JPH108029A - Stabilizer for heavy metal, stabilizing treatment of heavy metal, use of substance containing heavy metal and device for stabilizing treatment of heavy metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stabilizer for heavy metals capable of stabilizing the heavy metals by adsorbing and capturing the remaining heavy metals after adjusting pH of a substance containing the heavy metals, improving a handling property and a working safety at a low cost and useful for the treatment of a smut, etc. SOLUTION: This stabilizer for heavy metals contains at least a first component such as phosphoric acid, a primary phosphoric acid salt, a secondary phosphoric acid salt, a tripolyphosphoric acid salt and a hexametaphosphoric acid salt, capable of forming insoluble heavy metal compounds by reacting with the heavy metal components in a substance containing heavy metals while performing an adjustment of pH, and a second component such as thiourea, a silicic acid salt, an aluminic acid salt, an alginic acid salt, a Japanese acid clay, an activated clay, a bentonite, a diatomite, a gypsum, an artificial zeolite, a flyash, a silica fume, a synthetic aluminum silicate, a silica, a white carbon and a silica gel, capable of stabilizing the heavy metals by adsorbing and capturing the remaining heavy metal components. Further, it is preferable to perform the stabilization treatment of the heavy metals by using the above stabilizer for heavy metals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilizer for heavy metals, a method for stabilizing heavy metals, a method for using a substance containing heavy metals, and an apparatus for stabilizing heavy metals.

[0002]

2. Description of the Related Art Since dust and soot collected in a dust collection facility of a refuse incineration facility contains heavy metals such as lead, a method of stabilizing the heavy metals so that they do not elute and then performing final disposal such as landfilling is adopted. Have been. In Japan, four types of methods for stabilizing heavy metals as described above are defined by law. However, as a method that clears the strict elution standard value and can be applied practically, after all, the chemical kneading method has been frequently used. However, due to the stricter standards for heavy metal regulations in the country, the chemical kneading method that has been used until now has to use a large amount of chemicals.
As a result, the cost is unusually high and it is extremely difficult to implement practically.

That is, the organic chelating agent conventionally used is a method of chelating heavy metals using sodium dithiocarbamate of polyalkylamine or an organic compound having a mercapto group. Further, as a stabilizer using an inorganic compound, for example, there are techniques disclosed in JP-A-7-39847 and JP-A-7-185499. These methods involve fixing and immobilizing heavy metals with an inorganic substance.

Further, as another stabilizing method, there is a stabilizing method using an acid or another solvent. In this method, after mixing dust and water to form a slurry in a mixing tank, the first
A hydrochloric acid solution is added to the reaction tank to extract heavy metals and the like with an acid, and caustic soda and the like are added to the second reaction tank to temporarily store a heavy metal hydroxide slurry in a stabilization tank. Thereafter, the hydroxide slurry is sent to a dehydrator to be separated into a solid and a liquid, and the separated cake is solidified with cement or the like and then landfilled. Further, the hydroxide dehydration waste liquid is sent to a wastewater storage tank, pH is adjusted in a wastewater treatment facility, and the wastewater is disposed of after confirming a national wastewater standard value.

[0005]

Conventionally, organic chelating agents which have been widely used as stabilizers for heavy metals such as lead,
It has the disadvantage of being expensive and costly. It has been reported that sulfur dioxide and chelating agents used for pH adjustment cause unintentional reactions with dust and generate new harmful substances such as hydrogen sulfide, carbon disulfide and thiuram during the stabilization process. I have. It is difficult to stabilize the molten fly ash containing a high concentration heavy metal to within the above-mentioned reference value even if an organic chelating agent is added in an amount of 20 to 30%. After landfill treatment, microorganisms in the soil are expected to decompose the organic portion, and long-term stabilization performance is concerned. In general, it is well known that nitrogen-containing organic compounds are decomposed by soil bacteria, such as Nitromonas and Nitrobacter, and eventually become nitrogen gas.
Only harmful heavy metals will remain.

[0006] For example, according to Japanese Patent Application Laid-Open No. Hei 7-39847, the results of adding and kneading 40 parts of soot and dust with the stabilizing agent based on the inorganic compound are described in Examples. It does not conform to the legal standards of. The example described in JP-A-7-185499 is an example of a dissolution test 7 days after the stabilization treatment, and requires an extra curing step after the treatment, so that practicality cannot be expected. Further, it is merely a matter of stabilizing the inorganic material by enclosing the heavy metal, and no measurement value after one month is described.

[0007] The above-mentioned stabilization method using an acid or other solvent has the drawback that the processing steps are very complicated and the selection of materials for equipment is often limited. Specifically, soot and dust have characteristics such as "fine, scatter, absorb moisture, contain corrosive substances such as salts", etc., and based on these characteristics, `` settle, coagulate, clog, Wear, corrode, or block equipment. " Acid extraction of heavy metals from strongly alkaline dust requires a large amount of hydrochloric acid. The separated cake cannot be disposed of unless solidified with cement or the like. As a result, not only the cost is high, but also the processing steps are complicated and there are many problems in safety.

In the above description, lead has been mainly described as a heavy metal. However, heavy metals requiring stabilization include mercury and other harmful heavy metals in addition to lead. The present invention solves the above-mentioned problems of the conventional method for stabilizing heavy metals, and generally includes a wide range of heavy metal-containing substances including incinerated ash containing various heavy metals such as lead, waste liquid, contaminated soil, sludge, shredder dust, and the like. It can be used, in particular, the amount of lead eluted from dust can be reduced to the legal standard value of 0.3 ppm or less, maintaining safety at the time of pH adjustment, simplifying the treatment process, An object of the present invention is to provide a heavy metal stabilizer and a stabilization method capable of safely and efficiently treating and eliminating the high cost of the conventional heavy metal stabilization treatment.

