JPH09239339A - Waste treating material and treatment of waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize waste so that the harmful heavy metal contained in slag, soil, sludge and shredder dust as well as the incineration ash of city refuse are not eluted over a long period. SOLUTION: A treating material added with at least one kind among iron powder, amorphous aluminum hydroxide, silicon dioxide, silicate and phosphate, preferably iron powder and at least one kind among aluminum hydroxide, silicon dioxide, silicate and phosphate or more preferably iron powder, amorphous aluminum hydroxide and phosphate, is mixed with the waste contg. harmful materials such as lead, cadmium, mercury, chromium, copper and nickel, and the mixture or the mixture added with water, if necessary, is kneaded, cured and solidified to treat the waste. The porous silicon dioxide and aluminum silicate having 150-1000m<2> /g BET specific surface are preferably used as the silicon dioxide and silicate and at least one kind among the phosphates of magnesium, aluminum, calcium and iron as the phosphate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste treatment material and a treatment method effective for stabilizing a waste containing a harmful heavy metal or the like.

[0002]

2. Description of the Related Art Municipal solid waste has a bad odor, and conventionally, it has been considered that the treatment is completed by incineration to reduce the volume and discard the incinerated ash at the final disposal site. However, the aspect of municipal solid waste treatment has changed along with the change in the content of the solid waste. For example, plastics, color-printed papers, and dry batteries contain heavy metals such as cadmium (Cd), lead (Pb), chromium (Cr), mercury (Hg), and copper (Cu). Therefore, when these were incinerated, heavy metals remained in the incinerated ash. In addition, from the viewpoint of preventing air pollution, dechlorination is required to remove the chlorine generated by the incineration of waste, and slaked lime has been introduced from the flue. Slaked lime shows alkali when dissolved in water, but fly ash became highly alkaline because a large amount of slaked lime was required for dechlorination. Among the heavy metals, lead is likely to be eluted in a highly alkaline state, which is a problem similar to the elution of cadmium in a low alkaline ash without adding slaked lime.

[0003] Some heavy metals have biotoxicity such as carcinogenicity, mutagenicity and organ damage. For example, lead
It acts destructively on the kidneys along with cadmium, mercury and chromium. In addition, lead is known to have an inhibitory effect on heme synthesis of blood components and an influence on the nervous system together with mercury. It has been pointed out that cadmium may cause hypertension and decrease spermatogenic ability. Therefore, municipal waste incineration ash came to be considered as a hazardous waste. In Japan, from April 1995, municipal solid waste has been required to be sufficiently controlled as a specially controlled municipal waste to suppress the elution amount of heavy metals. for that reason,
Various treatments such as cements, powder chemicals, liquid chemicals, and melt processing are performed.

Among the various treatment methods described above, polyethyleneimine-bonded polymers with dithiocarboxyl groups are often used for the purpose of preventing the elution of harmful metals.
It is a low molecular weight liquid organic drug such as dibutyldithiocarbamate. Although this liquid organic chemical is excellent in stabilizing lead, it is 20 times more expensive than cement, its processing cost is high, and its long-term stability is not sufficiently proved. There is a problem that occurs. Further, this organic liquid chemical has a low ability to stabilize lead and cadmium when treating neutral ash, and dangerous hydrogen sulfide gas is generated. Thus, many problems have been pointed out with organic drugs.

Further, as a material for treating wastes, long-term stability, that is, harmful heavy metals are not re-eluted for a long period of time, is required due to the movement of residents around the final disposal site of wastes and the heightened awareness of environmental conservation. There is. This is because even if the heavy metal is stabilized in the treated product at the beginning of the treatment of the waste, if the waste treatment material in the treated product deteriorates during long-term storage, the heavy metal will leak out and the tarpaulin will disappear. If it breaks, heavy metals will leak out to the ground, and there is a danger of affecting the human body through groundwater. Therefore, it is important to reduce the elution of harmful heavy metals as much as possible over a long period of time. However, there is no dogma about long-term stability due to the variety of waste types. Under such circumstances, the availability test method has attracted attention as one of the evaluation methods.

