JP4061253B2 - Method for producing heavy metal treatment agent - Google Patents

Description

The present invention is a heavy metal effective in stabilizing harmful heavy metals such as lead, chromium, cadmium, mercury, copper, zinc or nickel contained in incineration ash generated mainly during incineration of municipal waste, industrial waste, etc. It is related with a processing agent and its manufacturing method.

In recent years, waste generated from cities, factories, etc. has increased. In particular, waste containing heavy metals that are likely to have a negative impact on the human body needs to be sufficiently detoxified for environmental measures. Is strongly demanded. For example, incineration ash discharged from incineration plants such as municipal waste and industrial waste, especially fly ash, contains a lot of heavy metals such as lead. Therefore, the `` cement solidification method '' and `` acid extraction method '' prevent heavy metals from eluting. ”,“ Melt-solidification method ”, or“ Chemical addition treatment method ”, and then final disposal such as landfill is required. In addition, regarding the treatment of dioxins in incineration ash regulated by the Special Measures Law for Countermeasures against Dioxins enforced in January 2000, existing facilities need to be treated by any of the above four methods.

  Of the above treatment methods, the drug addition treatment method is most frequently used because it is generally easier to handle than other methods. Conventionally used agents include organic chelating agents such as dithiocarbamic acid compounds and mercaptocarboxylic acid compounds. However, organic chelating agents are disadvantageous in that they are expensive and have high processing costs. In addition, organic chelating agents have been reported to produce harmful substances such as hydrogen sulfide and carbon disulfide by reacting with acidic chemicals used for pH adjustment or when decomposed when mixed with hot incineration ash. Has been. In addition, since the chelating agent is an organic substance, it is expected to be decomposed by microorganisms in the soil after the landfill treatment, and thus long-term stability is feared. As a stabilization treatment method using an inorganic compound, a method of treating incineration ash with phosphoric acid or a phosphate compound has been proposed, but this method has a sufficient treatment effect because the treatment pH range is limited. In order to achieve this, a pH adjuster or the like is required, and a large amount of drug addition is required to clear the current regulation value (lead 0.3 mg / l). In addition, since these are acidic substances, they have a drawback that the devices are easily corroded. (For example, see Patent Document 1)

Moreover, although the stabilization processing method by aluminum silicate etc. is also proposed, these methods similarly required much addition amount with respect to incineration ash, and the subject that the waste amount after a process increased significantly remained. (For example, see Patent Documents 2, 3, and 4)

Japanese Patent Publication No. 4-61710 JP-A-5-309354 Japanese Patent Laid-Open No. 10-8029 Japanese Patent Laid-Open No. 11-76981

The object of the present invention is to solve the above-mentioned problems of the prior art, and to stabilize various harmful heavy metals such as lead contained in incineration ash generated at the time of incineration such as municipal waste and industrial waste. Heavy metal treatment agent that is effective for the treatment of heavy metals, has no generation of harmful gas due to decomposition under high-temperature conditions, has very little corrosion of the device, and can be treated with a small amount of addition, and a method for producing the same Is to provide.

As a result of intensive studies to solve the above problems, the present inventors have used, among other things, main ash, incineration fly ash, molten fly by using the heavy metal treatment agent comprising the powdered aluminum phosphate silicate of the present invention. The inventors have found that harmful heavy metals in incinerated ash such as ash are fixed with high efficiency, and have completed the present invention. That is, the present invention comprises a silicon compound selected from sodium silicate, potassium silicate, and silica sol; an aluminum compound selected from aluminum sulfate, aluminum chloride, aluminum nitrate, and polyaluminum chloride; and phosphoric acid and a water-soluble phosphate. and selected phosphorous compounds _SiO 2 / _Al 2 _{O 3} molar ratio 0.03 to _3.0, by mixing and reacting in the range of _{P 2 O 5 / Al 2 O} 3 molar ratio from 0.01 to 1.5, precipitation The present invention relates to a method for producing a heavy metal treating agent selected from lead, zinc, and chromium comprising powdered aluminum phosphate silicate, wherein the product is separated and dried .

