JPH10263501A - Treatment agent for heavy metal-containing waste and method for stabilizing heavy metal-containing waste - Google Patents

Abstract

(57) [Problem] To provide 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. In particular, molten fly ash, empty cans, scrap iron, etc., generated when melting municipal garbage, industrial waste, sludge, etc. in which the pH of the eluate is 8 or less in a heavy metal elution test based on the Notification of the Environment Agency No. 13 To provide a waste treatment agent effective for insolubilizing and stabilizing heavy metals eluted from electric furnace ash and the like generated when regenerating an effective metal such as iron from a collected material, and a method for treating the same. SOLUTION: A treating agent for heavy metal-containing waste containing a latent hydraulic substance and an alkaline substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agent for treating heavy metal-containing waste, which is effective for insolubilizing and stabilizing heavy metals contained in general or industrial waste and sludge, and a method for treating the same. More specifically, in a heavy metal dissolution test based on the Notification of the Environment Agency No. 13, the pH of the eluate is 8 or less, such as molten fly ash generated when melting garbage, industrial waste, and sludge, The present invention relates to a waste treatment agent that is effective for insolubilizing and stabilizing heavy metals eluted from electric furnace ash generated when recycling effective metals such as iron from collected materials such as empty cans and scrap iron, and a method of 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, incineration ash, fly ash and industrial waste of city waste containing heavy metals,
Strict regulations are set for the treatment and disposal of specially managed waste.

Conventionally, as a method of stabilizing waste containing a heavy metal, a method of mixing with cement, adding water as needed, and kneading the mixture to prevent elution of heavy metal and the like, stabilize the landfill, and bury the landfill has been adopted. However, the standard value for the elution of heavy metals from landfill waste that has been applied since 1995 was 0.3 mg for lead, which is considered to be the most difficult to stabilize, in the elution test based on the Environment Agency Notification No. 13.
/ L or less was required. For this reason, it is difficult to clear this standard only by solidifying cement, which has been conventionally used. Therefore, various heavy metal-containing waste treating agents capable of suppressing elution of heavy metals such as lead with a small amount of addition have been developed. Among them, organic chelating agents have come to be used for alkaline heavy metal-containing waste such as incineration fly ash in garbage incineration plants.

[0004] As a method for stabilizing heavy metal-containing waste and greatly reducing the volume of waste, melting treatment has been developed and new equipment has begun to operate. Melt fly ash containing is generated.

Heavy metal-containing wastes such as electric furnace ash generated when recycling valuable metals such as iron from recovered materials such as molten fly ash and empty cans and scrap iron are different from fly ash in garbage incineration plants and are not alkaline. And acidic to neutral having a pH of 3 to 7.
In treating such heavy metal-containing wastes exhibiting acidity to neutrality, it is difficult to suppress the elution of heavy metals typified by lead to 0.3 mg / l or less even with the above-mentioned organic chelating agent. However, there is a serious problem that the elution amount of heavy metals increases again with time.

In the present specification, when referring to the pH of heavy metal-containing waste, it refers to the pH of the eluate when the heavy metal-containing waste is subjected to a dissolution test based on the Environment Agency Notification No. 13.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to suppress the elution of heavy metals from waste containing heavy metals in which the effluent represented by ash or electric furnace ash is neutral or acidic, and to stabilize the heavy metal ions. An object of the present invention is to provide a treating agent and a treating method capable of completely preventing secondary pollution by maintaining the effect of chemical conversion.

[0008]

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 provides (1) a treating agent for waste containing heavy metals, which comprises a latent hydraulic substance and an alkaline substance, and (2) the alkaline substance is a hydroxide of an alkaline earth metal. (1) The treating agent for heavy metal-containing waste according to (1), (3) the treating agent according to (2), wherein the alkaline earth metal is calcium hydroxide, and (4) the latent hydraulic material is granulated blast furnace slag. The treatment agent for heavy metal-containing waste according to any one of the above (1), (2) and (3), and (5) any one of the above (1) to (4) for the heavy metal-containing waste 6. A method for treating heavy metal-containing waste, which comprises mixing and kneading with the treatment agent for heavy metal-containing waste described in the above section and, if necessary, water. (6) The heavy metal-containing waste is notified by the Environment Agency No. 13 In the heavy metal dissolution test based on The method for treating heavy metal-containing waste described in (5) above, and (7) melting fly ash or metal generated when the heavy metal-containing waste is subjected to melting treatment of garbage, industrial waste, sludge, etc. (6) The method for treating heavy metal-containing waste according to the above (6), which is electric furnace ash generated during refining and recovery, and (8) the heat treatment of the kneaded material at a temperature of 40 ° C or higher. (7) The method for treating heavy metal-containing waste according to any one of (7), (9) above (5) to
(8) A stabilized product of a heavy metal-containing waste obtained by the treatment method according to any one of (8).

