WO2010052986A1

WO2010052986A1 - Insolubilizing agent

Info

Publication number: WO2010052986A1
Application number: PCT/JP2009/067434
Authority: WO
Inventors: 祐介松山; 浩志林; 晃一内田; 宙平尾
Original assignee: 太平洋セメント株式会社
Priority date: 2008-11-07
Filing date: 2009-10-06
Publication date: 2010-05-14
Also published as: JP2010131535A; JP4343259B1

Abstract

An insolubilizing agent which can sufficiently inhibit, even when added in a small amount, heavy metals and so on from being leached from heavily contaminated soil or wastewater. The insolubilizing agent contains a partial hydrate of soft-burned magnesia, said partial hydrate being prepared by subjecting a soft-burned magnesia obtained by burning a mineral comprising magnesium carbonate and/or magnesium hydroxide as the main component at 550 to 1,400°C to partial hydration. The content of magnesium oxide in the partial hydrate of soft-burned magnesia is 50 to 96.5mass%, the content of magnesium hydroxide therein is 3.5 to 50mass%, and the content of calcium therein is 5.0mass% or lower in terms of oxide.

Description

Insolubilizing material

The present invention relates to an insolubilizing material capable of suppressing the elution of the heavy metal etc. from the contaminated soil containing the heavy metal etc. or insolubilizing the heavy metal etc. in the waste water containing the heavy metal etc.

In recent years, soil has been contaminated with heavy metals such as lead, hexavalent chromium, and arsenic, fluorine, etc. (hereinafter also referred to as heavy metals) at sites of factories, offices, and industrial waste disposal sites. Often reported. Thus, when soil is contaminated with heavy metals or the like, there is a safety and health problem that the contamination spreads to the ground water and affects the human body and grains. Further, when the soil contamination concentration exceeds the environmental standard value, there is a problem that the site cannot be used as it is and the land cannot be used effectively. Therefore, it is desired to insolubilize heavy metals and the like to prevent the spread of contamination.
In addition, when treating wastewater containing heavy metals, etc., if the heavy metals can be insolubilized, liquid components with a reduced content of heavy metals can be easily obtained by solid-liquid separation, and wastewater treatment can be performed. It can be done efficiently.

Under such circumstances, various techniques for insolubilizing heavy metals and the like have been proposed.
For example, a heavy metal elution suppression solidifying material containing magnesium oxide has been proposed (Patent Document 1).
Further, a solidifying and insolubilizing agent for toxic substance-contaminated soil characterized by comprising MgO and / or a MgO-containing material has been proposed (Patent Document 2).
Further, 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 to the contaminated soil, the contaminated soil is solidified, and the pollutant There has been proposed a method for solidifying and insolubilizing contaminated soil and the like (Patent Document 3).
A method of incorporating a material into a solidifiable binder, the method comprising mixing the material with a binder as a slurry or for the formation of a subsequent slurry, wherein the binder is a source of caustic magnesium oxide. And a method including a step of adding a solidifying agent that promotes solidification of the binder to the slurry has been proposed (Patent Document 4).
Further, the powder X-ray diffraction spectrum at a wavelength of 1.5405 mm has a peak apex at 2θ = 42.8 ° ± 0.3 °, and the half width with respect to the baseline of the peak is 0.32 to 1 Latent crystalline magnesia characterized by an angle of 0.5 ° has been proposed (Patent Document 5).

JP 2003-117532 A JP 2003-225640 A JP 2003-334526 A JP 2005-523990 Gazette JP 2007-22902 A

According to the techniques of Patent Documents 1 to 5 using magnesium oxide (lightly burned magnesia or the like) as an insolubilizing material, elution of heavy metals and the like can be suppressed in soil with a low contamination concentration. However, the effect (elution suppression effect of heavy metals, etc.) is still insufficient for highly contaminated soil, and the elution amount of heavy metals, etc. is set to a predetermined value (for example, environmental standard value) or less. Therefore, there is a problem that the amount of the insolubilizing material used is increased and the cost is increased. Further, in this case, there is a problem that the volume after the addition of the insolubilizing material is increased, and secondary measures are required.
On the other hand, in the field of wastewater treatment technology including heavy metals and the like, an insolubilizing material that can sufficiently insolubilize heavy metals and the like with a small addition amount is desired.
Then, an object of this invention is to provide the insolubilization material which can fully suppress elution of heavy metals etc. with little addition amount with respect to soil with high pollution density | concentration, or waste_water | drain.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the insolubilized material containing a specific light-burned magnesia partial hydrate obtained by hydrating a part of light-burned magnesia, The inventors have found that the object can be achieved and completed the present invention.
That is, the present invention provides the following [1] to [8].
[1] (A) Lightly burned magnesia partial water obtained by hydrating a portion of lightly burned magnesia obtained by firing a mineral mainly composed of magnesium carbonate and / or magnesium hydroxide at 550 to 1,400 ° C. This light-burned magnesia partial hydrate has a magnesium oxide content of 50 to 96.5% by mass, a magnesium hydroxide content of 3.5 to 50% by mass, and contains calcium. A light-solubilized magnesia partial hydrate having a rate of 5.0% by mass or less in terms of oxides.
[2] The component according to [1], wherein the component (A) is a powder, and (B) 20 to 70 parts by mass of a powder containing calcium carbonate as a main component is included with respect to 100 parts by mass of the component (A). Insolubilized material.
[3] The insolubilized material has a Blaine specific surface area of 2,500 to 20,000 cm ² / g, and a Rosin-Rammler formula relating to the particle size distribution: R = 100exp (−bD _p ⁿ ) ( ^where R Is an integrated residual value (%), which represents the sieve residue, D _p is the particle size (μm), represents the size of the sieve eye, and b and n are constants). The insolubilizing material according to the above [1] or [2], which is a powder of 80 to 1.45.
[4] The insolubilizing material according to any one of [1] to [3], wherein the insolubilizing material is a powder having an average particle size of 20 to 40 μm.
[5] The insolubilizing material according to any one of the above [1] to [4], comprising (C) one or more additives selected from water-soluble sulfates and water-soluble chlorides.
[6] The insolubilizing material according to any one of [1] to [5], wherein the insolubilizing material is added to a granular or powdery solid.
[7] The insolubilizing material according to the above [6], which contains (D) gypsum in an amount of 50 parts by mass or less with respect to 100 parts by mass of the component (A).
[8] The insolubilizing material according to any one of [1] to [5], wherein the insolubilizing material is for addition to waste water.

