JP5599256B2 - Heavy metal elution control material and elution control method - Google Patents

Description

  The present invention relates to an elution inhibitor that can solidify a processing object such as contaminated soil containing heavy metals to suppress elution of heavy metals.

In recent years, many cases have been reported in which soil such as sites of factories, business establishments, or industrial waste disposal sites is contaminated with heavy metals such as lead, hexavalent chromium or arsenic, fluorine, and the like.
When soil is contaminated by heavy metals, etc., the contaminated area of heavy metals diffuses into the groundwater and eventually accumulates in the human body and grains via the contaminated groundwater, which adversely affects health Is concerned.
In addition, if the concentration of heavy metals in the soil exceeds the environmental standard value, the site cannot be used as it is, which is also a problem from the viewpoint of effective use of the land.

In order to cope with such problems, various techniques for insolubilizing heavy metals in contaminated soil to suppress or prevent heavy metals from eluting from the soil have been proposed.
For example, Patent Document 1 proposes a heavy metal elution suppressing solidified material containing magnesium oxide.
Patent Document 2 proposes a solidifying and insolubilizing agent for harmful substance-contaminated soil made of MgO and / or MgO-containing material.
Patent Document 3 solidifies the contaminated soil and the like by adding and mixing magnesium oxide baked at 700 to 1,000 ° C. and adjusted to a fineness of 4,000 cm ² / g or more into the contaminated soil. Thus, methods for solidifying and insolubilizing contaminated soil and the like for insolubilizing pollutants have been proposed.
Patent Document 4 discloses a method of incorporating a substance into a solidifiable binder, the method including a step of mixing the substance with a binder as a slurry or for the formation of the next slurry, A method has been proposed that includes a caustic magnesium oxide source and a step of adding to the slurry a solidifying agent that promotes solidification of the binder.
Patent Document 5 proposes a soil solidifying material mainly composed of magnesium oxide (preferably light calcined magnesium) and sulfate such as gypsum.
Patent Document 6 proposes a soil solidifying material containing specific magnesium oxide, sulfate such as magnesium, and calcium carbonate at a specific mass ratio.

JP 2003-117532 A JP 2003-225640 A JP 2003-334526 A JP 2005-523990 A JP 2003-193050 A JP 2007-161839 A

The techniques described in Patent Documents 1 to 6 using magnesium oxide as an insolubilizing material can suppress elution of heavy metals when applied to soil with a low degree of contamination. However, even if magnesium oxide or sulfate is added in a normal usage amount, the effect of suppressing elution of heavy metals is still insufficient for highly contaminated soil. On the other hand, if the elution amount of heavy metal is set to a predetermined value (for example, environmental standard value) or less, the amount of insolubilizing material used is excessively increased. In this case, (a) the cost becomes high, (b) the pH of the treated soil after the insolubilizing material is added, (c) the volume of the treated soil after the insolubilizing material is added increases excessively, and then There are problems such as processing time and cost.
Therefore, the present invention provides an elution inhibitor and elution material for heavy metals that can sufficiently suppress elution of heavy metals with a small addition amount even for a processing object such as soil having a high degree of contamination with heavy metals. It aims at providing the suppression method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor achieves the object of the present invention according to a composition containing light calcined magnesia partial hydrate and specific clay in a specific mass ratio. The present invention has been completed.

That is, the present invention provides the following [1] to [ 7 ].
[1] and light burned magnesia partially hydrated light burned magnesia partially hydrate comprising (A), Oite the allophane quantitative test, SiO ₂ (silica) from clay and _Al 2 _{O 3} (alumina) The clay (B) having a total extraction rate of 20% by mass or more and an extraction rate of Fe ₂ O ₃ from the clay of 9 to 30% by mass is represented by (A) / (B) = 0.2. A heavy metal elution suppressing material characterized by containing in a range of ˜20 (mass ratio).
[2] The clay (B) has an extraction rate of SiO ₂ from clay of 5% by mass or more and an extraction rate of Al ₂ O ₃ from clay of 15% by mass or more in the allophane quantitative test. The elution inhibitor for heavy metals according to [1] above.
[3] The clay (B) has an ignition loss at 750 ° C. of 10% or more, a SiO ₂ content of 30% by mass or more, a Fe ₂ O ₃ content of 8% by mass or more, and Al. The heavy metal elution inhibitor according to [1] or [2], wherein the content of ₂ O ₃ is 20% by mass or more.
[ 4 ] The light burned magnesia partial hydrate according to any one of [1] to [3], containing 65 to 96.5% by mass of magnesium oxide and 3.5 to 30% by mass of magnesium hydroxide. The elution inhibitor of heavy metals described.
[ 5 ] The above [1] to [4] containing 20 to 70 parts by mass of a calcium carbonate-containing material and / or 1 to 23 parts by mass of a gypsum-containing material with respect to 100 parts by mass of the light burned magnesia partial hydrate The elution inhibitor of heavy metals according to any one of the above.
[ 6 ] The heavy metal elution inhibitor according to any one of [1] to [ 5 ], which contains 0.2 to 300 parts by mass of an acid agent with respect to 100 parts by mass of the lightly burned magnesia partial hydrate.
[ 7 ] A method for suppressing elution of heavy metals, wherein 2 to 40 parts by mass of the elution inhibitor for heavy metals according to any one of [1] to [ 6 ] is added to and mixed with 100 parts by mass of the object to be treated.

