invention can be achieved by including the dolomite compound and ferrous sulfate in the anti-contamination material such as heavy metal, and further including a polymer material.
By including a dolomite compound in a proportion less than the above range, the insolubilization performance of heavy metals and the like and the soil hardness improvement performance are reduced, and by including more than the above range, the pH of the modified soil tends to become alkaline. .
Also, by containing ferrous sulfate in a proportion less than the above range, the reducing component is insufficient and the effect of insolubilization to arsenic, hexavalent chromium, etc. is reduced, and if it is contained in a proportion greater than the above range, the pH becomes acidic. This is not economical because the manufacturing cost increases.

Further, the content of MgO in the anti-contamination material such as heavy metal of the present invention is 0.5 to 8% by mass, preferably 0.5 to 5% as a value analyzed using a Rietveld method by powder X-ray diffraction. % By mass.
MgO in the pollution control material such as heavy metals is derived from the contained dolomite compound, specifically, is derived from semi-baked dolomite obtained by baking dolomite, and more preferably half It is derived from calcined dolomite.
If the MgO content is less than 0.5% by mass, the insolubilizing ability with respect to lead, fluorine, etc. is lowered. If it exceeds 8% by mass, the pH of MgO obtained is alkaline, so the pH of the resulting anti-pollution material such as heavy metals is 9 It exhibits the alkalinity described above, and therefore, the pH buffering ability makes it difficult to lower the pH, making it difficult to make the soil pH neutral.
In addition, when the amount of ferrous sulfate is increased in order to adjust the pH of the soil, the essential material mixing ratio of the dolomite and the polymer material that guarantees the soil strength improvement ability decreases, and the improved soil There is a possibility that the solidification performance is difficult to improve.

The dolomite compound contained in the pollution control material such as heavy metal of the present invention is arbitrarily selected from one and / or two or more kinds of dolomite materials so that the essential components CaMg (CO ₃ ) ₂ , MgO and CaCO ₃ are included. Can be mixed. As an example, when semi-baked dolomite and dolomite are used in combination, MgO in the pollution control material such as heavy metals of the present invention can be obtained by setting dolomite to 100 to 2000 parts by mass with respect to 100 parts by mass of the preferred semi-baked dolomite. Although content can be 0.5-8 mass%, according to the dolomite type material to be used, the said mixing | blending ratio is not received.

Furthermore, the pollution control material such as heavy metal of the present invention contains ferrous sulfate as an essential material.
By containing ferrous sulfate, it can be insolubilized more effectively with respect to heavy metals such as arsenic and hexavalent chromium by its high reducing action, and since it is acidic, By adjusting the blending ratio, the soil treated with the pollution control material such as heavy metal of the present invention can be kept neutral.
In addition, ferrous sulfate is presumed to have an effect as an inorganic flocculant, and it may be considered that it has a function of improving the soil hardness by electrically agglomerating fine particles in the soil.

The anti-contamination material such as heavy metal of the present invention further contains a polymer material as an essential material, and the polymer material is preferably in a powder form because it needs to react with moisture in the soil.
As the properties of the polymer material used in the present invention, it is easy to dissolve in cold water, the pH of the aqueous solution is in a neutral region, and since it corresponds to various soils, the effective pH region covers the range of weak acid to weak alkalinity. In particular, it is desirable to use one that exhibits thickening when dissolved in water.

As polymer materials, polymer flocculants have the effect of agglomerating fine particles by reacting with moisture in the soil and making the soil easier to tighten, and particles are bonded by reacting with moisture in the soil and thickening. The thickener to be used can be used suitably.
As the kind of the organic polymer flocculant, at least one selected from the group consisting of an anionic polymer flocculant, a nonionic polymer flocculant, and a cationic polymer flocculant can be used. It is an anionic polymer flocculant having a neutral solution pH and a high viscosity.
As the organic polymer flocculant, at least one selected from the group consisting of polyacrylamide, polyacrylate, polyamidine, sodium polyacrylate, polyethylene oxide, and sodium acrylate-acrylamide copolymer can be used. Particularly preferred is a polyacrylamide type, which has a high aqueous solution viscosity when dissolved in the same amount of water.

  Further, as the thickener, at least one selected from the group consisting of cellulose derivatives, polyamide derivatives, polyvinyl alcohol derivatives, guar gum, starch, xanthan gum and propylene glycol can be used, and particularly preferred is cellulose. The derivatives are hydroxyethyl methylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC), and methylcellulose (MC).

