JP2000093927A - Material for fixing hazardous substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide material for fixing hazardous substances for stably and inexpensively fixing heavy metals for a long time and enable fixture of not only heavy metals but also negative ions such as a chromate ion a bichromate ion, a hologen ions such as a chlorine ion, fluorine ion and the like, an aisenate ion, a phosphate ion, a nitrite ion, a nitiate ion and the like which are difficult to fix by the prior arts. SOLUTION: At least one of substances having re-hydration characteristic obtained by heating treatment of a calcium sulphoaluminate hydrate and by heating treatment of calcium aluminate hydrate is contained as a primary constituent. Or, a mixture of at least one of them and at least one kind selected from quick lime, slaked lime, gypsum, blast furnace water-granulated slag, Portland cement, iron sulfate, iron chloride, sodium hydrosulfide, sodium sulfide, thiourea, calcium polysulfide is more preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Waste and sludge discharged as a result of our industrial activities and daily living activities are on the increase, and it is necessary to detoxify these wastes for landfill disposal or reuse. It is urgent. The present invention
An object of the present invention is to provide a material that fixes harmful substances contained in these wastes and sludge and renders them harmless when buried or reused.

[0002]

2. Description of the Related Art Conventionally, as a method of detoxifying harmful substances (mainly heavy metals) contained in wastes and sludge, a method of solidification has been used, and solidification techniques include cement solidification and asphalt. There are methods such as solidification and melt solidification. In addition, a chemical treatment method has also been performed in which a liquid chelating agent is reacted with heavy metals in waste to form an insoluble heavy metal chelating compound.

[0003] For the solidification treatment with cement, a method is widely used in which waste and cement are weighed so as to have a predetermined ratio, a predetermined amount of water is added, and the mixture is kneaded and molded.
In the solidification treatment with cement, the effect of insolubilizing heavy metals as a stable hydroxide by an alkali component in the cement and the effect of adsorption and physical containment accompanying the solidification of the cement are used for immobilization. Therefore, the harmful substances to be solidified are heavy metals such as cadmium, lead, mercury, arsenic, and selenium, and it is difficult to solidify such as cyanogen and hexavalent chromium, and treat waste containing such harmful substances. Pre-processing is required in the case. Further, the Environment Agency Notification No. 5, as the "Standards for solid of waste containing metal or the like", it is shown that the addition of 1 m ³ per 150kg or more hydraulic cement.

Solidification by asphalt focuses on excellent asphalt adhesiveness, impregnation, water repellency, water resistance and chemical resistance, and is kneaded with waste to prevent contact with water. This is a treatment method that suppresses the elution of harmful substances. Solidification with asphalt is performed for sludge, radioactive waste, refuse incineration ash, etc. However, due to the cost and inadequate handling of asphalt, there are few cases where it is implemented compared to the cement method.

[0005] In the melting treatment, the waste is reduced to 1400 to 1600.
By heating to a high temperature of ° C., organic matter is decomposed and sealed and fixed in slag that generates heavy metals. This method is considered to have the highest safety, but heavy metals with relatively low boiling points such as mercury, lead, arsenic, and cadmium volatilize in the gas during the melting process and are collected as fly ash. Is disadvantageous in that a new processing problem occurs. Another problem is that the processing cost is the highest.

The immobilization with a liquid chelating agent involves kneading a nitrogen and sulfur organic chelating agent or a sulfur-free inorganic chemical with waste to immobilize heavy metals, but the chelating agent is expensive. For this reason, it is common to use it together with cement solidification. In the case of an organic chelating agent, there is a problem in terms of long-term stability (for example, acid rain and biodegradability).

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an inexpensive material for fixing harmful substances which stably fixes heavy metals over a long period of time. In addition, the immobilizing material of the present invention can be used not only for heavy metals, but also for chromate ions, dichromate ions, halogen ions such as chloride ions and fluorine ions, arsenate ions, and phosphate ions, which have been difficult with conventional methods. It is also possible to immobilize anions such as nitrite ions and nitrate ions.