The availability test method is 100 years to 1
It has been adopted in the Netherlands as a method for estimating the stability of the processed material when it is left for a long period of 000 years. This test is based on the 3rd Japan Society for Solid Waste Research Presentation, pp. 603-606 (1992) and Comparison of d
ifferent regulatory leaching test procedures forwa
ste materials and construction material, HA Van
der Sloot, D. Hoede, P. Bonouvrie; ECN-C-91-082,
Netherlands Energy Research Foundation ECN, 1991
), It is said to be a severe test method. Since the experimental procedure of this method is described in NEN7341 (1992), the details are omitted, but the characteristic of this test is that the solid-liquid ratio is increased, the particle size is decreased, and the pH is set low. This is the reason why it is called a severe dissolution test.

In addition, TCLP (Toxic Characteristic L
Eaching Procesure) method is a test method adopted in the United States. In this test, in order to dispose of the industrial waste at a low price, the worst situation is assumed in which the waste disposal agent intentionally disposes of the municipal waste containing organic substances such as garbage and the industrial waste at a ratio of 95: 5. ing. This test method is considered to be a dissolution test method suitable for reproducing leachate at landfills that have undergone such inappropriate disposal. Therefore, this test method can also be considered as a method for estimating the presence or absence of contamination of groundwater if the waterproof sheet should be torn during long-term storage.

The common point of both the availability test method and the TCLP method is that the extract is acidified.
Nitric acid is used in the availability test method, and acetic acid is used in the TCLP method. Heavy metals are easily dissolved under acidic conditions. Therefore, when a heavy metal can be stably treated using such a test method as a scale, it can be considered that the treatment material at that time has high long-term stability, although the treatment method is limited. For example, in the cement treatment, when the alkali of the cement is neutralized with an acid, the heavy metal insolubilized as a hydroxide is solubilized. In the organic liquid drug treatment, the pH of the drug is alkaline, so that the heavy metal not bound by sulfur is redissolved from the hydroxide. In addition, the acid promotes the decomposition of the drug itself. Thus, current treatment methods with cement or organic liquid chemicals appear to have long-term stability problems.

As described above, regarding the stabilization treatment of heavy metals in waste, it has excellent heavy metal stabilizing performance, has no odor, is inexpensive, and strongly prevents harmful heavy metals in waste from being re-eluted for a long period of time. A treatment material and a treatment method that can be stabilized are desired.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a waste treatment material effective for stabilizing the waste containing such heavy metals. In particular, the present invention, including the municipal waste incineration ash as described above,
An object of the present invention is to provide a waste treatment material and a treatment method capable of stabilizing harmful heavy metals contained in ore, soil, sludge and shredder dust so as not to be re-eluted for a long period of time.

[0011]

DISCLOSURE OF THE INVENTION As a result of intensive studies made by the present inventors for the purpose of solving the problems in the current state of waste treatment as described above, the waste treatment material and treatment method capable of achieving this objective. Came to get. That is, the treatment material of the present invention is
It has been found that a waste treatment material containing at least one selected from the group consisting of iron powder, amorphous aluminum hydroxide, silicon dioxide, silicates and phosphates is preferable. As a preferable compounding example of the present treatment material, iron powder to which at least one selected from the group consisting of amorphous aluminum hydroxide, silicon dioxide, silicate and phosphate is added (claim 2), Preferred is iron powder to which amorphous aluminum hydroxide and phosphate are added (claim 3). Also,
The silicon dioxide or silicate is preferably porous silicon dioxide or aluminum silicate having a BET specific surface area of 150 m ² / g or more and less than 1000 m ² / g. As the phosphate, magnesium salt,
It is preferably at least one selected from the group consisting of aluminum salts, calcium salts, and iron salts.
The treatment method of the present invention, the waste treatment material as described above,
It is mixed with waste containing at least one harmful substance selected from the group consisting of lead, cadmium, mercury, chromium, copper, and nickel, and kneaded by adding water as necessary to cure and solidify. is there. Wastes to which the method of the present invention can be applied include municipal waste incineration ash, slag, soil, sludge, and shredder dust.