Further, the present invention has been made in view of the above situation, and is basically a chemical kneading method, but is capable of stabilizing heavy metals which could not be achieved by the conventional chemical kneading method. Is achieved. The present invention also provides a method, an agent and an apparatus which are effective in stabilizing heavy metals even when applied to a method other than the chemical kneading method. The present invention has not been considered in the past for inorganic stabilizers which are more complicated to handle and less efficient in stabilization than organic chelating agents, and are hardly used practically. The invention provides a stabilizing agent and a stabilizing method whose stabilization rate is remarkably improved as compared with an organic chelating agent by devising.

That is, the present invention provides a completely new stabilizer and a stabilization method for converting a heavy metal in a waste into a sulfide in a contained state, wherein a thio group-containing compound is used as a central agent. It is based on a new technical idea. The conventional idea of stabilizers is to chelate heavy metals in waste or to stabilize them by enclosing them with inorganic substances.The present invention naturally prolongs the heavy metals in waste even when they are contained. By restoring the compound that has been stably present for a period of time, harmful heavy metals are stabilized, which is different from the conventional concept.

The inventor of the present invention has found that a legally regulated value can be cleared by using a stabilizer (such as phosphoric acid and primary phosphate) for adjusting pH by a buffering action and a stabilizer comprising thiourea. Urea contributes to stabilization of heavy metals
Rather than adsorbing and trapping heavy metals, it is thought to be a function of converting heavy metals into sulfides. That is, it is considered that heavy metals such as hydroxides and chlorides are sulfided with thiourea.

Further, the present invention provides a stabilizer which makes the action of the thio group-containing compound effective by using together a first component for adjusting the pH of the waste by a buffer action. Phosphoric acid, a first phosphate, or the like is used as the first component. In addition, the present invention, in order to make the stabilization more efficient,
Provide a stabilizer to which activated clay or a sulfate band is added.

[0013]

Means for Solving the Problems In the present invention, the stabilizer for heavy metals according to the first invention is a stabilizer which is mixed with a heavy metal-containing substance to stabilize a heavy metal component in the substance. And stabilize the heavy metals by adsorbing and capturing the heavy metals remaining after the pH adjustment. Among the present invention, the heavy metal stabilizer according to another invention is a stabilizer which is mixed with a heavy metal-containing substance to stabilize a heavy metal component in the substance, wherein the heavy metal component is adjusted at least while adjusting pH. And a second component which stabilizes the remaining heavy metal component by adsorbing / trapping it. As the first component, a compound that generates phosphate ions when used is preferable. Specifically, at least one of phosphoric acid, a first phosphate, a second phosphate, a tripolyphosphate, and hexametaphosphate
Preferably, it contains a species. Among them, the first phosphate is a preferable material.

The second component includes silicate, aluminate, alginate, acid clay, activated clay, bentonite, diatomaceous earth, gypsum, artificial zeolite, fly ash, silica fume, synthetic aluminum silicate, silica sand, It is preferable to include at least one of white carbon and silica gel. Of these, activated clay is a preferred material.

According to the present invention, elution is prevented by changing the heavy metal component to an insoluble compound by the action of the first component, and at this time, the pH is reduced by the buffering action of the first component.
The range in which the insolubilization reaction of the heavy metal component is efficiently performed,
For example, the pH is adjusted to about 10. Further, the elution of the heavy metal component is prevented by absorbing and capturing the heavy metal compound and the heavy metal ion by the action of the second component. Stabilization of the heavy metal is effectively achieved by synergistically exerting two different actions, that is, the generation of an insoluble heavy metal compound and the adsorption and capture of the heavy metal component.

Although a certain degree of stabilization is possible with only the first component, a large amount of the first component must be used in order to achieve a sufficient stabilizing action with the first component alone. First
The components are relatively expensive materials and therefore costly.
Moreover, simply using a large amount of the first component is inefficient in stabilizing heavy metals. Therefore, by adding a second component having a different stabilizing mechanism for heavy metals from the first component, it is possible to stabilize even heavy metal components that cannot be stabilized only by the first component. Since a relatively inexpensive material can be used for the second component, the use of a relatively large amount of the second component does not increase the cost.

Each of the first component and the second component may be added as an independent single drug, or a plurality of drugs may react or interact with each other during use to form the first component or the second component. In some cases, it exerts its effect. An agent may be involved in the action of both the first and second components. Specific examples of the stabilizer of the present invention will be given.

Phosphoric acid and a first phosphate can be used as the first component, and silicate can be used as the second component.
Phosphoric acid and a first phosphate can be used as the first component, and silicate and aluminate can be used as the second component. Phosphoric acid, a first phosphate and a tripolyphosphate can be combined as the first component, and silicate can be used as the second component. Phosphoric acid and a first phosphate can be used as the first component, and silicate, aluminate and alginate can be combined as the second component. Phosphoric acid can be used as the first component, and silicate and diatomaceous earth can be used as the second component. A second phosphate and a tripolyphosphate can be used as the first component, and a silicate can be used as the second component.

As a second component, acid clay, bentonite, gypsum, fly ash, quartz sand, white carbon, silica gel, or hydroxide, which forms a dense solidified material and traps and traps lead compounds and lead ions therein A fine powder containing silicon oxide as a main component, such as silica fume, which reacts with calcium to generate calcium silicate and confine and trap a lead compound or lead ion between crystal grains thereof can also be used. However, it is preferable that these materials are supplementarily added to the above-mentioned silicate, diatomaceous earth and the like.