[0008]

Means for Solving the Problems The harmful substance fixing material according to the present invention is a substance having rehydration properties obtained by heat treatment of calcium sulfoaluminate hydrate or heat treatment of calcium aluminate hydrate. Characterized in that at least one of them is contained as a main component. Alternatively, at least one of these and one or more of quick lime, slaked lime, gypsum, granulated blast furnace slag, portland cement, iron sulfate, iron chloride, sodium hydrosulfide, sodium sulfide, thiourea, and calcium polysulfide A mixture is more preferable.

In order to prepare the immobilizing material of the present invention, first, calcium sulfoaluminate hydrate as a starting material,
Alternatively, it is necessary to synthesize calcium aluminate hydrate. Calcium sulfoaluminate hydrate compound,
Trisulfate type (3CaO.Al ₂ O ₃ .3CaS
O ₄・ 32H ₂ O) and monosulfate type (3Ca
O.Al ₂ O ₃ .CaSO ₄ .12H ₂ O)
The trisulfate type is called ettringite and is naturally produced and can be used as a raw material of the present invention. As a method for synthesizing these calcium sulfoaluminate compounds, there are two methods, that is, a method of slurry synthesis in a wet method, and a method of synthesis by calcination and hydration in a solid phase. In the present invention, the method of wet synthesis is used. It is preferred to apply. For calcium aluminate hydrate, C ₄ AH ₁₉ , C ₄ AH ₁₃ , C ₄ AH ₁₁ , C _{3
AH 6, C 2 AH 8,} C 2 AH 5, C 4 A 3 H 3, C 4
AH ₁₀ , (C is CaO, A is Al ₂ O ₃ , H is H
₂ O) can be used in the present invention, but the synthesis method is not particularly limited as long as it is a currently known method. A method that can be synthesized at the lowest possible cost is desirable.

[0010] Even if calcium sulfoaluminate hydrate or calcium aluminate hydrate is directly added to waste, the effect of immobilizing harmful substances cannot be expected. Heat treatment of the synthesized calcium sulfoaluminate hydrate and calcium aluminate hydrate is required to immobilize harmful substances. In the case of calcium sulfoaluminate hydrate, the heat treatment is at least 150 ° C for ettringite and 200 ° C for monosulfate.
The above temperature is required. This heat treatment breaks the original crystal structure of the calcium sulfoaluminate from crystalline to amorphous. Further, these heat-treated products easily react with water to return to the original calcium sulfoaluminate hydrate. When the heat treatment temperature exceeds 400 ° C., gypsum is liberated and crystallized, but this does not affect the performance of the fixing material. Further, high-temperature heat treatment does not affect the performance of the harmful substance as an immobilizing material, but it is preferable to perform the heat treatment at as low a temperature as possible in consideration of economy. Calcium aluminate hydrate is, for example, C ₃ AH
_In the case of No. ₆ , when heat treatment is performed at 300 ° C. or more, C ₁₂ A ₇ H
When decomposed into CH (slaked lime) and further heated at 480 ° C. or higher, CH is dehydrated to C (quick lime). Other calcium aluminate hydrates are also thermally decomposed into calcium aluminate and slaked lime or quicklime. These pyrolyzed calcium aluminate compounds have very high reactivity with water. In this case, calcium gypsum aluminate hydrate is easily formed in the presence of gypsum or sulfate groups. In this case, as the type of gypsum to be added, any of anhydrous gypsum, gypsum hemihydrate and gypsum dihydrate can be used.

The heat-treated calcium sulfoaluminate hydrate or the heat-treated calcium aluminate hydrate alone is added to the waste to be treated, and an appropriate amount of water is added. By kneading
When rehydrated to produce calcium sulfoaluminate hydrate or calcium aluminate hydrate, harmful substances can be immobilized.However, quick lime, slaked lime, gypsum, granulated blast furnace slag, portland cement, sulfuric acid iron,
By adding and using one or more of iron chloride, sodium hydrosulfide, sodium sulfide, thiourea, and calcium polysulfide, the process of immobilizing harmful substances becomes more complete. In this case, the amount of addition is 100 parts by weight of the heat-treated calcium sulfoaluminate hydrate or the heat-treated calcium aluminate hydrate, and quick lime, slaked lime, gypsum, granulated blast furnace slag, portland cement. ,
Iron sulfate, iron chloride, sodium hydrosulfide, sodium sulfide,
Thiourea and calcium polysulfide are desirably 100 parts by weight or less. Further, it can be used in combination with a commonly used organic chelating agent. Regarding the method of addition, they may be added in a premixed state, or may be added in a batchwise manner.

