JPH07171541A - Agent and process for fixing heavy metal contained in waste - Google Patents

Abstract

PURPOSE:To fix heavy metals in various kinds of waste in the wide range of pH without generating hydrogen sulfide by using a fixing agent containing at least one kind of a specified quinoline, aminobenzene, dioxime salt and the like or a mixture of two kinds or more as an effective component. CONSTITUTION:Following components not containing sulfur and obtainable at low price are used as the compounds effective for fixing heavy metals in dust and incineration ash. The compounds are selected from sodium, potassium and ammonium salt of a quinoline compound such as 8-hydroxyquinoline, quinoline-8-carboxylic acid, quinoline-2-carboxylic acid, an aminobenzene compound such as o-aminobenzoic acid, m-aminobenzoic acid or p-aminobenzoic acid, and a dioxime compound such as dimethylglyoxime cyclohezanedione dioxime, and at least one kind of them or a mixture of them is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the treatment of fly ash and incineration ash generated from an municipal solid waste incineration plant, and waste such as dust, smoke and incineration ash generated from a metal melting furnace plant, or washing wastewater. Relates to an immobilization treatment agent and a treatment method for preventing heavy metals such as lead, cadmium, chromium, copper and mercury contained in these wastes from being eluted as heavy metal salts.

[0002]

2. Description of the Related Art Municipal solid waste contains various heavy metals such as lead, cadmium, chromium, copper, zinc, mercury, etc., so that the heavy metals are scattered from the waste gas into combustion exhaust gas during the incineration process. Exhaust gases from metal melting furnaces such as electric furnaces and incinerators also contain large amounts of lead, cadmium, copper, chromium, and mercury. These heavy metals scattered in the combustion exhaust gas are collected by an electric dust collector or a bag filter and discharged to the outside of the system. Further, the incinerator ash of the residue burned in the refuse incinerator contains a large amount of the various heavy metals. Usually, the discharged dust fly ash, dust, or incinerated ash is landfilled as it is or after being kneaded and granulated by adding cement, and the flue gas is washed with water to discharge the remainder after separating heavy metals.

[0003]

In the above fly ash, dust and incineration ash, lead is 1000 to 5000 mg / kg, cadmium is 20 to 500 mg / kg, and chromium is 20 to 5 mg.
It contains 00mg / kg, 500-5000mg / kg of copper, and 0.01-10mg / kg of mercury. It is highly possible that a part of it will be eluted into the water after landfill by rainwater and pollute the aquatic environment. . That is, when water is added to fly ash, dust, or incineration ash, the water changes to the alkaline side (pH 7 to 13), and heavy metals other than lead in the waste are extruded as hydroxides, but lead is the lead-lead acid. As it dissolves in water as salt, it elutes in rainwater. Therefore, there is a demand for means for immobilizing lead and heavy metals other than lead in fly ash, dust, and incineration ash so as not to pollute the aquatic environment. As a conventional treating agent for immobilizing heavy metals in fly ash and dust, dimethyldithiocarbamate, polydithiocarbamate, sodium sulfide, thiourea and other compounds having a sulfur or thiol group are used alone or as a mixture. Has been used. However, when these compounds are used, neutral or acidic fly ash,
Hydrogen sulfide is generated when added to dust or incinerated ash. Hydrogen sulfide is an extremely harmful substance, and a large amount of hydrogen sulfide not only adversely affects human health, but also may cause a fatal accident. Further, hydrogen sulfide significantly corrodes the equipment and further produces an offensive odor, so development of a heavy metal immobilization treatment agent that does not contain sulfur is desired.

Furthermore, the conventional treating agents are effective only in the alkaline range of pH 7-13. However, some of the dust in the metal melting furnace has an acidity of pH 4.5 to 7, and conventional treatment agents have no effect on these dusts.
There is a demand for an immobilization treatment agent that is effective even in an acidic pH range. An object of the present invention is to solve the above problems,
By using existing equipment that is relatively widespread and by immobilizing heavy metals such as lead, cadmium, chromium, copper, zinc, and mercury in fly ash, dust, incineration ash, and washing wastewater by a simple method, these Another object of the present invention is to provide an immobilization treatment agent and an immobilization treatment method that prevent the heavy metal of (1) from eluting into water and do not generate sulfide water. In particular, lead dissolves well in water in the alkaline region as the primary lead salt,
The immobilization treatment agent needs to have the ability to chemically react with lead and immobilize it.

