JPH1028954A - Waste treatment method and waste treatment material - Google Patents

Abstract

(57) [Problem] To provide a waste treatment method and a treatment material capable of stabilizing harmful heavy metals contained in alkaline incineration dust discharged from an incinerator so as not to be eluted again. SOLUTION: Waste glass containing harmful metals such as lead, cadmium, mercury, chromium, copper, nickel, zinc, etc. is incompatible with water glass and a specific surface area of 450 to 600 m ^2.
/ G of a powdery aluminum silicate having a weight ratio of the solid content of water glass to the solid content of aluminum silicate in the range of 20:80 to 80:20 is added, mixed and kneaded. Is cured at 40 ° C. or more and 100 ° C. or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art At present, about 48 million tons (19
(1988) General waste and about 310 million tons (1985)
Industrial waste is being discharged. This is also the year 2
In 2000, municipal waste is expected to reach about 80 million tons and industrial waste to reach about 600 million tons. Of this, about 70% of general waste is incinerated and about 20% is directly disposed of. In addition, about 40% of industrial waste is recycled, and about 30% is reduced in volume by incineration and disposed of.
About 30% are directly disposed of at final disposal sites. These incinerated municipal and industrial wastes contain a large amount of harmful heavy metals, and the regulations for disposal are going to be greatly strengthened.

For example, in the case of a municipal waste treatment plant, cadmium (Cd), lead (Pb), chromium (Cr), and mercury (H) are included in color-printed paper and cellophane contained in the garbage.
g), plastics such as copper (Cu), etc., contain cadmium, lead, zinc (Zn), chromium, mercury, and the like. By incineration of these, ash containing concentrated heavy metals is generated. In garbage incineration plants, this ash is often collected separately as main ash made of refuse moire and incinerated dust collected by a bag filter or the like.
Both the main ash and the incinerated dust contain heavy metals, but heavy metals are particularly easy to elute in the incinerated dust.

That is, in a garbage incineration plant, slaked lime or quick lime is blown in the exhaust path in order to capture hydrogen chloride gas generated during incineration. Since these are combined with hydrogen chloride gas to form calcium chloride, the concentration of hydrogen chloride gas in exhaust gas can be reduced. However, since unreacted slaked lime and quick lime remain in the incinerated dust, the incinerated dust becomes highly alkaline with a pH of 12 or more. If the incineration dust contains a high concentration of lead, this lead has the property of becoming water-soluble as a plumbate under high alkalinity, so that lead is eluted when the ash is discarded without being treated. Therefore, in the incineration plant, in order to prevent harmful metals from being eluted, incineration dust is mixed with cement, kneaded by adding water, then cured and solidified and disposed of, or mixed with main ash for landfill. However, since cement is alkaline, when a large amount of cement is added to such incinerated dust, elution of lead is not suppressed. According to the revised Waste Management and Public Cleansing Law enforced in April 1995, the regulated value of the amount of lead eluted is one-tenth of the conventional value.
It has been found that it is almost impossible to satisfy this regulation value only with cement. As described above, the conventional treatment method of simply solidifying with cement has various problems, and secondary pollution may occur unless the use is limited.

As described above, at present, there are problems with the processing materials and processing methods, and in addition, the shortage of land-based landfill sites in Japan has begun to cause a problem. There has been a demand for a processing method capable of stably stabilizing heavy metals so as not to elute.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a waste disposal method effective for stabilizing waste containing such harmful heavy metals.
In particular, the present invention provides a waste treatment method capable of stabilizing harmful heavy metals and the like contained in alkaline incineration dust discharged from municipal garbage incinerators and industrial waste incinerators as described above so that they do not elute again. And a processing material.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve such a problem, and as a result, by adding water glass and powdery aluminum silicate, harmful heavy metals in wastes were added. Was found to be stabilized, and a processing method capable of achieving this object was obtained. According to the method of the present invention, elution of heavy metals such as lead from the solidified waste material-processing material is drastically suppressed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a waste treatment method and a treatment material according to the present invention will be described in detail. First, the water glass used in the present invention will be described in detail. The water glass used in the present invention may be a general-purpose water glass. The composition of water glass is generally M ₂ O · nSiO
₂ (where M is a cation of water glass) and examples of the cation (alkali component) include Na and K. However, from the viewpoint of industrial availability and price, the cation is N
The water glass of a, that is, sodium silicate is preferred. Further, the ratio of M ₂ O to SiO ₂ , that is, n, is approximately in the range of n = 0.5 to 4. Since it is industrially easily available and inexpensive, it is an aqueous solution of n = 1 to 4. Is preferred. In addition, there is no problem even if the water glass used in the present invention contains unavoidable impurities such as iron. As the water glass, specifically, sodium silicate No. 1,
No. 2, No. 3, No. 4, sodium metasilicate, and sodium orthosilicate. The data for these water glasses are shown in Table 1 below. Here, in the case of sodium metasilicate, crystals easily precipitate in a liquid, and therefore, commercially available ones are handled as powders. Therefore, care must be taken so that sodium metasilicate does not precipitate when used.

