JP6787142B2 - Heavy metal pollution control material and heavy metal pollution control method using the pollution control material - Google Patents

Description

The present invention relates to a pollution control material for heavy metals and the pollution control method for heavy metals using the pollution control material, and in particular, insolubilizes heavy metals and the like, improves the strength of the treated soil by solidification performance, and re-mud the treated soil. The present invention relates to a pollution control material for heavy metals and the like having soil reforming performance capable of suppressing and maintaining a neutral soil pH, and a pollution control method for heavy metals and the like using the pollution control material.

Conventionally, as insolubilizing materials such as heavy metals in soil, iron powder-based insolubilizing materials such as ferric chloride and ferrous sulfate, cement-based insolubilizing materials, magnesium oxide (MgO) -based insolubilizing materials, quicklime, slag, and blast furnaces have been used. Soil solidifying materials made of slag-based materials are known.
Iron powder-based insolubilizers such as ferric chloride and ferrous sulfate have a problem that heavy metals that can be insolubilized are limited to arsenic and the like, and it is difficult to deal with complex pollution.

Cement-based solidifying materials, MgO-based solidifying materials, or soil solidifying materials using quicklime or blast furnace slag-based materials have been proposed.
However, due to the influence of these cements and quicklime, the pH of the reformed soil becomes stronger at 10 or more, and the pH of the insolubilized soil continues to be high for a long period of time. Therefore, it becomes strongly alkaline due to rainfall or the like. It is possible that groundwater will flow out to the surrounding environment and that it will affect vegetation. In addition, 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, Japanese Patent Application Laid-Open No. 2003-225640 (Patent Document 1) proposes a solidifying insolubilizing material to which an organic polymer flocculant or a plurality of insolubilizing aids are added to improve soil strength. Has been done.
Although such materials have excellent solidification and insolubilization properties, their pH tends to be more alkaline than that of untreated soil, and they may affect the surrounding environment in the same way as cement-based solidifying materials. There is a problem that the scope of application is restricted.

In order to prevent the soil pH from becoming alkaline, Japanese Patent Application Laid-Open No. 2014-185300 (Patent Document 2) is based on gypsum and blast furnace slag, and magnesium oxide and aluminum sulfate are added so that the pH becomes neutral. A conditioned soil solidifying material has been proposed.
However, although the pH is maintained at neutrality, the cone index of the improved soil is as low as about 200 to 400, which limits the use of the improved soil. Further, in order to improve the cone 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 and cost, and further, heavy metal There is no description about insolubilization performance.
Further, since gypsum-based solidifying material is water-soluble in dihydrate gypsum, which is a hydration product, there is a problem that it is remudified in an environment where it is exposed to water such as rainwater for a long period of time.

In the past, when modifying heavy metal-contaminated soil to improve soil strength, insolubilizing material and solidifying material were added separately, but materials that express solidification performance and insolubilizing performance with one material are expected. In addition, there is an increasing need for materials in which the pH of the improved soil is in the neutral region in order to suppress the impact on the surrounding environment.

As a pH-neutral solidified insolubilizer, Japanese Patent No. 5748015 (Patent Document 3) proposes a pH-neutral solidified insolubilizer in which light-baked MgO, aluminum sulfate, and ferrous sulfate are combined. Japanese Patent No. 5315096 (Patent Document 4) proposes a pH-neutral solidifying insolubilizing material containing calcined gypsum (hemihydrate gypsum), an aluminum compound, a calcium component and / or a magnesium component.
However, although these conventional solidified insolubilizers are excellent in pH neutrality maintaining ability and insolubilizing performance, they are based on gypsum like the pH neutral solidified materials, so even if the amount added is increased, the cone index of the improved soil will increase. The scope of application of the improved soil is restricted because it will be as low as about 200 kN / m ² and there is a risk that the soil whose strength has been improved by solidifying the treated soil will be remudified in the long term due to external moisture. There is a problem of receiving.