According to the insolubilizing material of the present invention, elution of heavy metals and the like can be sufficiently suppressed with a small amount of addition even to soil with high contamination concentration, heavy metal-containing dust such as incinerated ash, and the like.
Moreover, according to the insolubilizing material of the present invention, heavy metals can be sufficiently insolubilized with a small addition amount with respect to waste water containing heavy metals. In this case, by separating the drainage into solid and liquid, it is possible to easily obtain a liquid component having a reduced content of heavy metals and the like, and to efficiently perform the drainage treatment.

The insolubilizing material of the present invention includes (A) light-burned magnesia partial hydrate as an essential component, and further includes other optional components as necessary.
Examples of other optional components include (B) a powder mainly composed of calcium carbonate, (C) one or more additives selected from water-soluble sulfates and water-soluble chlorides, and (D) gypsum. It is done.
[(A) Lightly burned magnesia partial hydrate]
(A) Light-burned magnesia partial hydrate used in the insolubilizing material of the present invention is a light-burned magnesia obtained by baking a mineral mainly composed of magnesium carbonate and / or magnesium hydroxide at 550 to 1,400 ° C. A part is hydrated.
In the present invention, powdered magnesia partial hydrate is usually used.
Examples of minerals mainly composed of magnesium carbonate include magnesite and dolomite. In this case, the content of magnesium carbonate in the mineral is preferably 80% by mass or more, more preferably 85% by mass or more, and particularly preferably 90% by mass or more.
Examples of minerals mainly composed of magnesium hydroxide include brucite. In this case, the content of magnesium hydroxide in the mineral is preferably 80% by mass or more, more preferably 85% by mass or more, and particularly preferably 90% by mass or more.

Light-burned magnesia contains magnesium oxide as a main component. The light-burned magnesia partial hydrate obtained by partially hydrating light-burned magnesia used in the present invention contains magnesium hydroxide obtained by hydration and magnesium oxide in a specific ratio described later. By using such light-burned magnesia partial hydrate, it is possible to obtain a high inhibitory effect on elution of heavy metals or the like in solid matter such as soil or waste water.
The firing temperature varies depending on the presence or absence of optional components other than the component (A), but is 550 to 1,400 ° C., preferably 650 to 1,000 ° C. When the temperature is less than 550 ° C., light-burned magnesia is difficult to be generated. On the other hand, when the temperature exceeds 1,400 ° C., the effect of insolubilizing heavy metals and the like is reduced.
When the component (B) is not used, the calcination temperature is preferably 750 to 1,000 ° C., more preferably 860 to 950 ° C., and particularly preferably 870 to 920 ° C.
In the case of using the component (B), the firing temperature is preferably 750 to 900 ° C., more preferably 800 to 900 ° C., from the viewpoint of ease of formation of light-burned magnesia and an effect of suppressing elution of heavy metals. is there.

(A) The content of magnesium oxide in the light-burned magnesia partial hydrate varies depending on the presence or absence of optional components other than the component (A), but is 50 to 96.5% by mass, preferably 60 to 95% by mass, More preferred is 70 to 95% by mass, and particularly preferred is 75 to 95% by mass.
When the component (B) is not used, the magnesium oxide content is preferably 60 to 95% by mass, more preferably 70 to 94% by mass, and particularly preferably 75 to 93% by mass.
When the component (B) is used, the content of the magnesium oxide is preferably 65 to 96.5% by mass, more preferably 70 to 95% by mass, and particularly preferably 75 to 95% by mass.

(A) The content of magnesium hydroxide in the light-burned magnesia partial hydrate varies depending on the presence or absence of optional components other than the component (A), but is 3.5 to 50% by mass, preferably 3.5 to 40%. % By mass, more preferably 5 to 30% by mass, particularly preferably 6 to 20% by mass.
When the component (B) is not used, the magnesium hydroxide content is preferably 4 to 40% by mass, more preferably 5 to 30% by mass, and particularly preferably 6 to 20% by mass.
When the component (B) is used, the magnesium hydroxide content is preferably 3.5 to 30% by mass, more preferably 5 to 20% by mass, and particularly preferably 7 to 17% by mass.
When the content of magnesium oxide is less than 50% by mass or the content of magnesium hydroxide exceeds 50% by mass, the effect of insolubilization of heavy metals and the like decreases. On the other hand, when the content of magnesium oxide exceeds 96.5% by mass or the content of magnesium hydroxide is less than 3.5% by mass, particularly in soils highly contaminated with heavy metals, etc., heavy metals The effect which suppresses elution etc. falls.

In the present invention, the total content of calcium oxide and / or calcium hydroxide contained in the obtained light calcined magnesia partial hydrate is in terms of oxide in the light calcined magnesia partial hydrate (100% by mass). It is 5.0 mass% or less, preferably 4.0 mass% or less, more preferably 3.0 mass% or less, further preferably 2.5 mass% or less, and particularly preferably 2.0 mass% or less. When the content exceeds 5.0% by mass, the effect of suppressing elution of heavy metals and the like is reduced particularly in soils and the like highly contaminated with heavy metals and the like.
The light-burned magnesia partial hydrate is composed of other components (specifically, SiO ₂ , Fe ₂ O _3, etc.) other than the above components (MgO, Mg (OH) ₂ , CaO, Ca (OH) ₂ ). Impurities). The content of other components is preferably 4.0% by mass or less, more preferably 3.0% by mass or less, and particularly preferably 2.5% by mass or less. When this content rate exceeds 4.0 mass%, the effect which suppresses elution of heavy metals etc. may fall.

As a method for hydrating light-burned magnesia, it is sufficient that the content of each component (magnesium oxide, magnesium hydroxide, and calcium) in the obtained light-burned magnesia partial hydrate is within the above specific range. Although not limited, the following (1) or (2) method is mentioned, for example.
(1) A method of adding water to light-burned magnesia and mixing (2) A method of holding light-burned magnesia in an environment having a relative humidity of 80% or more for one week or more. The hydration reaction may be carried out after mixing with other components (for example, powder containing calcium carbonate as the main component (B)).
Moreover, it is preferable to grind lightly burned magnesia (or a mixture of lightly burned magnesia and other components) before the hydration reaction.

The Blaine specific surface area of the light magnesia constituting the insolubilized material of the present invention is preferably 2,500 to 20,000 cm ² / g, more preferably 4,800 to 10,000 cm ² / g, and still more preferably 5,200. It is ˜8,000 cm ² / g, particularly preferably 5,500 to 6,500 cm ² / g. By adjusting the value within the above numerical range, the effect of suppressing elution of heavy metals and the like can be enhanced, and in particular, elution can be suppressed in a small amount even for soils and the like where elution of heavy metals and the like is large. be able to. Moreover, when the Blaine specific surface area is 8,000 cm ² / g or less, addition in a difficult slurry becomes possible when the Blaine specific surface area exceeds 8,000 cm ² / g.