  Since the elution inhibitor of heavy metals of the present invention contains light-burned magnesia partial hydrate (A) and specific clay (B) at a specific mass ratio, it is suitable for processing objects such as soil with a high degree of contamination. In contrast, elution of heavy metals can be sufficiently suppressed with a small addition amount. In addition, since the addition amount is small as described above, the cost is low, the increase range of the pH of the processing object is small, and an excessive increase in the volume of the processing object can be avoided.

Heavy metals elution suppressing material of the present invention includes a light burned magnesia partially hydrate formed by partially hydrate the light burned magnesia (A), Oite the allophane quantitative test, SiO 2 _(silica) from clay And ( ₂ ) a clay (B) in which the total extraction rate of Al ₂ O ₃ (alumina) is 20% by mass or more and the extraction rate of Fe ₂ O ₃ from the clay is 9 to 30% by mass. /(B)=0.2-20 (mass ratio).
Heavy metals subject to elution suppression in the present invention are cadmium, lead, hexavalent chromium, arsenic, total mercury, alkylmercury, selenium, fluorine, boron and cyan, the second type specified hazardous substances, and items to be monitored This means nickel, molybdenum, antimony, nitrate nitrogen, nitrite nitrogen, etc. that need attention.
The mass ratio ((A) / (B)) of the light calcined magnesia partial hydrate (A) and the clay (B) is 0.2 to 20, preferably 0.3 to 10, more preferably 1 to 5, Especially preferably, it is 1-3. If the mass ratio is outside the range of 0.2 to 20, the elution suppression effect of heavy metals may not be sufficient.

Next, the light burned magnesia partial hydrate which is the first essential constituent of the present invention will be described.
The light-burned magnesia partial hydrate (A) can be obtained, for example, by baking a solid containing magnesium carbonate and / or magnesium hydroxide at 650 to 1,300 ° C.
The content of magnesium carbonate and / or magnesium hydroxide in the solid is 80% by mass or more, preferably 85% by mass or more, and more preferably 90% by mass or more. When the content is less than 80% by mass, the magnesium oxide component contained in the light-burned magnesia is small, and the elution suppression effect of heavy metals tends to decrease.
Examples of the solid material include magnesite, dolomite, brucite, or a lump or powdery material such as magnesium hydroxide obtained by precipitating a magnesium component in seawater with an alkali such as slaked lime.

  The firing temperature of the solid is usually 650 to 1,300 ° C, preferably 750 to 950 ° C, and more preferably 800 to 900 ° C. When the firing temperature is less than 650 ° C., light-burned magnesia is difficult to generate, and when the firing temperature exceeds 1,300 ° C., the elution suppression effect of heavy metals may be reduced. The firing time of the solid matter is usually 30 minutes to 5 hours, although it depends on the amount of charged solid matter and the particle size.

  The light-burned magnesia partial hydrate used in the present invention preferably contains 65 to 96.5% by mass of magnesium oxide and 3.5 to 30% by mass of magnesium hydroxide, and 70 to 95% by mass of magnesium oxide. And what contains 5-20 mass% of magnesium hydroxide is more preferable, and what contains 75-90 mass% of magnesium oxide and 7-17 mass% of magnesium hydroxide is especially preferable. If the value is within a preferable range, the elution suppressing effect of heavy metals can be further enhanced.

