JPH10272435A - Treatment agent for heavy metal-containing waste and stabilization method for heavy metal-containing waste - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When stabilizing heavy metal-containing waste, the elution of heavy metal ions can be stabilized below the reference value, and the effect of stabilizing the heavy metal ions is sustained to complete secondary To provide a treatment agent and a treatment method capable of preventing pollution. SOLUTION: A treating agent for heavy metal-containing waste characterized by containing a latent hydraulic substance and a polysaccharide, and a heavy metal characterized by mixing and kneading the treating agent with heavy metal-containing waste and water as required Stabilization method for contained waste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste treatment agent effective for insolubilizing and stabilizing heavy metals contained in general waste and industrial waste, and a method for treating the same. More specifically, heavy metals contained in wastes such as incinerator ash and fly ash generated from municipal garbage, industrial waste, sludge, and incinerators and melting furnaces, sludge and contaminated soil, etc.
The present invention relates to a waste treatment agent effective for stabilization treatment and a method for treating the same.

[0002]

2. Description of the Related Art In recent years, as wastes generated from cities and factories have increased, wastes containing heavy metals have been required to be sufficiently detoxified for environmental measures. In particular, general waste and industrial waste such as fly ash containing heavy metals are subject to strict regulations in the treatment and disposal as specially managed waste.

Conventionally, when disposing of waste containing heavy metals, a method of mixing with cement, adding water as necessary, and kneading the mixture to prevent elution of heavy metals and the like has been adopted. However, in the case of lead, which is considered to be the most difficult to stabilize, the amount of heavy metal eluted from the waste to be landfilled applied since 1995 was 0.3 mg / kg in the elution test based on the Environment Agency Notification No. 13. However, it is difficult to clear this standard with cement alone.

In the case of mixing and hardening waste, which is a typical cement such as ordinary Portland cement, the calcium hydroxide generated in the hydration process promotes hardening of the cement, but excessively hardens the cement. Generated calcium hydroxide increases the pH of the mixture of waste and cement, and increases the solubility of heavy metal ions such as lead, which is an amphoteric element. It is thought that it is damaged.

[0005] In addition, when cement is used, it is good to use it continuously, but when the treatment is interrupted, the remaining processed material will not be removed without cleaning the equipment such as a mixer or kneader. There is a problem in terms of maintenance workability that solidifies on the container wall.

Further, attempts have been made to capture and stabilize heavy metal ions by chemical treatment with a sulfur-containing chelating agent or the like. According to this, it is possible to stabilize to below the elution reference value. However, such a drug is not only expensive, but also has insufficient retention of heavy metal ions after the stabilization treatment. There is a problem that the elution amount of heavy metal ions increases.

[0007]

As described above, it is not only difficult to stabilize heavy metal ions below the elution standard with conventional heavy metal-containing waste treating agents and methods, but also to stabilize them. However, at present, there is a problem in the durability and durability of the retention, and there is a concern that secondary pollution may occur over time.

[0008] It is an object of the present invention to stabilize heavy metal-containing waste, and to stabilize the elution of heavy metal ions below a reference value, and to maintain the effect of stabilizing heavy metal ions to completely prevent secondary pollution. It is an object of the present invention to provide a treating agent and a treating method capable of preventing the occurrence of

[0009]

Means for Solving the Problems In view of such circumstances, the present inventors have intensively studied for a treating agent and a treating method that can completely stabilize heavy metal-containing waste, and as a result, have completed the present invention. . That is, the present invention