[0012]

In the treated material of the present invention, iron powder reduces less base material, so that it is excellent in stabilizing lead in waste,
It also has a slight effect on the stabilization of cadmium, and can stabilize lead and cadmium in neutral ash. Further, amorphous aluminum hydroxide can stabilize heavy metals by a neutralizing action, and can lower the pH of highly alkaline ash to insolubilize lead that is solubilized in high alkali. Silicon dioxide and silicates are particularly effective in stabilizing lead in highly alkaline ash. Furthermore, phosphate is excellent in stabilizing lead under acidic conditions.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The iron used in the present invention is preferably in the form of powder or particles. This is preferable from the viewpoint of reducing action, because the smaller the powder or particle size, the greater the activity. For example, reducing powder, spray powder, electrolytic powder, crushed powder, rapidly solidified powder, alloy powder, composite powder, coating powder and the like.
In addition, by-products obtained in the metal refining process and metal processing process (for example, steel scrap produced in the iron refining process and processing process, the slag that is generated during blowing is slag that is scattered by spilling or sloping). , Dust in baghouses, slag containing metallic iron, by-products from shot blasters, coarse-grained dust, etc.), such as those that contain impurities that are not commonly produced as products.

In the present invention, in addition to the iron powder, amorphous aluminum hydroxide, silicon dioxide, silicates, phosphates, etc. are used. These will be described below.

First, the aluminum hydroxide used in the present invention is an amorphous one whose peak is not observed by x-ray. The amorphous aluminum hydroxide used in the present invention may contain impurities such as crystalline aluminum hydroxide, nickel and boron. As the amorphous aluminum hydroxide, aluminum sludge obtained by concentrating and recovering aluminum hydroxide that is originally discarded in the aluminum processing process of the aluminum sash factory is preferable because it is relatively easy to obtain and inexpensive. For example, in an aluminum sash factory, the oil that has adhered to aluminum sashes, aluminum pipes, and other molded products made of aluminum is removed with sulfuric acid, and the alumite-treated waste liquid that coats nickel on the surface is used to prevent corrosion. Get out. In the factory, a coagulant is added to this waste liquid, precipitation filtration is performed, and then filter filtration is performed to recover aluminum hydroxide as aluminum sludge. Since this aluminum sludge contains about 75% by weight of water, it is difficult to handle as it is. Therefore, when used as a material for treating wastes, it is preferable in handling that the sludge is dried and crushed into a powder form. Aluminum sludge is dried at a temperature of 20
It is dried at 0 ° C or lower.

The silicon dioxide or silicate used in the present invention is preferably porous silicon dioxide or aluminum silicate. These porous silicon dioxides and aluminum silicates are known to be crystalline and amorphous, but any of them can be used here as long as they are powdery.

The larger the specific surface area of porous silicon dioxide, the higher the adsorption capacity for heavy metals such as lead, and the higher the alkali adsorption capacity. As the specific surface area increases, the heavy metal is stabilized and does not elute, but on the other hand, the bulk specific gravity of the treated material decreases and the treated material becomes bulky. For this reason, handling problems such as a reduction in the amount of treated material transported, a large silo for storage are required, and a small amount of treated material can be mixed in the same feeder as cement when mixed with waste. . Therefore, the specific surface area (by the BET method) of the porous silicon dioxide used in the present invention is 1
It is preferably 50 m ² / g or more and less than 1000 m ² / g. As such a porous silicon dioxide, BS
304, BS304F, Carplex # 67, Carplex # 80 (all manufactured by Shionogi Pharmaceutical Co., Ltd.) and the like, but not limited thereto.