[0009]

[Table 1]

Next, the aluminum silicate used in the present invention will be described in detail. Aluminum silicate is mainly composed of SiO ₂ and Al ₂ O ₃ , and natural aluminum silicate such as pumice, fly ash, kaolin, talc, bentonite, activated clay, diatomaceous earth, zeolite, etc. Are known. Table 2 shows the compositions of various aluminum silicates.

[0011]

[Table 2]

The aluminum silicate used in the present invention is in a powder form. Known types of aluminum silicate, such as crystalline, amorphous, amorphous, glassy, etc., can be used here as long as they are in powder form. Further, a drying process or a firing process may be performed. However, the aluminum silicate used in the present invention is not a zeolite used for a molecular sieve. That is, in such a zeolite, most of its specific surface area is distributed in a range of a pore size of 1 nm or less, and only molecules smaller than the pore size are adsorbed in a limited manner. However, such fine pores adsorb solvent molecules in the solution, and even trace amounts of water even in the air, without any gaps, so that heavy metal ions such as eluted lead may be adsorbed. However, even if the specific surface area is large, sufficient heavy metal stabilizing ability cannot be obtained. The ionic radius of a heavy metal greatly differs depending on its type, and the ionic radius further increases by coordinating with a large number of ions present in the waste to form a complex ion. Therefore, it is desirable that the surface area of the aluminum silicate used in the present invention is distributed over a wide range of pore diameters, not in a narrow range of pore size distribution like zeolite. The aluminum silicate used in the present invention is not a so-called pozzolanic substance such as fly ash or incinerator ash, and does not include activated clay having a low specific surface area, kaolin clay, diatomaceous earth, and limestone. As such aluminum silicate, there are synthetic products and natural products, and any of them can be used. Examples of the synthetic aluminum silicate include a synthetic aluminum silicate obtained by adding a soluble aluminum salt to a sodium silicate solution. In the case where the treatment material is prepared and stored in advance, it is preferable that the treatment material is anhydrous or has sufficient moisture removed in order not to promote deterioration due to moisture absorption of other additives such as cements. .

The aluminum silicate used in the present invention preferably has a large specific surface area. When a solid is subdivided into a powder, it exhibits physical and chemical peculiar properties. It is considered that a large part of the cause is due to the effect of the particle surface. In order to investigate such surface properties, it is better to know the sum of the surface areas of all particles contained in a unit amount of powder, that is, the specific surface area, than to examine the size and distribution of individual particles. The measurement of the specific surface area is described in a compendium ("Powder Physical Properties Illustration" edited by Japan Powder Industry Association, 19
75, Powder Engineering Research Group), the gas adsorption method (B
The ET method, the Harkins-Jura relative method), the liquid phase adsorption method, the immersion heat method (the Harkins-Jura absolute method), and the transmission method (Brain method) are known, but they are obtained by different measurement principles. The meaning of the results is not always the same. The specific surface area referred to in the method of the present invention is the above-mentioned BET.
The value is based on the surface area method.