[(B) Powder mainly composed of calcium carbonate]
For the insolubilizing material of the present invention, (B) a powder mainly composed of calcium carbonate can be used as an optional component.
(B) Although it does not specifically limit as powder which has calcium carbonate as a main component, For example, calcium carbonate powder for industrial use, calcium carbonate powder of a reagent, limestone powder, crushed shell of shellfish containing calcium carbonate as a main component, coral A pulverized product or the like can be used. Among these, limestone powder is preferably used from the viewpoint of cost.
(B) The content rate of the calcium carbonate in a component becomes like this. Preferably it is 80 mass% or more, More preferably, it is 85 mass% or more, Most preferably, it is 90 mass% or more.
The component (B) is used in the process of producing the insolubilized material of the present invention (i) an average particle diameter of 1 to 20 mm (preferably 2 to 10 mm), or (ii) a specific surface area of Blaine of 3,000 to 7,000 cm ² / The particle size is preferably adjusted so as to be g (preferably 4,000 to 6,000 cm ² / g). In the case of (i), it is preferable to mix with light-burned magnesia (component (A) before hydration) and pulverize these two materials at the same time, and then subject to hydration, and (ii) In the case of, it is preferable to mix with lightly-burned magnesia whose particle size has been adjusted and then subjected to hydration.
Component (B) is blended in an amount of 20 to 70 parts by weight, preferably 25 to 60 parts by weight, more preferably 30 to 50 parts by weight per 100 parts by weight of component (A). When the blending amount is less than 20 parts by mass, the elution suppressing effect of heavy metals and the like may be lowered depending on the properties of the component (A). On the other hand, when the said compounding quantity exceeds 70 mass parts, the ratio of the (A) component in an insolubilization material falls in connection with it, and the elution inhibitory effect of heavy metals etc. falls.

The insolubilizing material of the present invention containing the component (A) and the component (B) can be obtained, for example, by the following methods (a) to (c).
(A) a step of mixing lightly burned magnesia (material of component (A)) and calcium carbonate-containing material (material of component (B)) to obtain a mixture, and a mixture having a predetermined particle size by pulverizing the mixture And a step of hydrating the pulverized product of the mixture to obtain an insolubilized material containing a powder composed of light-burned magnesia partial hydrate and a powder mainly composed of calcium carbonate. Method (b) pulverizing light-burned magnesia to obtain a pulverized light-burned magnesia having a predetermined particle size; pulverizing a calcium carbonate-containing material to obtain a calcium carbonate-containing pulverized material having a predetermined particle size; Mixing the light-burned magnesia pulverized product and the calcium carbonate-containing pulverized product to obtain a mixture, hydrating the mixture, and comprising powder of light-burned magnesia partial hydrate and calcium carbonate as the main components And (c) pulverizing light-burned magnesia to obtain a light-burned magnesia pulverized product having a predetermined particle size, and hydrating the light-burned magnesia pulverized product. A step of obtaining a powder composed of light-burned magnesia partial hydrate, and a step of obtaining a calcium carbonate-containing pulverized product (powder mainly composed of calcium carbonate) having a predetermined particle size by pulverizing the calcium carbonate-containing product. And a step of mixing the powder composed of the light-burned magnesia partial hydrate and the calcium carbonate-containing pulverized product to obtain an insolubilizing material. Among these, the elution suppressing effect of heavy metals and the like, and workability From the viewpoint, the method (a) or (b) is preferred, and the method (a) is more preferred.

In the method (a), the light-burned magnesia before pulverization preferably has a particle size of 1 μm to 50 mm. Further, the calcium carbonate-containing material before pulverization preferably has a particle size of 1 μm to 50 mm, and more preferably 2 μm to 20 mm. By using the light-burned magnesia and the calcium carbonate-containing material before pulverization having such a particle size, the particle size constitution of the pulverized product as a mixture, and thus the insolubilized material, can be easily adjusted.
A light-burned magnesia having a particle size of 1 μm to 50 mm and a calcium carbonate-containing material having a particle size of 1 μm to 50 mm are pulverized simultaneously, and the Blaine specific surface area of a pulverized product made of a mixture of these two materials is 2 When adjusted within the range of 500 to 7,000 cm ² / g (preferably 4,500 to 7,000 cm ² / g, more preferably 5,000 to 6,500 cm ² / g), it is within the range of 1 to 5 μm. It is possible to obtain an insolubilized material that forms a frequency distribution curve of particle size having two peaks, a first peak and a second peak in the range of 20 to 50 μm. In this case, the ratio of the second peak (frequency%) / first peak (frequency%) is preferably 2 to 4.
Further, in the method (a), the light-burned magnesia and the calcium carbonate-containing material are pulverized at the same time, so that the work is simpler than the method (b) or (c) in which these are pulverized separately. Have

In the method (b) or (c), the light-burned magnesia preferably has a Blaine specific surface area of 2,500 to 7,000 cm ² / g, more preferably 4,500 to 7,000 cm ² / g, particularly Preferably, it is pulverized to 5,000 to 6,500 cm ² / g. The calcium carbonate-containing material is pulverized so that the specific surface area of branes is preferably 3,000 to 7,000 cm ² / g, more preferably 4,000 to 6,000 cm ² / g. The insolubilized material having the above-mentioned preferred particle size configuration can be obtained by mixing the light-burned magnesia pulverized product (or its partially hydrated product) having such a specific surface area with the calcium carbonate-containing pulverized product.
When the calcium carbonate-containing material already has the above-mentioned Blaine specific surface area, it can be used as it is without being pulverized.

[(C) One or more additives selected from water-soluble sulfates and water-soluble chlorides]
The insolubilizing material of this invention can contain the 1 or more types of additive chosen from (C) water-soluble sulfate and water-soluble chloride as needed. In particular, when the component (A) and the component (B) are used in combination, the effect of suppressing elution of heavy metals and the like can be further improved by adding the component (C).
Examples of the water-soluble sulfate include powders of ferrous sulfate (iron (II) sulfate), aluminum sulfate, potassium aluminum sulfate, sodium aluminum sulfate and the like. Examples of water-soluble chlorides include ferrous chloride (iron (II) chloride) and ferric chloride (iron (III) chloride). These can be used individually by 1 type or in combination of 2 or more types. Furthermore, these may be used in the form of powder or in the form of an aqueous solution.
Compounding amount of component (C) (However, when used as an aqueous solution, it is an amount in terms of solid content. When it is a hydrate, it is based on the mass excluding hydration water. The same applies hereinafter.) Is sufficiently 5% by mass or more in 100% by mass of the entire insolubilized material in order to sufficiently improve the elution suppression effect of heavy metals and the like.
Moreover, the compounding amount of the component (C) is 30% by mass or less in 100% by mass of the entire insolubilized material from the viewpoint that the elution suppressing effect of heavy metals and the like is not improved even if the compounding amount is too large. It is preferable that the content is 25% by mass or less.
In addition, when (C) component is used with the form of a powder, the particle size of this powder is although it does not specifically limit, From viewpoints of workability | operativity etc., 1 mm or less is preferable and 0.5 mm or less is more preferable.
Moreover, when using only (C) component with aqueous solution, the mixture of (A) component or (A) component and (B) component, and (C) component can also be added separately to object soil.