Aluminum silicate is silicic acid in which a part of silicon is replaced by aluminum.
Fly ash, kaolin, bentonite, activated clay,
Natural aluminum silicates such as diatomaceous earth and zeolite and synthetic aluminum silicates are known. Porous aluminum silicate has a larger specific surface area, a higher adsorption capacity for heavy metals such as lead, and a higher alkali adsorption capacity. Therefore, it is desirable that the specific surface area of the aluminum silicate be 150 m ² / g or more and less than 1000 m ² / g. Among these, synthetic aluminum silicate has a large specific surface area, a high lead adsorption capacity, and a high alkali adsorption capacity, and therefore can efficiently stabilize heavy metals such as lead. For such an aluminum silicate, Kyoward 700PE
L, KYOWARD 700PL (both manufactured by Kyowa Chemical Co., Ltd.) and the like are mentioned, but not limited thereto.

As the phosphate, a polyvalent metal salt of phosphoric acid is preferable. This polyvalent metal salt of phosphoric acid includes magnesium phosphate,
A large number of aluminum phosphates, calcium phosphates, iron phosphates, zinc phosphates, silver phosphates, etc. are known. Iron is preferred. Among the magnesium phosphate salts, preferred are dibasic magnesium phosphate and tribasic magnesium phosphate. Among them, tribasic magnesium phosphate is a highly alkaline waste, for example, when stabilizing heavy metals in fly ash,
Both the availability test and the Environmental Agency Notification No. 13 method show good performance. Other magnesium salts of phosphoric acid include monobasic magnesium phosphate, which deliquesce when stored. Therefore, it causes solidification and causes a problem when handling the powder on a large scale, which is not preferable. Among the aluminum phosphates, preferred are dibasic aluminum phosphate and tribasic aluminum phosphate. On the other hand, monoaluminum phosphate has a strong hygroscopic property, and the treatment material deteriorates as it is, which is not preferable. Calcium phosphate salts include primary calcium phosphate, secondary calcium phosphate,
Examples include tricalcium phosphate. Also, lime superphosphate,
That is, there are a mixture containing calcium dihydrogen phosphate hydrate and gypsum as a main component and a small amount of free phosphoric acid and calcium monohydrogen phosphate, and a mixture containing primary calcium phosphate such as lime superphosphate. The calcium phosphate salt used in the present treating material can be used in the form of powder. The iron phosphate salt used in the present invention can be used if it is industrially available as a powder. Of these phosphates used in the present invention magnesium, aluminum, calcium,
The iron salt may contain unavoidable impurities.

As described above, as the phosphate, dibasic magnesium phosphate, tribasic magnesium phosphate, dibasic aluminum phosphate, tribasic aluminum phosphate, monobasic calcium phosphate,
Examples include dicalcium phosphate, tricalcium phosphate, and iron phosphate. These are poorly soluble substances having low solubility in water. Here, “poorly soluble” means that the solubility in water at 25 ° C. to 30 ° C. is less than 5% by weight, and “soluble” means that the solubility is 5% by weight or more. For example, the solubility of monobasic magnesium phosphate, dibasic magnesium phosphate, and tribasic magnesium phosphate is 2 respectively.
0 wt% (anhydrous salt), 0.025 wt% (trihydrate),
0.02% by weight (tetrahydrate). Therefore, the first magnesium phosphate is soluble, but the second and third magnesium phosphates are poorly soluble.

As described above, in the waste treatment material according to the present invention, the iron powder in the treatment material is excellent in stabilizing lead, and also shows some effect in stabilizing cadmium. It is possible to stabilize lead and cadmium. Amorphous aluminum hydroxide can reduce the pH of highly alkaline ash to insolubilize highly alkaline solubilized lead. Silicon dioxide and silicates are particularly effective in stabilizing lead in highly alkaline ash. Phosphates are excellent in stabilizing lead under acidic conditions.
These iron powders, amorphous aluminum hydroxide, silicon dioxide, silicates, and phosphates are all odorless, and iron powders and amorphous aluminum hydroxides can be waste products. Therefore,
Depending on the alkalinity of the waste and the content of the heavy metal to be removed, it is possible to formulate a treatment material that is inexpensive, has high performance, and is excellent in long-term stability. As such a combination, it is preferable to mix at least one of iron powder and phosphate with at least one of amorphous aluminum hydroxide, silicon dioxide and silicate. Furthermore, powder water glass and iron powder,
You may combine powder water glass, iron powder, and aluminum sludge. In addition, it is within the scope of the present invention to treat only wastes that can be easily treated with only a treating material that is a combination of any of amorphous aluminum hydroxide, phosphate, silicon dioxide, and silicate. It is also within the scope of the present invention to combine iron powder and phosphate.