Heavy metal treating agent of the present invention, simply heavy metal-containing waste can immobilize only harmful heavy metals are added and mixed thereto, and the heavy metal treating agent, no corrosion of the apparatus since it is neutral, and Since heavy metals can be fixed with a small addition amount, the amount of waste after treatment can be greatly reduced.

Hereinafter, the manufacturing method of the heavy metal processing agent which concerns on this invention is demonstrated in detail. The manufacturing method of this invention aluminum phosphate silicate is as follows. The aluminum phosphate silicate of the present invention can be produced by mixing and reacting a silicon compound, an aluminum compound and a phosphorus compound as raw materials. Now, sodium silicate as a silicon compound, aluminum sulfate as an aluminum compound, and phosphoric acid as a phosphorus compound will be specifically described as examples.

Aluminum sulfate is added to sodium silicate within a molar ratio range of SiO ₂ / Al ₂ O ₃ = 0.03 to 3.0, and then phosphoric acid is added to P ₂ O ₅ / Al ₂ O ₃ = 0.01 to 1.5 mol. Add and mix within the ratio. Depending on the pH of the obtained slurry, neutralization with an acid or alkali neutralizing agent is performed as necessary. After the neutralization pH is stabilized, the obtained slurry is subjected to solid-liquid separation by a usual filtration method. The wet cake separated into solid and liquid is washed with water and dried. Subsequently, the heavy metal processing agent of this invention can be obtained by grind | pulverizing the obtained cake dried material.
As described above, the composition of the manufactured powdery aluminum phosphate silicate has a molar ratio of SiO ₂ / Al ₂ O ₃ = 0.05 to 2.6 and P ₂ O ₅ / Al ₂ O _3. = Mole ratio in the range of 0.01 to 1.2. As shown in the examples described later, when the composition deviates from this range, the ability to immobilize heavy metals is significantly reduced. Therefore, this composition is extremely important in the present invention. Now, an example of the method for producing the heavy metal treating agent of the present invention has been shown, but natural products can be used as long as they are within the above composition. As for the form, it may be in the form of powder, and any form such as crystal form and amorphous form can be used.

The raw materials for producing the heavy metal treating agent of the present invention will be described in detail. As the silicon compound, sodium silicate, potassium silicate, and silica sol are used. As the aluminum compound, aluminum sulfate, aluminum chloride, aluminum nitrate, and polyaluminum chloride are used. Examples of the phosphorus compound include phosphoric acid and water-soluble phosphate, and one or more of them can be used. In addition, it is recommended to use a waste liquid containing these raw materials from an economic and environmental viewpoint.
The order of addition of the silicon compound, aluminum compound, and phosphorus compound as raw materials is not particularly limited, and the aluminum compound may be added to the silicon compound, and then the phosphorus compound may be added. Conversely, the aluminum compound is added to the phosphorus compound. Then, a silicon compound may be added, or any method such as a method of adding a phosphorus compound to an aluminum compound and then adding a silicon compound may be used. These three kinds of raw materials may be added simultaneously.

  In the present invention, after reacting the silicon compound, the aluminum compound and the phosphorus compound, it is preferable to neutralize the pH of the slurry with an acid or alkali neutralizer to pH 3 to 10, preferably pH 5 to 8. As the neutralizing agent, sulfuric acid may be used for acid, and sodium hydroxide may be used for alkali. By adjusting the pH of the heavy metal treating agent of the present invention within the above range, the heavy metal immobilization ability is improved.

Next, with respect to the reaction temperature in the process of producing the heavy metal treating agent of the present invention, the reaction is optimally 50 ° C. or less, preferably around room temperature. When the reaction temperature is 50 ° C. or higher, the ability to immobilize heavy metals decreases. However, heating and aging the neutralized slurry after completion of the reaction is extremely effective, and the heavy metal immobilization ability is considerably improved. Although there is no special restriction | limiting regarding the heat aging temperature at this time, Preferably it is below a boiling point on an installation. The aging time is about 30 minutes to 1 hour.
As for the filtration method of the slurry liquid obtained after the reaction / neutralization, any separation method may be adopted as long as the solid-liquid separation can be performed, and examples thereof include centrifugal separation and filter press.
Regarding the method for drying the wet cake after the solid-liquid separation, a normal drying method may be used, and a stationary drying method, a spray drying method, and the like can be exemplified. The drying temperature may be any temperature as long as it is dried, but is preferably 150 ° C. or lower.