Japanese Unexamined Patent Publication No. 2003-225640 Japanese Unexamined Patent Publication No. 2014-185300 Japanese Patent No. 5748015 Japanese Patent No. 5315096

An object of the present invention is to solve the above-mentioned problems, to insolubilize heavy metals and the like in the soil, to improve the strength of the treated soil and to reform it, and to have a solidification performance and a remudification suppressing function, and to improve the soil. It is to provide a pollution control material such as a heavy metal capable of maintaining the performance of keeping the pH neutral.

Another object of the present invention is to apply the above-mentioned anti-contamination material for heavy metals of the present invention to soil contaminated with heavy metals and the like to insolubilize the heavy metals and the like, and to improve the strength and suppress remudification by solidifying the treated soil. It is to provide a heavy metal pollution control method using a heavy metal pollution control material that demonstrates the soil reforming performance.

The present invention has arrived at the present invention by finding that the above problems can be solved by including a specific material as an essential contained material in a specific blending ratio.

(1) The anti-pollution material for heavy metals, etc. contains semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and / or calcium carbonate, and a polymer material as essential components, and amorphous calcium silicate and / or It contains 50% by mass or more of calcium carbonate, 5 to 30% by mass of semi-baked dolomite, and 5 to 45% by mass of ferrous sulfate, and the polymer material is amorphous calcium silicate and / or carbonate. It is a pollution control material for heavy metals and the like, which is characterized by containing calcium, semi-baked dolomite and ferrous sulfate in a ratio of 0.1 to 10% by mass in terms of external percentage with respect to the total mass.

(2) The heavy metal pollution control material according to (1) above is characterized in that the heavy metal pollution control material is in powder form.

(3) In the heavy metal pollution control material of (1) or (2) above, the semi-calcined dolomite is the residual CaMg (CO ₃ ) _two- phase in the dolomite calcined product analyzed by the Rietveld method by powder X-ray diffraction. The content of is 0.4 ≦ x ≦ 35.4 (mass%).

(4) In any of the above (1) to (3) heavy metal pollution control materials, amorphous calcium silicate is at least one selected from the group consisting of blast furnace slag and steelmaking slag, and the polymer material is organic. It is a polymer flocculant and / or thickener, and the organic polymer flocculant is composed of a group consisting of polyacrylamide, polyacrylic acid ester, polyamidine, sodium polyacrylate, polyethylene oxide, and sodium acrylate-acrylamide copolymer. The thickener is at least one selected, and the thickener is at least one selected from the group consisting of a cellulose-based thickener, a polyamide-based thickener, and a polyvinyl alcohol-based thickener.

(5) The heavy metal pollution control method is a heavy metal pollution control method characterized by using any of the above (1) to (4) heavy metal pollution control materials mixed with soil.

The heavy metal pollution control material of the present invention and the heavy metal pollution control method using the control material can effectively insolubilize heavy metals in the soil, and improve the strength and suppress remudification by solidifying the treated soil. In addition to having soil reforming performance, it is possible to maintain the pH of soil treated with the pollution control material such as heavy metals according to the present invention in a neutral state.
Therefore, in the past, the insolubilized soil became alkaline, and there was concern that strongly alkaline groundwater would flow out to the surrounding environment due to rainfall or the like and affect the vegetation. According to this, since the pH of the improved soil is neutral, it is possible to deal with the site where the conventional insolubilizing material cannot be applied, and the applicable range of soil treatment contaminated with heavy metals or the like can be expanded.
In addition, since it is possible to suppress remudification due to moisture from the outside, it is possible to perform landfill treatment on the shore or coast of the lake.
In particular, if the elution amount of lead, arsenic, and fluorine, which are abundant in naturally-derived contaminated soil, slightly exceeds the soil elution amount standard, the effect of insolubilizing and exhibiting soil reforming performance is exhibited with a small amount of addition. ..

The present invention will be described with reference to the following preferred examples, but the present invention is not limited thereto.
The heavy metal pollution control material of the present invention contains semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and / or calcium carbonate, and a polymer material as essential components, and contains amorphous calcium silicate and / or It contains 50% by mass or more of calcium carbonate, 5 to 30% by mass of semi-baked dolomite, and 5 to 45% by mass of ferrous sulfate, and the polymer material is amorphous calcium silicate and / or carbonate. It is a pollution control material for heavy metals and the like, which contains calcium, semi-baked dolomite, and ferrous sulfate at a ratio of 0.1 to 10% by mass in terms of the total mass.