[0005]

[Means for Solving the Problems] As a compound used in the immobilization treatment agent of the present invention effective for immobilizing heavy metals in refuse incineration fly ash, dust in a metal melting furnace, and incinerator ash, the chemical structure is sulfur ( The following was taken up that does not include S) and is available at a low price in large quantities. These are 8-hydroxyquinoline (8-oxyquinoline), quinoline-8
-Quinoline compounds such as carboxylic acid and quinoline-2-carboxylic acid, aminobenzene compounds such as o-aminobenzoic acid (anthranilic acid), m-aminobenzoic acid and p-aminobenzoic acid, dimethylglyoxime, cyclohexane It is at least one selected from sodium, potassium and ammonium salts of dioxime compounds such as dione dioxime or a mixture thereof. Of these, 4-hydroxyquinoline, quinoline-8-carboxylic acid, and o-aminobenzoic acid are preferable in terms of price. The above-mentioned immobilization treatment agent can also be effectively used for flue gas and washing wastewater of incineration ash.

[0006]

The various fixing treatment agents of the present invention are used alone or
When seeds or more are mixed and added to wastes such as fly ash, dust, incineration ash, and washing wastewater, they are mixed with heavy metals or heavy metal salts in these wastes by chelate to fix the heavy metals. Prevents outflow to the outside by insolubilizing it in water. Further, the immobilization treatment agent of the present invention can be used in combination with various treatment agents conventionally used for the same purpose to further enhance the effect or facilitate the protrusion of metal salts in an aqueous solution and the coarsening of precipitated particles. ， Can prevent dissolution in water.

[0007]

EXAMPLE 8-Hydroxyquinoline, quinoline-8-carboxylic acid, quinoline-2-carboxylic acid, o-aminobenzoic acid, which is a typical example of an immobilization treatment agent for immobilizing heavy metals in various wastes according to the present invention The chemical structures of acid, dimethylglyoxime and cyclohexanedionedioxime, respectively

[Chemical 1] From

[Chemical 6] Shown in.

[0008]

[Chemical 1]

[0009]

[Chemical 2]

[0010]

[Chemical 3]

[0011]

[Chemical 4]

[0012]

[Chemical 5]

[0013]

[Chemical 6]

8-hydroxyquinoline, quinoline-8-
Carboxylic acid, quinoline-2-carboxylic acid, o-, m- and p-aminobenzoic acid, dimethylglyoxime or cyclohexanedionedioxime sodium salt, potassium salt and / or ammonium salt are eluted in water. It is necessary to add twice or more the number of moles of heavy metal. These immobilizing agents may be used alone or in admixture of two or more,
It is effective for fixing heavy metals in fly ash, dust, incineration ash, and wastewater. As an example, a heavy metal immobilization reaction of 8-hydroxyquinoline was performed.

[Chemical 7] Shown in.

[0015]

[Chemical 7]

Further, the immobilization treatment agent of the present invention is further mixed with an immobilization treatment agent which forms a complex salt with a metal such as dimethyldithiocarbamate or polydithiocarbamate, which has been used for the same purpose, and is further used. The effect can be enhanced. In addition, by combining it with a conventional polymer flocculant such as polyacrylamide, sodium polyacrylate, and guar gum, it is possible to facilitate the protrusion of metal salts and coarsening of precipitated particles in an aqueous solution, and Can be prevented from elution. The method and effect of the present invention will be described in detail with reference to various examples shown below. As Example 1 of the present invention, 8-hydroxyquinoline was added at various concentrations to 50 g of fly ash collected from an electric dust collector of an municipal solid waste incineration plant and 500 ml of water added thereto. After shaking the mixture at 200 times per minute for 6 hours,
Glass fiber with 1 micron diameter-filter paper
The concentrations of lead, cadmium, chromium, and copper in the filtrate filtered in Step 2. were analyzed by plasma emission spectrometry. The analysis results are shown in Table 1. In addition, what was made undetected here means that the detected value is 0.02 mg / l or less. As is clear from the above results, by adding 200 mg / l or more of 8-hydroxyquinoline to water containing fly ash, all of the above elements were not detected, and the elution of these heavy metals could be prevented.