The light-burned magnesia partial hydrate may contain calcium oxide and / or calcium hydroxide in addition to the above components. The total content of calcium oxide and / or calcium hydroxide in the light-burned magnesia partial hydrate is preferably 3.0% by mass or less, more preferably 2.5% by mass or less, in terms of oxide. 0 mass% or less is more preferable. When the content exceeds 3.0% by mass, the effect of inhibiting elution of heavy metals may be reduced when used in soil with a high degree of contamination by heavy metals.
The light-burned magnesia partial hydrate preferably contains 4.0 mass of components other than the above components (magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide) (for example, impurities such as silica and iron oxide). % Or less. If the content exceeds 4.0% by mass, the effect of inhibiting the elution of heavy metals may be reduced when used in soil with a high degree of contamination by heavy metals.
Blaine specific surface area of the light burned magnesia partially hydrate is preferably ^{3,000~7,000cm 2 / g, 4,000~6,800cm 2 /} g is more preferable. When the value is in the range of 3,000 to 7,000 cm ² / g, the elution suppressing effect of heavy metals increases.

Next, the clay which is the second essential constituent material of the present invention will be described.
In the allophane quantitative test , the clay used in the present invention has a total extraction rate of SiO ₂ and Al ₂ O ₃ from clay of 20% by mass or more , and an extraction rate of Fe ₂ O ₃ from clay of 9%. -30% by mass . When the total extraction rate of SiO ₂ and Al ₂ O ₃ from clay is less than 20% by mass, the elution suppressing effect of heavy metals tends to be reduced.
Extraction rate of the clay in allophane quantitative test, in SiO ₂ 5 wt% or more, _Al 2 _{O 3} at 15 wt% or more, and more preferably from 9 to 30 wt% in _Fe 2 _{O 3.} When the extraction rate of Fe ₂ O ₃ is 9 to 30% by mass, the elution suppressing effect of heavy metals tends to increase.
The allophane quantitative test referred to in the present invention refers to the allophane quantitative test of the Geotechnical Society of Japan (issued by the Geotechnical Society of Japan, Method and Explanation of Geomaterial Test-described in 2-part 2-pp970).

The extraction rate of SiO _{2 and the} like by the allophane quantitative test is determined by the following procedures (1) to (6).
(1) Drying and pulverizing clay Clay is put in a dryer at 40 ° C. and dried for 24 hours, and then pulverized. Next, the crushed clay is passed through a 0.42 mm sieve, and the clay passing through the sieve is recovered.
(2) Decomposition of organic matter To 2 g of the clay passed through the sieve, 50 ml of 10% by weight of hydrogen peroxide water was added and stirred, then 50 ml of 30% by weight of hydrogen peroxide solution was added and stirred, and further 30% by weight. 50 ml of hydrogen peroxide solution was added again and stirred to oxidatively decompose the organic matter contained in the clay.
Note that the time point at which the 30% by mass of hydrogen peroxide solution is added and the end point of the organic substance decomposition treatment are both determined at the end of foaming (at the end of the oxidative decomposition reaction).
(3) Measurement of organic matter content The clay after the organic matter decomposition is separated by filtration, and 50 ml of distilled water is added thereto to wash the decomposed organic matter and the like. The clay after washing is placed in a dryer at 105 ° C. and dried for 24 hours, and then the mass of the dried clay is measured to determine the content of organic matter in the clay.
(4) Recovery of acid extract, etc. 50 ml of 8 mol / L HCl aqueous solution is added to 1 g of the dried clay after decomposition of organic matter, and the mixture is shaken at a frequency of 200 times / min for 30 minutes, extracted with acid, filtered and extracted. While collecting (a), 50 ml of distilled water is added to the filtered acid-extracted clay to wash the acid contained in the clay, and the washing liquid (b) is collected.
(5) Recovery of alkali extract, etc. 50 ml of 0.5 mol / L NaOH aqueous solution is added to the washed clay of (4) above, and the mixture is shaken at the above frequency for 5 minutes for alkali extraction treatment. Separately, the extract (c) is recovered, and 50 ml of distilled water is added to the filtered clay after the alkali extraction treatment to wash the alkali contained in the clay, thereby recovering the cleaning solution (d).
(6) Calculation of extraction rate of SiO ₂ etc. The clay after washing in (5) is returned to the treatment in (4), and the treatments in (4) and (5) are further continued 4 times (5 cycles in total) ) After repeating, SiO ₂ (silica), Al ₂ O ₃ (alumina) and Fe ₂ O ₃ contained in the extract (a), (c) and cleaning liquid (b), (d) recovered in each cycle The total concentration of (iron oxide) is measured, and the extraction amount of each compound is calculated.
The extraction rate of _SiO 2, _Al 2 _{O 3} and _Fe 2 _{O 3} from clay, before the organic matter decomposition treatment clay (dry) per _1g, extraction of SiO 2, _Al 2 _{O 3} and _Fe 2 _{O 3} Convert to amount and display.