In addition, the polymer material has a neutral pH, and can further contribute to strength improvement and re-mudging suppression by solidifying the soil by binding fine particles in the soil to become aggregated particles. .
The content is 0.1 to 10% by mass, preferably 1 to 5% by mass, based on the total amount of the dolomite compound and ferrous sulfate.
When it exceeds 10 mass%, cost will become high and it is not economical. Moreover, there exists a risk that the soil modification performance will fall by excessive addition. Furthermore, addition of a large amount of organic matter to the soil is not environmentally preferable.

The anti-contamination material such as heavy metal of the present invention contains the above-mentioned dolomite compound, ferrous sulfate and a polymer material containing essential ingredients in the above proportions. (Promulgated on August 23, 3rd year) The pH of the test solution prepared by the method based on the method can be neutral (5.8 to 8.6, which is the uniform drainage standard of the Environment Agency). Therefore, the soil pH can be neutral (5.8 to 8.6).
Particularly preferably, semi-baked dolomite and dolomite are used as the dolomite compound.
Moreover, in the range which does not affect the insolubilization performance etc. of pollution control materials, such as heavy metals of this invention, in addition to the said essential content material, arbitrary materials for pH adjustment, such as aluminum sulfate and slaked lime, slag, calcium carbonate, etc. Any auxiliary material for soil improvement may be added.

  The antipollution material such as heavy metal of the present invention can be prepared by mixing using any method as long as the above dolomite compound, ferrous sulfate and polymer material can be mixed uniformly.

The heavy metal pollution control method of the present invention is a method of mixing the heavy metal pollution control material of the present invention and contaminated soil, but the mixing method is not particularly limited. For example, the soil surface layer is contaminated with heavy metals and the like. It is possible to apply soil mixing equipment similar to conventional powder insolubilizing materials, such as improvement by heavy machinery having a surface modification performance by spraying countermeasure materials and mixing equipment with soil.
By implementing the countermeasure method for heavy metals of the present invention, the pH of the soil is neutral (5.8 to 8.6).

  In addition, heavy metal and other pollution control materials are preferably used in the form of powder, and as a mixing device with contaminated soil, it can be mixed using a backhoe, a deep mixing machine, a stationary mixer, a power blender, etc. And the compounding quantity of countermeasure processing materials, such as a heavy metal with respect to treated soil, fluctuates with the moisture content of soil, the solidification intensity | strength of the required treated soil, etc., and can be designed arbitrarily.

In this way, heavy metals such as heavy metals are brought into contact with contaminated soil from which heavy metals, fluorine, etc. are eluted, so that the heavy metals eluted from the contaminated soil are insolubilized and the solidification performance of the soil and the re-mudging suppression function are improved. Thus, the pH of the treated soil can be kept neutral.
For example, the amount of elution of heavy metals, etc., in the soil is all within the standards for soil elution, measured according to the Soil Contamination Countermeasures Law, and conforms to the Environmental Agency Notification No. 46 (promulgated on August 23, 1991) The pH of the test solution prepared by the method is in the range of 5.8 to 8.6 defined in the uniform drainage standards of the Environment Agency. Further, the Corn index is the soil classification of “Regarding Soil Use Standards” by the Ministry of Land, Infrastructure, Transport and Tourism. It can be set to 400 kN / m ² or more as defined in the standard third-grade improved soil, and can be designed to reliably satisfy the environmental standard.

The invention is illustrated by the following examples and comparative examples.
(Preparation of simulated contaminated soil)
Simulated contaminated soil was prepared as follows.
A raw soil having the characteristics shown in Table 1 below was prepared as a raw soil to be used when preparing the simulated contaminated soil.

Next, aqueous solutions in which arsenic, lead, and fluoride reagents were dissolved were prepared.
Specifically, as an aqueous solution containing arsenic, an aqueous solution in which a predetermined amount of sodium arsenite [NaAsO ₂ ] (manufactured by Kanto Chemical Co., Ltd.) is added and dissolved in water is used as an aqueous solution containing lead. An aqueous solution in which a predetermined amount of lead nitrate [Pb (NO ₃ ) ₂ ] (manufactured by Kanto Chemical Co., Ltd.) is added and dissolved in water is sodium fluoride [NaF] (Kanto Chemical Co., Inc.) as an aqueous solution containing fluoride. An aqueous solution prepared by adding a predetermined amount of (made) to water was prepared.