[0017]

[Table 1]

As a second embodiment of the present invention, the electric furnace exhaust gas from a metal refining plant is treated with a bag filter to produce dust.
-Hydroxyquinoline, quinoline-8-carboxylic acid, quinoline-2-carboxylic acid and o-aminobenzoic acid were individually added to investigate the lead elution prevention effect.
In addition, the same test was performed as a comparative example by adding sodium dimethyldithiocarbamate according to the prior art alone. Water (500 ml) was added to the dust (50 g), and the above-mentioned four types of immobilization treatment agents and sodium dimethyldithiocarbamate were added at various concentrations, and a dissolution test was carried out based on the Environmental Agency Notification No. 13. The results of this dissolution test are shown in Table 2.
Shown in. The non-detection determination value is the same as that in the first embodiment. Quinoline-2-carboxylic acid and o-aminobenzoic acid are added at 100 mg / l or more to give 8-hydroxyquinoline and quinoline-8-carboxylic acid at 200 mg.
Addition of 1 / l or more completely prevented the elution of lead from dust, but sodium dimethyldithiocarbamate used in the comparative example was 300 mg / l for preventing elution of lead.
More than 1 liter was required.

[0019]

[Table 2]

As Example 3 of the present invention, in a plant in which municipal solid waste having a population of about 300,000 is incinerated in a fluidized bed incinerator, fly ash removed by an electric dust collector is mixed with 10% of Portland cement. In the process of kneading and granulating with 30% of water, 8-hydroxyquinoline,
The fly ash was granulated by adding 2% by weight of quinoline-2-carboxylic acid or o-aminobenzoic acid to the fly ash. The thus-granulated fly ash was subjected to a dissolution test based on the Environmental Agency Notification No. 13, and the results of the dissolved lead, cadmium and copper concentrations are shown in Table 3. The non-detection determination value is the same as that in the first embodiment. When granulating refuse incineration fly ash by adding cement, by adding 2% by weight of 8-hydroxyquinoline, quinoline-2-carboxylic acid or o-aminobenzoic acid to fly ash, It was possible to prevent the elution of heavy metals from the ash.

[0021]

[Table 3]

As Example 4 of the present invention, 500 ml of water was added to 50 g of dust in a metal refining plant,
Further, nitric acid or sodium hydroxide was added to adjust the pH to 5.0, 7.0 and 13.0, respectively. 8-hydroxyquinoline, o-aminobenzoic acid, dimethylglyoxime, cyclohexanedionedioxime Was added alone to 200 mg / l. This was shaken for 6 hours and then filtered through a glass filter having a pore size of 1 micron to analyze the lead ion concentration in the filtrate. The lead analysis values are shown in Table 4. The non-detection determination value is the same as that in the first embodiment. Among the added immobilization agents of the present invention, 8-hydroxyquinoline is in the neutral to alkaline region, dimethylglyoxime and cyclohexanedionedioxime are in the acidic to neutral region, and o-aminobenzoic acid is all It was possible to prevent the elution of lead in the pH range.

[0023]

[Table 4]

In Example 5 of the present invention, an immobilization treatment agent was added to sodium dimethyldithiocarbamate or sodium methylenebisdithiocarbamate according to the prior art in an amount of 10% by weight or 50% by weight, respectively, and the weight of the incineration fly ash was adjusted to the weight. 2% was added to conduct an elution test to test the effect of preventing elution of lead. The results are shown in Table 5, and for comparison, Table 6 shows the results of the dissolution test when one of the conventional immobilization treatment agent and the immobilization treatment agent of the present invention were added alone. The non-detection determination value is the same as that in the first embodiment. Compared to the analytical value of 22.4 mg / l in the case where the immobilization treatment agent was not added, all the results showed small values and had a sufficient elution prevention effect, and the immobilization treatment agent of the present invention was It was shown that it can be used in combination with the existing treatment agents for fixing heavy metals from fly ash, dust, incineration ash, etc.