[(D) gypsum]
The insolubilizing material of the present invention can contain gypsum when it is added to granular or powdery solids such as soil and incinerated fly ash.
By including an appropriate amount of gypsum, the solidification strength of a granular or powdery solid can be increased. The solidification strength can be evaluated by measuring uniaxial compressive strength.
Examples of gypsum include anhydrous gypsum, dihydrate gypsum, and hemihydrate gypsum.
The blending amount of gypsum is preferably 50 parts by mass or less, more preferably 3 to 35 parts by mass, and still more preferably 8 to 30 parts by mass in terms of anhydride with respect to 100 parts by mass of light-burned magnesia partial hydrate. Particularly preferred is 12 to 25 parts by mass.
When the amount of gypsum exceeds 50 parts by mass, not only the solidification strength is lowered, but also the effect of suppressing elution of heavy metals and the like is lowered.
The brane specific surface area of the gypsum constituting the insolubilizing material of the present invention is preferably 3,000 to 8,000 cm ² / g, more preferably 3,500 to 6,500 cm ² / g, still more preferably 4,000 to 6 000 cm ² / g, particularly preferably 4,500 to 5,500 cm ² / g. By adjusting the value within the above numerical range, the effect of suppressing elution of heavy metals and the like can be enhanced, and in particular, elution can be suppressed in a small amount even for soils and the like where elution of heavy metals and the like is large. be able to.
In addition, when gypsum already has the said Blaine specific surface area, it can use as it is, without grind | pulverizing.

The insolubilized material of the present invention has a Blaine specific surface area of 2,500 to 20,000 cm ² / g, and Rosin-Rammler formula for particle size distribution: R = 100 exp (−bD _p ⁿ ) ( ^where R is The integrated residual value (%) represents the sieve residue, D _p is the particle size (μm), the size of the sieve eye, and b and n are constants). It preferably has a particle size configuration of 80 to 1.45. By adjusting the particle size composition of the insolubilizing material as described above, it is possible to enhance the effect of suppressing the elution of heavy metals and the like. Can be suppressed.
The Blaine specific surface area of the insolubilized material is more preferably 4,800 to 10,000 cm ² / g, further preferably 5,200 to 8,000 cm ² / g, particularly preferably 5,500 to 6,500 cm ² / g. is there.
The n value in the Rosin-Rammler equation is more preferably 0.90 to 1.30, particularly preferably 0.95 to 1.20.
The n value in the Rosin-Rammler equation and the average particle size described later can be measured using, for example, Nikkiso Co., Ltd. 9320-X10 (particle size distribution measuring device). In the measurement, 0.05 g of a sample is added to 20 ml of dispersion medium ethanol contained in a 100 ml beaker, and ultrasonic dispersion is performed for 1 minute using an ultrasonic cleaning machine (VS-100, frequency 50 kHz) manufactured by ASONE. Measurement will be performed later. The measurement is performed under the condition that the refractive index of the sample is 1.72.
Moreover, the preferable numerical range of the n value in the Blaine specific surface area of the insolubilized material of the present invention and the Rosin-Rammler formula is determined by excluding the component (C).

The insolubilizing material of the present invention in the case of containing the component (A) and the component (B) has a Blaine specific surface area of 2,500 to 7,000 cm ² / g and a rosin-Rammler formula relating to the particle size distribution: R = 100exp (-bD _p ⁿ⁾ (wherein, R is accumulated residue value (%) represents the sieve residue, D _p is the particle size ([mu] m), represents the size of the sieve with, b, n is a constant. It is preferable to have a particle size configuration in which the n value in 0.90 to 1.20. By adjusting the particle size composition of the insolubilizing material as described above, it is possible to increase the elution suppression effect of heavy metals, etc., and to suppress the elution in a small amount even for soils with a large amount of elution of heavy metals, etc. it can.
(A) and component (B) Blaine specific surface area of the insoluble material of the present invention when containing the component, more preferably 4,500 ~ 7,000cm ² / g, particularly preferably 5,000 ~ 6,500cm ² / g. The n value in the Rosin-Rammler equation is more preferably 0.95 to 1.15.
In addition, the insolubilizing material of the present invention containing the component (A) and the component (B) preferably has an average particle size of 20 to 40 μm, more preferably 25 to 35 μm. When the average particle size of the insolubilized material is within the above range, the effect of suppressing elution of heavy metals, etc. can be enhanced. Can be suppressed.
In the present specification, the term “average particle size” means a 50% mass cumulative particle size.
Moreover, in the insolubilizing material of this invention in the case of containing (A) component and (B) component, it is preferable that there exist two peaks in the frequency distribution curve of the particle size obtained by measuring by the method similar to the above. Here, the first peak is preferably in the range of 1 to 5 μm, and the second peak is preferably in the range of 20 to 50 μm.

The insolubilizing material of the present invention can be obtained, for example, by the following method (a) when it comprises only the component (A) (lightly burned magnesia partial hydrate).
(A) A method comprising a step of pulverizing light-burned magnesia to obtain a pulverized product having a predetermined particle size, and a step of hydrating the pulverized product to obtain a powder comprising light-burned magnesia partial hydrate. When the insolubilizing material of the invention comprises only the component (A) (lightly burned magnesia partial hydrate) and the component (D) (gypsum), it is obtained, for example, by any of the following methods (b) to (d): .
(B) mixing lightly-burned magnesia and gypsum to obtain a mixture, pulverizing the mixture to obtain a pulverized mixture having a predetermined particle size, and hydrating the pulverized mixture. A process comprising: obtaining a mixture comprising a powder comprising light-burned magnesia partial hydrate and gypsum powder; and (c) pulverizing the light-burned magnesia to obtain a light-burned magnesia pulverized product having a predetermined particle size. Pulverizing gypsum to obtain a gypsum pulverized product having a predetermined particle size, mixing the light-burned magnesia pulverized product and the gypsum pulverized product to obtain a mixture, and hydrating the mixture And (d) pulverizing the light-burned magnesia to obtain a mixture of the powder comprising the light-burned magnesia partial hydrate and the gypsum powder. And the light baking A step of obtaining a powder comprising light-burned magnesia partial hydrate by hydrating a pulverized gnesia, a step of obtaining gypsum powder having a predetermined particle size by pulverizing gypsum, and the light-burning magnesia partial hydration A method comprising mixing a powder composed of a product and the gypsum powder to obtain a mixture thereof, and among these methods (b) to (d), an effect of suppressing elution of heavy metals and the like, And from the viewpoint of workability, the method (b) or (c) is preferable, and the method (b) is more preferable.