The heavy metals which can be stabilized in the present invention include, in addition to lead, zinc, aluminum, tin, arsenic which forms amphoteric hydroxide, mercury, cadmium, hexavalent chromium and the like. Phosphoric acid as the first component is used in the form of a phosphoric acid aqueous solution as it is, or in the form of powdered phosphor in a state in which the phosphoric acid aqueous solution is absorbed and supported on a powder having an adsorbing effect such as diatomaceous earth, that is, an adsorbent powder. Acids can be used. The powdered phosphoric acid is easy to handle such as transportation and storage, and the production of the stabilizer and the mixing operation with the heavy metal-containing substance are also facilitated. If a material corresponding to the above-mentioned second component such as diatomaceous earth is used as the absorbent powder, the phosphoric acid in the form of particles can exhibit the function as the second component in addition to the function as the first component. Become. However, in many cases, the function of the second component cannot be sufficiently achieved only by the granular phosphoric acid. Therefore, it is necessary to add a material to be the second component to the stabilizer separately from the granular phosphoric acid. preferable.

[0021] In the present invention, a stabilizer for a heavy metal according to still another invention is a stabilizer which is mixed with a heavy metal-containing substance to stabilize a heavy metal component in the substance, and comprises at least a thio group-containing compound. including. A thio group-containing compound is a compound having a thio group in the structure. As the thio group-containing compound, thiourea, particularly powdered thiourea, is preferred.

A thio group-containing compound can be used in place of the second component. Further, a thio group-containing compound can be further contained in addition to the first component and the second component. The thio group-containing compound reacts with a heavy metal to form an insoluble sulfide. The stabilization by the sulfide provides a more stable state than the stabilization by the first component and the second component. In particular, the stabilizing action of the thio group-containing compound gradually progresses even when the heavy metal-containing substance, which has been stabilized by the first component and the second component, is left in a landfill or the like. Make things. The insolubilized substance produced by the first component reacts with the thio group-containing compound to form a more stable sulfide. Therefore, it is effective for maintaining stability over time. There is a concern that the organometallic complex compound produced by the conventional polymer chelating agent will decompose over a long period of time. In addition, the thio group-containing compound,
The problem of odor and hydrogen sulfide generation due to the sulfide eluted can be solved.

The thiourea can be used in the form of a solution, but if powdered thiourea is used, the handling becomes easy. In particular, it is convenient to use in combination with the powdery first component or the second component. First component and second component
In addition to the components, a sulfate band can be further contained.

The sulfate band complements the pH adjusting function of the first component. Therefore, a smaller amount is sufficient compared to the amount of the sulfate band used as a conventional pH adjuster.
If a powdery sulfuric acid band is used, it is easy to handle, and it is convenient for producing a powdery stabilizer. The stabilizer containing the first phosphate, the powdery sulfuric acid band, and the powdery thiourea is easy to handle, and the mixing operation into dust and the like is easy, and the stabilizing action is efficient. Can be demonstrated.

The heavy metal-containing substance may be any substance that requires stabilization of the heavy metal contained therein, such as incineration ash, dust, waste liquid, contaminated soil, and sludge discharged from refuse incineration facilities and various factory facilities. Applicable to substances. The stabilizer of the present invention can exhibit particularly excellent functions when applied to dust as a heavy metal-containing substance. Soot and dust
There are incinerated soot and molten soot, which can be applied to any of them. However, they exhibit an excellent effect on molten soot containing a high concentration of heavy metals. In general, it is known that several hundred to several thousand ppm or more of lead is eluted from molten dust.

Finally, the shortage of the final disposal site for waste has become a serious social problem, and recycling is desired.
Therefore, by applying the present invention, the heavy metal components in the municipal waste incineration ash are also sulfided, so that the long-term stability performance is high,
Contribute to recycling roadbed materials, civil engineering materials, sidewalk blocks, etc. In the case of a production facility for recycled roadbed material, a kneader for incineration ash and a stabilizer, a press molding machine for the kneaded material, and a molded product crushed to 40 mm or less after curing for a certain period of time can be effectively used as recycled roadbed material. . The elution value of heavy metals after curing for a certain period of time can meet the environmental standard value related to soil contamination of recycling. This method is extremely simple compared to the high-temperature sintering and incineration ash melting methods, and reduces the processing cost and is easy to put into practical use. Further, there is no generation of molten fly ash and the like.

The heavy metal stabilizer of the present invention can contain at least a thio group-containing compound. The thio group-containing compound is preferably in the form of a powder in terms of handling. In particular, with thiourea, heavy metals can be sulfided without generating toxic gas in the stabilization treatment. Each heavy metal-containing substance has a difference in coexisting substance, heavy metal content, elution amount, and elution behavior. Therefore, the Portland cement, the blast furnace cement, and the sulfuric acid band can be efficiently stabilized by using them together according to the purpose and the heavy metal-containing substance.

[0028]

[Action]

(1) Action of first component The first component generates an insoluble heavy metal compound while adjusting the pH by a buffer action. Here, the insoluble heavy metal compound is, for example, lead hydroxide or the like, which precipitates when the heavy metal-containing substance becomes around pH 10. However, lead hydroxide is redissolved when the atmosphere becomes strongly alkaline again. However, when a phosphoric acid compound such as phosphoric acid or a first phosphate is used as the first component, lead hydroxide becomes lead phosphate, and becomes a strong insoluble compound which is unlikely to be dissolved again. In that sense, it is preferable to use a phosphate compound as the first component.

