JPH1071381A - Waste treatment agent and waste treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stabilizing treatment of a harmful metal in waste. SOLUTION: Powdery permanganate and/or a treatment agent containing manganate and at least one component selected from cement, silicon dioxide, aluminosilicate and amorphous aluminum hydroxide as main components is mixed with waste and, if necessary, water is added to the resulting mixture to be kneaded therewith to perform treatment. This treatment method is especially effective for the stabilization of Pb in incineration fly ash of urban waste refuse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating waste which is effective in stabilizing harmful metals and the like in wastes, and more particularly, to stabilizing harmful metals such as lead (Pb) in fly ash from incineration of wastes. The present invention relates to a method for treating waste that is effective for chemical conversion.

[0002]

2. Description of the Related Art At present, when disposing of waste containing harmful metals, cement is used as a treating agent. Cement and waste are mixed, water is added and kneaded, and then cured and solidified. A method of preventing and stabilizing metal and the like has been used. However, there are various problems in the conventional waste treatment method which is simply solidified with cement.
Unless the use is limited, secondary pollution may occur.
In particular, at the time of incineration of garbage, fly ash captured by an electric dust collector or a bag filter contains harmful metals such as Pb in a high concentration, but it is not sufficient in the conventional cement treatment. Because elution cannot be prevented, landfills are currently being disposed of with insufficient stabilization of harmful metals and the like, and the problem of secondary pollution after disposal is erupting.

As described above, today, it is difficult to stabilize waste containing harmful metals such as Pb to a state in which harmful metals such as Pb do not elute by simply solidifying with cement. It has become apparent outside. Therefore, harmful metals are reliably encapsulated and not re-eluted during land reclamation or ocean dumping.
There has been a demand for a method of treating waste that does not cause secondary pollution.

[0004] In view of such a situation, the present inventors have developed a waste treatment agent containing cement and solid acid as main components (Japanese Patent Application Laid-Open No. Hei 0-1990).
No. 8-0103939). However, due to chronic shortage of landfill sites,
The development of a more efficient waste treatment agent that can prevent harmful metal elution with a smaller amount of addition has been desired.

[0005]

Accordingly, in view of the current state of waste treatment, the present invention can more efficiently suppress elution of harmful metals and the like in waste, and can reduce the amount of added waste with a smaller amount of addition. It is an object of the present invention to provide a more efficient waste treatment agent and a waste treatment method that can prevent elution of harmful metals.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies with the aim of solving the above-mentioned problems in the prior art, and as a result, have developed a new waste treating agent and a new method of treating that can achieve this object. I got it. That is, the present invention provides a waste disposal method comprising mixing a waste disposal agent containing permanganate and / or manganate as a main component and waste, adding water as needed, and kneading the mixture. The main content is the processing method of the object.

It is generally known that Pb in waste incineration ash is easily eluted in an alkaline atmosphere. However, in an incinerator for municipal garbage and the like, Pb is used to reduce the amount of hydrogen chloride gas generated during operation. Since slaked lime is blown, the fly ash collected by the electrostatic precipitator and the fly ash collected by the bag filter generated under such operating conditions have a particularly large Pb elution amount. In contrast,
The processing method of the waste which mixes the processing agent containing permanganate and / or manganate as a main component used in the present invention and the waste, adds water as needed, and kneads the mixture is harmful. Shows high elution prevention effect on metals.

Although the mechanism of this action is not clear, it can be estimated as follows. That is, the permanganate (VII) ion or manganese (VI) ion in the treatment agent oxidizes the II-valent Pb ion in the waste to the hardly soluble IV-valent oxidized Pb or hydroxylated Pb, and When Mn itself in the treating agent is reduced and precipitated as insoluble Mn oxide or hydroxide Mn having a valence of IV, it co-precipitates with Pb ions, and the precipitate of this Mn compound adsorbs Pb ions. An action mechanism such as an action can be considered.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Many of the commercially available permanganates used in the present invention contain manganate, but the manganate and permanganate have almost the same effect of preventing Pb elution. Does not have any adverse effects. As permanganates and manganates, alkali metal salts such as sodium salt, potassium salt, calcium salt, barium salt,
Examples thereof include alkaline earth metal salts. In practical use, it is necessary to consider industrial availability and solubility in water.In this regard, potassium salts, sodium salts, calcium salts, and barium salts are particularly preferable, and rubidium salts and cesium salts are preferable. Absent.

