JP2000015222A - Methods for treating solid waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating solid waste which can fix both 'hard' metals such as lead and mercury and 'soft' metals such as zinc, cadmium, and nickel surely, and the solid waste can be treated surely while the re- elution of solidified metals being prevented completely. SOLUTION: In a method for treating solid waste, a metal scavenger having at least one kind of group shown by -(CH2)n -COOH (wherein n is an integer of 1-4) or -CH2 CHRCOOH (wherein R is -CH3 or -CH2COOH) or its salt which substituted for an active hydrogen atom and has bonded to a nitrogen atom in a molecule of polyamines as an functional group is added to the solid waste in order to fix the metals in the waste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for securely fixing harmful metals present in solid wastes such as incinerated ash, dust, slag, sludge, soil, shredder dust, etc., and to secure solid wastes. The present invention relates to a method for treating solid waste that can be treated.

[0002]

2. Description of the Related Art Various metals are contained in solid waste such as dust generated in garbage incineration plants, slag discharged from mines, activated sludge used in wastewater treatment, and contaminated soil. It often contains a large amount of heavy metals harmful to the human body, such as mercury, cadmium, lead, zinc, copper, and chromium. When metals are eluted from these solid wastes, there is a possibility that groundwater, rivers, seawater, etc. will be contaminated.

[0003] Conventionally, therefore, a method has been adopted in which solid waste is solidified with cement and then buried in landfills. However, when the solid waste comes into contact with seawater or rainwater, metal enters seawater or soil through the cement wall. There is a risk of elution, and this method was not always a safe treatment method. In order to solve such a problem, in recent years, a method of immobilizing a metal in solid waste using a metal collecting agent has been widely adopted. As a metal collecting agent, a compound having a dithioic acid group or a salt of a dithioic acid group as a functional group having excellent fixing ability to mercury or lead (dithioic acid type metal collecting agent) is widely used. For example, compounds having a structure in which a dithioic acid group or a salt of a dithioic acid group is bonded as a functional group to a nitrogen atom of an amine such as a polyalkylene polyamine such as ethylenediamine or triethylenetetramine or an amine such as polyethyleneimine have been known (Japanese Patent Publication No. HEI 9-222). 5-7079, Japanese Patent Publication 5-
No. 7080).

[0004]

However, dithioic acid type metal scavengers are said to have an excellent ability to immobilize metals such as mercury, lead, gold, silver, zinc, cadmium, copper and chromium. However, in actuality, it exerts a very good immobilization ability on so-called "hard" metals such as mercury, lead, gold and silver, but on the other hand so-called metals such as zinc, cadmium and nickel. The ability to immobilize "soft" metals was not always sufficient. Further, the conventional dithioic acid-type metal trapping agent has a problem in that when added to solid waste, there is a risk of generating harmful gas.

[0005] For this reason, conventionally, a special functional group has been introduced into amines, or copolymerized with other monomers copolymerizable with amines to form a skeleton of the metal collecting agent into a special structure. The aim was to improve the ability to immobilize "soft" metals, but the effect of improving the ability to immobilize "soft" metals was not always sufficient. In addition, the introduction of special substituents and the use of amines There is a problem in that a complicated operation is required for copolymerization, and the cost of the final reaction product becomes low due to a low yield. In addition, when solid waste is treated with a metal trapping agent, not only does the metal in the solid waste react quickly with the metal trapping agent, but also the solid waste after treatment becomes rainwater (particularly, It is also necessary to have an elution resistance such that the immobilized metal is not easily eluted from the solid waste even when exposed to acid rain). However, in the case of the above-mentioned conventional metal collectors which have improved the immobilization ability for "soft" metals, the elution resistance was insufficient, especially for "soft" metals.

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that at least one of dithioic acids or salts thereof is used.
When a metal trapping agent having a species and a specific functional group of a carboxylic acid type is used for the treatment of solid waste, the drawbacks of the conventional dithioic acid type metal collecting agent can be solved and “hard” metal In addition, it exhibits excellent immobilization ability even for “soft” metals, has excellent elution resistance of the immobilized metals, and emits harmful gases even when added to solid waste. It has been found that solid waste can be efficiently treated without any risk of occurrence and without problems such as high cost as in the method using a special metal collecting agent, thereby completing the present invention. Reached.