Next, the immobilizing function of the material for immobilizing harmful substances is described below.
explain about. Calcium sulfoaluminate hydrate
Ettringite is ｛Ca₃[Al (OH)₆] ・
12H₂O｝³⁺Skeleton whose columnar structure extends in the C-axis direction
Are formed, during which SO₄Contains tetrahedrons and water molecules
It has an embedded crystal structure. Keep a large amount of water of crystallization
In the crystallization, the ion is located at the position of the Al atom.
Metals such as Ti, Cr, Mn, Fe, Se, etc.
It is known to easily replace on. Also ｛Ca
₃[Al (OH)₆] ・ 12H₂O｝³⁺Between columnar structures
SO intervening in ₄ ^2-The ions are also CrO₄ ^2-, Cr₂
O₇ ^2-, AsO₃ ^3-, AsO₄ ^3-, Cl⁻,
F⁻, NO₃ ⁻, NO₂ ⁻, CO₃ ^2-, PO₄ ^3-I
It is also possible to replace it with ON or the like. On the other hand, monkey
Fate also [Ca₂Al (OH)₆・ 2H₂O]⁺of
It has a layered structure, and an ion half is located at the position of Al atom during crystallization.
It is ettringite to take in heavy metal ions of close diameter
Is the same as in the case of⁻+ 2H₂O
There is a vacancy, so OH⁻, AsO₃ ^3-,
AsO₄ ^3-, Cl⁻, SO₄ ^2-, PO₄ ^3-, NO
₂ ⁻Is taken in. In addition, calcium aluminate
When the compound is also hydrated, Ca²⁺Ti, C at ion position
Metal ions such as r, Mn, Fe, Se easily replace
It is known that The fixing material of the present invention is
Musulfoaluminate compound or calcium aluminum
The substitution reaction of these ions during the hydration crystallization of
Fixing machine to fix harmful substances in crystal structure
It is fine.

[0013] Therefore, the immobilization of the harmful substance is strong because the harmful substance is not simply adsorbed or physically fixed. Calcium sulfoaluminate hydrate or calcium aluminate hydrate is known to have extremely low solubility, is inorganic, and is known to exist stably for a long period of time. Excellent in terms of sex. In addition, AsO ₃ ³⁻ , AsO ₄ ³⁻ , and C ³ cannot be immobilized by the conventional method using a liquid chelate.
l ⁻ , F ⁻ , SO ₄ ²⁻ , PO ₄ ³⁻ , NO ₂ ⁻ , NO
₃ ^- It is also a feature that allows immobilization of anions such.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific examples and effects of the fixing material of the present invention will be described with reference to examples, but the present invention is not limited to the following examples.

[0015]

Example 1 57 parts by weight of calcium hydroxide (special grade reagent), 43 parts by weight of anhydrous aluminum sulfate and 400 parts by weight of water were weighed in a stainless steel beaker and heated to 50 ° C.
The mixture was stirred and reacted for 5 hours, and aged at room temperature for further 24 hours. After the completion of the reaction, the precipitate was filtered and dried at 50 ° C. to obtain 173 parts by weight of a solid content. The obtained solid was ettringite as a result of powder X-ray diffraction. Next, the obtained solid content was heat-treated at 200 ° C. for 3 hours using an electric furnace to obtain 100 parts by weight of a heat-treated product “A”. 100pp
10 parts by weight of the heat-treated product "A" was added to 100 parts by weight of a lead ion waste liquid having a concentration of m, and the mixture was stirred and mixed for 1 hour to fix lead in the waste liquid. After centrifugation of the supernatant, lead in the waste liquid was analyzed and found to be 0.33 ppm.

[0016]

COMPARATIVE EXAMPLE 1 57 parts by weight of calcium hydroxide (special reagent) and 43 parts by weight of anhydrous aluminum sulfate were added at 100 ppm.
Was added to 1000 parts by weight of lead waste liquid having a concentration of 1 and stirred and mixed for 1 hour to fix lead ions in the waste liquid. After centrifugation of the supernatant, lead in the waste liquid was analyzed and found to be 3.54 ppm.