In the present invention, as the specific surface area of the aluminum silicate used increases, the ability to stabilize heavy metals in the waste increases. In addition, when used in combination with water glass, the stabilization performance of heavy metals is improved more than when water glass is used alone. Therefore, when water glass and powdered aluminum silicate are used together as in the present invention, the total weight of the treatment material used is reduced as compared with the case where water glass is used alone. On the other hand, when the specific surface area of aluminum silicate is increased, harmful heavy metals are stabilized and no longer eluted.However, when the specific surface area is too large, the bulk specific gravity decreases and handling becomes difficult when mixing with waste. In addition, as the bulk density decreases, the capacity increases and large tanks must be installed in the waste storage facility. Therefore, the specific surface area of the powdery aluminum silicate used in the present invention is preferably 450 m ² / g or more and 600 m ² / g or less, and the bulk specific gravity is preferably 0.1 or more.
As such a powdery aluminum silicate,
For example, “Kyoword 700PEL” manufactured by Kyowa Chemical Co., Ltd.
(Specific surface area: 500 m ² / g). However, the aluminum silicate used in the present invention is not limited to this.

Next, the mixing ratio of the water glass and the aluminum silicate is approximately 20:80 to 8 by the weight ratio of the solid content of the water glass to the solid content of the aluminum silicate.
Preferably, the ratio is 0:20. When the mixing ratio of water glass is less than 20 parts by weight in terms of solid content, the improvement in performance due to the addition of water glass becomes unclear. When the mixing ratio of the water glass exceeds 80 parts by weight, the performance improvement due to the addition of aluminum silicate becomes unclear. The reason why a more preferable mixing ratio cannot be specified is that the mixing ratio varies depending on the type of the applied waste. For this reason, as a function of water glass, it is believed that the reaction of water glass with divalent metal ions in waste, for example, calcium ions, forms a water glass gel, which stabilizes heavy metals, and therefore, It is considered that the action of water glass is affected by the type and amount of the divalent metal ion in the waste, and the optimum compounding ratio varies depending on the type of the waste.

In the method for treating waste according to the present invention,
Curing the waste and the treatment material after kneading is an extremely effective means for sufficiently exhibiting the effect of the treatment material. This is because the processing material component and the waste component come into contact with each other by mixing and kneading, so that the reaction starts instantaneously and many effects of the processing material are exhibited, but the reaction gradually progresses thereafter. Probably suggestive.

The curing temperature depends on the heavy metal content of the waste, the amount of harmful metals eluted from the waste in the case of no treatment, and the target allowable amount of elution, for example, the amount of treated waste. It depends on the legal and regulatory values applied to the place where solids with the treated material are discarded. In general, when the curing temperature is lower than 40 ° C., since the harmful metal stabilizing performance of the treated material is low, it is preferable to cure at a temperature of 40 ° C. or higher. By setting the curing temperature to a higher temperature, the ability to stabilize harmful metals and the like is improved. However, when cured at a temperature exceeding 100 ° C., the moisture in the kneaded material evaporates rapidly, and the moisture for sufficiently solidifying is lost, so that the harmful metal stabilizing performance of the treated material may be significantly reduced. Not only is there
The treated material after curing becomes lumpy, and the treated material containing harmful metals may be scattered during transportation and the like, thereby contaminating the surrounding environment. Therefore, curing at a temperature exceeding 100 ° C. is not preferable. For the above reasons, the temperature for curing the kneaded material of waste and treatment material is 40 ° C.
The temperature is preferably from 100 ° C to 100 ° C. Also, considering that the working conditions are deteriorated by heating more than necessary, the curing temperature is preferably 40 ° C. or more and 80 ° C. or less.

The waste treatment method of the present invention as described above
This is also effective in a case where a place for curing the treated waste is not sufficiently secured in the waste disposal site. That is, according to the present invention, the curing time can be reduced by curing the kneaded material obtained by kneading the waste material and the treatment material at a predetermined temperature, and the treated material can be quickly solidified and discarded. .

Further, waste treatment plants, particularly intermediate treatment plants for waste incineration dust, are often provided in conjunction with waste incineration plants. Generally, in these incineration plants, heat generated during waste incineration is generally used. Is recovered as steam in a heat exchanger or the like, and furthermore, in some cases, power generation is performed using the steam. In the waste treatment method according to the present invention, the heat source for curing the mixture obtained by kneading the waste and the treatment material, the steam collected by the heat exchanger of the incineration plant as described above, and using this steam If the obtained electric power is utilized, energy can be used efficiently and it is industrially useful.