[0007]

That is, the method for treating solid waste according to the present invention comprises the following steps in which one molecule of amines is substituted with an active hydrogen atom of the amines and bonded to a nitrogen atom of the amines. A metal trapping agent having as a functional group at least one of the groups represented by the formulas (1) and (2) or a salt thereof and a dithioic acid group or at least one of the salts thereof is added to the solid waste. And fixing the metal in the solid waste.

[0008]

Embedded image-(CH ₂ ) _n -COOH (1) (where n is an integer of 1 to 4)

[0009]

Embedded image —CH ₂ CHRCOOH (2) (where R is —CH ₃ or —CH ₂ COOH)

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The metal scavenger used in the present invention is, for example, a functional group represented by the above formula (1) or (2) introduced into an amine and then reacted with carbon disulfide to obtain a dithioic acid group. Or by reacting an amine with carbon disulfide to introduce a dithioacid group, and then introducing a functional group represented by the above formula (1) or (2).

In order to convert the above-mentioned functional group into a salt form, a method of treating with an alkali after completion of the reaction or performing the above-mentioned reaction in the presence of an alkali is employed. Examples of the alkali include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, barium hydroxide and magnesium hydroxide, ammonia, sodium carbonate, and carbonate. Potassium, calcium carbonate and the like.

The above-mentioned amines are those represented by the above formulas (1) and (2) or salts thereof (the functional groups of these functional groups are
For convenience, it is called the first functional group. ) And at least one of
At least one of a dithioic acid group and a salt of a dithioic acid group (the functional groups of these functional groups are conveniently referred to as a second functional group).
It is necessary to be able to introduce species. Accordingly, in the case where the amines have an amino group in which two active hydrogen atoms are bonded to a nitrogen atom, any amine having at least one amino group may be used. If the compound has an imino group formed by bonding an active hydrogen atom, it is necessary to have at least two or more imino groups.

Examples of such amines include ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine,
Dipropylene triamine, dibutylene triamine, triethylene tetramine, tripropylene tetramine, tribubutylene tetramine, tetraethylene pentamine, tetrapropylene pentamine, tetrabutylene pentamine,
Polyalkylenepolyamines such as pentaethylenehexamine; aniline, phenylenediamine, xylenediamine, metaxylenediamine, monomethylaminopropylamine, iminobispropylamine, methyliminobispropylamine, 1,3-bis (aminomethyl) cyclohexane, 1, 3-diaminopropane, 1,4-diaminobutane, 3,5-diaminochlorobenzene, melamine, 1-aminoethylpiperazine, piperazine, diaminophenyl ether, 3,3'-dichlorobenzidine,
Examples include m-toluylenediamine and polyethyleneimine. In the case of polyethyleneimine, the average molecular weight is 3
A value of 00 or more is preferred.

In addition, an alkyl halide,
N-alkylpolyamines, N-hydroxyalkylpolyamines, N-acylpolyamines, etc. obtained by reacting epoxyalkanes or fatty acids can also be used as amines.

The N-alkyl polyamine includes N
-Alkylethylenediamine, N-alkylpropylenediamine, N-alkylhexamethylenediamine, N-
Examples thereof include alkylphenylenediamine, N-alkylxylenediamine, N-alkyldiethylenetriamine, N-alkyltriethylenetetramine, N-alkyltetraethylenepentamine, and N-alkylpentaethylenehexamine. The carbon number of the N-substituted alkyl group is 2 to
18 is preferred.

The N-hydroxyalkylpolyamine preferably has a hydroxyalkyl group having 2 to 28 carbon atoms. Examples of such a hydroxyalkyl group include a hydroxyethyl group, a hydroxypropyl group, a hydroxybutyl group, and a β-hydroxyalkyl group. A hydroxydodecyl group, a β-hydroxytetradecyl group, a β-hydroxyoctadecyl group, a β-hydroxyoctacosyl group and the like.

The acyl group of the N-acylpolyamine is
Those having 2 to 24 carbon atoms are preferred, and examples of such an acyl group include an acetyl group, a propionyl group, a butyryl group, a caproyl group, a lauroyl group, an oleoyl group, a myristiroyl group, a stearoyl group, a beheroyl group, and the like. .

