JPH11123376A - Treatment method for heavy metal-containing waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method for a heavy metal-containing waste for solidifying efficiently and stably heavy metals in the heavy metal-containing waste and preventing the elution of heavy metals. SOLUTION: In a treatment method, a heavy metal-containing waste A, an alkali metal compound or an alkali earth metal compound B, sulfur C and a metal salt having a standard electrode potential larger than that of cations of the component B are melt kneaded in the presence of a non-aqueous medium and then cooled and solidified. Further heavy metal containing waste A, a sulfide E and the metal salt having a standard electrode potential larger than that of cations of the component E are melt kneaded in the presence of a non- aqueous medium, and then cooled and solidified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for insolubilizing heavy metals such as lead, cadmium and chromium in heavy metal-containing waste,
It relates to a processing method for stabilization.

[0002]

2. Description of the Related Art In recent years, as the amount of garbage and waste generated from cities and factories has increased remarkably, heavy metals are contained in incinerated ash and fly ash discharged by incineration. There is a need for safer detoxification measures. Conventionally, a method of solidifying using cement has been proposed.However, while it is possible to simultaneously fix heavy metals and solidify wastes, it is difficult to completely fix heavy metals, and heavy metals from wastes are removed. Not only is it difficult to completely suppress the dissolution, but also it takes time to cure the cement. In addition, a method of eluting with a mineral acid has been proposed. However, the elution operation using an acid is not only complicated, but also has a disadvantage that the waste must be separately immobilized.

Further, as a treatment method for insolubilizing and rendering harmless heavy metals such as lead and cadmium in incinerator ash discharged from a general incinerator, for example, JP-A-53-39262 is known.
JP, JP-A-55-1830, JP-A-59-7830
No. 30,91, JP-A-63-111990, JP-A-9-24355, and the like. These are obtained by mixing and kneading water-soluble sulfides such as sodium sulfide and calcium sulfide with incineration ash and the like, and heavy metals in the incineration ash are detoxified as insoluble sulfides such as lead sulfide. However, in general, the solubility of heavy metal sulfides in water is very small, and the precipitated particles of heavy metal sulfides formed are extremely small, around 0.01 micron,
In addition, since many of them have relatively good dispersibility in water, they have a problem that they pass through filter paper having an average pore size of 1 micron in a test based on the notification of the Environment Agency Notification No. 13. Also,
JP-A-2-203981 discloses a method using a polymer containing an organic carboxylic acid to solve this problem, but has a problem that it is economically disadvantageous.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above point of view, and is intended to efficiently and stably fix heavy metals in heavy metal-containing waste and prevent heavy metal-containing waste from being eluted. It is an object to provide a processing method.

[0005]

The inventors of the present invention have studied to solve the problems of the conventional method and found that (A) heavy metal-containing waste, (B) hydroxide of alkali metal or alkaline earth metal or A method for treating a heavy metal-containing waste, which is obtained by melt-kneading an oxide and (C) sulfur in the presence of a non-aqueous medium and then cooling and solidifying, and (A) a heavy metal-containing waste and (D) a sulfide in a non-aqueous medium A method for treating heavy metal-containing waste that is melt-kneaded in the presence of and then cooled and solidified (Japanese Patent Application No. 9-17 / 1997).
No. 5902). However, excess sulfide may be eluted, which is not desirable for environmental protection. As a result of further studies, the present inventors have found that the object of the present invention can be effectively achieved by adding a specific metal salt, and have completed the present invention.

That is, the gist of the present invention is as follows. (1) (A): heavy metal-containing waste, (B): alkali metal compound or alkaline earth metal compound, (C): sulfur and (D): the standard electrode potential is larger than the cation of the component (B). After melting and kneading the metal salt in the presence of a non-aqueous medium,
A method for treating heavy metal-containing waste, comprising cooling and solidifying. (2) (A): heavy metal-containing waste, (E): sulfide and (F): a metal salt having a standard electrode potential higher than the cation of the component (E) are melt-kneaded in the presence of a non-aqueous medium. And then solidifying by cooling. (3) The method for treating heavy metal-containing waste according to (1) or (2), wherein the non-aqueous medium is at least one selected from sulfur, asphalt, a thermoplastic resin, and a thermosetting resin.

[0007]

Embodiments of the present invention will be described below. First, heavy metal-containing waste to be treated is the disposal of waste incineration ash, fly ash, sludge, slag, coal ash (fly ash), sludge, etc., containing heavy metals such as chromium, copper, cadmium, mercury, and lead. A thing. When containing water, it is preferable to dry it before the treatment.