Here, having a buffering action is not limited to a case where the buffering action itself is exerted, but also a case where it exerts a buffering action in cooperation with another drug. Other drugs
It is a component or a component added to the stabilizer, or a compound present in a heavy metal-containing substance such as dust. For example, when only phosphoric acid is used as the first component, it does not exert a buffering action by itself, but exerts a buffering action in cooperation with sodium silicate used as the second component.

In the following, the above description will be specifically described taking a dust and so on as an example. Calcium oxide in dust and soot reacts with water to generate calcium hydroxide, and lead ions are eluted from lead chloride and lead oxide in dust and the like. The phosphoric acid compound exerts a buffering action for lowering the pH of a mixed solution of this and dust to, for example, around 10, and maintaining the pH. At around pH 10, the calcium hydroxide reacts with lead ions to produce lead hydroxide.

[0031] Then, the above-mentioned phosphoric acid-based compound generates very stable lead phosphate which is insoluble in water after ionizing lead hydroxide. When a strong acid such as hydrochloric acid is used in place of the phosphoric acid compound contained in the weak acid, a large amount of calcium contained in the carrot elutes, so that the pH cannot be adjusted unless a large amount of the strong acid is used. Hydrochloric acid has no buffering action. On the other hand, since phosphoric acid and its salts are weakly acidic, calcium is hardly eluted. Also,
It reacts with the dissolved calcium hydroxide to form poorly soluble calcium phosphate, thereby neutralizing the alkali. Therefore, the amount used for pH adjustment is small. For this reason, phosphoric acid or a salt thereof is preferably used for stabilization of heavy metals contained in dust and the like.

(2) Function of Second Component The second component can adsorb and capture heavy metal compounds and heavy metal ions which remain without being insolubilized by the first component. Here, “adsorption / capture” means a physical and chemical adsorption or capture action, and may have both an adsorption action and a capture action.

As such a second component, for example, silicate and alginate gel in the presence of phosphoric acid to form a three-dimensional network structure, thereby preventing the movement of water molecules, thereby preventing the movement of heavy metal ions. Disturb and catch this. Further, the aluminate forms colloidal aluminum hydroxide, and the aluminum hydroxide adsorbs unreacted heavy metal compounds and residual heavy metal ions to the first component.

Diatomaceous earth also adsorbs unreacted heavy metal compounds and heavy metal ions. Diatomaceous earth reacts with calcium hydroxide to produce calcium silicate, and confine and trap heavy metal compounds and heavy metal ions between crystal grains. (3) Calcium hydroxide is generated by the reaction of calcium oxide and water in the dust, but phosphoric acid reacts with this calcium hydroxide to generate calcium phosphate, and unreacted between the calcium phosphate crystal particles. The heavy metal compounds and heavy metal ions are contained and trapped to prevent re-elution of heavy metals.

In the above description, lead has been described as an example of heavy metal, but stabilization can be achieved for heavy metals other than lead by the same reaction or action.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION

(Form of Stabilizer) Examples of the form of the heavy metal stabilizer include powders and liquids, as shown in Table 1, and are used depending on the heavy metal stabilization equipment. For example, if the heavy metal stabilization equipment has a storage tank or a liquid feed facility, the use of a liquid heavy metal stabilizer will improve the workability and reduce the labor. Are preferred. The heavy metal stabilizers in powder form have low bulk and light weight, and are easy to transport, store and handle. If the heavy metal stabilizer of the powder contains water inside, the water functions when mixed with dust and the like to exert a stabilizing action.

(Component of Stabilizer) Regarding the component of the heavy metal stabilizer, phosphoric acid as the first component is 75% from the viewpoints of high safety in handling and not freezing at low temperature.
% Aqueous solutions are preferred. Salts such as a first phosphate, a second phosphate, a tripolyphosphate, a silicate, an aluminate, and an alginate are preferably sodium salts from the viewpoint of cost reduction and easy handling, but are not limited thereto. Not something.

(Blending Ratio of Components) The blending ratio of the components constituting the heavy metal stabilizer is determined depending on the combination form of the first and second components and whether the stabilizer is powder or liquid. As an example, when the stabilizer uses phosphoric acid and a first phosphate as the first component and uses a silicate as the second component, the total of the first component and the second component is set to 100% by weight. , Phosphoric acid 15-40% by weight, primary phosphate 1
It can be carried out with 0 to 30% by weight and 45 to 65% by weight of silicate.

The stabilizer comprises phosphoric acid as the first component and the first component.
As an example of the case where a phosphate is used and a silicate and an aluminate are used as the second component, phosphoric acid is 15 to 40 with the total of the first component and the second component being 100% by weight.
%, First phosphate 10-30% by weight, silicate 25
４５45% by weight and aluminate 10-30% by weight.

The stabilizer is phosphoric acid as the first component,
An example of the case where a phosphate and a tripolyphosphate are used and a silicate is used as the second component is as follows. If the total of the first component and the second component is 100% by weight, phosphoric acid 10
~ 35 wt%, first phosphate 10-25 wt%, tripolyphosphate 10-30 wt%, silicate 35-60 wt%.

The stabilizer comprises phosphoric acid as the first component and the first component.
For example, when a phosphate is used and a silicate, an aluminate, and an alginate are used as the second component, assuming that the total of the first component and the second component is 100% by weight,
Phosphoric acid 15-35% by weight, primary phosphate 10-25% by weight, silicate 35-60% by weight, aluminate 5-25
% By weight, 2-8% by weight of alginate.