Examples of the pulverization method include a ball mill and a vibration ball mill. Regarding the classification method, it can be carried out with a normal classifier, a vibration sieve or the like. Next, regarding the particle size, for example, when used for incineration ash, it is preferably 500 μm or less, more preferably 250 μm or less from the viewpoint of reactivity with incineration ash.
Although the mechanism by which the aluminum phosphate silicate of the present invention stabilizes and stabilizes heavy metals is not clear, in addition to the ion exchange capacity of aluminum silicate and the capture of heavy metals by acting as a solid acid, the three components of phosphorus, aluminum and silicon have a structure It is presumed that a new heavy metal fixation and stabilization mechanism is formed by uniformly bonding within the inside. Even if these three components are added separately, the effects of the present invention cannot be obtained. That is, when aluminum sulfate, sodium silicate and phosphoric acid are separately added to a heavy metal-containing waste and treated, or when aluminum silicate and phosphoric acid are separately added and treated, the present invention aluminum phosphate silicate is added Thus, it is presumed that the mechanism of action on heavy metals is different from the case of treatment.

Next, the processing method of the heavy metal containing waste by the heavy metal processing agent of this invention is demonstrated. The treatment agent of the present invention may be used alone or in combination with other drugs. Particularly preferred combination drugs include mineral acid, aluminum sulfate, activated clay, acidic clay and the like. As a treatment method, the heavy metal treatment agent of the present invention, a concomitant drug, and water are added to the heavy metal-containing waste and kneaded well. There is no particular limitation regarding the order of addition of the heavy metal treating agent of the present invention, the concomitant drug and water to the waste, and these may be added simultaneously.
In addition, the treatment agents such as cement, water glass, aluminum silicate, phosphoric acid, aluminum phosphate, aluminum hydroxide, iron sulfate, iron chloride, chelating agent, zeolite, carbon dioxide gas, etc. that have been used so far are effective in the present invention. As long as it is not lowered, it does not prevent the combined use with the aluminum phosphate silicate of the present invention.

The heavy metal treating agent of the present invention may be directly added to the incineration ash generated from the incineration site and treated as described above, or the treated product may be molded and solidified by extrusion molding or the like as necessary. Moreover, it can also be used in the flue which processes acidic gas etc. In this case, the heavy metal treating agent of the present invention may be used alone, or may be used by mixing with chemicals such as slaked lime and activated carbon usually used in a flue. The waste to which the heavy metal treating agent of the present invention can be applied is a waste containing a harmful heavy metal such as lead, chromium, cadmium, mercury, copper, zinc or nickel, and in particular, the above-mentioned municipal waste and industrial waste. Incinerated ash, particularly main ash, incinerated fly ash, and molten fly ash are listed as good examples, but good results can be expected when applied to mines, soil, sludge, and the like.
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited only to the said Example. In Examples, unless otherwise specified, all “%” means “% by mass”.

In a 2 L beaker, 21.5 g of a sodium silicate solution (SiO ₂ : 28% manufactured by Tosoh Sangyo Co., Ltd.) was taken and diluted 20 times with distilled water. 100 g of an aluminum sulfate solution (Al ₂ O ₃ : 8% manufactured by Taki Chemical Co., Ltd.) was added to the solution with stirring, and then 2.9 g of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added and mixed. Subsequently, after neutralizing to pH 7 with 20% sodium hydroxide solution, the obtained slurry was filtered with No. 5A filter paper and washed with 500 ml of distilled water. The obtained wet cake was dried in a dryer at 105 ° C. for 12 hours. After drying, the mixture was pulverized in a mortar and classified with a sieve to 250 μm or less to obtain a heavy metal treating agent.