The first invention is based on (A): heavy metal-containing waste, (B): alkali metal compound or alkaline earth metal compound, (C): sulfur and (D): cation of component (B). Is a method for treating heavy metal-containing waste, which comprises melting and kneading a metal salt having a large standard electrode potential in the presence of a non-aqueous medium, followed by cooling and solidification. As the component (B), for example, NaOH, Na ₂ O, Na ₂ CO ₃ , KO
H, K ₂ O, Ca (OH) ₂ , CaO, Mg (O
H) ₂ and MgO, and one or more of them can be used. Among them, NaOH, CaO and KOH are preferred.
The form of use may be either powdery or granular.

The amount of the component (B) varies depending on the amount of the heavy metal in the heavy metal-containing waste, but may be about the same mole as the heavy metal. For example, in the case of fly ash, the heavy metal content is 0.01
Therefore, the component (B) may be about 0.1 to 10 parts by weight based on 100 parts by weight of fly ash (dry state). If the amount of the component (B) is too small, the effect of immobilizing the heavy metal may not be sufficient. If the amount is too large, the effect may not be commensurate with the amount and may be economically disadvantageous.

Next, there is no particular limitation on the sulfur of the component (C).
There may be mentioned those produced with the desulfurization of natural gas and petroleum fractions, and it is not necessary to use those having a particularly high purity. The form of use may be either powder or liquid.
If the amount of sulfur as the component (C) is at least equimolar to the component (B), it is sufficient for immobilizing heavy metals. For example, in the case of fly ash, the sulfur may be about 0.1 to 10 parts by weight based on 100 parts by weight of fly ash (dry state). If the amount of sulfur is too small, the effect of immobilizing heavy metals may not be sufficient. If the amount is too large, the effect may not be commensurate with the amount and may be economically disadvantageous.

Finally, as the component (D), a metal salt having a higher standard electrode potential than the cation of the component (B) is used. Examples of the metal include iron, aluminum, magnesium, zinc, and copper. Examples of the salt include sulfates, nitrates, carbonates, chlorides, and hydroxides. Specifically, ferrous sulfate, ferric sulfate, aluminum sulfate, iron chloride, and aluminum chloride ,
Examples thereof include magnesium sulfate, iron hydroxide, and aluminum hydroxide. The amount of the component (D) may be approximately equimolar to the amount (estimated amount) of excess sulfide generated by the reaction between the component (B) and the component (C).

As the non-aqueous medium in which the components (A) to (D) are dispersed, sulfur, asphalt, a thermoplastic resin, a thermosetting resin, and the like are suitably used, and are necessary for solidifying waste. Sulfur acts as a dispersing medium at the same time as the sulfurizing agent. Sulfur is as described above. As the asphalt, there are various asphalts, and natural asphalt, petroleum asphalt such as straight asphalt, blown asphalt, solvent deasphalted asphalt, and the like can be cited. 100
When asphalt is used, high strength can be imparted while sufficiently maintaining the excellent property of making the solidified body flame-retardant, and the range of use of the product is greatly expanded, which is preferable. In addition, as a solvent for deasphalting, propane, butane, and a mixture thereof are preferable. Examples of the thermoplastic resin include polyethylene, polypropylene, polystyrene, polycarbonate, nylon, polyvinyl chloride, and petroleum resin. Examples of the thermosetting resin include an epoxy resin, a xylene resin, a diallyl phthalate resin, a phenol resin, and an unsaturated polyester resin.

The amount of the non-aqueous medium is preferably 10 to 1000 parts by weight based on 100 parts by weight of the heavy metal-containing waste (in a dry state). A predetermined amount of the components (A) to (D) is melt-kneaded in the presence of a non-aqueous medium, but it is better to melt-knead the components (A) to (C), then add (D) and further melt-knead. preferable. In this case, it is preferable to melt-knead the components (A) and (C) and then add and melt the components (B). The components (B) and (C) are preferably melt-kneaded with a non-aqueous medium (excluding sulfur) in advance and used as master batch pellets in terms of handling.

The melting and kneading temperature is preferably 50 ° C. or more, more preferably 60 to 300 ° C. If the temperature is lower than 50 ° C., the reaction between the sulfur and the alkali metal does not proceed, and the sulfuration of the heavy metal may be insufficient. The kneading time is preferably about 1 to 40 minutes. For the kneading, an ordinary kneader used for kneading and kneading a powder and a liquid can be used, and examples thereof include wheel-type, blade-type, and roll-type kneaders. After kneading, by cooling and solidifying, the heavy metal can be immobilized and prevented from being eluted, and the elution of excess sulfide agent can be prevented. Even if the mixture is left as it is after kneading, it solidifies in several tens of minutes, but a solid can be quickly obtained by cooling with air or water. In addition, since it can be easily molded, it can be formed by filling a predetermined mold and cooling it, and can be used as a substitute for a concrete secondary product such as a block.