(1) A heavy metal-containing waste treating agent comprising a latent hydraulic substance and a polysaccharide, (2)
The treating agent according to (1), wherein the latent hydraulic substance is granulated blast furnace slag, (3) the treating agent according to (1) or (2), wherein the polysaccharide is a single polysaccharide, (4) The monopolysaccharide is α-starch, the treatment agent according to the above (3), (5) a heavy metal-containing waste, the treatment agent according to any one of the above (1) to (4), and if necessary. Adding heavy water, mixing and kneading, a method for treating heavy metal-containing waste,
(6) adding heavy metal-containing waste, the treating agent according to any one of the above (1) to (4), and, if necessary, adding water, mixing, kneading, and then heating at 40 ° C. or more. (7) Heavy metal-containing waste is incinerated ash, fly ash, contaminated soil, or metal that must meet the criteria set forth in Prime Ministerial Ordinance No. 5 (8) The method for treating heavy metal-containing waste according to the above (5) or (6), which is an industrial waste including the above. The above-mentioned (5) to (5) to (5) to (9), wherein the treatment agent and the basic substance described in any one of the above (1) to (4) are added to the heavy metal-containing waste having a neutral or acidic pH for treatment. (9) The processing method according to any one of (7) and (9).
The present invention relates to the treatment according to the above (8), wherein the basic substance is calcium hydroxide, and (10) a treated product obtained by the treatment according to any one of the above (5) to (9).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The latent hydraulic substance used as an essential component in the present invention does not cause a hydration reaction with water alone, but causes a hydration reaction when, for example, a stimulant or the like is added. Specific examples of the latent hydraulic substance that can be used include granulated blast furnace slag and converter slag. Among these latent hydraulic substances, granulated blast furnace slag is preferred. These latent hydraulic substances can be used alone or in combination of two or more.

When granulated blast furnace slag is used as a latent hydraulic material, its particle size is 2,000 c.
m ² / g or more can be used.
Those having a size of at least 00 cm ² / g can be used. The greater the Blaine specific surface area, the greater the effect of stabilizing heavy metals, but the higher the production cost and the more economically disadvantageous.

Although the mechanism of the stabilizing effect of the latent hydraulic substance on the heavy metal ions is not necessarily clear, it is considered that the latent hydraulic substance itself has the ability to adsorb heavy metal ions. In addition, the curing reaction of the latent hydraulic substance proceeds by the alkali ions contained in the heavy metal-containing waste, and the resulting various hydration products further strengthen the heavy metal ion exchange ability, diffusion suppression ability and adsorption ability. It is also considered to be expressed in a continuous manner.

The heavy metal-containing waste treating agent of the present invention further contains a polysaccharide as an essential component. Polysaccharides exhibit water absorption-swelling behavior or change into a paste in the presence of water.These changes are caused by sequestration of heavy metal compounds by free water and sequestration of heavy metal compounds, and by adhesion effects of heavy metal compounds. It is presumed that this contributes to stabilization of heavy metal-containing waste by confining it. With polysaccharides alone, if the heavy metal compound comes into contact with water first and changes to heavy metal ions, the containment effect of the polysaccharide will be weaker,
If it is in the form of heavy metal ions that have been ion-exchanged or adsorbed by the latent hydraulic substance, it can be more strongly contained,
The effect of stabilizing heavy metals, which has not been obtained conventionally, can be obtained. Further, as described later, when the heavy metal-containing waste contains a basic substance or is treated with a newly added basic substance, when the latent hydraulic substance is cured, the latent hydraulic substance and the paste-like polysaccharide are hardened. It is also considered that the mixture of saccharides forms a denser cured (hydrated) product and promotes the suppression of diffusion of heavy metal compounds and heavy metal ions. That is, the effect of stabilizing heavy metals becomes more remarkable than using each alone, and heavy metal compounds and heavy metal ions are firmly sealed in the hydrate of the latent hydraulic substance, so that elution of heavy metals can be suppressed for a long period of time, and acidic Heavy metals do not elute when exposed to rain.