In addition, as a suitable example of the clay mineral contained in the clay used in the present invention, imogolite, opal silica, allophane, activated aluminum, amorphous iron hydroxide of iron and aluminum, gypsite, halloysite, vermiculite, kaolinite, One type or two or more types of minerals selected from hydrous halloysite, smectite and chlorite can be mentioned.
Further, the content of these clay minerals in the clay is preferably 20% by mass or more, more preferably 35% by mass or more, and further preferably 50% by mass or more. If the content is less than 20% by mass, the ability to reduce the pH of the treated product may be lowered, or the elution suppressing effect of heavy metals may be reduced.

In addition, the clay used in the present invention has an ignition loss at 750 ° C. of 10% or more, a SiO ₂ content of 30% by mass or more, and a Fe ₂ O ₃ content from the viewpoint of the elution suppressing effect of heavy metals. The ratio is preferably 8% by mass or more and the content of Al ₂ O ₃ is 20% by mass or more.
In addition, the ignition loss test is conducted according to the Japanese Industrial Standard “Soil ignition loss test method” (JIS
A 1226: 2009).

  Furthermore, the maximum particle size of the clay used in the present invention is preferably 3 mm or less, more preferably 2 mm or less. When the maximum particle size is 3 mm or less, the elution suppressing effect of heavy metals tends to increase.

In this invention, 20-70 mass parts of calcium carbonate containing materials and / or 1-23 mass parts of gypsum containing materials can be contained with respect to 100 mass parts of light-burned magnesia partial hydrates.
When the content of the calcium carbonate-containing material is 20 to 70 parts by mass, the elution suppressing effect of heavy metals can be enhanced. Moreover, the elution inhibitory effect of heavy metals can be heightened that content of a gypsum containing material is 1-23 mass parts.

  Here, the calcium carbonate-containing material preferably contains 80% by mass or more of calcium carbonate, more preferably 85% by mass or more, and still more preferably 90% by mass or more. Examples of the calcium carbonate-containing material include industrial calcium carbonate powder, reagent calcium carbonate powder, limestone powder, ground shells of calcium carbonate, coral grounds, and the like. Among them, limestone powder is preferable because of its low cost.

  The gypsum-containing material preferably contains 80% by mass or more of calcium sulfate or calcium sulfate hydrate, more preferably 85% by mass or more, and still more preferably 90% by mass or more. Examples of the gypsum-containing material include anhydrous gypsum, hemihydrate gypsum, phosphate gypsum, and dihydrate gypsum. Specifically, as anhydrous gypsum, natural anhydrous gypsum and hydrofluoric acid anhydrous gypsum by-produced during the production of hydrofluoric acid can be used. As dihydrate gypsum, natural dihydrate gypsum, discharged dihydrate gypsum, etc. can be used. . Among the gypsum, anhydrous gypsum is excellent in the effect of reducing the pH of a solidified material such as solidified soil. Among anhydrous gypsum, natural anhydrous gypsum with a low content of harmful substances is preferable.

Blaine specific surface area of the calcium carbonate-containing material or gypsum-containing product is preferably ^{3,000~7,000cm 2 / g, 4,000~6,000cm 2 /} g is more preferable. When the value is less than 3,000 cm ² / g, the elution suppressing effect of heavy metals may be lowered. When the value exceeds 7,000 cm ² / g, the labor and cost for grinding increase.

The elution inhibitor of the present invention can contain an acid agent in order to suppress an increase in the pH of the solidified product.
The compounding quantity of an acidic agent is 0.2-300 mass parts normally with respect to 100 mass parts of light-burning magnesia partial hydrate, Preferably it is 0.4-200 mass parts, More preferably, it is 2-150. Part by mass. If the blending amount is less than 0.2 parts by mass, it is difficult to enhance the pH reduction effect of the solidified product. When the blending amount exceeds 300 parts by mass, not only a further improvement in the elution suppression effect of heavy metals can be obtained, but also the cost increases.

Examples of the acid agent include inorganic acids such as hydrochloric acid, sulfuric acid, and boric acid, and organic acids such as oxalic acid, citric acid, malic acid, and benzenesulfonic acid, and aluminum sulfate, polyaluminum chloride, ammonium sulfate, alum, ammonium chloride, One type or two or more types selected from acidic salts composed of strong acid and weak base, such as ferrous sulfate, ferric chloride, and ammonium benzenesulfonate can be used. In particular, (anhydrous) aluminum sulfate, ammonium sulfate, alum, ferrous sulfate or ferric chloride, which are inexpensive industrial products, are preferable as the acid agent used in the present invention.
The use form of the acid agent in the present invention is preferably a powder. The particle size of the powder is not particularly limited because the powder is water-soluble, but is preferably 1 mm or less and more preferably 0.5 mm or less from the viewpoint of workability and the like.