In the method of mixing aluminum silicate and water glass in the present treatment method, the two components may be mixed before mixing with the waste treatment material to mix the mixture with the waste material, The individual components may be stored separately until use and may be separately mixed with the waste.

Next, a method for treating waste with the treatment material of the present invention will be described. The treatment material of the present invention is characterized in that it is added to waste, and if necessary, water-kneaded material is kneaded and cured and solidified. As a preferred embodiment of the present invention, waste such as dust and incineration dust collected in a hopper is mixed with the above-mentioned waste treatment material from another hopper or a tank, and water is added thereto as necessary. In addition, they are sufficiently kneaded and extruded in a shaping apparatus.

The mechanism of stabilizing harmful heavy metals by the treatment method using a treatment material in which aluminum silicate and water glass are combined according to the present invention is not clear. However, it is considered that aluminum silicate promotes gelation of water glass as a solid acid, and as a result, the action of confining harmful metals by water glass is promoted. It is not clear why aluminum silicate is particularly preferable among solid acids, but it is presumed that gelation is particularly promoted due to its large surface area.

As the waste to which the treatment method and treatment material of the present invention can be applied, incineration ash, mine tailings, soil, and sludge of municipal waste and industrial waste are suitable. Incinerated ash includes main ash and incinerated dust. Incineration dust is a collection of dust and soot generated from incineration of municipal garbage and industrial waste, and dust and soot generated from a melting furnace.EP ash collected by an electric dust collector, Bag ash collected by bag filters and the like can be mentioned. In the present invention, the incinerated dust obtained in this manner is a target. On the other hand, main ash is ash discharged from the lower part of the incinerator at incinerators for municipal garbage and industrial waste, and includes harmful heavy metals. further,
In the present invention, sludge discharged from a mine, stabilization of heavy metals in soil contaminated with heavy metals and the like, and sludge containing heavy metals generated by wastewater treatment are also targeted.
Hazardous heavy metals can stabilize lead, cadmium, mercury, chromium, copper, nickel and zinc.

[0024]

EFFECT OF THE INVENTION By using the waste treatment material of the present invention, main ash or incineration dust discharged from incinerators of municipal garbage and industrial waste containing harmful heavy metals, or tailings, sludge,
Alternatively, when soil contaminated with heavy metals is treated, harmful heavy metals are efficiently stabilized and the amount of elution is reduced. In particular, EP discharged from incinerators for municipal waste and industrial waste
It is very effective in stabilizing incinerated dust such as ash and bag ash (especially highly alkaline EP ash and bag ash blown with slaked lime and quick lime). Hazardous heavy metals can stabilize lead, cadmium, mercury, chromium, copper, nickel, zinc and the like. In other words, by using the waste treatment material of the present invention, industrial waste containing harmful heavy metals, slurry sludge or dewatered cake sludge discharged after treatment of various waste liquids such as semiconductor factories and plating plants, or steel mills Stable harmful metals, such as harmful dust collected for work environment preservation in workplaces such as electric melting kilns, dust from municipal waste melting furnaces, and contaminated soil from landfill dumping And the amount of elution is suppressed.

[0025]

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

Example 1 In this example, as the aluminum silicate 1, a synthetic product “Kyoward 700PEL” (specific surface area 500 m ² / g) manufactured by Kyowa Chemical Industry Co., Ltd. was used. Further, sodium silicate No. 1 was used as sodium silicate. 50 g of incinerated dust containing a large amount of lead (heavy metal content: 1510 mg) discharged from an incineration plant
/ L), various samples (additives) shown in Table 3 below, and 30 g of water are put into a mortar and mixed well. Then 80 ° C
For 20 hours and passed through a 100-mesh sieve to obtain a sample. 20 g of the sample and 150 ml of pure water were added to 20
Pour into a 0 ml Erlenmeyer flask, shake at 37 ° C. for 2 hours, centrifuge, take 50 ml of the supernatant, concentrate hydrochloric acid,
Nitric acid was added in an amount of 5 ml each, concentrated by boiling for 10 minutes, and the lead concentration was determined by atomic absorption. The results are shown in Table 3.