A predetermined amount of each of the obtained arsenic-containing aqueous solution, lead-containing aqueous solution, and fluoride-containing aqueous solution was added to the raw soil, and the mixture was stirred and mixed by a soil mixer so as to be sufficiently mixed at a low speed. After the soil adhering to the container of the soil mixer and the paddle was scraped off, it was thoroughly mixed again at a low speed.
Next, each soil was sealed in a polyethylene bag in a room at 20 ° C. and cured for 7 days to prepare each of three types of simulated contaminated soils: arsenic simulated contaminated soil, lead simulated contaminated soil, and fluorine simulated contaminated soil.

  For each simulated contaminated soil, prepare a test solution in accordance with the Environmental Agency Notification No. 46 (promulgated on August 23, 1991) and set the concentration of heavy metals, etc. in the test solution to JIS K 0102 “Factory Wastewater Test Method”. Measured in conformity. Table 2 shows the results of measured amounts of arsenic, lead, and fluorine eluted from each simulated contaminated soil.

(Raw materials used)
The following materials were used in preparing pollution control materials such as heavy metals.
・ Dolomite (powder): Tochigi Kuzu production ・ Semi-baked dolomite (powder): Baking dolomite from Tochigi Kuzu production (Table 4)
・ Ferrous sulfate: Made by Sakai Chemicals Co., Ltd. Monohydrate powder ・ Dolomite (powder): Tochigi Kuzu production ・ Polymer material: Anionic polymer flocculant-Sanyo Chemical Industries ・ Hemihydrate gypsum: Kanto Chemical Co., Ltd. Made calcined gypsum powder

  The chemical composition of the dolomite (powder: Tokugi Prefecture Kuzu production) was measured in accordance with JIS M 8851: 1983 “Analytical Method of Dolomite”. The results are shown in Table 3 below.

  The chemical composition of semi-baked dolomite (powder) obtained by baking the above dolomite ((powder: Tokugi Prefecture Kuzu production) was measured according to JIS M 8851: 1983 “Method for Analyzing Dolomite”. It is shown in Table 4 below.

  About the said semi-baked dolomite (powder) and dolomite (powder: Tochigi Prefecture Kuzu production), the content of each component was measured using the Rietveld method by powder X-ray diffraction. The results are shown in Table 5.

(Heavy metal pollution control materials)
The above-mentioned raw materials used were mixed at the blending ratios shown in Table 6 below to prepare pollution control materials such as heavy metals.
In addition, although the mixing order in particular of each raw material is not restrict | limited, each raw material was mixed simultaneously and each pollution control material, such as each heavy metal, was manufactured. In Table 6, semi-calcined dolomite and dolomite, which are dolomite compounds, indicate the amount (% by mass) blended in the inner part of the total amount of dolomite compound and ferrous sulfate. The polymer material indicates an amount (% by mass) blended in an external ratio with respect to the total amount of semi-baked dolomite, ferrous sulfate and dolomite.

(Test example)
Test Example 1: Measurement of MgO content in pollution control material such as heavy metal For each pollution control material such as heavy metal, the content of MgO was measured using the Rietveld method by powder X-ray diffraction. The results are shown in Table 7 below.

Test Example 2: Insolubilization test for heavy metals, etc. To each 1 m ^{3 of the} above-mentioned simulated contaminated soil, 50 kg of each anti-pollution material for heavy metals shown in Table 6 was added and kneaded at a low speed for 2.5 minutes with a soil mixer. The soil adhering to the container and paddle of the soil mixer was scraped off, and again kneaded at a low speed for 2.5 minutes to prepare each test soil.
After preparing the test soil, a test solution was prepared for each test soil after 7 days (age 7 days) by a method based on the Environmental Agency Notification No. 46 (promulgated on August 23, 1991). Based on JIS K 0102 “Factory drainage test method”, arsenic, lead, and fluorine elution amounts were measured.
As Comparative Example 1, arsenic, lead, and fluorine elution amounts were measured in the same manner with respect to each simulated contaminated soil in which countermeasure materials such as heavy metals were not mixed with each simulated contaminated soil.
The results are shown in Table 7.