As an example of the case where phosphoric acid is used as the first component and silicate and diatomaceous earth are used as the second component, for example, 15 to 35% by weight of phosphoric acid and 20 to 40% of silicate Wt%, diatomaceous earth 35-55 wt%
Can be implemented. As an example of the case where the stabilizer uses a second phosphate and a tripolyphosphate as the first component and uses a silicate as the second component, the first component and the second component may be used.
Assuming that the total of the components is 100% by weight, the second phosphate 5-2
0% by weight, 5 to 25% by weight of tripolyphosphate and 65 to 90% by weight of silicate.

More preferably, phosphoric acid or a first phosphate is used as the first component, and as the second component,
A material obtained by using one or more materials selected from the group consisting of diatomaceous earth, white carbon, activated clay and synthetic aluminum silicate, and further adding a thiourea and a sulfate band. In this case, a preferable mixing ratio is 20 to 50% by weight of the first component and 10% by weight of the second component.
-40% by weight, thiourea 10-40% by weight, sulfate band 20-50% by weight.

When the stabilizer is liquid, the compounding ratio based on the solid component is the same as the compounding ratio of each stabilizer in the above powder. (Method for Preparing Stabilizer) Representative examples of the method for preparing the heavy metal stabilizer of the present invention are shown in FIGS. 1 and 2. When preparing a heavy metal stabilizer for powder, it should be noted that since the mixing ratio between the raw materials is large and the specific gravity difference is large, some raw materials are uniformly mixed so as not to be partially biased. Hereinafter, the preparation method will be described with reference to FIG.

From the viewpoint of the blending amount, the first component is smaller than the second component, so that only the first component is first mixed as shown in FIG. That is, first, the first component A ₁ and the first component A ₂ are uniformly mixed by a mixer having high mixing accuracy. Next, a ribbon blender elongated in the lateral direction at a predetermined ratio having a length to width ratio of at least 1 to 5 or more is placed on one end of the ribbon blender with the mixture A of the first component and the second component B _1.
And the second component B ₂ by mixing the mixture A, the single product B ₁ and the single product B
_In the order of _2, the mixture is stirred and mixed for about 3 minutes in the case of batch operation, and the mixing and stirring is performed with the average residence time being about 6 minutes in the case of continuous operation. Thereafter, the material (heavy metal stabilizer for powder) mixed and stirred in the ribbon blender is sent out from a bottom outlet of the ribbon blender to a bagging machine or a transport conveyor via a rotary valve.

On the other hand, when preparing the liquid heavy metal stabilizer, the mixing order of the raw materials must be properly adjusted in order to prevent operational dangers such as heat generation and scattering, sedimentation of the raw materials and gelation of the mixed solution. Note that it mixes uniformly. Hereinafter, the preparation method will be described with reference to FIG. As a standard preparation method, as shown in FIG. 2, a predetermined amount of water is first charged into the mixing tank I, then the first component A ₁ is gently charged with stirring, and then the first component A ₂ And stirred for about 3 minutes. At the also supplied a predetermined amount of water at the same time mixing tank II, then stirred with stirring second component B ₁ and the second component B ₂ and about 3 minutes was charged. Next, the liquid in the mixing tank I and the liquid in the mixing tank II are simultaneously charged into the mixing tank III, and are stirred and mixed for about 10 minutes. Thereafter, the product (liquid heavy metal stabilizer) obtained in the mixing tank III is fed to a drum can injector or a tank truck by an extraction pump.

[0047] However, the component B ₂ is used as the second component, for example, becomes a water quantity less the gel as sodium alginate, make insufficient stirring and mixing with B ₁ in the mixing vessel II because what is a process for preparing heavy metal stabilizers liquid when B ₂ is such as described above, differs in the following points and standard preparation methods described above.
That is, the B ₂ without feeding the mixing tank II, mixing tank II
In I, the liquid in the mixing tank I and the liquid in the mixing tank II were simultaneously charged, and then B ₂ was charged into this mixing tank III for the first time.
The point is that the mixture is stirred and mixed for 0 minutes.

(Method of Using Stabilizer) The heavy metal stabilizer according to the present invention can be applied to heavy metal-containing substances other than dust, but the method of using the dust will be specifically described below by taking dust as an example. I do. When using the above heavy metal stabilizer, it is necessary to efficiently convert heavy metal eluted only slightly from the dust into an insoluble compound or to adsorb / trap it, in order to reduce the processing cost of stabilizing the heavy metal in the dust. is important. Therefore, it is required that the heavy metal stabilizer is evenly distributed and permeated in the dust so that the chance of contact between the heavy metal stabilizer and the heavy metal is maximized.

In order to meet the above demand, a heavy metal stabilizer can be uniformly kneaded in the dust.
The selection of the structure of the kneader and the working method are important. In selecting a kneading machine, phosphoric acid or silicic acid reacts with the calcium component in the kneading process to form hard crystals,
Since this adheres to the machine wall to form a scale and hinders the stirring operation, it is necessary to consider the accuracy of the kneading and the maintainability of the kneading machine.

Therefore, as a recommended kneader, a screw type or a combination thereof with a vibrating type to enhance the kneading effect and having a self-cleaning function to prevent adhesion of scale can be mentioned. As a specific example of the working method, when the heavy metal stabilizer is a powder, a predetermined amount of water is added to the kneader, and then a predetermined amount of the heavy metal stabilizer is added to the kneader while rotating the stirrer of the kneader. Is slowly added over about 1 minute, and then sufficiently stirred or dissolved for about 3 minutes to sufficiently dissolve or disperse. Next, dust is gradually introduced into the kneader over about 1 minute while rotating the stirrer of the kneader, and then kneaded for 5 minutes. Thereafter, the kneaded material is taken out from the kneader.