[0017]

【table 1】

[0018]

Examples 2 and 3 77 parts by weight of aluminum sludge, 26 parts by weight of anhydrous gypsum, 40 parts by weight of quicklime and 30 parts of water shown in Table 1
0 parts by weight was weighed in a stainless beaker, heated to 70 ° C., and mixed and stirred for 3 hours to react. Aluminum sludge is
A sludge that is a by-product of neutralizing and discharging wastewater containing a large amount of aluminum salts, which is mainly produced in the surface treatment process of aluminum products, and contains a large amount of aluminum hydroxide and aluminum salts. Contains some impurities. After the completion of the reaction, the precipitate was filtered and dried at 50 ° C. to obtain 182 parts by weight of a solid content. The obtained solid was ettringite as a result of powder X-ray diffraction. Next, the obtained solid content was heat-treated at 500 ° C. for 3 hours using an electric furnace to obtain 100 parts by weight of a heat-treated product “B”.

Incinerated fly ash 100 having an elution amount shown in Table 2
The heat-treated product "B" was added to an appropriate amount of 40 parts by weight (Example 2), 60 parts by weight (Example 3), and water, and kneaded. Then, the mixture was cured at room temperature for 5 days and fixed. Was done. After 5 days, the immobilized product is pulverized in a mortar,
A dissolution test was carried out on particles having a particle size adjusted to 5 mm in accordance with Notification No. 13 of the Environment Agency. As a result, as shown in Table 2, the amount of heavy metals eluted from the fly ash was significantly reduced. In Table 2 and thereafter, "ND" means below the detection limit.

[0020]

Example 4 Incinerated fly ash 100 having the elution amount shown in Table 2
20 parts by weight of the heat-treated product "B", 10 parts by weight of iron sulfate, and 1 part by weight of sodium hydrosulfide are added to the parts by weight, and an appropriate amount of water is added and kneaded. The mixture is cured at room temperature for 5 days and fixed. Was done. When a dissolution test was conducted in the same manner as in Example 2, as shown in Table 2, the elution amount of heavy metals from incinerated fly ash was below the detection limit.

[0021]

Comparative Example 2 Incinerated fly ash 100 having the elution amount shown in Table 2
40 parts by weight of Portland cement was added to the parts by weight, an appropriate amount of water was added, and the mixture was kneaded, cured at room temperature for 5 days, and subjected to a fixing treatment. When a dissolution test was performed in the same manner as in Example 2 below, as shown in Table 2, the amount of dissolved heavy metals from incinerated fly ash was reduced, but did not satisfy the landfill standards.

[0022]

[Comparative Example 3] Incinerated fly ash 100 having an elution amount shown in Table 2
20 parts by weight of quick lime and 10 parts by weight of iron sulfate were added to the parts by weight, an appropriate amount of water was added, and the mixture was kneaded. When a dissolution test was performed in the same manner as in Example 2 below, as shown in Table 2, the amount of dissolved heavy metals from incinerated fly ash was reduced, but did not satisfy the landfill standards.

[0023]

[Table 2]

[0024]

EXAMPLE 5 50 parts by weight of aluminum sludge having the composition shown in Table 3, 37 parts by weight of anhydrous gypsum, and quicklime (with a CaO content of 93)
%) 40 parts by weight of water and 45 parts by weight of water are weighed in a stainless beaker, heated to 50 ° C., mixed and stirred for 5 hours to react,
Further aging was performed at room temperature for 24 hours. After the completion of the reaction, the precipitate was filtered and dried at 50 ° C. to obtain 136 parts by weight of a solid content. The obtained solid was monosulfate as a result of powder X-ray diffraction. Next, the obtained solid content was heat-treated at 400 ° C. for 3 hours using an electric furnace, and the heat-treated product “C” 100
Parts by weight were obtained.

