JPH0739847A - Waste stabilization treating agent and waste stabilization treatment - Google Patents

Abstract

PURPOSE:To provide a treating agent and treatment method capable of making a stabilization treatment in a manner as not to cause reelution by surely solidifying and sealing various harmful metals included in industrial waste. CONSTITUTION:This treating agent contains a hydrogen phosphate compd., sodium silicate and starch. The agent may contain at least one kind among cement, fly ashes and bentonite in addition to these components and the stabilization treatment effect excellent over a wide range is obtd. in such a case. The metals are surely solidified and sealed in spite of not provision of the curing period if the treating agent is mixed with waste contg. the harmful heavy metals, such as cadmium, lead, zinc and copper and the refuse is kneaded after addition of water thereto. As a result, the treating agent is extremely effective for the stabilization treatment of a wide range of the industrial waste and the stabilization treatment of the harmful metals is rapidly executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste stabilization treatment agent effective for detoxifying harmful heavy metals and a waste stabilization treatment method.

[0002]

2. Description of the Related Art Conventionally, when treating industrial waste containing harmful heavy metals, hydraulic cement is mixed at a ratio of 150 kg (weight part) or more to 1 ton (weight part) of industrial waste. However, a method is used in which water is further added and kneaded, then cured and solidified, and harmful metals are contained and treated. In addition, a sulfur-based chelating agent is mixed at a rate of 10 to 50 kg (parts by weight) or more with respect to 1 ton (parts by weight) of industrial waste, and water is further added and mixed to generate a sulfur-based chelate compound, which is stable. There is a method of chemical treatment. In addition, for industrial waste that is extremely difficult to treat and industrial waste that contains extremely large amounts of harmful heavy metal compounds, hydraulic cement is first applied after stabilizing treatment with a sulfur-based chelate compound. There is a case where a method of adding and solidifying is adopted.

However, these hydraulic cement solidification treatments, sulfur chelate stabilization treatments, or this 2
The treatment by the combined use of the two methods has various problems such as the occurrence of secondary pollution and the insufficient solidification treatment unless the industrial waste is used in a limited manner.

[0004] For example, in the case of a highly alkaline fly ash containing a large amount of alkaline components such as calcium hydroxide (Ca (OH ₂ )) and calcium oxide (CaO) generated from an incinerator for municipal solid waste, when treated by a conventional method. , Lead (P
b), cadmium (Cd), zinc (Zn), etc. have the property of being re-eluted in a highly alkaline atmosphere. Therefore,
Landfilling is carried out with insufficient detoxification treatment, and there is concern about secondary pollution after disposal.

In order to solve these problems, the inventors of the present invention have made various investigations, and as a result, in Japanese Patent Application No. 5-142917, a hazardous treatment using a treating agent containing cement and a hydrogen phosphate compound was carried out. It has been disclosed that if the substance is treated, re-elution of lead, cadmium, zinc and the like can be prevented, and stabilization treatment can be performed.

However, when attempting to treat highly alkaline fly ash in a refuse incinerator by using a treating agent containing cement and a hydrogen phosphate compound, the number of days until curing and solidification is required, and a curing place is required. Since problems may occur during out-of-site removal, there is a demand for the development of stabilizing treatment agents and treatment methods that do not require curing, from a refuse incinerator that does not have cement hardening equipment or curing space.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the problems in the prior art and enables solidification and encapsulation of industrial waste containing various harmful metals, and stabilization treatment to prevent re-elution. An object of the present invention is to provide a waste stabilization treatment agent and a waste stabilization treatment method that do not require curing until stabilization.

[0008]

The waste stabilization treating agent of the present invention is characterized by containing a hydrogen phosphate compound, sodium silicate and starch. In addition to the above components, the waste stabilization treatment agent of the present invention further contains at least one selected from the group consisting of cement, fly ash generated from a coal-fired power plant, and bentonite which is a clay mineral. In this case, it is possible to obtain a wider range of excellent stabilization treatment effects.

Furthermore, the present invention is also a method for stabilizing a waste containing at least one harmful metal selected from the group consisting of cadmium, lead, zinc and copper. The above waste, which is characterized by mixing a hydrogen phosphate compound, sodium silicate, and starch at a fixed ratio, and further kneading after adding water. Stabilization treatment can be achieved.