The second invention is characterized in that (A): heavy metal-containing waste, (E): sulfide and (F): a metal salt having a standard electrode potential larger than that of the cation of the component (E) are used as a non-aqueous medium. This is a method for treating heavy metal-containing waste, which comprises melt-kneading in the presence and then cooling and solidifying. Examples of the sulfide of the component (E) include sodium sulfide, sodium polysulfide, calcium sulfide, calcium polysulfide, potassium sulfide, potassium polysulfide, barium sulfide, barium polysulfide, ammonium sulfide, sodium hydrosulfide, and potassium hydrosulfide. And one or more kinds can be used. Among them, sodium polysulfide and calcium polysulfide are preferable.

The amount of the component (E) varies depending on the amount of the heavy metal in the heavy metal-containing waste, but may be about equimolar to the heavy metal. For example, in the case of fly ash, the heavy metal content is 0.01
Therefore, the amount of component (E) may be about 0.1 to 10 parts by weight based on 100 parts by weight of fly ash (dry state). If the amount of the component (E) is too small, the effect of immobilizing heavy metals may not be sufficient. If the amount is too large, the effect may not be commensurate with the amount and may be economically disadvantageous.

The component (F) is a metal salt having a higher standard electrode potential than the cation of the component (E), and is the same as the metal salt of the component (D) of the first invention. The amount of the component (F) may be approximately equimolar to the excess sulfide used as the component (E). As the non-aqueous medium in which the components (A), (E), and (F) are dispersed, sulfur, asphalt, thermoplastic resin, and the like are suitably used, and are necessary for solidifying waste.
The description of the type of the non-aqueous medium, kneading conditions and the like are the same as in the first invention. However, as for the order of addition, it is preferable to melt-knead the components (A) and (E), then add (F) and further melt-knead. By the treatment methods of the first and second inventions described above, not only can heavy metals in heavy metal-containing wastes be fixed and elution prevented, but also dioxins can be sealed.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto. Examples 1 to 5 and Reference Examples 1 and 2 [Example 1] In a 1-liter stainless steel container heated to 140 ° C, 60 g of propane deasphalted asphalt (penetration of 5) was taken from an electric dust collector of a refuse incinerator. 100 g of the collected dried fly ash A (pH = 12.5), powdered sulfur 1 of the reagent
0 g was sampled and melt-kneaded for 30 minutes. After kneading, 6 g of powdery sodium hydroxide was added, and stirring was continued for 15 minutes. Thereafter, 14 g of ferrous sulfate heptahydrate granular material was gradually added, and stirring was continued for another 10 minutes. Thereafter, the mixture was cooled to room temperature to obtain a solid.
The solid was subjected to a lead dissolution test and a polysulfide dissolution test as follows. That is, the solidified product was crushed and sieved with a resin sieve to obtain a sample having a particle size of 0.5 to 5 mm.
50 g of this sample was taken, and 5 parts of water adjusted to pH 6.0 was added.
After adding 00 cc, the mixture was shaken continuously for 6 hours with a shaker.
Next, the presence or absence of coloring was visually checked using a solution filtered with a 1-micron glass filter paper, but no coloring was observed, and it was revealed that polysulfide was not eluted. The lead concentration in the solution was measured. The lead concentration is 0.
It was 1 ppm or less (the same applies hereinafter in mg / liter), which was below the landfill standard. In addition, the measurement of the pH of the fly ash used for the sample is as follows. Take a 10g sample and add 10g
0 cc of ion-exchanged water was added and stirred for 3 minutes. The pH of this suspension was measured with a simple pH meter.

Example 2 In a 1-liter stainless steel container heated to 140 ° C., 60 g of propane deasphalted asphalt (penetration of 5) and fly ash A (same as in Example 1) 10
0 g and 10 g of powdered sulfur as a reagent were taken and melt-kneaded for 30 minutes. After kneading, 3 g of powdery sodium hydroxide was added, and stirring was continued for 15 minutes. Thereafter, 10 g of ferric sulfate hydrate granules were gradually added, and stirring was continued for another 10 minutes. Thereafter, the mixture was cooled to room temperature to obtain a solid. When a lead dissolution test and a polysulfide dissolution test were performed on this solidified product in the same manner as in Example 1, the lead concentration was 0.1 ppm or less, which was below the landfill standard. In addition, it was confirmed that polysulfide was not eluted.