[0025]

[Table 5]

[0026]

[Table 6]

As Example 6 of the present invention, the effect of the addition of the immobilization treatment agent of the present invention on the removal of heavy metals contained in the mixed waste water such as the cleaning water of the flue gas of the municipal solid waste incinerator and the waste leachate Was tested. After adding 50 mg / l of dimethylglyoxime, cyclohexanedionedioxime or o-aminobenzoic acid to the waste water and stirring,
After filtering with No. 5 filter paper, the concentrations of cadmium, lead and mercury in the filtrate were analyzed. The test results are shown in Table 7. Cadmium and lead are 0.02 mg / l or less, and mercury is 0.02 mg / l or less.
The amount of 005 mg / l or less was not detected. The results of the tests showed that the addition of the immobilizing agent according to the invention makes it possible to remove heavy metals in the wastewater.

[0028]

[Table 7]

[0029]

The fixing agent of the present invention has the following effects on the treatment of heavy metals contained in the fly ash, dust, incineration ash, and the effluent of washing water for flue gas. 1. Elution of heavy metals can be prevented with a smaller amount than conventional heavy metal immobilization agents. 2. Since the chemical structure of the immobilization treatment agent does not contain sulfur, there is no generation of hydrogen sulfide gas during use, and safe operation can be secured. 3. Acidic to alkaline (pH
Effectively works in a wide range from 4.5 to 14). Further, the immobilization treatment agent of the present invention may be added directly to various wastes or washing wastewater and mixed almost uniformly.

Claims (4)

[Claims] 1. A method for preserving the aquatic environment by preventing the infiltration of heavy metal salts from wastewater such as refuse incinerator fly ash, incinerator ash, and metal melting furnace dust, or from the washing wastewater,
In order to prevent the elution of heavy metals by immobilizing heavy metals or heavy metal salts by mixing with the solid waste such as the refuse incinerator fly ash, incinerator ash or metal melting furnace dust, or the washing wastewater, 8
-Quinoline compounds such as -hydroxyquinoline, quinoline-8-carboxylic acid, and quinoline-2-carboxylic acid, o-aminobenzoic acid, m-aminobenzoic acid, p-
An aminobenzene compound such as aminobenzoic acid, a dioxime compound such as dimethylglyoxime or cyclohexanedionedioxime as an active ingredient, and one or more kinds of heavy metals that can be eluted into water from the waste or the washing wastewater. An agent for immobilizing heavy metals contained in waste, wherein the number of moles is at least twice the total number of heavy metals in the waste and the mixture is mixed. 2. A mixture of one or more of the immobilization treatment agents according to claim 1, and the total number of moles of heavy metals that can be eluted into water from the waste or the heavy metals in the washing wastewater. If the waste is solid, it is discarded as it is, and in the case of washing wastewater, the precipitate is filtered or precipitated to remove and separate, and then discarded. A method for immobilizing heavy metals contained in waste, which is characterized by the above. 3. The immobilization treatment agent according to claim 1 is mixed at room temperature and normal pressure with an immobilization treatment agent that forms a complex salt with a metal such as a conventional treatment agent such as dimethyldithiocarbamate or polydithiocarbamate. 3. The effect of preventing elution of the heavy metal is further enhanced by adding as an additive.
A method for immobilizing heavy metals contained in the described waste. 4. Protrusion of heavy metal salt particles by mixing the immobilization treatment agent according to claim 1 with a polymer flocculant such as polyacrylamide, sodium polyacrylate, and guar gum, and using them together. The method for immobilizing heavy metal contained in waste according to claim 2, wherein the coarsening is facilitated and the elution of the heavy metal is prevented.