[0010]

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 is a substance which is not cured only by mixing with water but is cured by further adding a stimulant such as an alkali. Specific examples of the latent hydraulic substance that can be used include granulated blast furnace slag, converter slag, coal ash, volcanic ash, and rice ash. Among these latent hydraulic substances, granulated blast furnace slag and converter slag are preferable, and granulated blast furnace slag is particularly preferable in terms of quality stability. 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.
00 cm ² / g or more, more preferably 4,000 to ²
Those having a density of 000 cm ² / g can be used.

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 is promoted by the alkaline substance used together with the latent hydraulic substance, and the resulting various hydration products strengthen the ion exchange ability, sealing ability and adsorption ability of heavy metals. It is also considered to be expressed in a continuous manner.

The heavy metal-containing waste treating agent of the present invention contains an alkaline substance as an essential component.

Examples of alkaline substances that can be used include:
Alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal carbonates such as sodium carbonate and potassium carbonate, and alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide and barium hydroxide ,
Examples thereof include silicates of alkali metals such as sodium silicate, potassium silicate, and sodium metasilicate, and cements represented by Portland cement. Considering the handling and cost of these alkaline substances,
Preferably hydroxides of alkaline earth metals, cements,
More preferred are hydroxides of alkaline earth metals, particularly preferred are calcium hydroxide.

The use ratio between the latent hydraulic substance and the alkaline substance is generally 90/10 to 10/90 (weight ratio), preferably 75/25 to 25/75 (weight ratio).

The heavy metal-containing waste treating agent of the present invention can be obtained by mixing a latent hydraulic substance and an alkaline substance at a predetermined ratio.

The amount of the heavy metal-containing waste treating agent of the present invention varies depending on the type and properties of the heavy metal-containing waste, but is generally 1 to 2 parts per 100 parts by weight of the heavy metal-containing waste.
0 parts by weight, preferably 2 to 15 parts by weight, more preferably 3 to 10 parts by weight. If the amount is less than 1 part by weight, the effect of stabilizing heavy metals cannot be expected. If the amount is more than 20 parts by weight, the effect of stabilizing heavy metals is sufficient. However, it is difficult to reduce the volume of the treated body after the stabilization treatment. .

Heavy metals in wastes take various forms and their details are largely unknown. However, in general, heavy metals form zwitterions in water. However, even on the acidic side, the solubility of heavy metal ions in water increases. Therefore, the solubility of heavy metals in water takes a minimum value at a certain pH. For example, in the case of a heavy metal hydroxide, its solubility generally shows a minimum value in the pH range of 9 to 11.5. Therefore, for a heavy metal-containing waste that exhibits neutrality or acidity, a certain effect is produced by simply controlling the pH thereof to stabilize the heavy metal. However, simply controlling the pH cannot maintain the heavy metal stabilizing effect for a long period of time. For example, the amount of heavy metal eluted greatly changes due to the influence of the atmospheric atmosphere such as acid rain.

The method for treating heavy metal-containing waste according to the present invention will be described below.

In the method for treating heavy metal-containing waste of the present invention, the heavy metal-containing waste and the treating agent of the present invention are mixed and kneaded. Water is added when the heavy metal-containing waste does not contain water, or when it is contained but insufficient for mixing and kneading. The amount of water used depends on the water content of heavy metal-containing waste,
Although it depends on its particle size, it is generally 5 to 50 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of heavy metal-containing waste (in terms of dry state). However, the amount varies depending on the shape of the stabilized body after the stabilization treatment, that is, whether it is pelletized or granulated.

In the method for treating heavy metal-containing waste of the present invention, the equipment for mixing and kneading the treating agent of the present invention, heavy metal-containing waste, and water (optional component), and the order of addition thereof are not particularly limited. The treatment agent of the present invention mixed in advance may be mixed with heavy metal-containing waste, or each component constituting the treatment agent of the present invention may be mixed with 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.

In the present invention, heat treatment is performed as necessary to further improve the treatment effect. In the heat treatment, heat generated during kneading may be used, or the kneaded material may be heated as it is or after kneading.
The heating temperature is 40 ° C. or higher, preferably 50 ° C. or higher. The heating method may be a known method such as a mechanical method or a physicochemical method as described above. Although the heating time depends on the thermal conductivity of the kneaded material, it is usually 5 minutes or more, preferably 10 minutes or more. It is.

There is no particular limitation on the waste that can be treated with the heavy metal waste treating agent of the present invention. For example, garbage such as municipal garbage, industrial waste, sludge, or the like, or incineration ash (incineration) obtained by incinerating them Fly ash), fly ash, granular industrial waste, etc. can be treated alone or in combination, but the pH of the eluate is 8 or less in the heavy metal dissolution test based on the Environment Agency Notification No. 13. Heavy metal-containing waste is preferable. Among them, molten metal such as municipal waste, industrial waste, molten fly ash generated when melting and processing sludge, and valuable metals such as iron are recovered from collected materials such as empty cans and scrap iron. Electric arc ash that is sometimes generated is particularly preferred.

