JP5248066B2 - Solid heavy metal fixing agent and incineration ash treatment method - Google Patents

Description

  The present invention relates to a solid heavy metal fixing agent and a method for treating incinerated ash. More specifically, the present invention is intended to fix heavy metals contained in heavy metal-containing wastes, for example, main ash and fly ash discharged from various combustion furnaces such as garbage incinerators and various melting furnaces such as ash melting furnaces. The present invention relates to a particularly suitable solid heavy metal fixing agent and a method for treating incineration ash using the same.

  In general, combustion ash generated from a waste incinerator contains high concentrations of heavy metals harmful to the human body such as lead, mercury, cadmium, chromium, arsenic, and selenium. In order to prevent soil, groundwater and river contamination due to heavy metal elution, treatment selected from the four types of cement solidification method, acid extraction method, chelate solidification method, and melt solidification method, which are required to be treated based on the Ministry of Health and Welfare notification, is applied. And final disposal. Among these four types of treatment methods, many chelate solidification methods that are particularly easy and inexpensive are employed. In general, metal sulfide powders including iron sulfide and aqueous solutions of dithiocarbamic acid alkali salts are used as heavy metal fixing agents (see, for example, Patent Documents 1 to 4).

  When a fly ash treatment agent used as a heavy metal fixing agent used for the fly ash treatment, particularly an alkali salt of dithiocarbamate is used as a fly ash treatment agent, it is generally used as an aqueous solution. For this reason, due to its properties, the amount of waste when the active ingredient increases due to its low content and the fly ash treated with this fly ash treatment agent is disposed of by landfill treatment, etc. There are various problems such as increase, precipitation of solids from the fly ash treating agent aqueous solution, generation of fly ash and toxic gases such as carbon disulfide and hydrogen sulfide.

  In order to improve these problems, a method of adding other components such as xanthate (see Patent Documents 5 and 6), a dithiocarbamic acid alkali salt derived from a bifunctional amine such as piperazine (Patent Document 7) ) Etc. have been put to practical use. However, especially in the latter case, the metal-fixing ability is lower than that of a general alkali salt of dithiocarbamate (for example, potassium diethyldithiocarbamate). In these solutions, an increase in the amount of fly ash treatment agent is inevitable. .

  In addition, due to the recent dioxin problem and the improvement and development of garbage incinerators aimed at reducing or recycling fly ash, main ash and fly ash generated from blast furnace systems and gasification melting furnaces, etc. The content of harmful heavy metals has increased compared to the prior art, and particularly in the case of molten fly ash, secondary fly ash enriched in heavy metals is generated, and conventionally used heavy metal fixing agents such as dithiocarbamine are used. There are many cases where harmful heavy metals cannot be fixed even if the amount of acid alkali salt added is greatly increased.

  On the other hand, as the solid heavy metal fixing agent, a metal sulfide typified by iron sulfide is used as an inorganic chelating agent. In general, these powder chelating agents are difficult to uniformly permeate and disperse in the ash, resulting in the use of excess drug. In addition, what is obtained by drying an aqueous dithiocarbamic acid alkali salt solution into a powder form (see, for example, Patent Document 8) often cannot maintain the powder state for a long time, and is disadvantageous in terms of cost.

  As a solution to these problems, the present applicant has proposed a solid heavy metal fixing agent using a metal salt of dithiocarbamate that is hardly soluble in water (Patent Document 9). Although this drug has a high effect of fixing heavy metals, both fly ash and the drug are solid, and therefore, when a small amount of drug is added, technology and time may be required for uniform mixing of the drug. As a result, due to the poor dispersibility, there has been a case where an amount of drug more than that necessary for immobilizing heavy metals is added. Further, as an improvement, the present applicant has proposed a heavy metal fixing agent with improved mixing and dispersibility by adding a filler (Patent Document 10). Compared to the drug alone, this product also improves the uniform mixing of the drug into the fly ash and can reduce the amount of pure drug required, while increasing the amount of waste by adding the filler. I can't deny that.

Therefore, it has a high ability to immobilize harmful heavy metals from the industry related to waste incinerators, and main ash and fly ash can be mixed with chemicals without using special equipment. There is a strong demand for the development of a new heavy metal fixing agent that can reduce the amount of hydrogen.
JP 08-332475 A Japanese Patent Laid-Open No. 08-224560 JP-A-57-107298 JP 49-099978 A Japanese Patent Application Laid-Open No. 08-041017 JP 09-234450 A Japanese Patent Laid-Open No. 08-224560 JP-A-11-114528 JP 2003-154336 A JP 2003-136039 A

  As described above, the heavy metal fixing agents conventionally used are useful, but heavy metal fixing ability may not be sufficient depending on applications. For this reason, a large amount of heavy metal fixing agent is used, which causes an increase in the use cost of the heavy metal fixing agent and an increase in the total amount of waste treatment products.

  Moreover, when mixing of a heavy metal fixing agent and incineration ash is not favorable, it becomes impossible to prevent elution of heavy metals efficiently. As a result, an excessive amount of the heavy metal fixing agent is used, which causes an increase in the use cost of the heavy metal fixing agent and an increase in the total amount of waste treatment products.

  The present invention relates to a heavy metal fixing agent that can immobilize heavy metals contained in incinerated ash and prevent elution thereof, has a high ability to immobilize harmful metals and is well mixed with incinerated ash, The present invention provides a heavy metal fixing agent capable of fixing a harmful metal sufficiently and efficiently even when used in a small amount.