In each of the above methods (a) to (d), the light-burned magnesia before pulverization preferably has a particle size of 1 μm to 50 mm. The gypsum before pulverization preferably has a particle size of 1 μm to 100 mm, and more preferably 2 μm to 50 mm. By using light-burned magnesia and gypsum before pulverization having such a particle size, the particle size of the insolubilized material of the present invention can be easily adjusted.

The addition amount of the insolubilizing material of the present invention, when used as an additive to a granular or powdered solid material (for example, soil, incineration ash, etc.), the properties of the addition object, construction conditions, the elution amount and addition of heavy metals, etc. Although depending on the required performance of the object, generally 50 to 400 kg is preferable, more preferably 100 to 350 kg, per 1 m ³ of a granular or powdery solid. When the amount is less than 50 kg, the effect of suppressing elution of heavy metals and the like is insufficient. When the amount exceeds 400 kg, the improvement effect of elution of heavy metals and the like reaches a peak, and the volume after treatment increases and the treatment cost also increases.
In this case, as the method for adding the insolubilizing material, dry addition in which the insolubilizing material is added and mixed in powder form, or slurry addition in which water is added and mixed as a slurry can be employed. The water / insolubilized material mass ratio in the case of slurry addition is preferably 0.5 to 1.5, more preferably 0.8 to 1.2.
The insolubilizing material of the present invention is particularly preferably used for soil, but other than soil, for example, sewage sludge incineration ash, chicken manure incineration ash, papermaking sludge incineration ash, incineration ash such as coal incineration ash, incinerator For dust such as incinerated fly ash collected by dust collecting means such as bag filters and electric dust collectors from exhaust gas, and for particulate solids such as tunnel sludge, concrete glass and slag contaminated by heavy metals Can be used.

The amount of the insolubilizing material of the present invention, when used as an additive to waste water, depends on the properties of the object to be added and the construction conditions, the amount of elution of heavy metals, the required performance of the object to be added, etc. The amount is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 4 parts by mass, and particularly preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the waste water.
If the amount is less than 0.1 parts by mass, the effect of suppressing elution of heavy metals in the waste water is insufficient. When the amount exceeds 10 parts by mass, the improvement effect of the elution of heavy metals in the wastewater reaches its peak, and the processing cost increases.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[1. When containing component (A) and component (B)]
[Manufacture of insolubilized materials]
(Insolubilized material A)
Magnesite (magnesium carbonate content: 97% by mass) was calcined at 850 ° C. to obtain light calcined magnesia. Subsequently, after mixing the obtained light-burned magnesia and a calcium carbonate-containing material having an average particle diameter of 8 mm (crushed limestone; calcium carbonate content: 95% by mass), the mixture was pulverized to have a Blaine specific surface area of 5,500 cm. A pulverized product of ² / g was obtained.
The obtained pulverized product is stored in a storage room with a relative humidity of 100% for 10 days to hydrate part of the light-burned magnesia, and the powder (component (A)) comprising the light-burned magnesia partial hydrate Insolubilized material A containing powder (component (B)) containing calcium carbonate as a main component was obtained.
The frequency distribution curve of the particle size for the insolubilized material A has a first peak of 1.5 μm and a second peak of 30 μm, a frequency of the first peak of 1%, a frequency of the second peak of 3%, and a second peak ( The ratio of (frequency%) / first peak (frequency%) was 3.
(Insolubilized material B)
Insolubilized material B was obtained in the same manner as insolubilized material A except that the hydration condition was changed to 20 days in a storage room at 100% relative humidity.
The frequency distribution curve of the particle size for the insolubilized material B has a first peak of 1.5 μm and a second peak of 30 μm, a frequency of the first peak of 1%, a frequency of the second peak of 3%, and a second peak ( The ratio of (frequency%) / first peak (frequency%) was 3.
(Insolubilized material C)
Magnesite (magnesium carbonate content: 97% by mass) was fired at 850 ° C. and then pulverized to obtain a lightly baked magnesia pulverized product having a Blaine specific surface area of 5,500 cm ² / g. Subsequently, the obtained light-burned magnesia pulverized product was mixed with a calcium carbonate-containing product having a Blaine specific surface area of 5,000 cm ² / g (limestone pulverized product; calcium carbonate content: 95% by mass), and the resulting mixture was obtained. Is stored in a storage room at a humidity of 100% for 10 days to hydrate part of the light-burned magnesia pulverized product, and the powder (component (A)) consisting of the light-burned magnesia partial hydrate and calcium carbonate are mainly used. Insolubilized material C containing powder (component (B)) as an ingredient was obtained.

(Insolubilized material D)
Insolubilized material D was obtained in the same manner as insolubilized material A except that the hydration conditions were changed to 20 days in a storage room with a relative humidity of 60%.
(Insolubilized material E)
(A) Same as insolubilized material A except that magnesite (calcium content: 5.2% by mass in terms of oxide) having a higher calcium content than insolubilized material A was used as the raw material of component (A). Insolubilized material E was obtained.
(Insolubilized material F)
Magnesite (magnesium carbonate content: 97% by mass) was calcined at 850 ° C. to obtain light calcined magnesia. Subsequently, after mixing the obtained light-burned magnesia and a calcium carbonate-containing material having an average particle diameter of 8 mm (pulverized limestone; calcium carbonate content: 95% by mass), the obtained mixture was pulverized to obtain a Brain ratio. A pulverized product having a surface area of 5,500 cm ² / g was obtained. Subsequently, the obtained pulverized product and magnesium hydroxide (reagent grade 1) were mixed to obtain an insolubilizing material H.

