JPH09285773A - Waste treatment agent and treatment method - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To stabilize wastes containing harmful heavy metals and the like, particularly harmful heavy metals contained in alkaline fly ash discharged from an incinerator for municipal solid waste, so as not to be eluted again. SOLUTION: A waste treatment agent containing an alkali metal silicate such as water glass and an oxidizing agent aqueous solution such as hydrogen peroxide or hydrogen peroxide or a water-soluble oxidizing agent as a main component and containing a heavy metal. 3 for 100 parts by weight of municipal waste incineration ash
˜30 parts by weight, and if necessary, water is added and kneaded, and preferably, the water glass is 9% by weight or more and 38.5% by weight or less in terms of sodium silicate solid content.
Hydrogen peroxide is 0.45 wt% or more and 22.5 wt% 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 agent and a treatment method effective for stabilizing treatment of wastes containing harmful heavy metals and the like.

[0002]

2. Description of the Related Art Today, in Japan, about 48 million tons (19
1988) general waste and about 310 million tons (1985)
(Year) industrial waste is discharged. By the year 2000, it is predicted that general waste will reach about 80 million tons and industrial waste will reach about 600 million tons. Of this, about 70% of general waste is incinerated and about 20% is directly disposed of. About 40% of industrial waste is recycled and about 3%
About 30% is directly disposed of at the final disposal site by reducing the volume by incineration. 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 an urban waste treatment plant, cadmium (Cd), lead (Pb), chromium (Cr), mercury (H) are contained in the color-printed paper and cellophane contained in the waste.
g), arsenic (As), copper (Cu), and other plastics contain cadmium, lead, zinc (Zn), chromium, mercury, arsenic, etc. A concentrated ash is obtained. At the incineration site, it is becoming more common to collect this ash by dividing it into main ash, which is made up of dust and refuse, and fly ash, which is collected by a bag filter or the like. Heavy metals are contained in both the main ash and the fly ash, but the heavy metals are particularly easily eluted in the fly ash. At the incinerator, slaked lime or quick lime is blown in the middle of the exhaust route to capture hydrogen chloride gas generated during incineration. Since these combine with hydrochloric acid gas to form calcium chloride, the concentration of hydrochloric acid gas in the exhaust gas can be reduced. However, since unreacted slaked lime and quick lime in the exhaust gas remain in the fly ash, the fly ash becomes highly alkaline with a pH of 12 or more. Fly ash contains a high concentration of lead, and this lead has the property of being water-soluble as a lead acid salt in a highly alkaline environment. Therefore, if the ash is untreated, lead will be eluted. At the incineration plant, fly ash is mixed with cement, mixed with water and kneaded, then cured and solidified for disposal or landfilled with main ash for the purpose of solidifying the waste and preventing elution of harmful metals. ing. However, since cement is alkaline, when a large amount of cement is added to such fly ash, the elution of lead is not suppressed. Therefore, the conventional treatment method of simply solidifying with cement has various problems, and secondary pollution may occur unless the application is limited.

Although a chelating agent has been experimentally used for fly ash treatment, 6% or more based on the weight of fly ash is not added to fly ash having a particularly high alkali content and a high lead content. And some things are not suppressed below the regulation value. In general,
The unit price of such a chelating agent is 50 times to 8 times that of cement.
Since it is 0 times as expensive, it is considered to be a heavy burden in terms of running cost.

As described above, it has been found that there are various problems in the stabilization treatment of heavy metals in wastes using the conventional cement and chelating agent. In addition, the shortage of landfill landfill sites in Japan is beginning to become a problem, and with the addition of a small amount of treatment agent, a treatment agent that can strongly stabilize harmful heavy metals in waste so as not to be re-eluted. A treatment method was desired.

[0006]

DISCLOSURE OF THE INVENTION The present invention is to provide a waste treatment agent effective for stabilizing treatment of wastes containing such harmful heavy metals. In particular, the present invention aims to provide a waste treatment agent capable of stabilizing harmful heavy metals contained in alkaline fly ash discharged from an incinerator so as not to be eluted again as described above. It is what

[0007]

Means for Solving the Problems As a result of intensive studies to solve such problems, the present inventors have obtained a waste treatment agent which can achieve this object. That is, the treatment agent of the present invention is a silicate of an alkali metal such as water glass,
A waste treatment agent characterized by being used in combination with an oxidizing agent such as hydrogen peroxide.