First, the waste stabilization treatment agent of the present invention will be described in detail. In the waste stabilization treatment agent of the present invention, the three components of hydrogen phosphate compound, sodium silicate, and starch mainly contribute to the stabilization treatment. Sodium monohydrogen acid (Na ₂ HPO ₄ ), sodium dihydrogen phosphate (NaH
₂ PO ₄ ), ammonium dihydrogen phosphate (NH ₄ H ₂ P
O ₄ ), ammonium monohydrogen phosphate ((NH ₄ ) ₂ HP
O ₄ ), potassium monohydrogen phosphate (K ₂ HPO ₄ ), potassium dihydrogen phosphate (KH ₂ PO ₄ ), aluminum dihydrogen phosphate (Al (H ₂ PO ₄ ) ₃ ) and the like.
Also, sodium silicate has a chemical formula of Na ₂ O · nSiO ₂ · n
It is represented by H ₂ O, and there are three types of ortho, meta, and anhydrous, but there is no significant difference in the stabilizing treatment effect, and all can be used, but ortho and anhydrous are preferable from the viewpoint of ease of use. Furthermore,
Regarding the starch contained in the treatment agent of the present invention, an intermediate product composed of a mixture of soluble starch, dextrin, maltose, D-glucose, etc., which is produced when boiling in a dilute acid for a long time is used. Generally, what is called soluble starch or alpha starch is used.

The above-mentioned three kinds of compounds are the main constituents of the present invention. In addition, depending on the type of industrial waste,
Combine with cement, fly ash and bentonite.
Cement is Portland cement type (normal, super early strength,
Various types of heat resistance (sulfate, etc.) can be used. Fly ash uses fly ash collected by an electrostatic precipitator (EP) discharged from a coal-fired power plant,
Brands such as coal production destinations are not particularly limited,
All can be used. Bentonite is effective in acid clay that has been activated by immersing it in hydrochloric acid or sulfuric acid for a long time, but it is more effective than acid clay in SiO ₂ (silicon dioxide) / Al ₂ O ₃
Na-based bentonite or Ca-based bentonite having a low (4-6) molar ratio of (alumina) can also be used.

Next, the mixing ratio of each component in the waste stabilization treatment agent of the present invention will be described. The mixing ratio of each component in the present invention is appropriately adjusted depending on the target industrial waste, but the hydrogen phosphate compound is 5 to 90 parts by weight, sodium silicate is 1 to 50 parts by weight, and starch is 1
Cement, fly ash, and bentonite are mixed in the range of 0 to 70 parts by weight, respectively.

The addition amount of the hydrogen phosphate compound varies depending on the coexisting amount of the alkali metal in the target industrial waste, but if it is added in too large a quantity, the pH may drop too much, and harmful metals may elute. Therefore, the mixing ratio in the range of 50 to 90 parts by weight is particularly preferable. The amount of sodium silicate added is
Similar to the hydrogen phosphate compound, it increases or decreases depending on the coexisting amount of alkali metal, but since the pH of sodium silicate alone shows high alkali, it shows high alkali when added too much,
Since harmful metals may be redissolved, it is particularly preferable to use within the range of 5 to 30 parts by weight. Starch is
It exerts a synergistic effect of further stabilizing the reaction product of a hydrogen phosphate compound or sodium silicate and a harmful metal, and since there are no inhibiting factors such as pH, it is possible to increase the addition amount, but with starch alone The stabilizing effect is slightly inferior to hydrogen phosphate compounds and sodium silicate, so 5 to 3
It is particularly preferable to use within the range of 0 parts by weight.

Cement and fly ash are used for pH adjustment when treating acidic ash discharged from the intermediate treatment industry of industrial waste. These components are added so that the pH after treatment with the stabilizing agent of the present invention is within the range of 9 to 13, and 0 to 7 although varying depending on the use conditions.
It is preferably used within the range of 0 parts by weight, particularly within the range of 20 to 40 parts by weight. It should be noted that although cement and fly ash are used properly depending on the price, cement contributes to stabilization treatment better than fly ash, so cement is preferred. Fly ash is very effective for hazardous waste with a low pH buffer. On the other hand, bentonite can be added in the range of 0 to 70 parts by weight because the adsorption effect by ion exchange is recognized, but the amount of water added increases as the amount of addition increases, and more preferably 5 to 20 parts by weight. Within the range of.