Preferably, the antifouling material for heavy metals and the like of the present invention is in powder form. The powder form facilitates handling and workability at the construction site. Further, when mixed with soil, it can rapidly react with water in the soil to adsorb heavy metals and the like and insolubilize them. Further, the amorphous calcium silicate and / or calcium carbonate and the polymer material absorb water and react with each other to solidify the soil, and the soil can be efficiently reformed.

Here, the heavy metal and the like mean a heavy metal and a halogen, and examples of the heavy metal include one or more kinds of heavy metals such as manganese, chromium, copper, cadmium, mercury, selenium, lead, arsenic and cadmium. Examples of halogens include dioxin such as chlorine and fluorine, trichloroethylene, tetrachloromethane, chlorinated diphenyl, chlorinated paraffin, and boron contained in Type 2 Specified Hazardous Substances stipulated in the Soil Contamination Countermeasures Law. It can, but is not limited to these heavy metals and halogens.

The present invention contains semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and / or calcium carbonate, and a polymer material as essential components in the anti-pollution material for heavy metals, etc., and the respective contents are described above. By setting the amount within the range, heavy metals and the like can be effectively insolubilized, and the soil can be reformed by improving the strength of the improved soil (improving solidification performance) and suppressing remudification. The above effect of keeping the pH of the improved soil neutral can also be achieved at the same time.

As the semi-baked dolomite, which is an essential content material used for the anti-contamination material for heavy metals of the present invention, any semi-baked dolomite available on the market can be used, regardless of the place of origin or the composition of the raw material dolomite.
Dolomite has a double salt structure in which the molar ratio of dolomite CaCO ₃ and magnesite MgCO ₃ is 1: 1 and Ca ²⁺ ions and Mg ²⁺ ions are alternately layered with CO ₃ ^2- groups in between. Generally, it means that the ratio of magnesium carbonate is 10 to 45% by mass. Dolomite is abundant in Japan, and adsorbents such as heavy metals using dolomite are advantageous in terms of cost and environmental load.

Semi-baked dolomite greatly contributes to the development of insolubilization performance of heavy metals and the like, and has a pH of 9 to 10 which is weakly alkaline as compared with MgO-based and light-baked dolomite, so that it is preferably used in the present invention. Can be done.

In particular, as semi-calcined dolomite, the content of the residual CaMg (CO ₃ ) _two- phase in the dolomite calcined product analyzed by the Rietveld method by powder X-ray diffraction is 0.4 ≦ x ≦ 35.4 (mass%). ), The semi-baked dolomite can be preferably used.
This is because the _two phases of CaMg (CO ₃ ) contained in the semi-calcined dolomite are quantified and the residual amount is within the above range, so that the composition of the dolomite ore as a raw material differs depending on the production area, the firing temperature, etc. This is because the dolomite can have the maximum excellent adsorption performance for heavy metals and the like regardless of the setting of the firing conditions.

When dolomite is calcined, it exhibits a decomposition reaction represented by CaMg (CO ₃ ) ₂ → MgO + CaCO ₃ + CO ₂ . It is considered that pores are formed by the above-mentioned thermal decomposition by firing dolomite and exhibit the insolubilizing ability of heavy metals and the like.
In the present invention, the residual amount of the dolomite phase (CaMg (CO ₃ ) ₂ phase) in the semi-calcined dolomite obtained by calcining dolomite is analyzed by the Rietveld method by powder X-ray diffraction, and the residual CaMg (CO ₃ ) ₂ phase is analyzed. If the content of semi-calcined dolomite is 0.4 ≦ x ≦ 35.4 (mass%), preferably 1.8 ≦ x ≦ 17.4 (mass%), the dolomite is excellent insolubilizing heavy metals and the like. Performance can be obtained.
By setting the content of the residual CaMg (CO ₃ ) _two phase within the above range, it is possible to realize better insolubilization of heavy metals and the like.