In a 2 L beaker, 14.8 g of a sodium silicate solution (SiO ₂ : 28% manufactured by Tosoh Sangyo Co., Ltd.) was taken and diluted 20 times with distilled water. 100 g of an aluminum sulfate solution (Al ₂ O ₃ : 8% manufactured by Taki Chemical Co., Ltd.) was added to the solution with stirring, and then 9.3 g of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added and mixed. Next, after neutralizing to pH 7 with 20% sodium hydroxide solution, the resulting slurry was heated and aged for 1 hour under boiling, then filtered through No. 5A filter paper and washed with 500 ml of distilled water. The obtained wet cake was dried in a dryer at 105 ° C. for 12 hours. After drying, the mixture was pulverized in a mortar and classified with a sieve to 250 μm or less to obtain a heavy metal treating agent.

Take 100 g of aluminum sulfate solution (Al ₂ O ₃ : manufactured by Taki Chemical Co., Ltd.) in a ₂ L beaker and add 5.7 g of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.) to the solution under stirring. Then, a solution obtained by diluting 10.9 g of a sodium silicate solution (SiO ₂ : 28%, manufactured by Tosoh Sangyo Co., Ltd.) 20 times was added and mixed. Subsequently, after neutralizing to pH 7 with 20% sodium hydroxide solution, the obtained slurry was filtered with No. 5A filter paper and washed with 500 ml of distilled water. The obtained wet cake was dried in a dryer at 105 ° C. for 12 hours. After drying, the mixture was pulverized in a mortar and classified with a sieve to 250 μm or less to obtain a heavy metal treating agent.

In a 2 L beaker, 2.2 g of a sodium silicate solution (SiO ₂ : 28%, manufactured by Tosoh Sangyo Co., Ltd.) was taken and diluted 20 times with distilled water. 100 g of aluminum sulfate solution (Al ₂ O ₃ : 8% manufactured by Taki Chemical Co., Ltd.) was added to the solution with stirring, and then sodium dihydrogen phosphate dihydrate (manufactured by Kanto Chemical Co., Ltd.) 7.5 g Were added and mixed. Then, after neutralizing to pH 7 with 20% sodium hydroxide solution, the obtained slurry was filtered with No. 5A filter paper and washed with 500 ml of distilled water. The obtained wet cake was dried in a dryer at 105 ° C. for 12 hours. After drying, the mixture was pulverized in a mortar and classified with a sieve to 250 μm or less to obtain a heavy metal treating agent.

[Comparative Example 1]
In a 5 L beaker, 61.5 g of sodium silicate solution (SiO ₂ : 28% manufactured by Tosoh Sangyo Co., Ltd.) was taken and diluted 20 times with distilled water. 100 g of an aluminum sulfate solution (Al ₂ O ₃ : 8% manufactured by Taki Chemical Co., Ltd.) was added to the solution with stirring, and then 2.9 g of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added and mixed. Then, after neutralizing to pH 7 with 20% sodium hydroxide solution, the obtained slurry was filtered with No. 5A filter paper and washed with 500 ml of distilled water. The obtained wet cake was dried in a dryer at 105 ° C. for 12 hours. After drying, the mixture was pulverized in a mortar and classified with a sieve to 250 μm or less to obtain a heavy metal treating agent.

[Comparative Example 2]
In a 5 L beaker, 0.17 g of a sodium silicate solution (SiO ₂ : 28%, manufactured by Tosoh Sangyo Co., Ltd.) was taken and diluted 20 times with distilled water. 100 g of an aluminum sulfate solution (Al ₂ O ₃ : 8% manufactured by Taki Chemical Co., Ltd.) was added to the solution with stirring, and then 11.2 g of 85% phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added and mixed. Then, after neutralizing to pH 7 with 20% sodium hydroxide solution, the obtained slurry was filtered with No. 5A filter paper and washed with 500 ml of distilled water. The obtained wet cake was dried in a dryer at 105 ° C. for 12 hours. After drying, the mixture was pulverized in a mortar and classified with a sieve to 250 μm or less to obtain a heavy metal treating agent.