Example 3 In a 1-liter stainless steel container heated to 140 ° C., 60 g of propane deasphalted asphalt (penetration of 5) and fly ash A (same as in Example 1) 10
0 g and 10 g of powdered sulfur as a reagent were taken and melt-kneaded for 30 minutes. After kneading, 3 g of powdery sodium hydroxide was added, and stirring was continued for 15 minutes. After that, aluminum sulfate hydrate granules 8
g was added slowly and stirring was continued for another 10 minutes. Thereafter, the mixture was cooled to room temperature to obtain a solid. When a lead dissolution test and a polysulfide dissolution test were performed on this solidified product in the same manner as in Example 1, the lead concentration was 0.1 ppm or less, which was below the landfill standard. In addition, it was confirmed that polysulfide was not eluted.

Example 4 In a 1-liter stainless steel container heated to 140 ° C., 60 g of propane deasphalted asphalt (penetration 5) and fly ash A (same as in Example 1) 10
0 g and 10 g of powdered sulfur as a reagent were taken and melt-kneaded for 30 minutes. After kneading, 3 g of powdery sodium hydroxide was added, and stirring was continued for 15 minutes. Then aluminum chloride hexahydrate granules 3
g was added slowly and stirring was continued for another 10 minutes. Thereafter, the mixture was cooled to room temperature to obtain a solid. When a lead dissolution test and a polysulfide dissolution test were performed on this solidified product in the same manner as in Example 1, the lead concentration was 0.1 ppm or less, which was below the landfill standard. In addition, it was confirmed that polysulfide was not eluted.

Example 5 In a 1-liter stainless steel container heated to 140 ° C., 60 g of propane deasphalted asphalt (penetration of 5) and fly ash A (same as in Example 1) 10
0 g and 10 g of powdered sulfur as a reagent were taken and melt-kneaded for 30 minutes. After kneading, 20 g of sodium sulfide nonahydrate was gradually added, and stirring was further continued for 15 minutes. Thereafter, 10 g of ferrous sulfate heptahydrate granular material was gradually added, and stirring was continued for another 10 minutes. Thereafter, the mixture was cooled to room temperature to obtain a solid. When a lead dissolution test and a polysulfide dissolution test were performed on this solidified product in the same manner as in Example 1, the lead concentration was 0.1 ppm or less, which was below the landfill standard. In addition, it was confirmed that polysulfide was not eluted.

Reference Example 1 In a 1-liter stainless steel container heated to 140 ° C., 60 g of propane deasphalted asphalt (penetration of 5) and fly ash A (same as in Example 1) 10
0 g and 10 g of powdered sulfur as a reagent were taken and melt-kneaded for 30 minutes. After kneading, 6 g of powdery sodium hydroxide was added, and stirring was continued for 15 minutes. Thereafter, the mixture was cooled to room temperature to obtain a solid. The solid was subjected to a lead dissolution test and a polysulfide dissolution test in the same manner as in Example 1. The lead concentration was 0.1 p.
pm or less and below the landfill standard. However, the filtered solution was colored yellow, and the elution of polysulfide was confirmed.

Reference Example 2 In a 1-liter stainless steel container heated to 140 ° C., 60 g of propane deasphalted asphalt (penetration of 5) and fly ash A (same as in Example 1) 10
0 g and 10 g of powdered sulfur as a reagent were taken and melt-kneaded for 30 minutes. After kneading, 3 g of powdery sodium hydroxide was added, and stirring was continued for 15 minutes. Thereafter, the mixture was cooled to room temperature to obtain a solid. The solid was subjected to a lead dissolution test and a polysulfide dissolution test in the same manner as in Example 1. The lead concentration was 0.1 p.
pm or less and below the landfill standard. However, the filtered solution was colored yellow, and the elution of polysulfide was confirmed.

[0025]

According to the present invention, the elution can be prevented by efficiently fixing the heavy metals in the heavy metal-containing waste, and no excessive polysulfide is eluted. is there.

Claims (3)

[Claims] (A): heavy metal-containing waste, (B): alkali metal compound or alkaline earth metal compound,
(C): Sulfur and (D): A metal salt having a standard electrode potential higher than that of the cation of the component (B) is melt-kneaded in the presence of a non-aqueous medium, and then solidified by cooling. How to handle things. (A): heavy metal-containing waste; (E): sulfide; and (F): a metal salt having a standard electrode potential higher than the cation of the component (E) in the presence of a non-aqueous medium. A method for treating heavy metal-containing waste, comprising kneading and then cooling and solidifying. 3. The method for treating heavy metal-containing waste according to claim 1, wherein the non-aqueous medium is at least one selected from sulfur, asphalt, thermoplastic resin, and thermosetting resin.