[0008]

The mechanism of the present invention will be described. The mechanism of action of the present invention is not always clear. However, it is believed that the treatment agent of the present invention can stabilize heavy metals in wastes by the combined effect of several mechanisms.

First, in alkali metal silicates such as water glass, the free silicate ions directly react with polyvalent metal ions such as heavy metals to stabilize the heavy metals. In addition, alkali metal silicates such as water glass react with the polyvalent metal salt and solidify when the waste contains a large amount of polyvalent metal salt such as calcium as in the case of municipal refuse incineration ash. By covering the surface of the waste with this reaction product, the elution of heavy metals can be prevented. Further, the solidified product of the silicate produced as described above is in a gel state, has a high activity, and has a large surface, so that a heavy metal is adsorbed on the surface.

On the other hand, an oxide such as hydrogen peroxide is a free silicate ion of the alkali metal silicate or a silicate solidified product which is a reaction product of the silicate and the polyvalent metal ion in the waste. Activates the surface and promotes reaction with heavy metal ions. Also, since municipal waste incineration ash and the like are alkaline in most cases, a large amount of lead elutes, which is regarded as a problem. It is considered that lead is dissolved as zincate ions in an alkaline solution, and the oxidation number of lead at this time is divalent. Oxides such as hydrogen peroxide oxidize lead in zincate ions,
Since it is tetravalent lead, lead acid is produced. The lead ion is
It also produces insoluble compounds in the alkaline region with many metal ions such as calcium.

The treating agent of the present invention effectively suppresses the elution of heavy metals by the combined effect of the above mechanisms.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The alkali metal silicate used in the present invention will be described in detail. Examples of alkali metal silicates include sodium silicate, potassium silicate, and lithium silicate. From the viewpoints of availability and price, water glass industrially produced in large quantities is desirable. Types of water glass such as ortho, No. 1, No. 2, No. 3, No. 4, and the like are defined by the composition ratio of Na ₂ O and SiO ₂ , and any of these is used as the present invention. However, a mixture thereof may be used. Further, each water glass includes a solution glass and a powder glass. In the present invention, it is preferable to use a solution glass, but a powder glass may be used after being dissolved.

The oxidizing agent used in the present invention will be described.
The oxidizing agent used in this treatment agent is an aqueous solution or water-soluble,
Hydrogen peroxide, hydrogen peroxide water, potassium persulfate, sodium persulfate, ammonium persulfate, perchloric acid, sodium perchlorate, sodium chlorite, sodium peroxide, coconut powder, advanced coconut powder, potassium permanganate, etc. Is mentioned. Among these oxidizing agents, hydrogen peroxide, hydrogen peroxide solution, and sodium peroxide are preferable from the viewpoint of safety and stability.

Next, a method for producing the waste treatment agent according to the present invention will be described. The treatment agent may be prepared by mixing the respective components in advance, mixing the respective components at the time of use, or adding the respective components simultaneously to the waste. Further, when the waste is treated, the cement, the chelating agent and other treating agent components, and the waste may all be mixed at the same time, and there is no particular limitation on the mixing method or order.

The content of each component in the treating agent varies depending on the fly ash to be used. Industrial products of water glass and hydrogen peroxide water are available in various concentrations. Therefore, the content of each component is expressed by the concentration of solid content for silicates and the concentration of hydrogen peroxide for hydrogen peroxide. As the content of hydrogen peroxide, the effect is exhibited even in a very small amount, but considering the stability of the product and the like, the hydrogen peroxide concentration is preferably 0.45% by weight or more. Further, when the content of hydrogen peroxide is too large, oxygen is generated and bubbles occur, so that it is preferably 22.5% by weight or less. The silicate content is preferably 9% by weight or more, because if the amount is too small, a sufficient effect cannot be obtained. On the other hand, if the concentration of silicates is too high, the viscosity of the treating agent becomes too high, so the solid content concentration of No. 3 water glass is preferably 38.5% by weight or less.
Further, when it is necessary to adjust the pH, an acid agent such as aluminum sulfate, sulfuric acid, phosphoric acid, hydrochloric acid or magnesium sulfate may be added. Also, such as phosphates and carbonates,
It is also possible to further add an additive that stabilizes the heavy metal by another mechanism. Therefore, there is no particular limitation on the mixing ratio of each component.