[0015]

[Function] The waste stabilization treatment agent of the present invention is capable of stabilizing harmful heavy metals without re-elution even in a highly alkaline atmosphere, mainly because hydrogen phosphate and sodium silicate directly react with harmful heavy metals. It depends largely on it. In particular, a reaction product of a hydrogen phosphate compound and a harmful heavy metal has extremely low solubility in water and excellent stability as compared with a product of a hydroxide or a sulfide. Further, the phosphoric acid compound reacts with harmful heavy metals in the acidic region, but does not react with it in an alkaline atmosphere. On the other hand, the hydrogen phosphate compound has a wide pH range in which it reacts, and the reaction range slightly differs depending on the harmful heavy metal, but lead and the like react in both the strong acid range and the strong alkali range.

[0016] Sodium silicate is an alkaline substance having a strong buffering property, and reacts with water when sodium silicate is subjected to stabilization treatment and reacts with hydroxides dissociated from silicon dioxide or alumina and harmful heavy metals to form a gel-like substance. Works to contain it. As starch, soluble starch and α-starch are used, but the reaction mechanism of starch itself is not clear in many unknown parts, but various starches produced by the adhesive effect by the reaction of starch with water It is presumed that it functions to contain the reaction product.

Cement and fly ash are used to shift the pH to the alkaline side when the industrial waste of interest is in the acidic range. Cement is used when there are many coexisting substances of industrial waste and strong buffering property, and fly ash is used otherwise. Bentonite is
It has a large ion-exchange capacity and acts as an ion-exchange adsorbing agent for coexisting substances of harmful heavy metals and wastes, but its effect is smaller than that of hydrogen phosphate compounds and sodium silicate.
In addition, bentonite has a very large water absorption capacity, so when mixing hydrogen phosphate compounds, sodium silicate and starch, adding bentonite will prevent moisture and stabilize the life of the stabilizer. Becomes longer.

The stabilizing agent of the present invention is characterized by containing a hydrogen phosphate compound, sodium silicate, starch and the like. The treating agent of the present invention containing a mixture of such three kinds of compounds. By using, a treatment method that does not require a curing period or a curing space can be applied. That is, it is also a feature that the curing and solidifying period required when cement or the like is used is eliminated by sodium silicate or starch. Sodium silicate and starch have the property of solidifying after reacting with water if a large amount thereof is used, and by utilizing this property, a treatment requiring no curing period can be performed.

Due to such an action, the treatment agent of the present invention can be stabilized without the need for a curing period without re-elution of harmful heavy metals contained in industrial waste. Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0020]

[Example] As the waste to be treated, fly ash generated from a refuse incinerator was used. This fly ash detoxifies harmful gases such as hydrogen chloride and sulfur oxides,
Calcium hydroxide and calcium oxide are blown into the flue, and unreacted calcium hydroxide and calcium oxide are collected by the bag filter and the electrostatic precipitator and are mixed. Therefore, fly ash containing harmful metals is in a highly alkaline atmosphere, and lead and zinc are often eluted.

Example 1 Treatment Experiment of Stabilizing Agent of the Present Invention Using Constituents Alone First, in order to confirm the effect of the constituents of the stabilizing agent of the present invention, the following treatment with each component alone was performed. An experiment was conducted. Addition amount (1) Sodium dihydrogen phosphate: 25 to 250 parts by weight (2) Sodium orthosilicate: 12.5 to 125 parts by weight (3) Soluble starch: 12.5 to 125 parts by weight

To 1 ton of the above fly ash, each component of the above-mentioned waste stabilization treatment agent of the present invention was added by changing the addition amount within the above-mentioned weight part%, and 600 kg of water was added.
Was added, and after kneading, the elution amount of each harmful metal was measured by the elution test method of Notification No. 13 of the Environment Agency without setting a curing period. The experimental results at this time are shown in Table 1. In addition, in Table 1, the elution amount of the waste incinerator fly ash used in the experiment in the case of no treatment and the industrial waste containing metal etc. announced on February 17, 1973 of Prime Minister's Ordinance No. 5 Judgment standard values are also shown.