Such suitable semi-baked dolomite has a residual CaMg (CO ₃ ) _two- phase content of 0.4 ≦ x ≦ 35.4 (mass%) in the dolomite fired product analyzed by the Rietveld method by powder X-ray diffraction. ), It can be manufactured by firing.
The temperature at which the dolomite is calcined is not particularly limited, and the dolomite can be calcined at a temperature at which the dolomite is usually calcined to produce semi-calcined dolomite, for example, 650 to 1000 ° C. The firing time is not limited as long as the content of the residual CaMg (CO ₃ ) _two phases is 0.4 ≦ x ≦ 35.4 (mass%).

The blending amount of the semi-baked dolomite is 5 to 30% by mass, preferably 5 to 15% by mass in the insolubilizing material such as heavy metals.
If it is less than 5% by mass, the insolubilizing ability for lead and fluorine decreases, and if it exceeds 30% by mass, the pH of the obtained anticontamination material such as heavy metals is 9 or more, which is alkaline, and therefore the pH is difficult to decrease due to the pH buffering ability. As a result, a large amount of ferrous sulfate is required, and the mixing ratio of amorphous calcium silicate and / or calcium carbonate and polymer materials, which guarantees the ability to improve soil strength, is reduced, resulting in improvement. It becomes difficult to improve the solidification performance of the soil.

Further, the antifouling material for heavy metals and the like of the present invention contains ferrous sulfate as an essential material.
By containing ferrous sulfate, due to its high reducing action, it can be more effectively insolubilized with heavy metals such as arsenic and hexavalent chromium, and because it is acidic, it is a material containing other essential materials. By adjusting the blending ratio, it is possible to maintain the soil treated with the pollution control material such as heavy metals of the present invention in a neutral state.
In addition, ferrous sulfate is presumed to have an effect as an inorganic flocculant, and it is also considered that ferrous sulfate has a function of electrically aggregating fine particles in the soil to improve soil hardness.

The blending amount of ferrous sulfate is 5 to 45% by mass, preferably 10 to 30% by mass in the insolubilizing material such as heavy metals.
If it is less than 5%, the reducing property is lowered, the insolubilizing effect on arsenic, hexavalent chromium and the like is lowered, and if it exceeds 45% by mass, the pH tends to be acidic and the manufacturing cost is high, which is not economical.

The heavy metal pollution control material of the present invention further contains amorphous calcium silicate and / or calcium carbonate as essential materials.
As the amorphous calcium silicate, any commercially available amorphous calcium silicate can be used, and for example, at least one selected from the group consisting of blast furnace slag and steelmaking slag can be preferably used. More suitable is blast furnace slag, and particularly suitable is blast furnace granulated slag.
For example, blast furnace slag and the like have a pH of about 9 to 10 and are weakly alkaline, and have latent hydraulic limeness and develop strength over a long period of time, so that they have the effect of modifying and improving the solidification performance of soil. , It can be used particularly preferably.
Calcium carbonate elutes calcium and reacts with aluminum components in the soil to precipitate ettringite-like hydrates, which firmly binds soil particles to promote agglomeration and improve soil solidification performance. Obtainable.
Amorphous calcium silicate and calcium carbonate can be used alone or in combination, and when used in combination, the use design can be performed in any ratio.

The blending amount is 50% by mass or more, preferably 60% by mass or more in the insolubilizing material such as heavy metals.
If the amount added is less than 50% by mass, the solidification performance of the improved soil deteriorates, which is not desirable.
The composition of the slag to be used is not particularly limited, but a slag-blended slag blended with gypsum can be preferably used because it promotes hydraulic limeness.
Further, the slag is preferably in powder form, and the specific surface area of the brain is 8,000 cm ² / g or less, more preferably 3,000 to 5,000 cm ² / g, which solidifies and improves the soil. Desirable from the point of view. Furthermore, in order to suppress the elution of heavy metals from the slag itself, it is necessary that the elution amount and content of all the specific hazardous substances contained in the slag itself are below the environmental standard values.