Also, the pH of the arsenic simulated contaminated soil solution prepared by a method based on Environment Agency Notification No. 46 (promulgated on August 23, 1991) is measured according to JIS Z8802: 2011 “pH measurement method”. did.
These results are shown in Table 7 below.

Test Example 3: Soil solidification test To 1 m ^{3 of the} above arsenic-containing simulated contaminated soil, 50 kg of various anti-pollution materials such as heavy metals shown in Table 6 were added and kneaded at a low speed for 2.5 minutes with a soil mixer. The soil adhering to the container of the soil mixer and the paddle was scraped off, and again kneaded at a low speed for 2.5 minutes to prepare a test soil.
After preparing the test soil, each test soil was filled into 10 cm molds stipulated in JISA 1210: 2009 “Soil compaction test method by tamping” in three layers and sealed at 20 ° C. until the age of 7 days. After curing, the cone index was measured in accordance with JIS A 1228 “Soil compaction test method by tamping”.
The results are shown in Table 7 below.

Test Example 4: Soil re-sludge test To 1 m ^{3 of the} arsenic-containing simulated contaminated soil, 50 kg of various anti-pollution materials such as heavy metals shown in Table 6 were added and kneaded at a low speed for 2.5 minutes with a soil mixer. Thereafter, the soil adhering to the container of the soil mixer and the paddle was scraped off and kneaded again at a low speed for 2.5 minutes to prepare a test soil.
After preparing the test soil, each test soil was filled into 10 cm molds stipulated in JISA 1210: 2009 “Soil compaction test method by tamping” in three layers and sealed at 20 ° C. until the age of 7 days. After curing, it was demolded to obtain a specimen. The specimen was put into a water tank storing room temperature tap water, and left still for 24 hours in a state where the specimen was completely immersed in water, and the presence or absence of re-mudging was confirmed by visual inspection from how the specimen collapsed (1 Second immersion). In the case of “not re-mudged” or “part of collapse” of the specimen, the specimen was taken out of water and dried at 30 ° C. for 24 hours. The specimen was allowed to stand for 24 hours in a state where it was completely immersed again in water, and the presence or absence of re-mudging was confirmed by visual observation from the state of collapse of the specimen (second immersion). The results are shown in Table 7.

In Table 7, an arsenic elution amount that was not more than the following soil elution amount standard based on the Soil Contamination Countermeasures Law was accepted (arsenic: 0.01 mg / L).
The test solution pH was determined to be within the range of 5.8 to 8.6 defined by the uniform drainage standards of the Environment Agency.
The corn index passed 400 kN / m ² or more as stipulated in the third type improved soil of the soil classification criteria of “Regarding the Soil Use Standard” of the Ministry of Land, Infrastructure, Transport and Tourism.
The re-mudging test was evaluated as ○ when the initial shape of the specimen was maintained, Δ when part of the specimen was broken or cracked, and x when the shape disappeared and became muddy. The above-mentioned two underwater immersion tests were carried out, and even after the second immersion, the initial shape was maintained, and a specimen that could not be visually observed for collapse or cracking was evaluated as acceptable (O).

From Table 7 above, in the examples using the pollution control materials such as heavy metals of the present invention, the arsenic elution amount in the test soil of 7 days of age is all within the soil elution amount standard, and the pH of the test solution is uniform. It was within the drainage standard range, the cone index was 400 kN / m ² or more, and the specimen did not re-mud.
In the examples, the measurement results of Test Examples 2 to 4 evaluated by the same method for the lead-containing test soil and the fluorine-containing test soil are the amounts of elution of lead and fluorine in the test soil of 7 days of age. Were all within the soil elution standard (According to the Soil Contamination Countermeasures Law, the standard was below the soil elution standard. Lead: 0.01 mg / L, fluorine: 0.8 mg / L) ( Table 7). Further, the test solution pH was uniformly within the drainage standard range and the cone index was 400 kN / m ² or more, and the specimen was not re-mudged and no collapse was observed.

The anti-contamination material C1 such as heavy metal that does not contain the polymer material of Comparative Example 2 has a corn index higher than that of the simulated contaminated soil itself of Comparative Example 1, but is less than 400 kN / m ² and is the first water The specimen re-mudged by immersion.
This is because the corn index is improved by the precipitation of ettringite and hydrate by the reaction of calcium ions and magnesium ions eluted from semi-baked dolomite and dolomite and sulfate ions eluted from ferrous sulfate, but the polymer material is It does not exist and there is no agglomeration effect of fine grains in the soil. Therefore, it is considered that the growth of the corn index is low and the re-mudging suppression effect is not exhibited.