[0025]

[Table 3]

Incinerated fly ash 100 having the elution amount shown in Table 2
60 parts by weight of the heat-treated product "C" was added to the parts by weight, 10 parts by weight of Portland cement and 1 part by weight of sodium hydrosulfide were added, and an appropriate amount of water was added and kneaded, followed by curing at room temperature for 5 days. An immobilization treatment was performed (Example 5).
After 5 days, the immobilized product was pulverized and subjected to a dissolution test based on the notification of the Environment Agency Notification No. 13 with the particle size adjusted to 0.5 to 5 mm. As a result, as shown in Table 2, the elution amount of heavy metals from the incinerated fly ash was below the measurement limit.

[0027]

Example 6 50 parts by weight of the heat-treated product "B" was added to 100 parts by weight of the sludge having an elution amount shown in Table 4, and 30 parts by weight of ferric chloride was further added. After kneading, the mixture was cured at room temperature for 5 days and fixed. When a dissolution test was performed in the same manner as in Example 2, as shown in Table 4, the dissolution amount of heavy metal (Pb) from the sludge was below the measurement limit.

[0028]

Comparative Example 4 50 parts by weight of Portland cement was added to 100 parts by weight of the sludge having the elution amount shown in Table 4, 30 parts by weight of ferric chloride was further added, and an appropriate amount of water was added and kneaded. After curing for 5 days at room temperature, an immobilization treatment was performed. When a dissolution test was carried out in the same manner as in Example 2, the amount of lead (Pb) dissolved from the sludge was reduced as shown in Table 4, but did not satisfy the landfill standard.

[0029]

[Table 4]

[0030]

Example 7 Aluminum sludge 118 having the composition shown in Table 3
Parts by weight, 75 parts by weight of slaked lime, and 500 parts by weight of water were weighed in a stainless beaker, heated to 70 ° C., and mixed and reacted for 5 hours. After completion of the reaction, the precipitate was filtered and dried at 50 ° C. to obtain 128 parts by weight of a solid content. The obtained solid was C ₃ AH _{6 as} a result of powder X-ray diffraction. Next, the obtained solid content was heat-treated at 400 ° C. for 3 hours using an electric furnace to obtain 100 parts by weight of a heat-treated product “D”. This heat-treated product was a mixture of C ₁₂ A ₇ H and CH as a result of powder X-ray diffraction.

20 parts by weight of the heat-treated product "D" was added to 100 parts by weight of the crushed fluorescent tube showing the elution amount of mercury shown in Table 5, and an appropriate amount of water was added and kneaded. Cured and fixed. After 5 days, the immobilized product was pulverized and subjected to a dissolution test based on the notification of the Environment Agency Notification No. 13 with the particle size adjusted to 0.5 to 5 mm. as a result,
As shown in Table 5, the elution amount of mercury was reduced.

[0032]

Example 8 20 parts by weight of heat-treated product "D", 10 parts by weight of iron sulfate, and 1 part by weight of sodium hydrosulfide per 100 parts by weight of a crushed fluorescent tube showing the amount of mercury shown in Table 5 Was added, and an appropriate amount of water was further added. The mixture was kneaded, cured for 5 days at room temperature, and fixed. After 5 days, the immobilized product was pulverized and subjected to a dissolution test based on the notification of the Environment Agency Notification No. 13 with the particle size adjusted to 0.5 to 5 mm. As a result, as shown in Table 5, the elution amount of mercury was significantly reduced.

[0033]

[Table 5]

[0034]

Embodiment 9 The heat-treated product "C" 10 prepared in Embodiment 2
0 parts by weight of AsO₃ ^3-Factories containing 20 ppm of ions
Add to 2000 parts by weight of waste liquid, stir and mix, and mix As
O₃ ^3-Immobilization of ions was performed. Centrifuge supernatant
Later, the arsenic in the waste liquid was analyzed and found that AsO₃ ^3-ion
Was reduced to 0.17 ppm.

[0035]

Comparative Example 5 50 parts by weight of Portland cement was mixed with As
It was added to 1000 parts by weight of a factory waste liquid containing 20 ppm of O ₃ ^3- ion, and mixed by stirring to immobilize AsO ₃ ^3- ion in the waste liquid. After centrifugation the supernatant was analyzed arsenic in the effluent, _AsO ^{3 3 -} ions 3.8ppm
The extent of the decline was not sufficient to meet the drainage standards.