The heavy metal pollution control material of the present invention further contains a polymer material as an essential material, and the form of the polymer material is preferably a powder form because it needs to absorb water from soil and react.
The properties of the polymer material used in the present invention are that it is easily dissolved in cold water, that the pH of the aqueous solution is in the neutral range, and that it is compatible with various soils, so that the effective pH range covers the range of weak acid to weak alkaline. It is desirable to use one that shows thickening when dissolved in water.

As a polymer material, a polymer flocculant that reacts with water in the soil to aggregate fine particles to make the soil easier to tighten, and a polymer flocculant that reacts with water in the soil to thicken the particles to bind the particles. A thickener to be used can be preferably used. As the type 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, and more preferably one is particularly preferable. It is an anionic polymer flocculant with a neutral solution pH and high viscosity. As the organic polymer flocculant, at least one selected from the group consisting of polyacrylamide, polyacrylic acid ester, polyamidine, sodium polyacrylate, polyethylene oxide, sodium acrylate-acrylamide copolymer can be used. However, more preferable is a polyacrylamide type, which has a high aqueous 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 suitable ones are cellulose. Derivatives are hydroxyethyl methyl cellulose (HEMC), hydroxypropyl methyl cellulose (HPMC), and methyl cellulose (MC).

In addition, the above-mentioned polymer material has a neutral pH, and further binds fine particles in the soil to form aggregated particles, which can contribute to improvement of strength and suppression of remudification by solidifying the soil. ..
The blending amount is 0.1 to 10% by mass, preferably 1 by mass, based on the total amount of the semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and / or calcium carbonate. ~ 5% by mass.
If it exceeds 10% by mass, the cost becomes high and it is not economical. Moreover, adding a large amount of organic matter to the soil is environmentally unfavorable.

The heavy metal pollution control material of the present invention contains the above semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and / or calcium carbonate, and the essential content material of the polymer material in the above blending ratio. When mixed with soil, the pH can be set to neutral (5.8 to 8.6, which is a uniform drainage standard).
Further, in addition to the above-mentioned essential containing materials, any material for pH adjustment such as aluminum sulfate and slaked lime may be added as long as it does not affect the insolubilization performance of the pollution control material such as heavy metals of the present invention.

The heavy metal pollution control material of the present invention uses any method as long as the semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and / or calcium carbonate, and the polymer material can be uniformly mixed. Can be mixed and prepared.

Further, the heavy metal pollution control method of the present invention is a method of mixing a heavy metal pollution control material and a contaminated soil, but the mixing method is not particularly limited, and for example, a heavy metal pollution control material on the soil surface layer. It is possible to apply the same soil mixing equipment as the conventional powder insolubilizer, such as improvement by heavy machinery having surface modification performance and mixing equipment with soil.

In addition, as the anti-contamination material for heavy metals, etc., the powder form is preferably used, and as a mixing device with contaminated soil, it is excessive to mix using a backhoe, a deep mixing treatment machine, a stationary mixer, a power blender, or the like. Therefore, the blending amount of the heavy metal or the like countermeasure treatment material for the treated soil varies depending on the water content of the soil, the required solidification strength of the treated soil, and the like, and can be arbitrarily designed.

In this way, by bringing the anti-contamination material such as heavy metals into contact with the contaminated soil from which heavy metals and fluorine are eluted, the heavy metals and the like eluted from the contaminated soil are insolubilized, and the solidification performance of the soil and the function of suppressing remudification are improved. This makes it possible to maintain the pH of the treated soil in a neutral state.
For example, the elution amount of heavy metals, etc. in soil is within the soil elution amount standard for all elution amounts measured based on the Soil Contamination Countermeasures Law, and also complies with 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 specified in the uniform wastewater standard of the Environment Agency, and the cone index is the soil classification of "Regarding the soil utilization standard" of the Ministry of Land, Infrastructure, Transport and Tourism. It can be 400 kN / m ² or more specified in the standard type 3 improved soil, and it can be designed to surely satisfy the environmental standard.

The present invention will be described with reference to the following examples and comparative examples.
(Preparation of simulated contaminated soil)
The simulated contaminated soil was prepared as follows.
As the raw soil used when preparing the simulated contaminated soil, the raw soil having the characteristics shown in Table 1 below was prepared.