The polysaccharide that can be used in the present invention is not particularly limited, but specific examples include agarose, α-amylose, and β-amylose.
Monopolysaccharides such as amylose, amylopectin, starch, α-starch, mannan, amylodextrin, erythrodextrin, acrodextrin, glycogen, cellulose, carboxymethylcellulose, hydroxypropylcellulose, dextran, inulin, galactan, chitin, chitosan, alginic acid and the like; These derivatives, pectin, hyaluronic acid, chondroitin sulfate, complex polysaccharides such as heparin and derivatives thereof can be mentioned, a single polysaccharide or a derivative thereof is preferable, α-starch, dextrin, alginic acid, carboxymethylcellulose, hydroxy Propyl cellulose and hydroxypropyl methyl cellulose are more preferred, and α-starch is particularly preferred. These polysaccharides may be used alone or in combination of two or more.

The polysaccharide can be used as it is as a powder, but it can also be used as an aqueous solution or aqueous dispersion in order to uniformly mix it with the heavy metal-containing waste. The concentration of the polysaccharide when used in an aqueous solution or aqueous dispersion varies depending on the type of polysaccharide and the type of waste, but is usually 0.5%.
-20% by weight, preferably 1-10% by weight.

The amount of the polysaccharide used depends on the type and particle size of the latent hydraulic substance or the type of waste, but is generally 5 to 1000 parts by weight, preferably 10 to 800 parts by weight, per 100 parts by weight of the latent hydraulic substance. Parts by weight, more preferably 2 parts by weight
0 to 500 parts by weight. Although the heavy metal-containing waste treating agent of the present invention is usually in a powder state, it can also be handled as a slurry liquid composition. That is, a dispersant is added to the latent hydraulic substance and the polysaccharide as necessary, and then mixed,
By kneading, the slurry of the present invention can be obtained. In the above, as the dispersant, a water-soluble polymer such as poly (meth) acrylic acid which is generally used as a fluidization imparting agent for a cement composition can be used. For the department,
It is usually 0.1 to 10 parts by weight, preferably 0.3 to 7 parts by weight, particularly preferably 0.5 to 5 parts by weight.

Since the heavy metal-containing waste treating agent of the present invention contains a latent hydraulic substance and a polysaccharide as main components, it absorbs moisture during use or storage as in the case of using cement, and becomes unusable. This is advantageous in terms of equipment maintenance because there is no possibility that the solidified material will not adhere to the inner wall of the apparatus and become unusable unless the apparatus is washed with water for several hours after use. In addition, there is an advantage that the powdery composition can be handled as a liquid composition in the form of a slurry as described above when it is possible to handle the powdery work but dislikes the powder work. Other advantages that can be handled as a liquid composition do not require large-scale equipment such as silos because the volume is smaller than that stored as a powder,
It can be mentioned that mixing and kneading with heavy metal-containing waste becomes easy.

If the heavy metal-containing waste is municipal garbage incineration fly ash in which the eluate in the dissolution test of the Environment Agency Notification No. 13 is alkaline, the heavy metal-containing waste treating agent of the present invention undergoes a hydration reaction to stabilize the heavy metal. Enhance the chemical effect. Further, when the eluate of the elution test of the Environment Agency Notification No. 13 such as electric furnace ash, molten fly ash, and contaminated soil is a neutral or acidic heavy metal-containing waste, a basic substance is added to the treating agent of the present invention. It is preferable to add the compound to cause a hydration reaction.

Specific examples of the basic substance which can be used in the present invention include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, carbonates of alkali metals such as sodium carbonate and potassium carbonate, and calcium hydroxide. And alkali earth metal hydroxides such as magnesium hydroxide, barium hydroxide and the like, and alkali metal silicates such as sodium silicate, potassium silicate and sodium metasilicate. In consideration of handleability and cost, among these basic substances, it is preferable to use an alkali metal hydroxide or an alkaline earth metal hydroxide, and among them, calcium hydroxide is particularly preferable.

In the basic substance, the ratio between the latent hydraulic substance and the basic substance is usually 90/10 to 10/90 (weight ratio), preferably 75/25 to 25/75 (weight ratio). Use in quantity. The basic substance may be added in advance to the treatment agent of the present invention, but is preferably used in the treatment method of the present invention described later. In the former case, the treating agent does not contain water and avoids moisture absorption during storage.