The method for producing a heavy metal elution suppressing material of the present invention mainly comprises a mixing step, a pulverizing step and a partial hydration step. Below, a manufacturing method is demonstrated for every embodiment of an elution suppression material.
(I) Manufacture of an elution inhibitor (hereinafter also referred to as a first elution inhibitor) containing light-burned magnesia partial hydrate and clay and not containing calcium carbonate, gypsum, and acid agent. Method Examples of the production method include the following (a) to (c).
(A) A mixing step of mixing light-burned magnesia and clay to obtain a mixture, a pulverizing step of pulverizing the mixture to obtain a pulverized product having a predetermined particle size, and a part of the light-burned magnesia in the pulverized product as water A production method comprising a partial hydration step of obtaining a light-burned magnesia partial hydrate by summing.
(B) a first pulverizing step of pulverizing light-burned magnesia to obtain a pulverized light-burning magnesia having a predetermined particle size; and a second pulverizing step of pulverizing clay to obtain a pulverized clay having a predetermined particle size. (However, the order of the first pulverization step and the second pulverization step is not limited.), A mixing step of mixing the light baked magnesia pulverized product and the clay pulverized product to obtain a mixture, and the light calcination in the mixture. A production method comprising a partial hydration step of partially hydrating magnesia to obtain a light-burned magnesia partial hydrate.
(C) a first pulverization step of pulverizing light-burned magnesia to obtain a light-burned magnesia pulverized product having a predetermined particle size; A partial hydration step to be obtained, and a second pulverization step for pulverizing clay to obtain a pulverized product of clay having a predetermined particle size (however, the order of the first pulverization step and the second pulverization step is not limited). The manufacturing method including the mixing process which mixes the ground material of the said light-fired magnesia partial hydrate, and the said clay ground material.
In the partial hydration step in (a) to (c), water is added to the pulverized product or mixture and the mixture is stirred and mixed, or the pulverized product or mixture is mixed in an atmosphere having a relative humidity of 80% or more. This is done by holding for more than a week.

Among the (a) to (c), from the viewpoint of the elution suppressing effect of heavy metals and the workability, the production method (a) or (b) is preferable, and the production method (a) is more preferable.
The production method (a) has the advantage that the pulverization process is simplified compared to the production method (b) or (c) in which light-burned magnesia and clay are simultaneously pulverized, so that they are individually pulverized.

(Ii) A method for producing an elution inhibitor (hereinafter also referred to as a second elution inhibitor) containing a calcium carbonate-containing material and / or a gypsum-containing material (d) light-burned magnesia, clay, calcium carbonate, A mixing step of mixing a gypsum-containing material to obtain a mixture, a pulverizing step of pulverizing the mixture to obtain a pulverized product having a predetermined particle size, and partially hydrating light-burned magnesia in the pulverized product The manufacturing method including the partial hydration process which obtains a light-burning magnesia partial hydrate.
(E) a first pulverizing step for pulverizing light-burned magnesia to obtain a pulverized light-burning magnesia having a predetermined particle size; and a second pulverizing step for pulverizing clay to obtain a pulverized clay having a predetermined particle size. A third pulverizing step of pulverizing the calcium carbonate-containing material and / or gypsum-containing material to obtain a pulverized product of calcium carbonate-containing material and / or gypsum-containing material having a predetermined particle size (provided that the first to the third pulverizing materials) The order of the steps is not limited.), A mixing step of obtaining a mixture by mixing the light-burned magnesia pulverized product, the clay pulverized product, and the pulverized product of the calcium carbonate-containing material and / or the gypsum-containing material, A production method comprising a partial hydration step of partially hydrating light-burned magnesia in a mixture to obtain a light-burned magnesia partial hydrate.
(F) A first pulverization step of pulverizing light-burned magnesia to obtain a light-burned magnesia pulverized product having a predetermined particle size; A partial hydration step to obtain, a second pulverization step of pulverizing clay to obtain a clay pulverized product having a predetermined particle size, and pulverizing a calcium carbonate-containing material and / or gypsum-containing material to obtain a carbonic acid having a predetermined particle size. A third pulverization step for obtaining a pulverized product of calcium-containing material and / or gypsum-containing material (however, the order of the first to third pulverizing steps is not limited), and a pulverized product of the light-burned magnesia partial hydrate; The manufacturing method including the mixing process of mixing the pulverized material of the clay and the pulverized material of the calcium carbonate-containing material and / or the gypsum-containing material.
In addition, the partial hydration process in (d)-(f) can be performed similarly to the partial hydration process of the 1st elution suppression material demonstrated by said (i).
Among (d) to (f), the production method (d) or (e) is preferred, and the production method (d) is more preferred, from the viewpoint of the elution suppression effect of heavy metals and workability.