The anti-contamination material C2 such as heavy metal shown in Comparative Example 3 does not contain a polymer material, and the content of the dolomite compound is outside the scope of the present invention, and the MgO content is large. Because of the large amount, the insolubilization performance of lead, arsenic, and fluorine is high, but the growth of the corn index is almost less than that of the simulated contaminated soil itself in Comparative Example 1 because there are few substances with soil coagulation effect performance and solidification performance. It was less than 400 kN / m ² , and the specimen was re-mudged by first immersion in water.

Regarding the pollution control material C3 such as heavy metal shown in Comparative Example 4, since the MgO content was 0, the amount of elution of fluorine exceeded the soil elution amount standard although the pH became neutral.
This is thought to be because there is no physical adsorption to the micropores present in the semi-fired dolomite and a poorly soluble compound is not formed by the reaction of fluoride ions with the semi-fired dolomite component.

About the pollution control material C4, such as heavy metals which do not contain ferrous sulfate shown in the comparative example 5, pH became 9.1 and alkaline. The amount of arsenic and lead elution exceeded the soil elution standard.
Arsenic is considered to be because ferrous sulfate is not contained and hardly soluble iron arsenate does not precipitate.
It is thought that lead does not contain sulfates and hardly soluble compounds such as lead sulfate are not produced.

About countermeasure material C5, such as a heavy metal shown in the comparative example 6, although it contains all the semi-baked dolomite, ferrous sulfate, dolomite, and a polymeric material, it is hydrated because the content of a dolomite compound falls outside the scope of the present invention. Sediment precipitation was reduced, soil solidification performance was low, and the corn index was less than 400 kN / m ² . Moreover, since there were many compounding quantities of ferrous sulfate, pH of the modified soil became acidic with 5.7. Since the anionic polymer flocculant is acidic and reduces the agglomeration effect of the soil particles, the cone index was less than 400 kN / m ² .

  Since the countermeasure material C7 such as heavy metal shown in Comparative Example 7 is a single half-water gypsum, the insolubilization performance, solidification performance, and re-mudging suppression effect did not reach the acceptance criteria.

  The anti-contamination material for heavy metals and the like, and the anti-contamination method for heavy metals using the anti-corrosion material of the present invention can insolubilize heavy metals and halogens efficiently, and solidify the soil and improve the strength while keeping the improved soil neutral. It can be used effectively for soil improvement where heavy metals, halogens, etc. elute, and can be used in large quantities by excavation and construction work such as tunnels and dams. It can be effectively applied to the treatment of contaminated soil from which the generated heavy metals are eluted.

Claims (5)

Dolomite compound, ferrous sulfate and polymer material as essential components, 55 to 95% by mass of dolomite compound and 5 to 45% by mass of ferrous sulfate in the total amount of dolomite compound and ferrous sulfate In addition, the polymer material is contained in a proportion of 0.1 to 10% by mass with respect to the total amount of the dolomite compound and ferrous sulfate, and MgO is contained in the pollution control material such as heavy metal. the unrealized 0.5-8 wt%, wherein the polymeric material is an organic polymeric flocculant and / or thickener, wherein the organic polymer flocculant is polyacrylamide, polyacrylic acid ester, polyamidine, polyacrylic acid At least one selected from the group consisting of soda, polyethylene oxide and sodium acrylate-acrylamide copolymer, the thickener is a cellulose thickener, a polyamide thickener, and Characterized in that at least one selected from the group consisting of polyvinyl alcohol thickener, heavy metals pollution abatement material.   The heavy metal pollution control material according to claim 1, wherein the heavy metal pollution control material is in a powder form. In the pollution control material such as heavy metal according to claim 1 or 2, the dolomite compound is an essential component containing CaMg (CO ₃ ) ₂ , MgO, CaCO ₃ , and at least one dolomite compound is used. Heavy metal pollution control materials. A heavy metal pollution control method, comprising mixing the heavy metal pollution control material according to any one of claims 1 to 3 with soil. The heavy metal pollution control method according to claim 4, wherein the pH of the soil to which the heavy metal pollution control material is added is neutral (5.8 to 8.6).