[0027]

[Table 3]

When the results of Examples 1-1 to 1-3 shown in Table 3 are compared with Comparative Examples 1-1 to 6, the amount of lead eluted by adding 10% by weight of the waste treatment material of the present invention to the waste. Is lower than the lead elution amount when aluminum silicate or sodium silicate No. 1 is added alone.

(Example 2) In this example, as the aluminum silicate 1, a product manufactured by Kyowa Chemical Co., Ltd., "Kyoward 700PEL" (specific surface area: 500 m ² / g)
Were used as the aluminum silicates 2 and 3, having a specific surface area of 250 and 400 m ² / g. Further, sodium silicate No. 1 was used as sodium silicate.
50 g of incineration dust containing a large amount of lead (heavy metal content: 1100 mg / L) discharged from the municipal waste incineration plant,
Various samples (additives) and 30 g of water shown in Table 4 below are put into a mortar and mixed well. Then, at 45 ° C or 2
Cured at 0 ° C. for 20 hours and passed through a 100-mesh sieve to obtain a sample. 20 g of the above sample and 150 ml of pure water
Was poured into a 200 ml Erlenmeyer flask, shaken at 37 ° C. for 2 hours, centrifuged, and 50 ml of the supernatant was taken. 5 ml each of concentrated hydrochloric acid and nitric acid was added, and the mixture was concentrated by boiling for 10 minutes. The concentration was quantified. Table 4 shows the results
It was shown to.

[0030]

[Table 4]

When the results of Example 2-1 shown in Table 4 are compared with Comparative Examples 2-1 and 2, the lead stabilizing performance of the waste treatment material of the present invention increases as the specific surface area of aluminum silicate increases. It turns out that it improves. In addition, it is understood that the lead stabilization performance is further improved by increasing the curing temperature.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location C02F 11/00 B09B 3/00 ZAB 301S ZAB 304A 304K (72) Inventor Masakazu Kamikita Kobe City, Hyogo Prefecture 5-51-401, Takaba-cho, Nada-ku (72) Inventor Kazuhiro Hara 20-6, Nakatsu-cho, Ibaraki-shi, Osaka (72) Inventor Takafumi Suzuki 5006-243, Shido-cho, Shido-cho, Okawa-gun, Kagawa Prefecture (72) Inventor Hisae Sobue 81-2, Kobutsuyamacho, Takamatsu City, Kagawa Prefecture

Claims (10)

[Claims] 1. A waste glass containing at least one harmful metal selected from the group consisting of lead, cadmium, mercury, chromium, copper, nickel, and zinc has a water glass and a specific surface area of 450 to 600 m ² / g. A waste treatment method, comprising mixing and kneading the powdered aluminum silicate. 2. A waste glass containing at least one harmful metal selected from the group consisting of lead, cadmium, mercury, chromium, copper, nickel and zinc, water glass and a specific surface area of 450 to 600 m ² / g. A powdery aluminum silicate and water are mixed and kneaded. 3. The main constituent of the water glass is SiO ₂ /
The waste disposal method according to claim 1 or _{2, wherein the} composition is water glass having an M ₂ O composition ratio of 4.0 or less (where M is a cation of water glass). 4. The water glass is sodium silicate No. 1, No. 2,
The waste treatment method according to any one of claims 1 to 3, wherein the waste is a sodium metasilicate or a sodium orthosilicate. 5. The waste disposal method according to claim 1, wherein a weight ratio of the solid content of the water glass to the solid content of the aluminum silicate is 20:80 to 80:20. 6. The waste treatment method according to claim 1, wherein the waste, water glass, and aluminum silicate are mixed, kneaded, and then cured. 7. The method for treating waste according to claim 6, wherein the curing temperature is 40 ° C. or higher and 100 ° C. or lower. 8. The incinerated ash such as incinerated dust, main ash, and molten dust, or the incinerated ash of industrial waste,
The waste treatment method according to any one of claims 1 to 7, wherein the method is slag, soil, or sludge. 9. The waste disposal method according to claim 8, wherein said incinerated ash is incinerated dust having a high alkalinity. 10. A water glass solution having a specific surface area of 450 to
A waste treatment material comprising a powdery aluminum silicate of 600 m ² / g, wherein a weight ratio of the solid content of the water glass solution to the solid content of the aluminum silicate is in a range of 20:80 to 80:20. .