When the heavy metal stabilizer is liquid, a predetermined amount of water is added to the kneader, and then the predetermined amount of the heavy metal stabilizer is added to the kneader over about 30 seconds while rotating the stirrer of the kneader. Inject slowly. Next, dust is gradually introduced into the kneader over about 1 minute while rotating the stirrer of the kneader, and then kneaded for 5 minutes. Thereafter, the kneaded material is taken out from the kneader.

The amount of heavy metal contained in the dust is
Since the amount depends on the type of equipment at the refuse incineration plant, the amount of lead dissolved in soot and dust is measured in advance by a lead dissolution test according to the Environment Agency Notification No. 13 of the Law Concerning the Treatment and Cleaning of Waste, and the heavy metal stability of the present invention is determined. It is preferable to use a certain amount of soot and dust which shows the measured value with respect to a certain amount of the agent.

(Stabilizing method) In the method for stabilizing heavy metals according to the present invention, the heavy metal compound is insolubilized by the first component in a state where the pH is stabilized by the buffering action, and the heavy metal compound which remains without being insolubilized. And heavy metal ions are second
Adsorbed and captured by components. However, there may be heavy metal components adsorbed and trapped by the second component before being insolubilized by the first component, and heavy metal components adsorbed and trapped by the second component in the insolubilized state.

[0054]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to the following examples. (Lead Amount and Legal Standard) First, a heavy metal stabilizer having the composition shown in Table 1 was prepared. The composition (g) is represented by the amount added to 100 g of the heavy metal-containing substance.

[0055]

Table 1 Example Composition (g) of heavy metal stabilizer 1st component 2nd component Others ────────────────────────────────── 1 Phosphoric acid: 3 Silicate: 6 Water: 10 liquid Primary phosphate: 2──────────────────────────────────2 Phosphoric acid: 3 Silicate: 4 Water: 72 Liquid Primary phosphate: 2 Aluminate: 2 ──────────────────────────── ──────3 Phosphoric acid: 2 Silicate: 4 Water: 10 Liquid Primary phosphate: 1 Tripolyphosphate: 1.5 ────────────────── ────────────────4 Phosphoric acid: 2 Silicate: 4 Water: 102 Liquid Primary phosphate: 1 Aluminate: 1 Alginate: 0.33─ ────────────────────────────────── 5 Phosphoric acid in powder form: 16.5 Silicate: 7-Powder ─────────────────────────────────── 6 Second phosphate: 1.5 silicate: 15 Water: 10 Liquid tripolyphosphate: 3 ─────────────────────────────────── 7 Primary phosphate: 10 Thiourea: 5 powder ８ 8 Primary phosphate: 6 activity Clay: 9 Thiourea: 3 Powder ─────────────────────────────────── 9 Primary phosphate : 6 activated clay: 3.3 thiourea: 1.7 powder sulfuric acid band: 4 ────────────────────────────────── ─ 10 Primary phosphoric acid : 8 Activated clay: 4.4 Thiourea: 2.3 Powder Sulfuric acid band: 5.3 ────────────────────────────────── Here, the powdered phosphoric acid is produced by the following materials and methods.

Powdery diatomaceous earth was charged into a blender, and while stirring, liquid 75% phosphoric acid was pressurized with a pump to form a spray and was blown into the blender to absorb phosphoric acid into the powder. Next, to the above heavy metal stabilizer, 100 g each of dust and soot with a lead elution amount of 32 ppm in an elution test according to the Environment Agency Notification No. 13 was added, and the mixture was mortared for 5 to 10 minutes.
Kneaded well. After the kneaded material was allowed to stand for 24 hours, an elution test was performed according to the notification of the Environment Agency No. 13, and the elution amount of lead was measured by an atomic absorption method. Table 2 shows the results.

[0057]

[Table 2] As is clear from Table 2, in each of the examples, the measured value of the lead elution amount was 0.3 mg / l (ppm) which is the legal standard value.
)

(Cost required to keep the amount of lead eluted below the legal standard value) Using a polymer chelating agent and a liquid sulfuric acid band which have been widely used in the past, the amount of lead eluted was defined by the legal standard. It is also possible to set the value to 0.3 ppm or less. In this case, the amounts of the chelating agent and the liquid sulfuric acid band are 3 to 5 g and 80 g, respectively, per 100 g of dust when the amount of lead eluting from the dust is 32 ppm. Liquid sulfuric acid bands are relatively inexpensive, but chelating agents are expensive, and the overall material costs are significantly higher.

On the other hand, the required amount of the heavy metal stabilizer (total amount of the active ingredients contained in the heavy metal stabilizer) in each of the above-mentioned examples is based on 100 g of the dust when the amount of the dissolved lead is 32 ppm. 8.5 to 23.
5 g, which is clearly less than the conventional stabilizer. In addition, since the unit price of each component is lower than that of the chelating agent, the cost of the entire stabilizer is reduced.

(Stabilization of molten fly ash) A heavy metal stabilizer having the composition shown in Table 3 was prepared. Powder ingredients were used for all the components to obtain a powdery stabilizer.