The treating agent of the present invention can be obtained by uniformly mixing the above components at a predetermined ratio. When the powdery treatment agent of the present invention is obtained, the respective components may be powder-mixed by a known mixing method. The method of mixing when obtaining the liquid treatment agent of the present invention is not particularly limited, but a predetermined amount of a dispersant (arbitrary component) and water are mixed to form an aqueous solution, and then the previously mixed latent water is mixed. The method of adding to a powder component such as a hard substance, a polysaccharide, or a basic substance is preferable because the whole can be easily uniform.

The method for treating heavy metal-containing waste of the present invention is carried out by mixing and kneading the treating agent of the present invention, heavy metal-containing waste, and water (optional component) described below. The equipment for mixing and kneading them and the order of adding them are not particularly limited. Further, the treating agent of the present invention prepared in advance may be mixed with the heavy metal-containing waste, or each component constituting the treating agent of the present invention may be mixed with the heavy metal-containing waste. As a method of mixing, for example, in the case of performing a batch process, a kneader-ruder type or an Erich-type mixing kneader equipped with a stirrer can be used. When the treatment is performed continuously, the mixture may be kneaded using a uniaxial or biaxial paddle-type kneader or a pan-type granulator. The time required for processing (mixing, kneading time)
There is no particular limitation as long as the waste and the treating agent can be uniformly kneaded.

Although the treatment method of the present invention may be carried out at room temperature, it is preferable to carry out a heat treatment in order to bring out the effect of stabilizing heavy metals in a short time. In the heat treatment, heat generated during kneading may be used, or heating may be forcibly performed during kneading. Further, the processed material after the kneading may be forcibly heated. The heating temperature is preferably set to 40 ° C. or higher, more preferably 50 ° C. or higher. The method of forcible heating may be a known method such as a mechanical or physicochemical method. The heating time varies depending on the thermal conductivity, size, heating method, and the like of the kneaded material or the processed material, and cannot be said unambiguously, but is usually 5 minutes or more, preferably 10 minutes or more. From the viewpoint of workability, a maximum of 24 hours is sufficient.

Water is added when the heavy metal-containing waste does not contain water, or when it does not suffice for mixing and kneading. The amount of water used depends on the water content of the heavy metal-containing waste and its particle size, but is generally 5 to 100 parts by weight of the heavy metal-containing waste (converted to the dry state).
It is 50 parts by weight, preferably 10 to 40 parts by weight. The amount of water to be added depends on the shape of the treated body after the stabilization treatment, that is, whether it is pelletized or granulated.

There are no particular restrictions on the waste that can be used to stabilize heavy metal ions with the treatment agent of the present invention. For example, garbage such as municipal garbage, industrial waste, sludge, or the like, or incineration ash (eg, incinerated ash) (Incinerated fly ash) or the like can be treated alone or in combination. Among these heavy metal-containing wastes, garbage incineration ash, fly ash, contaminated soil such as granular industrial waste, or industrial (general) waste containing metals that must satisfy the criteria set forth in Prime Ministerial Ordinance No. 5 Is most suitable for treatment with the treatment agent of the present invention.

According to the treatment agent and treatment method of the present invention, heavy metals in heavy metal-containing waste are stabilized, and heavy metals are hardly eluted from the kneaded material after treatment. In the dissolution test by the method for examining metals and the like contained in the produced industrial waste, the elution amount of heavy metal ions is less than the landfill regulation value described in Prime Ministerial Ordinance No. 5.

The treated product of the present invention thus obtained may be used as it is or may be pulverized as necessary to be used as aggregate for cement / concrete or aggregate for road pavement. It can be used as civil engineering and construction materials by molding into a shape. Accordingly, various admixtures such as pulverized slow-cooled slag, ferrochrome slag, silica, alumina, talc, silica sand, silica powder, clay, kaolin, calcium carbonate, and ceramic pulverized for the purpose of their use. Material, inorganic filler such as titania, zirconia, river sand, fiber such as glass fiber, carbon fiber, vinylon fiber, nylon fiber, aramid fiber, polypropylene fiber, acrylic fiber, polyester, cellulose fiber, steel fiber, alumina fiber, etc. May be added. Also, a setting retarder such as sugar and glucose,
A surface treatment agent such as a silane coupling agent, a pigment, or the like may be used as needed.