(Insolubilized material A-1)
Ferrous sulfate monohydrate (particle size: 0.1 to 0.3 mm) was added to the insolubilized material A to obtain insolubilized material A-1. The ratio of ferrous sulfate is 10% by mass in 100% by mass of the entire insolubilized material A-1.
(Insolubilized material A-2)
Ferrous sulfate monohydrate (particle size: 0.1 to 0.3 mm) was added to the insolubilized material A to obtain an insolubilized material A-2. The ratio of ferrous sulfate is 20% by mass in 100% by mass of the entire insolubilized material A-2.
(Insolubilized material A-3)
Aluminum sulfate anhydrous salt (particle size: 30 to 60 μm) was added to the insolubilized material A to obtain an insolubilized material A-3. The proportion of aluminum sulfate in 10% by mass of the entire insolubilized material A-3 is 10% by mass.
(Insolubilized material A-4)
Aluminum sulfate anhydrous salt (particle size: 30 to 60 μm) was added to the insolubilized material A to obtain an insolubilized material A-4. The proportion of aluminum sulfate is 20% by mass in 100% by mass of the entire insolubilized material A-4.
(Insolubilized material A-5)
To insolubilized material A, ferric chloride hexahydrate (mixing ratio; 10 mass%, special grade reagent) was added to obtain insolubilized material A-5.
(Insolubilized material A-6)
To insolubilized material A, ferric chloride hexahydrate (mixing ratio: 20 mass%, special grade reagent) was added to obtain insolubilized material A-6.
(Insolubilized material A-7)
To insolubilized material A, ferrous chloride tetrahydrate (mixing ratio: 10 mass%, special grade reagent) was added to obtain insolubilized material A-7.
(Insolubilized material A-8)
To insolubilized material A, ferrous chloride tetrahydrate (mixing ratio: 20 mass%, special grade reagent) was added to obtain insolubilized material A-8.

[Examples 1 to 3, Comparative Examples 1 to 4]
Using the insolubilizing materials A to F (Examples 1 to 3, Comparative Examples 1 to 2 and 4) or without using the insolubilizing materials (Comparative Example 3), the following elution tests 1 to 4 for heavy metals and the like were performed. went. The results are shown in Table 1.
Further, for each insolubilized material, the component composition, Blaine specific surface area, n value of rosin-Rammler formula, and average particle diameter were determined by the following methods. These are shown together in Table 1.
(Elution test for heavy metals 1; Arsenic elution test)
The amount of insolubilized material shown in Table 1 was added to arsenic-contaminated soil (water content ratio: 70%), and the amount of arsenic eluted from the improved soil at 7 days of age was measured according to the Ministry of the Environment Notification No. 46 did. The environmental standard value for arsenic is 0.01 mg / liter.
(Elution test 2 for heavy metals; fluorine elution test)
The amount of insolubilized material shown in Table 1 was added to fluorine-contaminated soil (water content: 75%), and the amount of fluorine eluted from the improved soil on the 7th day of age was measured according to the Ministry of the Environment Notification No. 46 did. The environmental standard value of fluorine is 0.8 mg / liter.
(Elution test for heavy metals 3; Lead elution test)
The amount of insolubilized material shown in Table 1 was added to lead-contaminated soil (water content: 70%), and the amount of lead elution from the improved soil on the age of 7 days was measured according to the Ministry of the Environment Notification No. 46 did. The environmental standard value for lead is 0.01 mg / liter.
(Elution test for heavy metals 4; elution test for hexavalent chromium)
The amount of insolubilized material shown in Table 1 was added to the hexavalent chromium-contaminated soil (water content: 80%), and the amount of hexavalent chromium elution from the improved soil on the 7th day of age was specified in the Ministry of the Environment Notification No. 46 Measured in conformity. The environmental standard value for hexavalent chromium is 0.05 mg / liter.

(Component composition)
Calculated from X-ray diffraction, thermogravimetric analysis and chemical analysis values.
(Brain specific surface area)
It measured according to "JISR5201".
(Average particle size, n value of Rosin-Rammler formula)
In a 100 ml beaker, 20 ml of ethanol (dispersion medium) and 0.05 g of an insolubilizing material were added, and ultrasonically dispersed for 1 minute using an ultrasonic cleaner (VS-100, frequency 50 kHz) manufactured by AS ONE. Then, using Nikkiso 9320-X10 (particle size distribution measuring device), the average particle size (50% mass cumulative particle size) and the n-value of the Rosin-Rammler equation were determined. Note that the refractive index of the sample is assumed to be 1.72.

[Examples 4 to 11]
Using the insolubilized materials A-1 to A-8, the elution tests 1, 2, and 4 (elution test for arsenic, fluorine, hexavalent chromium) of heavy metals and the like were performed in the same manner as in Example 1. The results are shown in Table 2.

[Examples 12 to 14, Comparative Example 5]
Elution tests 1 to 4 for heavy metals were conducted with insolubilizing materials A, A-1, and A-5 added to incinerated ash containing heavy metals, or without adding the insolubilizing materials. The test method is the same as in Example 1. The results are shown in Table 3.

From Table 1, it can be seen that according to the insolubilizing material of the present invention, the amount of elution of heavy metals (arsenic, fluorine, lead, hexavalent chromium) can be reduced below the environmental standard value with a small addition amount (Example 1). ~ 3). On the other hand, Comparative Example 1 in which hydration is insufficient and the content of magnesium hydroxide is outside the scope of the present invention, and (A) the content (calculated in terms of oxide) of calcium in the light-burned magnesia partial hydrate is In Comparative Example 2, which is outside the scope of the present invention, it may be necessary to add a larger amount of insolubilizing material than Examples 1 to 3 in order to reduce the amount of elution of heavy metals and the like to an environmental standard value or less. Recognize. It turns out that it replaces with the partial hydrate of light-burning magnesia, and the elution suppression effect of heavy metals etc. is inadequate in the comparative example 4 which used together light-burning magnesia and the magnesium hydroxide which is a reagent. In Comparative Example 3, no insolubilizing material is used, so that it can be seen that a large amount of heavy metals are eluted.
In addition, it can be seen from Table 2 that the addition of sulfate (ferrous sulfate, aluminum sulfate) can reduce the amount of elution of heavy metals and the like below the environmental standard value with a smaller amount of use (Examples 4 to 4). 11).
Furthermore, it can be seen from Table 3 that the insolubilizing material of the present invention has an excellent insolubilizing effect even for incineration ash.