Next, the mixing ratio of each component in the treated material will be described. The mixing ratio of these is appropriately adjusted, but the general mixing ratio is 10 to 100% by weight of iron powder or phosphate with respect to the waste treatment material, but a more preferable range is 10 to 50%. % By weight. This is because when a large amount of iron powder is added, it becomes unevenly distributed in the treated material and stable treatment becomes impossible, and when a large amount of phosphate is added, the treated material becomes expensive.

The waste treatment material of the present invention is mixed with a waste containing at least one harmful substance selected from the group consisting of lead, cadmium, mercury, chromium, copper and nickel, and water is mixed as necessary. It is preferable that the added one is kneaded to be cured and solidified. As such a waste to which the present invention can be applied, incineration ash, slag, soil and sludge are particularly preferable. Incinerated ash includes main ash and fly ash. Fly ash is dust collected from the incineration of municipal waste and industrial waste, and dust collected from a melting furnace, and EP ash collected by an electric dust collector, An example is bug ash that is collected by a bag filter. On the other hand, main ash is ash discharged from the lower part of the incinerator at incinerators for municipal solid waste and industrial waste, and includes harmful heavy metals. Furthermore, the present invention is also applicable to ore slag discharged from mines, stabilization of heavy metals in soil contaminated with heavy metals, and sludge containing heavy metals generated by wastewater treatment.

In a preferred embodiment of the present invention, wastes such as dust and fly ash collected in the hopper are mixed with the above-mentioned waste treatment material from another hopper, and water is added to the mixture if necessary. And knead well in the shaping device and extrude. Generally, in the conventional treatment method using cement, 10 to 30 parts by weight of cement is added to 100 parts by weight of dust and kneading is performed. When the treatment material of the present invention is used, better performance is obtained than when the same amount of cement is added. Therefore, for example, when a long-term stabilizing performance of heavy metal equivalent to that of cement is desired, a smaller amount than that of cement may be added, and the volume of the solidified product can be expected to be reduced. Further, when the conventional cement does not sufficiently stabilize the heavy metal for a long period of time, a strong heavy metal stabilizing effect can be expected by adding the same amount of treatment material as the cement.

[0025]

INDUSTRIAL APPLICABILITY Using the waste treatment material of the present invention, EP ash and bag ash (particularly EP ash in which slaked lime or quick lime is blown) discharged from an incinerator for industrial waste containing toxic heavy metals and municipal solid waste. When treated with dust such as (or bug ash), it has excellent heavy metal stabilizing performance, has no odor, is inexpensive, and can strongly stabilize harmful heavy metals in waste so that it does not re-elute for a long period of time. Therefore, the waste treatment material of the present invention is very effective in stabilizing industrial waste and fly ash such as EP ash and bag ash discharged from an incinerator for municipal solid waste.

[0026]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1 Iron powder (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the treating material of the present invention. Neutral fly ash (P containing a large amount of lead and cadmium discharged from municipal waste incineration plants (P
b content 20000 mg / Kg, Cd 120 mg / K
g, 1.8 g against 30 g of untreated pH 6.6 (pH of the extract according to the Environmental Agency Notification No. 13 method, the same applies hereinafter))
Kneading is performed by adding iron powder and 18 g of water at 20 ° C.
I was allowed to cure for one day. Then, in order to investigate the detoxification effect when using this treated material, 20 g of the treated product was added to 400 ml of acetic acid solution (pH
The mixture was shaken at 4.9) for 3 hours, and the elution concentrations of lead and cadmium were measured. The experimental results at this time are shown in Table 1 below. From the results of Table 1, iron powder stabilizes lead,
It can be seen that the concentration of cadmium is also decreasing.