[0023]

[Table 1]

From the experimental results shown in Table 1, it is understood that each component constituting the waste stabilization treatment agent of the present invention characteristically acts on the stabilization treatment of harmful heavy metals. First, 125 kg of sodium dihydrogen phosphate
Although the amount of lead, zinc, cadmium, and copper eluted is extremely reduced by the addition of, the pH value also decreases with the increase of the added amount. On the other hand, sodium orthosilicate has a strong buffering property even if the amount added is increased, and thus the pH value does not change, but the amount of lead eluted is slightly higher than that of sodium dihydrogen phosphate and soluble starch. However, the elution amount of zinc is extremely smaller than that of the other components, and it can be seen that it is effective for the stabilization treatment of zinc. It should be noted that soluble starch hardly changes in pH value even if the amount added is increased.
It is also effective for stabilizing lead, but the amount of zinc eluted is higher than other components. As described above, it was confirmed from the results of this experiment that the three kinds of components constituting the waste stabilization treatment agent of the present invention are specifically effective for the stabilization treatment of waste.

Example 2 Comparative Experiment of Stabilization Treatment of MSW Incinerated Fly Ash with Various Treatment Agents The stabilizer of the present invention was prepared by using the fly ash discharged from the MSW incinerator in a highly alkaline atmosphere. A comparative experiment was conducted between the stabilization method used, a conventional cement solidification stabilization method, and a stabilization method such as a sulfur-based chelating agent (trade name: Eporba 500, manufactured by Miyoshi Yushi Co., Ltd.). The mixing ratio of each component in the stabilizing agent of the present invention used in the experiment is as follows. Addition amount (1) Sodium dihydrogen phosphate: 87.5 parts by weight (2) Sodium orthosilicate: 2.5 parts by weight (3) Soluble starch: 10.0 parts by weight

100 kg, 150 kg, and 200 kg of the stabilizing agent of the present invention having the above composition ratio was added to 1 ton of fly ash discharged from the above-mentioned municipal waste incinerator,
After adding 600 kg of water and kneading, the elution amount of each harmful metal was measured by the elution test method of Notification No. 13 of the Environmental Agency. On the other hand, in the conventional cement solidification stabilization method, 3 tons of ordinary Portland cement was added to 1 ton of the same fly ash.
00 kg, 400 kg, 500 kg are added respectively, and water 6
After adding 00 kg and kneading, the mixture was allowed to stand for 7 days under a curing condition and then subjected to the same dissolution test as above. Also, the sulfur-based chelating agent is 30k for 1 ton of the fly ash.
g, 40 kg, and 50 kg were added, 300 kg of water was added, and after kneading, the same dissolution test as above was performed. The experimental results at this time are shown in Table 2. In addition, in Table 2, the elution amount of the above-mentioned fly ash in the case of no treatment and the judgment standard value concerning industrial waste containing metals and the like, which was announced on February 17, 1973 of Prime Ministerial Ordinance No. 5, are also shown. did.

[0027]

[Table 2]

As shown in Table 2, the stabilizing agent of the present invention has a remarkable effect on the stabilizing treatment of the elution amount of lead with respect to fly ash discharged from a municipal solid waste incinerator in a highly alkaline atmosphere. It was observed that 100kg was added to 1 ton of fly ash, which cleared the judgment standard value and landfill disposal was possible. Compared with the stabilizing agent of the present invention, the lead elution amount was not stabilized in this experiment in which the commonly used addition amounts of ordinary Portland cement and sulfur chelating agent were added. The amount of each stabilizing agent added is determined in consideration of both the treatment price and the post-treatment capacity, but the maximum amount of all three stabilizing agents shown here is the standard. Therefore, depending on the type of fly ash, stabilization treatment can be performed with a smaller amount, but conversely, increasing the amount of each treatment agent even for fly ash that is extremely difficult to treat is economical and post-treatment. It becomes difficult because of the problems associated with landfill disposal due to the capacity. Although the use of sulfur-based chelating agents and cement solidification methods in combination with other additives is being investigated, the current situation is that they have not been put to practical use. The waste stabilization treatment agent of the present invention does not require any combined use with other additives and can perform stabilization treatment of harmful metals.