[Comparative Example 3]
In a 5 L beaker, 16.0 g of sodium silicate solution (SiO ₂ : 28% manufactured by Tosoh Sangyo Co., Ltd.) was taken and diluted 20 times with distilled water. 100 g of an aluminum sulfate solution (Al ₂ O ₃ : 8% manufactured by Taki Chemical Co., Ltd.) was added and mixed into the solution under stirring. Then, after neutralizing to pH 7 with 20% sodium hydroxide solution, the obtained slurry was filtered with No. 5A filter paper and washed with 500 ml of distilled water. The obtained wet cake was dried in a dryer at 105 ° C. for 12 hours. After drying, the mixture was pulverized in a mortar and classified with a sieve to 250 μm or less to obtain a heavy metal treating agent.
"Heavy metal treatment test"
The heavy metal treating agents obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were analyzed using a fluorescent X-ray apparatus, and SiO ₂ / Al ₂ O ₃ (molar ratio) and P ₂ O ₅ / Al ₂ were analyzed. O ₃ (molar ratio) was determined. The results are shown in Table 1.

Incineration fly ash was treated with a heavy metal treating agent having the above composition, and a heavy metal elution test was conducted. The incineration fly ash used was the incineration fly ash (Pb 0.15%, Zn 0.66%, Cr 110ppm; Pb elution amount 31.7mg / l) at the K City garbage treatment plant. After 15% of the heavy metal treating agent obtained in Examples and Comparative Examples and 30% of water were added to the ash and kneaded, the dissolution test was conducted by the method described in Notification No. 13 of the Environment Agency in 1973. The dissolution test results are shown in Table 2.
In addition to the above heavy metal treating agent, the reagent aluminum silicate (manufactured by Yoneyama Pharmaceutical Co., Ltd., Al ₂ O ₃ · 3SiO ₂ ) is used as Comparative Example 4 in the same proportion as above and 85% phosphoric acid solution as Comparative Example 5 (Wako Pure Chemicals, reagent grade) results when used in the same proportion as above, and as Comparative Example 6 when 10% of the heavy metal treatment agent of Comparative Example 3 and 85% phosphoric acid 6% are used together (SiO ₂ / Al ₂ O ₃ = 0.95, P ₂ O ₅ / Al ₂ O ₃ = 0.53) are also shown in Table 2.
In addition, in Example 5, the heavy metal treatment agent of Example 3 was added to the incineration fly ash (Pb 0.10%, Zn 0.43%, Cr 60ppm; Pb elution amount: 18.2 mg / l) at the A municipal waste incineration plant. The dissolution test results are also shown in Table 2.

As is apparent from the dissolution test results shown in Table 2, the composition is extremely important even with the same powdery aluminum phosphate silicate, and it is easily treated with the heavy metal treatment agent of the present invention for lead landfill standards. The lead elution amount can be reduced to 0.3 ppm or less. As for heavy metals other than lead, the elution amounts were Zn 1 ppm or less and Cr 0.05 ppm or less in any of the examples. Thereby, it was confirmed that the heavy metal processing agent of this invention is effective with respect to the waste containing harmful heavy metals, such as lead.

The heavy metal treatment agent of the present invention is composed of aluminum phosphate silicate, and is excellent in heavy metal immobilization ability when treating waste containing harmful heavy metals, especially incineration ash, for example, lead elution, which is the standard for lead reclamation. Since the amount can be reduced to 0.3 ppm or less, it is very effective for detoxifying heavy metal-containing waste.

Claims (2)

A silicon compound selected from sodium silicate, potassium silicate, and silica sol; an aluminum compound selected from aluminum sulfate, aluminum chloride, aluminum nitrate, and polyaluminum chloride; and phosphorus selected from phosphoric acid and water-soluble phosphate Compound with SiO ₂ / Al ₂ O ₃ Molar ratio 0.03-3.0, P ₂ O ₅ / Al ₂ O ₃ Heavy metal treatment selected from lead, zinc, and chromium consisting of powdered aluminum phosphate silicate characterized by mixing and reacting in a molar ratio of 0.01 to 1.5, separating and drying the precipitated product Manufacturing method. The method for producing a heavy metal treatment agent according to claim 1, wherein the heavy metal is a heavy metal contained in municipal waste incineration ash or industrial waste incineration ash.