[2. When component (B) is not included]
[Preparation of insolubilized material]
The following insolubilized materials G to T were prepared.
(1) Insolubilizing material G: A material obtained by pulverizing light-burned magnesia obtained by firing magnesite at 890 ° C. and storing it in a storage room with a relative humidity of 100% for 10 days. (2) Insolubilizing material H: A pulverized product obtained by pulverizing light-burned magnesia obtained by firing magnesite at 890 ° C. for 20 days in a storage room with a relative humidity of 100%. (3) Insolubilizing material I: “Insolubilizing material A ”18 parts by mass of natural anhydrous gypsum having a specific surface area of 5,500 cm ² / g of brain relative to 100 parts by mass and mixed (4) Insolubilized material J: Blaine relative to 100 parts by mass of“ insolubilized material B ” 18 parts by mass of natural anhydrous gypsum having a specific surface area of 5,500 cm ² / g were added and mixed. (5) Insolubilized material K: Blaine specific surface area of 5,500 cm ² / g with respect to 100 parts by mass of “insolubilized material A” 3 masses of natural anhydrous gypsum Added, mixed ones (6) insoluble material L: which "insoluble material A" natural anhydrite of Blaine specific surface area of 5,500cm ² / g were added 50 parts by weight per 100 parts by weight, were mixed (7) Insolubilizing material M: After pulverized light magnesia obtained by firing magnesite at 890 ° C., the particle size was adjusted with an air jet sieving apparatus, and then stored in a storage room with a relative humidity of 100%. (8) Insolubilized material N: pulverized product obtained by pulverizing light-burned magnesia obtained by firing magnesite at 890 ° C., and adjusting the particle size with an air jet sieving apparatus, and then relative humidity 100 (9) Insolubilized material O: A pulverized product obtained by pulverizing light-burned magnesia obtained by firing magnesite at 890 ° C. in a storage room having a relative humidity of 60%. For 20 days (10) Insolubilized material P: a pulverized product obtained by pulverizing light-burned magnesia obtained by firing magnesite at 890 ° C. and stored for 50 days in a storage room with a relative humidity of 100% (11) Insolubilized material Q: a pulverized product obtained by pulverizing light-burned magnesia obtained by firing magnesite with a high calcium content at 890 ° C. and stored in a storage room with a relative humidity of 100% for 10 days (12 ) Insolubilizing material R: Magnesium hydroxide 11.5 which is a reagent (manufactured by Kanto Chemical Co., Ltd .; special grade) with respect to 100 parts by mass of pulverized product obtained by pulverizing light-burned magnesia obtained by baking magnesite at 890 ° C. (13) Insolubilized material S: pulverized product obtained by pulverizing light-burned magnesia obtained by firing magnesite with a high calcium content at 890 ° C., having a relative humidity of 100% Storage room (14) Insolubilized material T: A pulverized product obtained by pulverizing light-burned magnesia obtained by firing magnesite with a high calcium content at 890 ° C., stored at a relative humidity of 100% Stored in the room for 10 days

[Preparation of contaminated soil, etc.]
The following contaminated soil, incineration fly ash, and drainage were prepared.
(1) Arsenic-contaminated soil To arsenic-contaminated soil, 0.04 g of sodium hydrogen arsenate 7-hydrate is added to and mixed with 2000 g of silt soil with a wet density of 1.67 g / cm ³ and a water content of 51.5%. Got.
(2) Fluorine-contaminated soil 0.06 g of potassium fluoride was added to and mixed with 2000 g of viscous soil having a wet density of 1.53 g / cm ³ and a water content ratio of 76.3% to obtain fluorine-contaminated soil.
(3) Lead-contaminated soil 0.50 g of lead (II) nitrate was added to and mixed with 2000 g of sandy soil with a wet density of 1.71 g / cm ³ and a water content ratio of 10.5% to obtain lead-contaminated soil. .
(4) Incineration ash Incineration ash (city waste incineration ash) was recovered from incinerators for general household waste.
(5) Arsenic-contaminated wastewater 0.0043 parts by mass of sodium hydrogen arsenate (manufactured by Kanto Chemical Co., Inc .; special grade) was added to 100 parts by mass of water to obtain arsenic-contaminated wastewater.
(6) Fluorine-contaminated wastewater 0.0058 parts by mass of potassium fluoride (manufactured by Kanto Chemical Co., Inc .; special grade) was added to 100 parts by mass of water to obtain fluorine-contaminated wastewater.
(7) Lead-contaminated wastewater 0.0032 parts by mass of lead nitrate (II) (manufactured by Kanto Chemical Co., Ltd .; special grade) was added to 100 parts by mass of water to obtain lead-contaminated wastewater.

[Test method]
(1) Component composition of insolubilized material Calculated from X-ray diffraction, thermogravimetric analysis, and chemical analysis values.
(2) Blaine specific surface area Measured according to "JIS R 5201".
(3) Rosin-Rammler n value In a 100 ml capacity beaker, 20 ml of ethanol (dispersion medium) and 0.05 g of insolubilized material were added, and an ultrasonic cleaner (VS-100, frequency 50 kHz, manufactured by AS ONE) ) For 1 minute. Thereafter, the n value of the rosin-Rammler type was determined using 9320-X10 (particle size distribution measuring device) manufactured by Nikkiso Co., Ltd. Note that the refractive index of the sample is assumed to be 1.72.
(4) Uniaxial compressive strength An insolubilizing material was added to the contaminated soil to obtain improved soil on the age of 7 days. The uniaxial compressive strength of the improved soil was measured according to JIS A 1216.

(5) Dissolution test 1 (arsenic)
(A) Soil An insolubilizing material was added to arsenic-contaminated soil (water content ratio: 70%), and the amount of arsenic eluted from the improved soil at 7 days of age was measured according to the Ministry of the Environment Notification No. 46. The environmental standard value for arsenic is 0.01 mg / liter.
(B) Incineration ash An insolubilizing material was added to the incineration ash, and the amount of arsenic eluted from the improved incineration ash on the age of 7 days was measured according to the Ministry of the Environment Notification No. 46.
(C) Wastewater An insolubilizing material was added to the arsenic-contaminated wastewater, and the amount of arsenic eluted from the wastewater after shaking at 200 times / minute for 4 hours was measured. At this time, the pH after addition of the insolubilizing material was also measured.

(6) Dissolution test 2 (fluorine)
(A) Soil Fluorine-contaminated soil (water content: 75%) was added with an insolubilizing material, and the amount of fluorine eluted from the improved soil at the age of 7 days was measured according to the Ministry of the Environment Notification No. 46 method. The environmental standard value of fluorine is 0.8 mg / liter.
(B) Incineration ash An insolubilizing material was added to the incineration ash, and the amount of fluorine eluted from the improved incineration ash on the age of 7 days was measured according to the Ministry of the Environment Notification No. 46.
(C) Wastewater An insolubilizing material was added to the fluorine-contaminated wastewater, and the amount of arsenic eluted from the wastewater after shaking for 4 hours at 200 times / minute was measured. At this time, the pH after addition of the insolubilizing material was also measured.

(7) Dissolution test 3 (lead)
(A) Soil An insolubilizing material was added to lead-contaminated soil (water content ratio: 70%), and the amount of lead eluted from the improved soil on the age of 7 days was measured according to the Ministry of the Environment Notification No. 46 method. The environmental standard value for lead is 0.01 mg / liter.
(B) Wastewater The insolubilizing material was added to the lead-contaminated wastewater, and the amount of arsenic eluted from the wastewater after shaking for 4 hours at 200 times / minute was measured. At this time, the pH after addition of the insolubilizing material was also measured.