The stabilized material treated by the treatment method of the present invention hardens as it is, and the amount of heavy metal eluted is extremely low. It can be used as an aggregate for paving materials or, if necessary, formed into a plate or block to be used as civil engineering or construction material.

[0026]

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

Examples 1 to 4 With respect to 100 parts by weight of electric furnace ash (hereinafter referred to as A ash),
The amount (parts by weight) of Blaine specific surface area of 4,000 c
The treating agent for heavy metal-containing waste of the present invention obtained by mixing m ² / g blast furnace granulated slag and calcium hydroxide and water were added in the amounts (parts by weight) shown in Table 1 and kneaded. The lead elution amount after 24 hours was measured according to the Environment Agency Notification No. 13 test. Table 1 shows the results. The properties of untreated A ash are also described.

[0028]

[Table 1]

Examples 5 to 7 In the same manner as in Examples 1 to 4 except that granulated blast furnace slag, various alkaline substances, and water were used in the amounts and types shown in Table 2 with respect to 100 parts by weight of A ash. Table 2 shows the results of the processing.

[0030]

[Table 2]

Examples 8 to 14 Except that 5 parts by weight of granulated blast furnace slag shown in Table 3 and the kinds and amounts of alkaline substances and water shown in Table 3 were added to the molten fly ash from the refuse incineration plant. Table 3 shows the results of the heavy metal stabilization treatment performed in the same manner as in Examples 1 to 4.

[0032]

[Table 3]

Examples 15 to 23 The treated bodies obtained in Examples 1 to 3 and 5 to 10
Table 4 shows the results of measuring the lead elution amount after curing at room temperature for one month and half a year based on the notification of the Environment Agency Notification No. 13.

[0034]

[Table 4]

As can be seen from Table 4, the lead elution amount (see Tables 1 to 3) which was 0.04 to 0.21 mg / l in 24 hours after the kneading (stabilizing) treatment was different from that of the latent hydraulic substance. With the progress of the hydration reaction, the concentration falls below the detection limit in one week to one month.

Examples 24 to 27 Example 3 except that the kneading temperature and the processing time were as shown in Table 5.
Table 5 shows the results of the heavy metal stabilization treatment performed in the same manner as described above.

[0037]

[Table 5]

As apparent from Table 5, the kneading temperature was set at 40 ° C.
By doing so, the hydration reaction of the latent hydraulic substance proceeds, and the effect of stabilizing heavy metals is further enhanced.

[0039]

According to the agent for treating heavy metal-containing waste of the present invention, immediately after treatment, the action of the latent hydraulic substance and the action of the hydration reaction product, which is the reaction product of the latent hydraulic substance and the alkaline substance, Further, the stabilizing effect of the heavy metal can be maintained for a long time after the treatment. Therefore, the treating agent for heavy metal-containing waste of the present invention is suitable for stabilizing heavy metal-containing waste, and can stabilize the elution of heavy metal ions to a high degree. It is an unprecedented treatment agent for heavy metals. Further, the treatment method of the present invention can easily stabilize heavy metal-containing waste without using a special device. Further, since the treated body obtained by the treatment method of the present invention can impart strength equal to or higher than the solidification of cement, it can be recycled as civil engineering and building materials such as aggregate and pavement material.

Claims (9)

[Claims] An agent for treating heavy metal-containing waste, comprising a latent hydraulic substance and an alkaline substance. 2. The treatment agent according to claim 1, wherein the alkaline substance is a hydroxide of an alkaline earth metal. 3. The treating agent according to claim 2, wherein the alkaline earth metal is calcium hydroxide. 4. The treating agent according to claim 1, wherein the latent hydraulic substance is granulated blast furnace slag. 5. A heavy metal-containing waste, characterized in that the heavy metal-containing waste is treated with the heavy metal-containing waste treating agent according to any one of claims 1 to 4, and optionally mixed with water, followed by mixing and kneading. Processing method. 6. The waste containing heavy metals is notified by the Environment Agency Notification No. 13.
PH of the eluate in heavy metal dissolution test
The processing method according to claim 5, wherein is equal to or less than 8. 7. The heavy metal-containing waste is fly ash generated when performing melting treatment of garbage, industrial waste, sludge, or the like, or electric furnace ash generated when refining and recovering metal. Processing method. 8. The method for treating heavy metal-containing waste according to claim 5, wherein the kneaded material is heated at a temperature of 40 ° C. or higher. 9. A stabilized treated body of heavy metal-containing waste obtained by the treatment method according to any one of claims 5 to 8.