(Iii) Production method of an elution inhibitor (hereinafter also referred to as a third elution inhibitor) further containing an acid agent Examples of the production method include the first or second described in (i) and (ii) above. A method of adding and mixing an acidic agent to the second elution suppressing material can be mentioned.

The n value in the rosin-Rammler type of the elution inhibitor of the present invention is preferably 0.70 to 1.40, more preferably 0.95 to 1.15. If the n value of the elution suppressing material for heavy metals is in the range of 0.70 to 1.40, the elution suppressing effect of heavy metals can be enhanced, and it is also effective for soil with a high content of heavy metals. . Incidentally, Rosin-Rammler ^{_{formula, R = 100exp (-bD p n}} ) ( wherein, R is accumulated residue value (%) represents the sieve residue, D _p is the particle size ([mu] m) sieve It represents the size of the eye, and b and n are constants.
The measurement of the n value in the Rosin-Rammler method is performed, for example, by placing 20 ml of ethanol and 0.05 g of a sample in a 100 ml beaker, and ultrasonically dispersing for 1 minute using an ultrasonic cleaner (VS-100 manufactured by ASONE, frequency 50 kHz). , And after adjusting the refractive index of the sample to 1.72, it can be performed using a particle size distribution measuring apparatus (9320-X10 manufactured by Nikkiso Co., Ltd.).

  The addition amount of the elution inhibitor of the present invention is preferably 2 with respect to 100 parts by mass of the object to be treated, although it depends on the properties of the object to be treated and the construction conditions, the amount of elution of heavy metals and the required performance of the solidified material. -40 mass parts, More preferably, it is 6-30 mass parts. When the addition amount is less than 2 parts by mass, it is difficult to uniformly mix the elution inhibitor into the object to be treated. When the added amount exceeds 40 parts by mass, the cost increases, the pH of the solidified product significantly increases, the volume of the solidified product increases, and the subsequent processing takes time and cost. Can occur.

  As a method for adding an elution inhibitor for heavy metals, a dry addition method in which the elution inhibitor is added as a powder to the object to be processed and mixed, or water is added to the elution inhibitor to form a slurry, and then the slurry is added. A slurry addition method of adding to and mixing with the object to be treated can be employed. The mass ratio of the water / elution inhibitor of the elution inhibitor slurry is preferably 0.5 to 1.5, preferably 0.8 to 1.2, although it depends on the properties of the object to be treated and the content of heavy metals. More preferred.

Examples of the treatment target of the elution control material of the present invention include soil containing heavy metals, incineration ash, and dusts. In addition, as the treatment object, from the viewpoint of sufficiently obtaining the effect of suppressing the increase in pH of the solidified treatment which is one of the effects of the present invention, commercially available magnesium oxide (for example, Kanto Chemical Co., Ltd.) is used for the treatment object 1 m ^3. It is preferable that the pH of the mixture obtained by adding and mixing 100 kg / m ^{3 (} special grade reagent manufactured by a company) is preferably 10.3 or more, and more preferably 10.6 or more. In addition, the measuring method of the said pH is performed based on JGS0211-2009.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
1. Preparation of each constituent material of elution inhibitor (1) Light-burned magnesia pulverized product (M1) and light-burned magnesia partial hydrate (W1)
Magnesite containing 97% by mass of magnesium carbonate was fired at 850 ° C. for 30 minutes in an electric furnace (manufactured by Chugai Engineering Co., Ltd., model: KSL-2) to obtain light-burned magnesia. Next, the light calcined magnesia was pulverized to obtain a light calcined magnesia pulverized product (M1) having a Blaine specific surface area of 6,500 cm ² / g. Further, the pulverized product is left in a constant temperature and humidity chamber at a temperature of 20 ° C. and a relative humidity of 100% for 10 days to hydrate a part of the light burned magnesia, thereby lightly burned magnesia having a specific surface area of 6,500 cm ² / g. Partial hydrate (W1) was obtained.
The light-burned magnesia partial hydrate (W1) contained 88.0% by mass of magnesium oxide and 8.5% by mass of magnesium hydroxide.
(2) Lightly burned magnesia ground product (M2) and lightly burned magnesia partial hydrate (W2)
Magnesite containing 95% by mass of magnesium carbonate was baked in the electric furnace at 870 ° C. for 30 minutes to obtain light-burned magnesia. Next, the light-burned magnesia was pulverized to obtain a pulverized light-burned magnesia (M2) having a specific surface area of 5,900 cm ² / g. Further, the pulverized product is left in a constant temperature and humidity chamber at a temperature of 20 ° C. and a relative humidity of 80% for 20 days to hydrate a part of the light-burned magnesia, and the light-burned magnesia having a Blaine specific surface area of 5,900 cm ² / g. Partial hydrate (W2) was obtained.
The light-burned magnesia partial hydrate (W2) contained 79.5% by mass of magnesium oxide and 17.0% by mass of magnesium hydroxide.