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

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 above-mentioned raw soil, and the mixture was stirred and mixed with a soil mixer so as to be sufficiently mixed at a low speed. After scraping off the soil adhering to the container and paddle of the soil mixer, the mixture was thoroughly mixed again at low speed.
Next, each soil was sealed in a polyethylene bag in a room at 20 ° C. and cured for 7 days to prepare three types of simulated contaminated soil, arsenic simulated soil, lead simulated soil, and fluorine simulated soil.

For each simulated contaminated soil, prepare a test solution by a method in accordance with Notification No. 46 of the Environmental Agency (promulgated on August 23, 1991), and set the concentration of heavy metals in the test solution to JIS K 0102 "Factory wastewater test method". Measured according to. The results of the measured amounts of arsenic, lead, and fluorine eluted from each simulated contaminated soil are shown in 2 below.

(Raw materials used)
The following materials were used in preparing the anti-pollution materials for heavy metals.
・ Semi-baked dolomite (powder): Kuzu production in Tochigi prefecture ・ Iron sulfate: Monohydrate powder manufactured by Sakai Chemical Co., Ltd. ・ Amorphous calcium silicate: Blast furnace slag fine powder manufactured by Nittetsu Sumikin Slag Products Co., Ltd. (Product name: Esment 4000 Brain with plaster)
・ Calcium carbonate: Kanto Chemical Co., Ltd. Deer first grade powder ・ Polymer material: Polymer coagulant-Himo, thickener-Matsumoto Yushi Pharmaceutical Co., Ltd. ・ Semi-hydrated gypsum: Kanto Chemical Co., Inc. baked gypsum powder

The chemical composition of the semi-baked dolomite (powder): produced in Kuzu, Tochigi Prefecture) was measured in accordance with JIS M 8851: 1983 "Analytical method of dolomite". The results are shown in Table 3 below.

(Pollution control materials for heavy metals, etc.)
Each of the above raw materials used was mixed at the blending ratio shown in Table 4 below to prepare each heavy metal or other pollution control material.
The mixing order of each raw material is not particularly limited, but each raw material is mixed at the same time to produce a pollution control material such as each heavy metal. In Table 4, the polymer material was blended in an external proportion (mass%) with respect to the total mass of amorphous calcium silicate and / or calcium carbonate, semi-baked dolomite, and ferrous sulfate. ) Is shown.

(Test example)
Test Example 1: Insolubilization test of heavy metals, etc. To 1 m ^{3 of the} above simulated contaminated soil, 50 kg of each heavy metal contamination countermeasure material shown in Table 4 is added, and the mixture is 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 kneaded again at low speed for 2.5 minutes to prepare each test soil.
After preparing the test soil, for each test soil 7 days later (7 days old), a test solution was prepared by a method in accordance with Notification No. 46 of the Environment Agency (promulgated on August 23, 1991), and the test solution was being tested. The concentration of heavy metals, etc. was measured according to JIS K 0102 "Factory Wastewater Test Method", and the amounts of arsenic, lead, and fluorine eluted were measured.
As Comparative Example 1, the amounts of arsenic, lead, and fluorine eluted were measured in the same manner for each simulated contaminated soil in which a countermeasure material such as a heavy metal was not mixed with each simulated contaminated soil.
The results are shown in Table 5.

In addition, the pH of the test solution of the above arsenic simulated contaminated soil prepared by the method conforming to Notification No. 46 of the Environment Agency (promulgated on August 23, 1991) is measured according to JIS Z8802: 2011 "pH measurement method". did.
These results are shown in Table 5 below.

Test Example 2: Soil solidification test To 1 m ^{3 of the} above arsenic-containing simulated contaminated soil, 50 kg of anti-contamination materials such as various heavy metals shown in Table 4 was added and kneaded with a soil mixer at low speed for 2.5 minutes. The soil adhering to the container and paddle of the soil mixer was scraped off and kneaded again at low speed for 2.5 minutes to prepare the test soil.
After preparing the test soil, each test soil is filled in three layers in a 10 cm mold specified in JIS A 1210: 2009 "Soil compaction test method by compaction" 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 compaction”.
The results are shown in Table 5 below.