It is preferable that cement, silicon dioxide, aluminum silicate and amorphous aluminum hydroxide are further added to the waste treatment agent containing permanganate or manganate as a main component used in the present invention. These are relatively expensive because they have an effect of preventing Pb elution, as shown in JP-A-08-010739, and also reduce the amount of permanganate or manganate used with a severe redox reaction. Will be useful for.

The cements used in the present invention include hydraulic cements such as Portland cement, (ordinary, ultra-high strength, high strength, etc.), mixed cement type (fly ash, blast furnace, silica, etc.), lime and gypsum. Such an air-hardened cement can be exemplified. In the present invention, two or more of these may be used in combination, and may be appropriately selected and used depending on the properties of the waste to be treated, the state of the treatment, and the like.

The silicon dioxide used in the present invention is preferably in the form of fine powder having a large specific surface area from the viewpoint of excellent stabilization of heavy metals, particularly preferably having a specific surface area of 150 m ² / g or more. Known types of silicon dioxide include crystalline, amorphous, amorphous, glassy, and the like. Here, powdery silicon dioxide can be used. Silicon dioxide can be used either as a synthetic product or a natural product. Examples of the natural product include finely divided silicon dioxide obtained by acid-treating acid clay or activated clay and pulverizing the same.

The aluminum silicate used in the present invention is preferably in the form of a fine powder having a large specific surface area in that it is excellent in stabilizing heavy metals, similarly to the above silicon dioxide.
In particular, the specific surface area is preferably 150 m ² / g or more. Known types of aluminum silicate, such as crystalline, amorphous, amorphous, glassy, etc., can be used here as long as they are powdery. This aluminum silicate can be used either as a synthetic product or a natural product.

The aluminum hydroxide used in the present invention is amorphous in X-ray diffraction. The amorphous aluminum hydroxide used in the present invention may contain inevitable impurities in the production process, such as crystalline aluminum hydroxide, nickel, and boron. As the aluminum hydroxide used in the present invention, aluminum sludge obtained by concentrating and recovering aluminum hydroxide that is produced in the aluminum processing process of an aluminum sash factory and originally discarded is preferable because it is relatively easily available and inexpensive. . For example, in an aluminum sash factory, wastewater that has undergone alumite treatment that removes oil adhering to molded products made of aluminum such as aluminum sashes and aluminum pipes with sulfuric acid, and coats nickel with nickel for the purpose of corrosion prevention. Get out. In the factory, a flocculant is added thereto, and the precipitate is filtered, and then filtered to collect aluminum hydroxide as aluminum sludge. Since this aluminum sludge contains about 75% of water, it can be dried, pulverized, and used in powder form. Generally, drying is performed under the condition that the product temperature is 200 ° C. or less. In addition, of course, commercially available amorphous powdery aluminum hydroxide can of course be used. Although the mechanism by which amorphous aluminum hydroxide exhibits the effect of preventing the elution of Pb is not clear, it is conceivable that the pH adjusting effect by neutralization of the waste and the adsorption of harmful metal ions are considered.

The waste to which the method of the present invention is applied is not particularly limited except that it contains toxic metals.
The effect is remarkable when applied to municipal refuse incineration main ash and / or incineration fly ash, which has been particularly difficult to treat in the prior art.

The mixing ratio of the treating agent and the waste in the method of the present invention cannot be unconditionally limited because the degree of the effect varies depending on the kind of the waste and its properties, but the harmful metal content in the waste, the untreated Considering the amount of harmful metals eluted from waste in the case and the target allowable amount of harmful metals, etc. This is a factor in determining the amount of the treatment agent. In fact, for almost all wastes, the solid content of permanganate or manganate in the treating agent is not more than 5 parts by weight per 100 parts by weight of the waste, and Pb is regulated by Pb. It can be controlled to a certain 0.3 ppm or less. Although the stabilization performance of heavy metals improves with the addition amount of the processing agent, the addition of the processing agent more than necessary increases the volume of the processed material and causes problems such as the inability to secure a landfill for the processed material. This not only increases the cost in many cases, but also causes excess elution of permanganate or manganate. In order to prevent excess permanganate and manganate from being eluted, excess permanganate and manganate may be reduced by adding a reducing substance after waste treatment. This is within the scope of the present invention.