[0061]

[Table 3] Example Composition of heavy metal stabilizer (g) ( 30g in total) 1st component 2nd component Others １１ 11 Phosphoric acid: 15 Diatomaceous Sat: 15 １２ 12 Phosphoric acid: 15 White carbon: 8 Silicate: 7 １３ 13 First phosphate: 15 White carbon: 8 Activated clay: 7-14 Phosphoric acid: 10 Diatomaceous earth: 10 Thiourea: 4 sulfate band : 6 １５ 15 Acid: 7 Diatomaceous earth: 7 Thiourea: 10 Sulfuric acid band: 6 ────────────────────────────────── 16 Phosphoric acid: 13.8 White carbon: 9.2 Thiourea: 3.5 Sulfuric acid band: 3.5───────────────────────────────── １７ 17 Primary phosphate: 6.7 Diatomaceous earth: 6.6 Thiourea: 10 sulfate band: 6.7 ───────────────────────────── １８ 18 Phosphate: 6.7 Diatomaceous earth: 6.6 Thiourea: 6.7 Sulfate band: 10 ───────────────────────── ───────── 19 First phosphate: 6.7 White carbon: 6.6 Thiourea: 6.7 Sulfate band: 10 ───────── ２０ 20 first phosphate: 6.6 white car Bon: 10 Sulfate band: 6.7 Thiourea: 6.7 ────────────────────────────────── 21 Primary phosphoric acid Salt: 10 White carbon: 6.6 Sulfuric acid band: 6.7 Thiourea: 6.7 ２２ 22 Primary phosphate: 6 Activated clay: 9 Thiourea: 7 Sulfuric acid band: 8 ─────────────────────────────── ─── 23 1st phosphate: 15 activated clay: 6 thiourea: 3 sulfate band: 6 ─────────────────────────── ２４ 24 First phosphate: 12 Synthetic thiourea: 3.5 Aluminum: 6.5 Sulfuric acid band: 8 ─────────────────────同 様 Using 30 g of the obtained heavy metal stabilizer, Carried out the dissolution test, and the results are shown in Table 4. The soot and dust used as the heavy metal-containing material is molten fly ash and contains 2100 lead.
ppm High-concentration heavy metal-containing substance eluted.

[0062]

[Table 4] As a result of the above test, the stabilizers of Examples 14 to 24 were able to exert an excellent stabilizing effect even on high-concentration heavy metal-containing substances.

A commercially available liquid chelating agent was mixed with the same amount of 3
When the same measurement was performed after adding and kneading 0 parts by weight, the lead elution amount was 400 mg / l. (Application to Heavy Metals in General) It was verified that the stabilizer of the present invention also has a stabilizing effect on heavy metals other than lead. As the heavy metal-containing substance, the same molten fly ash as in the above example was used.

<Incorporation of Stabilizer: Mixing Amount for 100 g of Melt Fly Ash> Example 25: Monobasic sodium phosphate 12.0 g Activated clay 6.5 g Sulfuric acid band 8.0 g Thiourea 3.5 g Total 30 g Examples described above The dissolution test was carried out in the same manner as described above, and the results are shown in Table 5. In addition, the test was performed on the samples after 1, 7, and 60 days after the treatment.

[0065]

[Table 5] Example 25: 溶出 Heavy metal elution amount (mg / l) Before heavy metal treatment After treatment: 1 day: 7 days: 60 days ────────────────────────────── Lead 2100 0.14 <0.01 <0.01 Mercury 0.0018 <0.0005 <0.0005 <0.0005 Cadmium 0.03 <0.01 <0.01 <0.01 Hexavalent chromium 0.14 <0.02 <0.02 <0.02 ──────────────────────────結果 As a result, it was confirmed that the stabilizer of the present invention was effective for heavy metals other than lead. Further, in Example 25, the elution amount of lead was smaller after 7 days than after 1 day, and the elution amount was not increased even after 60 days, indicating that the stabilizing action over a long period was excellent.

(Stabilization of Incinerated Ash) A heavy metal stabilizer having the composition shown in Table 6 was prepared. Powder ingredients were used for all the components to obtain a powdery stabilizer. As a comparative example, a stabilizer made of Portland cement alone was used.

[0067]

[Table 6] Example Composition of heavy metal stabilizer (g) 1st component 2nd component Others ────────────────────────────────── 26 Activated clay: 1.7 Portland cement: 8 Thiourea: 0.3-27 Primary phosphate: 0.25 Bentonite: 0.25 Porto Land Activated clay: 0.25 Cement: 9 Thiourea: 0.25 $ 28 No. 1 phosphorus Acid salt: 0.3 Bentonite: 0.3 Portland Activated clay: 0.3 Cement: 8.8 Thiourea: 0.3 ────────────────────────────── ──── 29 Phosphate: 0.4 Bentonite : 0.4 Portland activated clay: 0.4 Cement: 8 Silica fume: 0.4 Thiourea: 0.4 ─────────────────────────────── ─── Comparative example Portland cement: 10 焼 Incineration as a heavy metal-containing substance 10 parts by weight of the obtained heavy metal stabilizer was added to 100 parts by weight of ash, and 5 parts were
After kneading for 10 to 10 minutes, the kneaded material was packed in a mold, and a test body molded by a compression molding machine was produced. After 1 day and 30 days, the test specimen was subjected to a dissolution test according to the notification of the Environment Agency No. 46. Table 7 shows the results. The heavy metal-containing material was incinerated ash, and the lead elution amount before the treatment was 2.7 ppm.

[0068]

[Table 7] As a result, it was confirmed that the stabilizer of the present invention was also effective against incinerated ash. In addition, after curing for a certain period, the condition of 0.01 mg / l, which is the environmental standard value for soil contamination of recycling, has been cleared. Therefore, it is possible to provide the best method that can recycle waste with excellent safety in the long term.