Next, a method of treating waste with the treating agent of the present invention will be described. The treatment method of the present invention is characterized in that the treatment agent as described above is added to waste, and water is added as necessary to knead. In a preferred embodiment of the present invention, the waste treatment agent supplied from the chemical tank is mixed with wastes such as dust and fly ash collected in the hopper, and water is added to the waste treatment agent as necessary. In addition, it is sufficiently kneaded in the shaping device and extruded. In general, in a conventional treatment method using cement, 10 to 30 parts by weight of cement is added to 100 parts by weight of waste and kneading is performed.
This is because it is not realistic to add 30 parts by weight or more of the treating agent from the viewpoint of reducing the volume of the treated material. When the treatment agent of the present invention is used, superior performance is obtained as compared with the case where the same amount of cement is added. Therefore, for example, when a heavy metal stabilizing ability 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, in the conventional cement, even if 30 parts by weight is added, the stabilization of heavy metals is often insufficient. In such a case,
By adding the same amount of the treatment agent of the present invention as in the case of cement,
A stronger heavy metal stabilizing effect can be expected. As described above, the amount of the present treatment agent added to fly ash is preferably 30 parts by weight or less from the viewpoint of reducing the volume of the treated material. Even in the same incinerator, the Pb content of the material to be treated changes greatly, so from the viewpoint of stably producing the effect of the treating agent, add 3 parts by weight or more of this treating agent to the waste. Is desirable.

[0017]

INDUSTRIAL APPLICABILITY By using the waste treatment agent of the present invention, EP ash or 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. Or bug ash), harmful heavy metals,
In particular, Pb is efficiently stabilized and the elution amount is reduced, which is very effective for stabilization treatment. Lead in harmful heavy metals,
It can stabilize cadmium, mercury, chromium, copper, nickel, zinc, etc. Further, by using the waste treatment agent of the present invention, it is possible to treat industrial treatment products containing high concentrations of copper, mercury, etc. discharged from semiconductor factories and plating factories. For example, sludge-like sludge and dewatered cake sludge discharged after processing various waste liquids such as semiconductor factories and plating factories, or harmful dust collection dust for the work environment conservation in the workplace such as electric furnace melting furnaces in steel mills, Fly ash from a municipal refuse melting furnace or contaminated soil from landfill disposal can be stabilized, and harmful heavy metals are stabilized and the amount of elution is suppressed.

[0018]

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) No. 3 water glass solution (solid content concentration: 38.5% by weight) and hydrogen peroxide solution (concentration: 30% by weight) were mixed, and a treating agent 1 as shown in Table 1 was prepared. 1 to 1-
3 was produced. Further, a water glass solution alone and a hydrogen peroxide solution alone were used as Comparative Agents 1-1 and 1-2. Table 1 also shows the calculated values of the solid content concentration (% by weight) of water glass and the hydrogen peroxide concentration (% by weight) contained in the treatment agent as the concentration of the active ingredient in the treatment agent. Indicated.

[0020]

[Table 1]

Incineration fly ash containing a large amount of lead discharged from an urban refuse incineration plant
Elution amount of Pb by method No. 100 mg / L, pH of eluate 1
2.02) 30 g of the above treating agents 1-1 to 1
-3, or 6 g of comparative agents 1-1 and 1-2 (20 parts by weight for fly ash) and 9 g of water (30 parts by weight for fly ash)
Was added and kneaded well. The kneaded product was aged at 20 ° C. for 7 days, then crushed, and the Pb elution amount and the pH of the eluate were measured by the Environmental Agency Notification No. 13 method. The results are shown in Table 2.
Shown in

[0022]

[Table 2]

As is clear from the results shown in Table 2, as compared with the comparative example in which the water glass solution or the hydrogen peroxide solution was used alone, the present treatment agent in which the water glass solution and the hydrogen peroxide solution were mixed was Also, the Pb concentration can be kept low.
That is, this result indicates that a synergistic effect can be obtained by using water glass and hydrogen peroxide in combination.