[0028]

[Table 1]

(Example 2) 40 parts by weight of iron powder (manufactured by Wako Pure Chemical Industries, Ltd.) was mixed with 60 parts by weight of porous silicon dioxide (specific surface area 250 m ² / g) to prepare the waste treatment material 1 of the present invention. Obtained. As a comparative example, early strength cement was prepared. Fly ash containing a large amount of lead discharged from an municipal waste incineration plant (Lead elution amount of 36 mg without treatment under the Environmental Agency Notification No. 13 method)
/ L, pH 12.08) 0.9 g (3
(Part by weight) the above treated material and 18 g of water were added and kneading was performed, and the mixture was cured at 20 ° C. for 1 day. Then, as a method for estimating the stability when a treated product treated with these treating materials was left for a long period of time, an extraction test under an acidic extract was carried out with reference to the TCLP method in the United States. That is, the waste material is dried and then passed through a mesh having a mesh of 5.0 mm. To 10 g of this treated product, 500 ml of an acetic acid aqueous solution adjusted to pH 4.9 is added and shaken for 20 hours. After shaking, the solid-liquid was separated and the lead concentration was measured. As a comparative example, 0.9 g (3 parts by weight) of cement alone was added and the same treatment was performed. The results are shown in Table 2 below. In addition, Table 2 also shows the lead elution amount according to the Environmental Agency Notification No. 13 method.

[0030]

[Table 2]

From the experimental results shown in Table 2, the waste treatment material of the present invention in which iron powder and porous silicon dioxide are used together stabilizes heavy metals even in an acidic extract as compared with the case of using cement alone. It can be seen that the effect is excellent.

(Example 3) 17.3 parts by weight of iron powder (manufactured by Wako Pure Chemical Industries, Ltd.) was mixed with 83.3 parts by weight of aluminum sludge to obtain a waste treatment material 2 of the present invention. Fly ash containing a large amount of lead discharged from an municipal waste incineration plant (Lead elution amount of 32 mg / L, p without treatment under the Environmental Agency Notification No. 13 method)
30 parts by weight (9 g) of treatment material 2 and 29 g of water were added to 30 g of H12.42), and the mixture was kneaded and cured at 20 ° C. for 1 day. Further, as Comparative Example 4, 25 parts by weight of aluminum sludge (7.5 g) and 29 parts of water were added to 30 g of fly ash.
g was added and kneading was performed. After curing these at 20 ° C. for 1 day, an extraction test according to the Environmental Agency Notification No. 13 method was conducted. The results are shown in Table 3 below.

[0033]

[Table 3]

From the experimental results in Table 3, p of aluminum sludge was determined.
Although the amount of lead elution can be reduced by the H reduction effect, the lead stability performance is improved by further adding iron powder thereto. Thus, iron has a stabilizing effect on lead even under highly alkaline conditions.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C02F 11/00 101 B09B 3/00 304K

Claims (7)

[Claims] 1. A waste treatment material comprising at least one selected from the group consisting of iron powder, amorphous aluminum hydroxide, silicon dioxide, silicates and phosphates. 2. A waste treatment material comprising iron powder and at least one selected from the group consisting of amorphous aluminum hydroxide, silicon dioxide, silicates and phosphates. 3. A waste treatment material comprising iron powder to which amorphous aluminum hydroxide and a phosphate are added. 4. The silicon dioxide or silicate is BE
The waste treatment material according to claim 1, which is a porous silicon dioxide or aluminum silicate having a T specific surface area of 150 m ² / g or more and less than 1000 m ² / g. 5. The waste treatment material according to claim 1, wherein the phosphate is at least one selected from the group consisting of magnesium salt, aluminum salt, calcium salt, and iron salt. 6. The waste treatment material according to claim 1, wherein the waste treatment material contains at least one harmful substance selected from the group consisting of lead, cadmium, mercury, chromium, copper, and nickel. A waste treatment method, which comprises mixing together with water, kneading the mixture with water added if necessary, and curing and solidifying. 7. The waste treatment method according to claim 6, wherein the waste is incinerated ash of municipal solid waste, slag, soil, sludge, or shredder dust.