[0069]

Since the heavy metal stabilizer and the method for stabilizing heavy metals of the present invention are constituted as described above, for example, the amount of lead eluted from soot and dust is reduced to 0.3 ppm or less, which is the revised legal standard value. And the effect of stabilizing heavy metals is high. In addition, the first component is not only insoluble,
Since it also has a function of adjusting H, the pH adjustment and the insolubilization reaction can be performed simultaneously in the same step.
It is not necessary to provide a separate step only by adjustment, and the heavy metal stabilization processing operation is simplified.

Since the first component has a buffering action, even a weak acid such as a phosphoric acid compound can weakly alkalinize fly ash and the like under a strong alkaline atmosphere. Since it is not necessary to use a strong acid as a pH adjuster, work safety is improved. Further, the heavy metal stabilizer of the present invention is less expensive than conventional polymer chelating agents. Therefore, the cost required for stabilizing the heavy metal-containing substance can be significantly reduced as compared with the conventional method, and the high cost of the stabilization treatment of the heavy metal can be eliminated. The agent is easy to handle.

[Brief description of the drawings]

FIG. 1 is a process diagram of a method for preparing a heavy metal stabilizer representing an embodiment of the present invention.

FIG. 2 is a process diagram of a method for preparing a heavy metal stabilizer representing another embodiment.

Claims (20)

[Claims] 1. A stabilizer which is mixed with a heavy metal-containing substance to stabilize a heavy metal component in the substance, and which stabilizes the heavy metal by adsorbing and trapping the heavy metal remaining after pH adjustment. Agent. 2. A stabilizing agent mixed with a heavy metal-containing substance to stabilize a heavy metal component in the substance, wherein at least a pH is adjusted and a reaction with the heavy metal component produces an insoluble heavy metal compound. A heavy metal stabilizer comprising: a component; and a second component that stabilizes the remaining heavy metal component by adsorbing and capturing the component. 3. The heavy metal stabilizer according to claim 2, wherein the first component adjusts pH with a substance whose aqueous solution is acidic. 4. The heavy metal stabilizer according to claim 3, wherein the first component adjusts the pH by a buffering action. 5. The method according to claim 1, wherein the first component is phosphoric acid, a first phosphate,
The heavy metal stabilizer according to claim 4, comprising at least one of a second phosphate, a tripolyphosphate and a hexametaphosphate. 6. The heavy metal stabilizer according to claim 5, wherein the phosphoric acid aqueous solution as the first component is powdery or granular powdery phosphoric acid supported on an adsorptive powder. 7. The second component is thiourea, silicate, aluminate, alginate, acid clay, activated clay, bentonite, diatomaceous earth, gypsum, artificial zeolite, fly ash, silica fume, synthetic silica aluminum,
The heavy metal stabilizer according to any one of claims 2 to 6, comprising at least one of silica sand, white carbon, and silica gel. 8. A stabilizer mixed with a heavy metal-containing substance to stabilize a heavy metal component in the substance, wherein the stabilizer comprises at least a thio group-containing compound. 9. The heavy metal stabilizer according to claim 1, further comprising at least a thio group-containing compound. 10. The heavy metal stabilizer according to claim 8, wherein the thio group-containing compound is thiourea. 11. The heavy metal stabilizer according to claim 1, further comprising Portland cement or blast furnace cement. 12. The method according to claim 1, further comprising a sulfate band.
11. The heavy metal stabilizer according to any one of 10. 13. A method for stabilizing a heavy metal component in a heavy metal-containing substance, the method comprising stabilizing a heavy metal using the heavy metal stabilizer according to any one of claims 1 to 12. 14. The stabilization of a heavy metal according to claim 13, wherein a stabilizing agent for the heavy metal is added and kneaded in a state where the heavy metal component is contained in the heavy metal-containing substance to stabilize the heavy metal in the substance. Processing method. 15. A stabilization method for stabilizing a heavy metal component in a heavy metal-containing substance by adding and kneading the substance to a heavy metal-containing substance, wherein the heavy metal is sulfided in a state contained in the substance. Processing method. 16. The heavy metal-containing substance is sulfided using a powdery or granular thio group-containing compound.
3. The method for stabilizing heavy metals according to 1.). 17. The method according to claim 15, wherein after converting the heavy metal in the heavy metal-containing substance to a hydroxide, the heavy metal is sulfided.
7. The method for stabilizing heavy metals according to 6. 18. A method of using a stabilized heavy metal-containing substance, comprising: a molding material obtained by the stabilization treatment according to any one of claims 13 to 17; How to use heavy metal-containing substances used as sidewalk blocks. 19. A method for stabilizing a heavy metal component in a heavy metal-containing material by mixing the heavy metal stabilizer according to claim 2 with a heavy metal-containing material, comprising the step of mixing with a heavy metal-containing material. In the method for stabilizing heavy metals, the step of mixing the first component and the step of mixing the second component are stabilized with a time difference. 20. A stabilization method for stabilizing a heavy metal component in a heavy metal-containing substance by mixing a heavy metal stabilizer with the heavy metal-containing substance, comprising: a feeder for supplying the heavy metal-containing substance to a kneading machine; In addition to a feeder that supplies the stabilizing agent into the kneader, a feeder that supplies water into the kneader, a device for compression-molding the kneaded material, and a crushing device for crushing the compressed molded product after a certain period of time And a stabilization treatment device for heavy metals.