Further, polycondensed polyamines obtained by polycondensing the above amines with epihalohydrin such as epichlorohydrin, epibromhydrin, epiiodohydrin, bromomethyloxirane, etc. can also be used as amines.

In order to introduce the functional groups represented by the above formulas (1) and (2) into the above-mentioned amines, the amines and monohalogenated carboxylic acids such as monochloroacetic acid, monochloropropionic acid and monochlorobutyric acid are used. Examples of the method include a method of reacting, a method of reacting an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, and itaconic acid, and a method of reacting with an unsaturated carboxylic acid ester, acrylonitrile, and the like, followed by hydrolysis.

The metal scavenger used in the present invention needs to have at least one first functional group and at least one second functional group.
It may have two or more of either or both of the second functional groups. When it has two or more first functional groups, those functional groups may be the same or different, and when it has two or more second functional groups, those functional groups are the same. Or different.

The first functional group and the second functional group are introduced as N-substituents bonded to the nitrogen atom of amines. Polyamines polycondensed with epihalohydrin are used as amines. In such a case, the dithioacid group or a salt thereof is not limited to the case in which the dithioacid group is bonded to a nitrogen atom, and may include those bonded to an oxygen atom by replacing a hydrogen atom of a hydroxyl group generated in an epihalohydrin skeleton portion. good.

The solid waste to be treated by the metal treating agent of the present invention includes, for example, incinerated ash, dust, slag, sludge, soil, shredder dust and the like generated in a garbage incineration plant. When the solid waste is collected incineration ash, dust, slag, sludge, soil, shredder dust, etc., the treatment agent of the present invention is added to these wastes in powder form or as an aqueous solution. It can be treated by methods such as spraying, spraying, and kneading. In the case of dust, a method of contacting the treating agent of the present invention with the dust during the incineration process in an incinerator and collecting the treated dust with a bag filter may be employed.

In the method of the present invention, the method of adding the metal treating agent to the solid waste is not particularly limited. For example, by contacting the treating agent of the present invention with the waste by the above-described method, the solid waste can be added. The metal inside can be immobilized. The amount of the metal scavenger added to the solid waste is adjusted according to the amount of metals contained in the solid waste. The addition amount of the metal trapping agent is preferably 0.1 to 10% by weight of the amount of metals in the solid waste. In addition, other metal-collecting agents (for example, dithioic acid-type metal-collecting agents other than those described above) can be used together with the metal-collecting agent as long as the intended purpose of the present invention is not impaired.

The solid waste treated by the method of the present invention may be subjected to final disposal by solidifying the treated waste with cement, if necessary. When the waste after treatment is solidified with cement or the like and finally disposed of, the waste treated by the method of the present invention has a secondary effect due to the elution of metals in the waste even when the amount of cement used is smaller than in the conventional method. There is little risk of contamination.

[0025]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. The metal trapping agents used in the examples and comparative examples are as follows.

Metal Scavenger 1 Two moles of sodium acrylate were reacted with 1 mole of diethylenetriamine and then reacted with 2 moles of carbon disulfide to obtain 2 moles of sodium propionate and 2 moles of sodium dithioate per mole of diethylenetriamine. A metal collector in which 2 moles are introduced as a functional group.

Metal Scavenger 2 After reacting 0.2 mole of acrylonitrile per mole of polyethyleneimine and then reacting with 0.6 mole of carbon disulfide, sodium propionate was obtained per mole of polyethyleneimine. A metal collector in which 0.2 mol and 0.6 mol of sodium dithioate are introduced as functional groups.

Metal Scavenger 3 After reacting 2 mol of sodium methacrylate per mol of ethylenediamine, and reacting with 1.7 mol of carbon disulfide, potassium 2-methylpropionate 2 mol per mol of ethylenediamine was obtained. Moles and potassium dithioate
A metal collector in which 7 mol is introduced as a functional group.

Metal Scavenger 4 After reacting 2 mol of sodium monochloroacetate per mol of tetraethylenepentamine, reacting with 3 mol of carbon disulfide, 2 mol of sodium acetate per mol of tetraethylenepentamine was obtained. A metal trapping agent in which a mole and 3 moles of sodium dithioate are introduced as functional groups.