[0036]

Example 10 20 parts by weight of the heat-treated product "B", 10 parts by weight of iron sulfate, and 1 part by weight of sodium hydrosulfide were added to 100 parts by weight of the sludge showing the elution amount of hexavalent chromium shown in Table 6. After addition, an appropriate amount of water was added and kneaded, followed by curing at room temperature for 5 days to perform an immobilization treatment. Thereafter, when a dissolution test was performed in the same manner as in Example 2, as shown in Table 6, the dissolution amount of hexavalent chromium from the sludge was reduced.

[0037]

Example 11 20 parts by weight of the heat-treated product "D" was added to 100 parts by weight of the sludge showing the elution amount of hexavalent chromium shown in Table 6, and an appropriate amount of water was added and kneaded. And immobilized. Thereafter, when a dissolution test was performed in the same manner as in Example 2, as shown in Table 6, the dissolution amount of hexavalent chromium from the sludge was reduced.

[0038]

Example 12 20 parts by weight of the heat-treated product "D" and 10 parts by weight of iron sulfate were added to 100 parts by weight of the sludge showing the elution amount of hexavalent chromium shown in Table 6, and an appropriate amount of water was added. After kneading, the mixture was cured at room temperature for 5 days and fixed. Thereafter, when a dissolution test was performed in the same manner as in Example 2, as shown in Table 6, the dissolution amount of hexavalent chromium from the sludge was reduced.

[0039]

[Table 6]

[0040]

Example 13 20 parts by weight of the heat-treated product "B" was added to 100 parts by weight of fly ash exhibiting a chlorine elution amount of 4544 ppm, kneaded by adding an appropriate amount of water, and then cured at room temperature for 5 days and fixed. Processing was performed. When a dissolution test was performed in the same manner as in Example 2, the dissolution amount of chlorine was reduced to 2367 ppm.

[0041]

Example 14 heat-treated product "B" 200 parts by weight of fluorine ions ^(F -) plant effluent 100 containing 401.9ppm
It was added to 0 parts by weight and mixed with stirring to fix F ^- ions in the waste liquid. After centrifugation the supernatant was analyzed fluorine ions in the effluent, F ^- ions 8.100ppm
Had fallen.

[0042]

Example 15 871.12 ppm of phosphate ion (P
O 4 ^_3-) per 100 parts by weight of the sludge showing the elution amount, the heat-treated product "B" were added 20 parts by weight, of water curing was performed by immobilizing treated with 5 days at room temperature after kneading by adding an appropriate amount of . When a dissolution test was performed in the same manner as in Example 2, the dissolution amount of phosphate ions was reduced to 0.04 ppm.

[0043]

Example 16 heat-treated product "B" 200 parts by weight of nitrite ion ^_(NO 2 -) was added to 1000 parts by weight of plant effluent containing 2348.04Ppm, stirring mixed liquid waste NO ₂
^- was immobilization of the ion. After centrifugation the supernatant was analyzed nitrite ions in the effluent NO ₂ ^- ions 5
It had fallen to 34.72 ppm.

[0044]

By adding the product of the present invention to waste or waste water containing harmful substances, the elution of harmful substances can be significantly reduced as compared with the conventional fixation treatment using cement or asphalt, and It is also possible to immobilize anions that only cations have, which is of great industrial significance.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 7/345 C04B 22/14 D 22/14 B09B 3/00 ZAB (72) Inventor Tsukasa Kamei Isehara, Kanagawa 604-8 Shimo-Ochiai, Tokyo 72-72 Inventor Teruo Urano 775-3, Ishizuka-cho, Sano-shi, Tochigi Large-sized Senba 2681

Claims (2)

[Claims] 1. A method for heat-treating calcium sulfoaluminate hydrate or calcium aluminate hydrate, comprising as a main component at least one of the substances having rehydration properties. Harmful substance fixing material. 2. A method for heat-treating calcium sulfoaluminate hydrate or calcium aluminate hydrate and at least one of rehydratable substances, quicklime, slaked lime, gypsum, and blast furnace water. Crushed slag,
A harmful substance fixing material, which is a mixture with one or more of Portland cement, iron sulfate, iron chloride, sodium hydrosulfide, sodium sulfide, thiourea, and calcium polysulfide.