(3) Clay pulverized product Ten types of clays a to j having the component composition and extraction rate shown in Table 1 were pulverized to obtain a clay pulverized product passing through a 2 mm sieve. In addition, the ignition loss in Table 1 is a value at 750 ° C.
In addition, all used clay contains 70 mass% or more of clay minerals.

(4) Calcium carbonate-containing material Granular limestone containing 92% by mass of calcium carbonate was pulverized to obtain a calcium carbonate-containing material having a Blaine specific surface area of 5,500 cm ² / g.

(5) Gypsum-containing material Lump-shaped natural anhydrous gypsum containing 91% by mass of calcium sulfate was pulverized to obtain a gypsum-containing material having a brain specific surface area of 5,000 cm ² / g.

2. Preparation of Elution Suppressing Material According to the formulation shown in Table 2, Table 3 and Table 4, each constituent material of the elution inhibiting material is mixed using a Henschel mixer (model number: FM20B) manufactured by Mitsui Miike Manufacturing Co., Ltd. Materials A1 to A20 and B1 to B22 were prepared.

3. Arsenic dissolution test and pH measurement Water was added to the dissolution inhibitors A1 to A10 and B1 to B11 shown in Table 2 to prepare an dissolution inhibitor slurry of water / elution inhibitor = 1 (mass ratio). Next, with respect to 100 parts by mass of the arsenic-contaminated soil (water content ratio: 70%), the amounts shown in Table 5 (amount of the elution inhibitor in the slurry) were added to and mixed with these elution inhibitor slurries, and JGS0821- Specimens were produced in accordance with 2009 “Method for Producing Specimens Without Compaction of Stabilized Soil”. Moreover, the contaminated soil which does not add an elution suppression material slurry was made into the control example (comparative example 12).
These specimens were subjected to wet air curing in a constant temperature room at 20 ° C., and then the pH of the specimens at the age of 7 days was measured in accordance with the Geotechnical Society Standard JGS0211-2009. In addition, the amount of arsenic eluted from the specimen was determined by the Ministry of the Environment Notification No. 46 and K
It was measured according to 0120-2008 61.4 “ICP mass spectrometry”. The environmental standard value for arsenic is 0.01 mg / liter.
The results of the arsenic dissolution test and pH measurement are shown in Table 5.

  As shown in Table 5, in Examples 1 to 10, the arsenic elution amount was less than the environmental standard value (0.01 mg / liter), whereas in Comparative Examples 1 to 12, both exceeded the environmental standard value. ing. Moreover, in Examples 9-10, since the acidic agent is used, pH is low. From these results, the first elution inhibitor (A1 to A6) described in (i), the second elution inhibitor (A7 to A8) described in (ii), and (iii) The third elution inhibitor (A9 to A10) described has an extremely high elution suppression effect for arsenic, and the third elution inhibitor (A9 to A10) described in (iii) It can be seen that the pH reduction effect is high.

4). Elution test of fluorine and measurement of pH Water was added to the elution inhibitor A11 to A18 and B12 to B21 shown in Table 3 to prepare an elution inhibitor slurry of water / elution inhibitor = 1 (mass ratio).
Next, the amount shown in Table 6 (the amount of the elution inhibitor in the slurry) was added to and mixed with 100 parts by mass of these elution inhibitor slurries (water content ratio 65%), and JGS0821- Specimens were produced in accordance with 2009 “Method for Producing Specimens Without Compaction of Stabilized Soil”. Moreover, the contaminated soil which does not add the elution suppression material slurry was made into the control example (comparative example 23).
After these specimens were wet-cured in a constant temperature room at 20 ° C., the pH of the specimens at the age of 7 days was measured in accordance with the Geotechnical Society Standard JGS0211-2009. The amount of fluorine eluted from the specimen was measured according to Ministry of the Environment Notification No. 46 and Appendix 6 of the Environmental Agency Notification No. 59 of December 1986, “Ion Chromatograph Method”. The environmental standard value of fluorine is 0.8 mg / liter.
Table 6 shows the results of the fluorine elution test and pH measurement.