Test Example 3: Soil remudification test To 1 m ^{3 of the} above arsenic-containing simulated contaminated soil, 50 kg of anti-contamination materials such as various heavy metals shown in Table 4 was added and kneaded at low speed for 2.5 minutes with a soil mixer. After that, the soil adhering to the container and paddle of the soil mixer was scraped off and kneaded again at low speed for 2.5 minutes to prepare the test soil.
After preparing the test soil, each test soil is filled in 3 layers in a 10 cm mold specified in JIS A 1210: 2009 "Soil compaction test method by compaction" and sealed at 20 ° C. until the age of 7 days. After curing, the mold was removed to obtain a specimen.
The specimen was placed in a water tank containing tap water at room temperature, left to stand for 24 hours while the specimen was completely immersed in water, and the presence or absence of remudification was visually confirmed from the way the specimen collapsed (1). Second immersion).
When the initial shape of the specimen was maintained (not remudized) and when the specimen was partially collapsed, the specimen was taken out of water and dried at 30 ° C. for 24 hours. Then, the specimen was allowed to stand for 24 hours in a state of being completely immersed in water again, and the presence or absence of remudification was visually confirmed from the way the specimen collapsed (second immersion).
The results are shown in Table 5 below.

In addition, the elution amount of arsenic, lead, and fluorine was accepted as being less than or equal to each soil elution amount standard based on the Soil Contamination Countermeasures Law (arsenic: 0.01 mg / L, lead: 0.01 mg / L, fluorine: 0). .8 mg / L).
The pH of the test solution was accepted in the range of 5.8 to 8.6 specified by the uniform wastewater standard of the Environment Agency.
The corn index passed the test of 400 kN / m ² or more specified in the Type 3 improved soil of the soil classification standard of the Ministry of Land, Infrastructure, Transport and Tourism's "Standards for Utilization of Soil".
In the remudification test, the case where the initial shape of the specimen was maintained was evaluated as ◯, the case where a part of the specimen was broken or cracked was evaluated as Δ, and the case where the shape disappeared and became mud was evaluated as ×. The above two immersion tests in water were carried out, and those in which the initial shape was maintained even after the second immersion and no collapse or cracks could be visually observed in the specimen were accepted.

From Table 5 above, in the examples using the anti-pollution material such as heavy metals containing all of the semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and / or calcium carbonate of the present invention, and the polymer material, the material The elution amount of arsenic, lead, and fluorine in the test soil of 7 days old is all within the soil elution amount standard, the test solution pH is within the uniform drainage standard range, the cone index is 400 kN / m ² or more, and the specimen is It did not re-mud.
In the examples, the value of the cone index measured by the same method for the lead-containing test soil and the fluorine-containing test soil was 400 kN / m ² or more.

Regarding the heavy metal contamination countermeasure materials C1 and C2 which do not contain the polymer materials of Comparative Examples 2 and 3, the cone index was higher than that of the simulated contaminated soil itself of Comparative Example 1, but it was less than 400 kN / m ² . The specimen was re-mud by the first immersion in water.
This is because the corn index is improved by the formation of ettringite by the reaction of amorphous calcium silicate and sulfate ion, but the corn index is increased because there is no polymer material and there is no aggregation effect of fine particles in the soil. It is probable that it became low and the effect of suppressing remudification did not appear.

Regarding the heavy metal contamination countermeasure material C3, which does not contain amorphous calcium silicate and / or calcium carbonate and a polymer material shown in Comparative Example 4, the growth of the cone index is compared because it does not contain a substance having soil solidification performance. Compared with the simulated contaminated soil of Example 1, it was less than 400 kN / m ² . In addition, the specimen was remudized by the first immersion in water.

Regarding the pollution control material C4 for heavy metals and the like, which does not contain semi-baked dolomite shown in Comparative Example 5, the elution amount of fluorine exceeded the soil elution amount standard although the pH became neutral.
It is considered that this is because there is no physical adsorption to the micropores existing in the semi-calcined dolomite and the poorly soluble compound is not formed by the reaction of fluoride ions with the semi-calcined dolomite component.