[0029]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 150 parts by weight of α-starch was blended with 100 parts by weight of granulated blast furnace slag having a specific surface area of 4,000 cm ² / g, and the resulting mixture was mixed with powder by a planetary mixer. A treating agent was obtained. Incineration fly ash obtained from an incineration plant for municipal garbage (lead content 1960 mg / kg, lead elution amount 53.4 ppm based on Environmental Notification 13) or less, referred to as A fly ash
100 parts by weight and 5 parts by weight of the treatment agent are added and mixed,
After adding 33 parts by weight of water and kneading, the mixture was cured at room temperature for 24 hours and subjected to a dissolution test based on the notification of the Environment Agency Notification No. 13, and the results are shown in Table 1. Table 2 shows the amount of lead eluted after curing at room temperature for 1 to 13 weeks.

Examples 2 to 7 Powders of each amount of α-starch shown in Table 1 were mixed with 100 parts by weight of granulated blast furnace slag having a specific surface area of 4,000 cm ² / g to obtain a treating agent. . The amount of each treatment agent shown in Table 1 was added to 100 parts by weight of fly ash A, treated in the same manner as in Example 1, and the elution amount of lead when an elution test was performed is shown in Table 1. . Table 2 shows the amount of lead eluted after curing at room temperature for 1 to 13 weeks. Note that, in Table 2, the lead elution amount of Announcement No. 13 indicates the amount of lead eluted in an elution test based on Notification No. 13 of the Environment Agency (the same applies hereinafter).

[0032]

Table 1 Table 1 Content of α-starch Treatment agent for A fly ash Lead elution amount (parts by weight) Addition amount (parts by weight) (ppm) Example 1 150 5 0.14 Example 2 20 15 0. 25 Example 3 50 10 0.23 Example 4 100 7 0.18 Example 5 250 3 0.13 Example 6 500 3 0.08 Example 7 800 3 N.P. D. Note that in Table 1, N.I. D. Indicates 0.01 or less (the same applies hereinafter).

[0033]

Table 2 Annealing amount of lead No. 13 (ppm) Curing time After 1 week After 4 weeks After 8 weeks After 13 weeks Example 1 0.08 0.03 N.V. D. N. D. Example 2 0.03 N.P. D. N. D. N. D. Example 3 0.06 N.P. D. N. D. N. D. Example 4 0.07 N.P. D. N. D. N. D. Example 5 0.10 0.06 N.P. D. N. D. Example 6 N.P. D. N. D. N. D. N. D. Example 7 N.P. D. N. D. N. D. N. D.

Examples 8-12 2.5 parts by weight of granulated blast-furnace slag having a specific surface area of 4,000 ccm ² / g mixed with 100 parts by weight of the heavy metal-containing waste shown in Table 3 in advance and α-starch After adding 1.5 parts by weight, adding and kneading the amount of water shown in Table 3,
After curing for 24 hours, a lead dissolution test based on the notification of the Environment Agency Notification No. 13 was performed. The results are shown in Table 3.

[0035]

Table 3 Amount of water added to waste Announcement No. 13 Lead elution (parts by weight) Lead elution (ppm) (ppm) Example 8 Fly ash 2.85 28.17 Example 9 Incinerated ash 0 . 50 10 N.P. D. Example 10 Incinerated ash + fly ash 7.10 12 0.24 (55/75 (weight ratio) mixture)) Example 11 Sludge 8.3 10 0.22 Example 12 Concentrated waste liquid 12.3.0 0.28

Examples 13 to 18 100 parts by weight of fly ash A and 50 parts by weight of various polysaccharides were mixed with 50 parts by weight of granulated blast furnace slag having a specific surface area of brane as shown in Table 4 to obtain powders. After adding and mixing 5 parts by weight of the treating agent and adding and kneading 33 parts by weight of water, the mixture was cured under the processing conditions shown in Table 4 and subjected to a dissolution test based on the notification of the Environment Agency No. 13 in Table 4. Are also shown.