  As shown in Table 6, in Examples 11 to 18, the elution amount of fluorine was less than the environmental standard value (0.8 mg / liter), whereas in Comparative Examples 13 to 23, all exceeded the environmental standard value. ing. Moreover, in Examples 17-18, since the acidic agent is used, pH is low. From these results, the first elution inhibitor (A11 to A14) described in (i), the second elution inhibitor (A15 to A16) described in (ii), and (iii) The third elution inhibitor (A17 to A18) described has a very high fluorine elution inhibitory effect, and the third elution inhibitor (A17 to A18) described in (iii) above has a reduced pH. It turns out that an effect is high.

5. Lead dissolution test and pH measurement Water was added to the dissolution inhibitor A19, A20 and B22 to prepare a dissolution dissolution material slurry of water / elution inhibitor = 1 (mass ratio).
Next, the amount shown in Table 8 (amount of the elution inhibitor in the slurry) was added to and mixed with 100 parts by mass of these elution inhibitor slurries (water content ratio 50%), and JGS0821-2009. Specimens were produced in accordance with “Method for producing specimens without compaction of stabilized soil”. Moreover, the incineration fly ash which does not add an elution suppression material slurry was made into the control example (comparative example 25).
After these specimens were wet-cured in a constant temperature room at 20 ° C., the pH of the specimens at the age of 7 days was measured in accordance with the Geotechnical Society Standard JGS0211-2009. The amount of lead elution from the specimen was measured in accordance with Ministry of the Environment Notification No. 46 and JIS K 0120-2008 5.4 “ICP Mass Spectrometry”. The environmental standard value for lead is 0.01 mg / liter.
Table 7 shows the results of the lead dissolution test and pH measurement.

  As shown in Table 7, in Examples 19 to 20, the elution amount of lead is less than the environmental standard value (0.01 mg / liter), whereas in Comparative Examples 24 to 25, all exceed the environmental standard value. ing. From these results, the first elution inhibitor (A19) described in (i) and the second elution inhibitor (A20) described in (ii) have an extremely high lead elution inhibitory effect. I understand that.

Claims (7)

And light burned magnesia partially hydrated light burned magnesia partially hydrate comprising (A), Oite the allophane quantitative test, the total extraction rate of SiO ₂ and Al ₂ O ₃ from clay 20 wt% The clay (B) having an extraction rate of Fe ₂ O ₃ from the clay of 9 to 30% by mass in the range of (A) / (B) = 0.2 to 20 (mass ratio). A heavy metal elution inhibitor characterized by containing. In the allophane quantitative test, the clay (B) is SiO from clay. ₂ Extraction ratio of 5% by mass or more and Al from clay ₂ O ₃ The heavy metal elution suppression material according to claim 1, wherein the extraction ratio is 15% by mass or more. The clay (B) has a loss on ignition at 750 ° C. of 10% or more, and SiO 2 ₂ The content of 30% by mass or more, Fe ₂ O ₃ The content of 8% by mass or more, and Al ₂ O ₃ The heavy metal elution suppressing material according to claim 1, wherein the content ratio of the heavy metal is 20% by mass or more. Light burned magnesia partially hydrated magnesium oxide 65 to 96.5 wt%, and, the heavy metals according to any one of claims 1 to 3 containing 3.5 to 30 wt% magnesium hydroxide Elution inhibitor. To light burned magnesia partially hydrate 100 parts by weight of calcium-containing substance 20 to 70 parts by weight of carbonate, and / or, according to any one of claims 1-4 containing gypsum-containing product to 23 parts by weight Elution inhibitor for heavy metals. The elution inhibitor of heavy metals according to any one of claims 1 to 5 , comprising 0.2 to 300 parts by mass of an acidic agent with respect to 100 parts by mass of light-burned magnesia partial hydrate. A method for suppressing elution of heavy metals, comprising adding 2 to 40 parts by mass of the elution inhibitor for heavy metals according to any one of claims 1 to 6 to 100 parts by mass of the object to be treated.