In the waste treatment method of the present invention, mixing the treating agent and the waste and curing the mixture after kneading is an effective means for fully exhibiting the effect of the treating agent. This is within the scope of the present invention. This suggests that, in the treatment method of the present invention, the reaction starts instantaneously due to the contact between the treating agent component and the waste component, thereby exhibiting the effect, but the reaction gradually progresses thereafter. I have. The curing time is generally preferably 6 hours or more. It is also possible to further develop a curing effect by heating. The curing temperature at that time is preferably 40 ° C. or more and 100 ° C. or less. Although the effect is not clear, it is considered that the reaction that proceeds during curing is accelerated by heating the mixture by heating to the above temperature range. It is also presumed that the reaction product generated at that time will be in a more stable state, and the effect of more securely preventing the contained harmful metal from being eluted will be improved.

In the method for treating waste according to the present invention, when the treating agent is mixed and kneaded with the waste, it is ensured that the treating agent component of permanganate or manganate and the waste sufficiently come into contact with each other. This is important for achieving the effect. Therefore, it is also within the scope of the present invention to dilute the treating agent with water in advance, or to mix or knead the treating agent and waste, add water, and further knead. Moisture content by waste,
Although it cannot be said unconditionally because the wettability with the treatment agent is different, in the case of relatively dry waste such as incineration fly ash, the sum of the moisture in the treatment agent and the added water is 1
It is preferably 25 parts by weight or more based on 00 parts by weight. However, it should be noted that if the water content is too large, problems such as poor handling of the waste after kneading and the treatment agent not exhibiting a predetermined effect may occur.

[0019]

Although the mechanism for stabilizing Pb and the like by the waste treatment method of the present invention is not necessarily clear, permanganate (VII) or manganese (VI) ion in the treatment agent is
II-valent Pb ion in waste is hardly soluble in IV-valent oxidized Pb
Or the action of oxidizing to Pb hydroxide, and Mn itself in the treating agent is reduced to make it hardly soluble, so that the Mn oxide or Mn hydroxide having a low valency of IV
Due to the mechanism of coprecipitation with Pb ions during precipitation as well as the mechanism by which the precipitate of the Mn compound adsorbs Pb ions, harmful metals in waste, especially in fly ash from waste incineration It can be considered that Pb is stabilized.

[0020]

According to the present invention, by treating a waste containing a harmful metal using the waste treatment agent and the waste treatment method of the present invention, the harmful metal in the waste is stabilized.
Pb in waste incineration fly ash is stabilized, and the amount of elution is reduced.

[0021]

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

(Comparative Example 1) Analysis result of Pb content of fly ash collected by bag filter generated in municipal garbage incineration facility, and dissolution test of this fly ash as it is without treatment, according to Notification of the Environment Agency No. 13 (Japan) Table 1 shows the results of analyzing the amount of Pb eluted and the pH of the eluate.

[0023]

[Table 1]

Comparative Examples 2 to 6 Silicon dioxide (1) and aluminum silicate (1) having the properties shown in Tables 2 and 3 were used. In addition, ordinary Portland cement manufactured by Ube Cement was used as the cement. A muddy aluminum sludge obtained from an aluminum processing company, dried at 105 ° C. for 4 hours, and then pulverized was used as the amorphous aluminum hydroxide.
A waste treatment agent according to the prior art was prepared under the compounding conditions shown in Table 4 using the above-mentioned silicon dioxide, aluminum silicate, cement, and amorphous aluminum hydroxide as components, and was used for the fly ash of Comparative Example 1 shown in Table 1. The mixture was mixed, kneaded by adding water, and this was cured at 20 ° C. for 24 hours. After curing,
The kneaded material was pulverized, classified with a sieve having a mesh size of 5 mm, and 50 g of the material passed through the sieve was fractionated and subjected to a dissolution test according to the Notification of the Environment Agency No. 13 (Japan). At this time, an experiment was carried out in increments of 1% (weight%, the same applies hereinafter) with the addition amount of the waste treatment agent, and the minimum addition amount necessary for the Pb elution amount to fall below 0.3 ppm was determined. Table 4 shows the results.