(8) Dissolution test 4 (hexavalent chromium)
An insolubilizing material was added to the incinerated ash, and the elution amount of hexavalent chromium from the improved incinerated ash on the age of 7 days was measured according to the Ministry of the Environment Notification No. 46 method. The environmental standard value for hexavalent chromium is 0.05 mg / liter.

[Examples 15 to 22, Comparative Examples 6 to 10]
As shown in Table 4, when various insolubilizing materials were added to the contaminated soil (Examples 15 to 22, Comparative Examples 6 to 9) and when no insolubilizing materials were added (Comparative Example 10), Uniaxial compressive strength (abbreviated as “uniaxial strength” in Table 4) was measured. The results are shown in Table 4.
In Table 4, “addition amount (kg / m ³ )” represents the addition amount (kg) of the insolubilizing material to 1 m ³ of contaminated soil before the addition of the insolubilizing material.

From Table 4, when the insolubilizing material corresponding to the present invention is used (Examples 15 to 22), the amount of arsenic and the like eluted from the contaminated soil can be kept low with a small addition amount, and the uniaxial compressive strength is also good. It turns out that it is a value. On the other hand, in Comparative Examples 6 and 7, the magnesium hydroxide content is out of the numerical range defined in the present invention, so that arsenic, fluorine and lead are eluted at the same added amount as compared with Examples 15 to 22. The amount is large. In Comparative Example 8, since the calcium content (as oxide) exceeds the numerical range defined in the present invention, the amount of arsenic, fluorine, and lead eluted with the same amount of addition as compared with Examples 15-22 Is big. In Comparative Example 9, not a light-burned magnesia partial hydrate but a mixture of light-burned magnesia and magnesium hydroxide, which is a reagent, is used. Therefore, compared with Examples 15 to 22, arsenic and fluorine at the same addition amount are used. The amount of lead elution is large. In Comparative Example 10, since the insolubilizing material is not used, the amount of arsenic, fluorine, and lead eluted is very large.

[Examples 23 to 24, Comparative Examples 11 to 14]
As shown in Table 5, the amounts of arsenic and the like eluted when various insolubilizing materials were added to incinerated ash (Examples 23 to 24, Comparative Examples 11 to 13) and when no insolubilizing materials were added (Comparative Example 14). It was measured. The results are shown in Table 5.
In Table 5, “addition amount (kg / m ³ )” represents the addition amount (kg) of the insolubilizing material relative to 1 m ³ of the incinerated ash before the addition of the insolubilizing material.

Table 5 shows that when the insolubilizing material corresponding to the present invention is used (Examples 23 to 24), the amount of arsenic and the like eluted from the incinerated ash can be kept low with a small addition amount. On the other hand, in Comparative Examples 11 and 12, since the magnesium hydroxide content is out of the numerical range defined in the present invention, the elution amounts of arsenic, fluorine, and hexavalent chromium are the same as in Examples 23 to 24. It can be seen that in order to keep it low, the amount of insolubilizing material added must be larger than in Examples 23-24. In Comparative Example 13, since the calcium content (in oxide equivalent) exceeds the numerical range defined in the present invention, the leaching amounts of arsenic, fluorine, and hexavalent chromium are as low as those in Examples 23 to 24. It can be seen that the amount of insolubilizing material added must be larger than those in Examples 23 to 24 in order to suppress it. In Comparative Example 14, since no insolubilizing material was used, the elution amount of arsenic, fluorine, and hexavalent chromium was very large.

[Examples 25 to 28, Comparative Examples 15 to 20]
As shown in Table 6, the amounts of arsenic and the like eluted when various insolubilizing materials were added to the contaminated wastewater (Examples 25 to 28, Comparative Examples 15 to 19) and when no insolubilizing materials were added (Comparative Example 20). It was measured. The results are shown in Table 6.
In Table 6, “addition amount to waste water (mass%)” represents the addition amount (mass%) of the insolubilizing material relative to 100 mass% of the waste water before the addition of the insolubilizing material.

Table 6 shows that when the insolubilizing material corresponding to the present invention is used (Examples 25 to 28), the amount of arsenic and the like eluted from the contaminated wastewater can be kept below the drainage standard with a small addition amount. On the other hand, in Comparative Examples 15 and 16, the magnesium hydroxide content is out of the numerical range defined in the present invention. Therefore, compared with Examples 25 to 28, arsenic, fluorine and lead are eluted at the same addition amount. The balance of quantity is bad. In Comparative Examples 17 and 18, since the calcium content (as oxide) exceeds the numerical range defined in the present invention, arsenic, fluorine, and lead at the same addition amount compared to Examples 25 to 28. The amount of elution is large. In Comparative Example 19, since a mixture of light-burned magnesia and magnesium hydroxide as a reagent was used instead of light-burned magnesia partial hydrate, arsenic and fluorine at the same addition amount compared to Examples 25 to 28 The amount of lead elution is large. In Comparative Example 20, since no insolubilizing material is used, the amount of elution of arsenic, fluorine, and lead is very large.

Claims

(A) A lightly burned magnesia partial hydrate obtained by hydrating a portion of lightly burned magnesia obtained by firing a mineral mainly composed of magnesium carbonate and / or magnesium hydroxide at 550 to 1,400 ° C. In the light-burned magnesia partial hydrate, the magnesium oxide content is 50 to 96.5% by mass, the magnesium hydroxide content is 3.5 to 50% by mass, and the calcium content is oxidized. Lightly burned magnesia partial hydrate, which is 5.0% by mass or less in terms of product,
Insolubilizing material characterized by containing.
The insolubilizing material according to claim 1, wherein the component (A) is a powder, and 20 to 70 parts by mass of (B) a powder containing calcium carbonate as a main component per 100 parts by mass of the component (A).
The insolubilizing material is a Blaine specific surface area of 2,500 ~ 20,000cm 2 / g, and wherein the Rosin-Rammler about the particle size distribution: R = 100exp (-bD p n ) ( wherein, R integrated residual it is the partial value (%) represents the sieve residue, D p is the particle size ([mu] m), represents the size of the sieve with, b, n are constants.) n values at 0.80 ~ The insolubilized material according to claim 1 or 2, which is 1.45 powder.
The insolubilizing material according to any one of claims 1 to 3, wherein the insolubilizing material is a powder having an average particle diameter of 20 to 40 µm.
The insolubilizing material according to any one of claims 1 to 4, comprising (C) one or more additives selected from water-soluble sulfates and water-soluble chlorides.
The insolubilizing material according to any one of claims 1 to 5, wherein the insolubilizing material is for addition to a granular or powdery solid material.
The insolubilizing material according to claim 6, comprising (D) gypsum in an amount of 50 parts by mass or less with respect to 100 parts by mass of the component (A).
The insolubilizing material according to any one of claims 1 to 5, wherein the insolubilizing material is for addition to waste water.