Example 3: Comparative experiment of various stabilizing treatment agents using acidic ash discharged from incineration of industrial waste Incineration treatment is often used as an intermediate treatment of industrial waste. The constituent components of the discharged acidic ash are significantly different from the constituent components of the fly ash of municipal solid waste, and often contain a large amount of acidic components. Therefore, the amount of toxic heavy metals eluted without treatment is very large, and there is a problem that the stabilization treatment cannot be performed with conventional techniques such as cement. Using this acidic ash, a comparative experiment was conducted between the treatment with the stabilizing agent of the present invention and the conventional cement solidification method.
Other conventional techniques include sulfur-based chelating agents, but when added to such acidic ash, harmful gas (hydrogen sulfide) is generated, which is dangerous and cannot be applied. Therefore, no sulfur-based chelating agent is used for treating this acidic ash.

As the waste stabilization treatment agent of the present invention, the following compositions (1) and (2) were prepared and used. The treatment agent of the present invention used cement, fly ash, and bentonite in combination with the above-mentioned three types of constituent components for the purpose of adjusting the pH during the stabilization treatment. The mixing ratio is shown below.

Waste stabilization treatment agent of the present invention- (1) Addition amount (1) Sodium dihydrogen phosphate: 20% by weight (2) Sodium orthosilicate: 30% by weight (3) Soluble starch: 15% by weight ( 4) Ordinary Portland cement: 30% by weight (5) Bentonite: 5% by weight Waste stabilization treatment agent of the present invention- (2) Addition amount (1) Sodium dihydrogen phosphate: 20% by weight (2) Sodium orthosilicate : 20% by weight (3) Soluble starch: 15% by weight (4) Fly ash: 40% by weight (5) Bentonite: 5% by weight

Then, to 1 ton of the above-mentioned acidic ash, 4 parts of each of the stabilizing treatment agents- (1) and (2) of the present invention are added.
00 kg and 600 kg of water were added and kneaded, and the elution amount of each harmful metal was measured by the elution test method of Notification No. 13 of the Environmental Agency without setting a curing period. On the other hand, as a conventional technique for comparison, 400 kg of ordinary Portland cement and 60 parts of water
When 0 kg is added, kneading and no curing period is set,
The elution amount of each harmful metal was measured after a curing period of 7 days, which is a conventional technique of the cement method. The results at this time are shown in Table 3. In addition, Table 3 shows the amount of harmful metals contained in acidic ash, the amount of elution in the case of no treatment, and the industrial waste containing metals and the like announced on February 17, 1973, Prime Minister's Ordinance No. 5. The judgment reference values for the products are also shown.

[0033]

[Table 3]

As can be seen from the experimental results in Table 3, the waste stabilization treatment agent of the present invention containing a dihydrogen phosphate compound, sodium orthosilicate and soluble starch is discharged when industrial waste is incinerated. Even for fly ash, which shows strong acidity,
It was clarified that it can be applied by combining inexpensive raw materials such as cement and fly ash. Table 3
In particular, it shows a remarkable effect on lead stabilization treatment, and unlike the conventional cement solidification stabilization treatment, all judgment criteria can be cleared and landfill disposal can be performed without special curing period. . On the other hand, in the stabilization treatment of cement, it was found that the length of the curing period had a great influence on the elution amount of lead and zinc. In the results of this experiment, the lead judgment standard value was not cleared, and 400 kg of cement was added. After 7 days of curing, the stabilization treatment was insufficient and landfill disposal was not possible.

[0035]

INDUSTRIAL APPLICABILITY The waste stabilization treatment agent of the present invention is suitable for treating industrial waste containing harmful metals, and can stably contain harmful metals without re-elution even in a highly alkaline atmosphere. It is very effective for stabilizing industrial waste over a wide range. Further, the treating agent of the present invention is also useful for fly ash exhibiting strong acidity, which is discharged when industrial waste is incinerated. Moreover, the treatment agent of the present invention does not require a curing period until the harmful metal is stabilized, so that the treatment can be performed rapidly and a place for curing is not required. Further, by using the treatment method of the present invention using such a waste stabilization treatment agent, industrial waste containing harmful metals can be promptly stabilized.

Claims (3)

[Claims] 1. A waste stabilization treatment agent comprising a hydrogen phosphate compound, sodium silicate, and starch. 2. The waste stabilization treatment agent according to claim 1, further comprising at least one selected from the group consisting of cement, fly ash and bentonite. 3. A waste material containing at least one harmful metal selected from the group consisting of cadmium, lead, zinc and copper is mixed with a hydrogen phosphate compound, sodium silicate and starch, and water is added. A waste stabilization treatment method characterized by kneading afterwards.