The pH of the heavy metal pollution control material C5, which does not contain ferrous sulfate shown in Comparative Example 6, was 9.3, which was alkaline.
In addition, the elution amount of arsenic and lead exceeded the soil elution amount standard.
It is considered that arsenic does not contain ferrous sulfate and poorly soluble iron arsenate does not precipitate.
It is considered that lead does not contain sulfate and a poorly soluble compound such as lead sulfate is not produced.

The heavy metal countermeasure material C6 shown in Comparative Example 7 contains all of semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and polymer material, but the amount of amorphous calcium silicate is 20% by mass. The soil solidification performance was low due to the small amount, and the cone index was less than 400 kN / m ² . In addition, a part of the specimen collapsed by the first immersion in water, and the specimen was remudified by the second immersion in water after drying.

Regarding the heavy metal countermeasure material C7 shown in Comparative Example 8, the cone index was 400 kN / m ² or more because the hemihydrate gypsum reacted with the water in the soil and changed to dihydrate gypsum and the water content ratio decreased. , Amorphous calcium silicate and / or calcium carbonate is not contained, and a part of the specimen collapses due to the dissolution of dihydrate gypsum by the first immersion in water, and the specimen is subjected to the second immersion in water after drying. It became muddy again.

The heavy metal countermeasure material C8 shown in Comparative Example 9 is a hemihydrate gypsum alone and does not contain amorphous calcium silicate and / or calcium carbonate, so insolubilization performance, solidification performance, and remudification suppressing effect are the acceptance criteria. It didn't arrive.

The heavy metal pollution control material of the present invention and the heavy metal pollution control method using the control material can efficiently insolubilize heavy metals and halogens, and solidify the soil to improve its strength while keeping the improved soil neutral. It can be effectively used for soil modification in which heavy metals and halogens are eluted because it has an excellent effect of suppressing remudification. For example, it can be effectively applied to the treatment of contaminated soil in which a large amount of heavy metals and the like generated by excavation work and construction work of tunnels and dams are eluted, and further, landfill treatment of lake shores and coasts becomes possible.

Claims (5)

Semi-baked dolomite, ferrous sulfate, amorphous calcium silicate and / or calcium carbonate, and polymer material are essential components, and amorphous calcium silicate and / or calcium carbonate is semi-baked in an amount of 50% by mass or more. It contains 5 to 30% by mass of dolomite and 5 to 45% by mass of ferrous sulfate, and the polymer materials are amorphous calcium silicate and / or calcium carbonate, semi-baked dolomite, and sulfuric acid. A pollution control material for heavy metals and the like, which is characterized by containing 0.1 to 10% by mass of the total mass of monoiron. The heavy metal pollution control material according to claim 1, wherein the heavy metal pollution control material is in the form of a powder. In the heavy metal pollution control material according to claim 1 or 2, the semi-baked dolomite has a residual CaMg (CO ₃ ) ₂ phase content of 0 in the dolomite fired product analyzed by the Rietveld method by powder X-ray diffraction. A pollution control material for heavy metals and the like, which is characterized in that it is .4 ≤ x ≤ 35.4 (mass%). In the heavy metal or the like pollution control material according to any one of claims 1 to 3, the amorphous calcium silicate is at least one selected from the group consisting of blast furnace slag and steelmaking slag, and the polymer material is an organic polymer aggregate. An agent and / or a thickener, wherein the organic polymer flocculant is at least selected from the group consisting of polyacrylamide, polyacrylic acid ester, polyamidine, sodium polyacrylate, polyethylene oxide, sodium acrylate-acrylamide copolymer. A heavy metal or the like contamination countermeasure material, wherein the thickener is at least one selected from the group consisting of a cellulose-based thickener, a polyamide-based thickener, and a polyvinyl alcohol-based thickener. A heavy metal pollution control method, characterized in that the heavy metal pollution control material according to any one of claims 1 to 4 is mixed with soil and used.