(Example 2) No. 3 water glass solution (solid content concentration: 38.5% by weight) and hydrogen peroxide solution (concentration: 30% by weight) were mixed, and a treating agent 2 as shown in Table 3 was prepared. 1 to 2-
3 was produced. Further, the water glass solution alone was used as the comparative agent 2-1. In addition, in Table 3, as the concentration of the active ingredient in the treating agent, the solid content concentration (wt%) of water glass and the concentration of hydrogen peroxide (wt%) contained in the treating agent are shown.
The calculated value is also shown.

[0025]

[Table 3]

Incinerated fly ash containing a large amount of lead discharged from an urban refuse incinerator (Environmental Agency Notification 13 without treatment)
Elution amount of Pb by method No. 100 mg / L, pH of eluate 1
2.02) To 30 g, the treating agents 2-1 to 2-3 or the comparative agent 2-1 in the amounts shown in Table 4 and 9 g of water (30 parts by weight with respect to fly ash) were added, Kneaded After curing the kneaded material at 20 ° C for 7 days, it is crushed and notified by the Environment Agency 1
The amount of Pb eluted and the pH of the eluate were measured by Method 3. The results are shown in Table 4.

[0027]

[Table 4]

As is clear from the results shown in Table 4, as compared with the comparative example in which the No. 3 water glass solution was used alone, all the present treatment agents prepared by mixing the water glass solution with hydrogen peroxide water were used. The Pb concentration can be kept low. That is, this result indicates that a synergistic effect can be obtained by adding a small amount of hydrogen peroxide to water glass.

(Example 3) No. 3 water glass solution (solid content concentration: 38.5% by weight) and hydrogen peroxide solution (concentration: 30% by weight) were mixed, and a treating agent 3 as shown in Table 5 was prepared. 1 was produced. Further, the water glass solution alone was used as the comparative agent 3-1. In addition, Table 5 also shows the calculated values of the solid content concentration (% by weight) of water glass and the concentration of hydrogen peroxide (% by weight) contained in the treatment agent as the concentration of the active ingredient in the treatment agent. It was

[0030]

[Table 5]

As shown in Table 6, two types of incineration fly ash containing a large amount of lead, which are discharged from the municipal waste incineration plant 30
18 g of water (60 parts by weight with respect to fly ash) and 18 g of water were added and kneaded well. The kneaded product was aged at 20 ° C. for 7 days, then crushed, and the amount of Pb eluted and the pH of the extract were measured by the Environmental Agency Notification No. 13 method. The results are shown in Table 7.

[0032]

[Table 6]

[0033]

[Table 7]

As is clear from the results shown in Table 7, as compared with the comparative example in which the water glass solution was used alone, all of the present treatment agents in which the water glass solution and the hydrogen peroxide solution were mixed kept the Pb concentration low. I am able to. It can also be seen that the same effect can be seen for different fly ash.

Claims (5)

[Claims] 1. A waste treatment agent comprising an alkali metal silicate and an oxidizing agent aqueous solution or a water-soluble oxidizing agent as main components. 2. The alkali metal silicate is water glass, and the aqueous oxidant solution or the water-soluble oxidant is hydrogen peroxide.
Select from the group consisting of hydrogen peroxide water, potassium persulfate, sodium persulfate, ammonium persulfate, perchloric acid, sodium perchlorate, sodium chlorite, sodium peroxide, coconut powder, advanced coconut powder, and potassium permanganate. The waste treatment agent according to claim 1, wherein the waste treatment agent is at least one. 3. The waste treatment agent according to claim 1, wherein the alkali metal silicate is water glass and the aqueous oxidant solution or the water-soluble oxidant is hydrogen peroxide or hydrogen peroxide solution. . 4. A water glass containing 9% by weight or more and 38.5% by weight or less in terms of sodium silicate solid content, and 0.45% by weight or more and 22.5% by weight or less of hydrogen peroxide. Waste treatment agent according to item 3. 5. The waste treatment agent according to any one of claims 1 to 4,
A waste treatment method, characterized in that 3 to 30 parts by weight are added to 100 parts by weight of municipal waste incineration ash containing a heavy metal, and water is added and kneaded if necessary.