[0025]

[Table 2]

[0026]

[Table 3]

(Examples 1 to 7) The potassium permanganate and potassium manganate used were reagent powders, and the other materials used were the same as those used in the comparative examples.
These, potassium permanganate, potassium manganate,
Cement, silicon dioxide, aluminum silicate, and amorphous aluminum hydroxide were used as constituents to prepare the waste treatment agent according to the present invention under the blending conditions shown in Table 4, and the fly ash of Comparative Example 1 shown in Table 1 was used. Mix, add water and knead,
This was cured at 20 ° C. for 24 hours. After curing, the kneaded material was pulverized, classified with a sieve having a mesh size of 5 mm, and 50 g of the material passed through the sieve was collected and subjected to a dissolution test according to the Notification of the Environment Agency No. 13 (Japan). At this time, the experiment was performed with the addition amount of the waste treatment agent in increments of 1%, and the Pb elution amount was 0.3 pp.
The minimum addition amount required to cut m was determined. Table 4 shows the results.

[0028]

[Table 4]

Examples 8 to 10 Silicon dioxide (2) and aluminum silicate (2) having the properties shown in Tables 2 and 3 were used. The same cement as described above was used. A waste treatment agent according to the present invention was prepared under the mixing conditions shown in Table 5 using the silicon dioxide, aluminum silicate, and cement as constituents, mixed with the fly ash of Comparative Example 1 shown in Table 1, and added with water. The mixture was cured at 20 ° C. for 24 hours. After curing, the kneaded material was pulverized, classified with a sieve having a mesh size of 5 mm, and 50 g of the material passed through the sieve was collected and subjected to a dissolution test according to the Notification of the Environment Agency No. 13 (Japan).
At this time, an experiment was performed with the addition amount of the waste treatment agent in increments of 1%, and the minimum addition amount necessary for the Pb elution amount to fall below 0.3 ppm was determined. Table 5 shows the results.

[0030]

[Table 5]

From Comparative Examples 2 to 6 and Examples 1 to 10,
Permanganate, the waste treatment agent of the present invention containing manganate as a main component, and cement, silicon dioxide,
It can be seen that the waste treating agent of the present invention containing aluminum silicate and amorphous aluminum hydroxide can prevent the elution of Pb in the waste with an extremely small addition amount as compared with the conventional waste treating agent. From the comparison between Examples 4, 5, and 7 and Examples 8, 9, and 10, the specific surface area of the silicon dioxide or aluminum silicate used was 150 m ² / g.
It is understood that the above is preferable. From the above, the effect of the waste disposal method of the present invention became clear.

Claims (9)

[Claims] Claims 1. Main components are powdered permanganate and / or manganate and at least one component selected from cement, silicon dioxide, aluminum silicate and amorphous aluminum hydroxide. Waste treatment agent. 2. The permanganate or manganate is at least one alkali metal salt or alkaline earth metal salt selected from potassium salts, sodium salts, calcium salts, and barium salts. The waste treating agent according to 1. 3. The silicon dioxide or aluminum silicate has a specific surface area of 150 m ² / g or more.
The waste treatment agent described in the above. 4. Disposal characterized by mixing a processing agent containing powdered permanganate and / or manganate as a main component and waste, adding water as required, and kneading. How to handle things. 5. The permanganate or manganate is at least one alkali metal salt or alkaline earth metal salt selected from potassium salts, sodium salts, calcium salts, and barium salts. 4. The method for treating waste according to 4. 6. The method for treating waste according to claim 4, wherein said treating agent further comprises at least one component selected from cement, silicon dioxide, aluminum silicate and amorphous aluminum hydroxide. 7. The silicon dioxide or aluminum silicate has a specific surface area of 150 m ² / g or more.
Waste treatment method as described. 8. The waste according to claim 4, wherein said waste contains lead.
Waste treatment method as described. 9. The waste disposal method according to claim 4, wherein the waste is municipal waste incineration main ash and / or incineration fly ash.