Metal Scavenger 5 1 mole of methyl acrylate was reacted with 1 mole of diethylenetriamine, saponified with 1 mole of sodium hydroxide, and then reacted with 3 moles of carbon disulfide to obtain 1 mole of diethylenetriamine. , Sodium propionate 1
A metal trapping agent in which a mole and 3 moles of sodium dithioate are introduced as functional groups.

Metal collecting agent 6 Sodium diethyldithiocarbamate

Examples 1 to 5, Comparative Example 1 For 100 g of slag containing 390 mg / kg of mercury, 450 mg / kg of zinc and 210 mg / kg of nickel,
The amount of the metal collector shown in Table 1 as a solid content was 0.5
g of the aqueous solution of the metal trapping agent was sprayed onto the slag surface and kneaded, and then left for 100 minutes. 50 g of 100 g of the treated slag treated in this manner is pH adjusted
= 7 in 500 ml of pure water adjusted to 7
After shaking for 0 minutes, the concentration of the metal eluted in the water was measured by the atomic absorption method. On the other hand, the remaining 50 g of treated slag
At room temperature in 500 ml of pure water at pH = 4.
After shaking for 20 minutes, the eluted metal concentration was measured. The results are shown in Table 1.

[0033]

[Table 1]

Examples 6 to 10 and Comparative Example 2 The metal collection shown in Table 2 per 100 g of dust in a garbage incineration plant containing 360 mg / kg of mercury, 5780 mg / kg of lead, 583 mg / kg of cadmium, and 573 mg / kg of nickel. An aqueous solution of a metal collecting agent was added to the agent so that the addition amount as a solid content was 1.3 g, and the mixture was kneaded for 10 minutes. The metal elution test from the treated dust after the treatment was performed in the same manner as in Examples 1 to 5, using pure water having a pH of 7;
This was performed using pure water having a pH of 4. Table 2 shows the results.

[0035]

[Table 2]

Examples 11 to 15, Comparative Example 3 520 mg / kg of mercury, 3570 mg / kg of nickel,
With respect to 100 g of soil containing 5630 mg / kg of zinc and 312 mg / kg of lead, the metal collector shown in Table 3 was added so that the added amount as a solid content was 2 g,
After kneading for 15 minutes, it was cured for 2 days. The elution test of the metal from the treated soil thus treated was performed using pure water having a pH of 7 and pure water having a pH of 4 in the same manner as in Examples 1 to 5. Table 3 shows the results.

[0037]

[Table 3]

[0038]

According to the method of the present invention, a metal in solid waste is immobilized by using a metal collecting agent having a specific carboxylic acid type functional group together with at least one of dithioic acid groups and salts thereof. By adopting the method, not only is the ability to immobilize on "hard" metals such as mercury and lead, but also the ability to immobilize on "soft" metals such as zinc, cadmium and nickel. For this reason, according to the method of the present invention, even if a “hard” metal or a “soft” metal is contained in the solid waste, the metal in the solid waste can be reliably fixed, Due to the excellent elution resistance of the immobilized metal, even if the solid waste after treatment is exposed to acid rain, the metal may elute from the solid waste and cause recontamination. Therefore, solid waste can be safely treated.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C09K 3/00 108 B09B 3/00 304K (72) Inventor Takeshi Shimizu 4-66, Horikiri, Katsushika-ku, Tokyo No. 1 Miyoshi Oil & Fat Co., Ltd. (72) Inventor Masafumi Moriya 4-66-1, Horikiri, Katsushika-ku, Tokyo F-term in Miyoshi Oil & Fat Co., Ltd. 4D059 AA03 AA11 AA12 AA13 AA14 AA15 AA30 BG00 BK30 DA01 DA02 DA08 DA34 DA38 DA41 DA66 DB03 DB04 DB06 DB08 DB40 EB11

Claims (1)

[Claims] 1. A molecule of an amine which is substituted with an active hydrogen atom of the amine and bonded to a nitrogen atom of the amine.
A solid waste containing a metal collector having at least one of the groups represented by the following formulas (1) and (2) or a salt thereof and a dithioic acid group or at least one of the salts thereof as a functional group: A method for treating solid waste, comprising adding and fixing metals in the solid waste. -(CH ₂ ) _n -COOH (1) (n is an integer of 1 to 4) -CH ₂ CHRCOOH (2) (where R is -CH ₃ or -CH ₂ COOH)