[0037]

Table 4 Specific surface area Treatment conditions of polysaccharide Annealing No. 13 (cm ² / g) Type Lead elution amount (ppm) Example 13 2,000 Alginic acid 40 ° C.-18 hours 0.12 Example 14 3, 000 Chitosan 55 ° C-12 hours 0.18 Example 15 6,000 Sweet potato starch 70 ° C-6 hours 0.27 Example 16 8,000 HPC 80 ° C-4 hours 0.09 Example 17 10,000 Cellulose 90 ° C -2 hours 0.22 Example 18 13,000 CMC 80 ° C-4 hours 0.06 where HPC is hydroxypropylcellulose, CMC
Represents carboxymethyl cellulose.

Examples 19 to 21 Blast furnace granulated slag 3 having a specific surface area of 4,000 cm ² / g with respect to 100 parts by weight of electric furnace ash generated by a steelmaking company.
24 hours after the addition of the treating agent of the present invention consisting of 3 parts by weight of α-starch and the amount of calcium hydroxide shown in Table 5 and the amount of water shown in Table 5 (parts by weight), and kneading. Table 5 also shows the results of measurement of the amount of lead eluted in accordance with the Environment Agency Notification No. 13 test.

[0039]

Table 5 Table 5 Amount of water added to the treating agent of the present invention Eluate Lead elution amount pH of calcium hydroxide (mg / l) Blending amount (parts by weight) Untreated ash 0 6.4 21 Example 19 2 * 5 20 9.4 0.02 Example 20 2.5 20 9.4 0.03 Example 21 2 18 9.3 0.09

[0040]

The treatment agent for heavy metal-containing wastes of the present invention comprises:
It is suitable for stabilizing heavy metal-containing waste, and can stabilize the elution of heavy metal ions to a high degree, and its effect is continuous. Further, the treatment method of the present invention can easily stabilize heavy metal-containing waste without using a special apparatus. Furthermore, the treated product obtained by the treatment method of the present invention can be used (recycled) as a civil engineering building material such as an aggregate or a pavement material having a strength higher than that of a solidified cement.

Claims (10)

[Claims] 1. A treating agent for heavy metal-containing waste, comprising a latent hydraulic substance and a polysaccharide. 2. The treating agent according to claim 1, wherein the latent hydraulic substance is granulated blast furnace slag. 3. The treating agent according to claim 1, wherein the polysaccharide is a single polysaccharide or a derivative thereof. 4. The single polysaccharide is α-starch.
The treating agent according to the above. 5. A heavy metal-containing waste, a treating agent according to any one of claims 1 to 4, and water if necessary.
A method for treating heavy metal-containing waste, comprising mixing and kneading. 6. A mixture comprising a heavy metal-containing waste, the treating agent according to any one of claims 1 to 4, and water as required, followed by mixing and kneading, followed by heat treatment at 40 ° C. or higher. Of heavy metal-containing waste. 7. The incineration ash of a heavy metal-containing waste in a garbage incineration plant,
7. The method for treating heavy metal-containing waste according to claim 5, wherein the waste is fly ash, contaminated soil, or industrial waste containing metals that must satisfy the criteria set forth in Prime Ministerial Decree No. 5. 8. The heavy metal-containing waste according to any one of claims 1 to 4, wherein the pH of the eluate after the dissolution test according to the Environment Agency Notification No. 13 is neutral or acidic. The treatment method according to any one of claims 5 to 7, wherein the treatment is performed by adding a treatment agent and a basic substance. 9. The method according to claim 8, wherein the basic substance is calcium hydroxide. 10. A processed product obtained by the processing method according to claim 5.