  As a result of intensive studies in view of the above problems, the present inventors have determined, as a heavy metal fixing agent for treating main ash and fly ash, a heavy metal fixing agent comprising a combination of a specific solid dithiocarbamate and a specific surfactant. Compared to the conventional use of potassium N, N-diethyldithiocarbamate and the use of solid dithiocarbamate alone, carbon disulfide etc. The inventors have found that no toxic gas is generated and have arrived at the present invention.

〔式［Ｉ］中、Ｒ^１およびＲ^２は、それぞれ独立して、炭素数１〜８のアルキル基、ベンジル基またはシクロヘキシル基を示す。また、Ｒ^１およびＲ^２は、その一方がエチル基である場合、残りの一方がフェニル基であることができ、そしてＲ^１およびＲ^２は、それぞれ結合してペンタメチレン基、オキシジエチレン基、イミノジエチレン基またはテトラメチレン基を形成していてもよい。Ｙは、ＺｎまたはＦｅであり、Ｘは２または３の整数を示す。〕 Such a heavy metal fixing agent according to the present invention comprises a dithiocarbamic acid metal salt represented by the following formula [I] and a surfactant.

[In Formula [I], R ¹ and R ² each independently represent an alkyl group having 1 to 8 carbon atoms, a benzyl group, or a cyclohexyl group. In addition, when ^one of R ¹ and R ² is an ethyl group, the other one can be a phenyl group, and R ¹ and R ² are bonded to each other to form a pentamethylene group, an oxydiethylene group, An iminodiethylene group or a tetramethylene group may be formed. Y represents Zn or Fe, and X represents an integer of 2 or 3. ]

  Such a heavy metal fixing agent according to the present invention is preferably composed of at least one inorganic filler selected from the group consisting of activated carbon, silica, slaked lime, clay, iron oxide, iron hydroxide and cement. Include.

  Such a heavy metal fixing agent according to the present invention has, as a preferred embodiment, metal dithiocarbamate and alkyltrimethylammonium chloride represented by the above formula [I], wherein Y is Zn, polyoxyethylene fatty acid ester, dioctylsulfosuccinate salt Consisting of at least one surfactant selected from the group consisting of sorbitan fatty acid esters, aliphatic monocarboxylates, long-chain alcohol polyoxyethylene adducts, polyoxyethylene-added alkyl sulfates and phosphate ester salts .

  Such a heavy metal fixing agent according to the present invention has, as a preferred embodiment, a metal salt of dithiocarbamate and alkyltrimethylammonium chloride represented by the formula [I] wherein Y is Fe, polyoxyethylene fatty acid ester, dioctylsulfosuccinate ester salt , A sorbitan fatty acid ester, a higher alcohol sulfate sodium, and at least one surfactant selected from the group consisting of alkylbenzene sulfonates.

  And the processing method of incineration ash by this invention is characterized by knead | mixing and processing the said solid heavy metal fixing agent and incineration ash.

  The heavy metal fixing agent according to the present invention is a solid agent comprising a dithiocarbamate metal salt represented by the above formula [I] and a surfactant, or a solid agent comprising the above dithiocarbamate metal salt, a surfactant and an inorganic filler. It is a state-of-the-art chemical and has good mixability with incineration ash, and can firmly fix metals contained in incineration ash, particularly heavy metals that have a large impact on the human body and surrounding environment, such as mercury, lead, chromium, and cadmium. The elution of the metal can be reliably prevented.

  The heavy metal fixing agent according to the present invention has a high metal fixing ability and good dispersibility in incineration ash, so that it is necessary to use only a small amount of conventional heavy metal fixing agent for incineration ash to be treated. Can prevent the elution of heavy metals.

  Furthermore, since the heavy metal fixing agent according to the present invention has a high metal fixing ability and good mixing and dispersibility in incineration ash, even in facilities that currently use conventional solid heavy metal fixing agents, Without changing, the required heavy metal elution prevention effect can be obtained by using a small amount of the incinerated ash to be treated as compared with the conventional heavy metal fixing agent.

[Heavy metal fixative]
The heavy metal fixing agent according to the present invention comprises a dithiocarbamic acid metal salt represented by the following formula [I] and a surfactant.

〔式［Ｉ］中、Ｒ^１およびＲ^２は、それぞれ独立して、炭素数１〜８のアルキル基、ベンジル基またはシクロヘキシル基を示す。また、Ｒ^１およびＲ^２は、その一方がエチル基である場合、残りの一方がフェニル基であることができ、そしてＲ^１およびＲ^２は、それぞれ結合してペンタメチレン基、オキシジエチレン基、イミノジエチレン基またはテトラメチレン基を形成していてもよい。Ｙは、ＺｎまたはＦｅであり、Ｘは２または３の整数を示す。〕 Such a heavy metal fixing agent according to the present invention can comprise the above metal salt of dithiocarbamate, a surfactant, and further an inorganic filler.

[In Formula [I], R ¹ and R ² each independently represent an alkyl group having 1 to 8 carbon atoms, a benzyl group, or a cyclohexyl group. In addition, when ^one of R ¹ and R ² is an ethyl group, the other one can be a phenyl group, and R ¹ and R ² are bonded to each other to form a pentamethylene group, an oxydiethylene group, An iminodiethylene group or a tetramethylene group may be formed. Y represents Zn or Fe, and X represents an integer of 2 or 3. ]

Here, as R ¹ and R ² , a methyl group, an ethyl group, and a butyl group are particularly preferable.
Y represents Zn or Fe. X is 2 when Y is Zn, and X is 2 or 3 when Y is Fe.

  Therefore, particularly preferred specific examples of the main dithiocarbamate metal salt according to the present invention include, for example, zinc N, N-dimethyldithiocarbamate, iron N, N-dimethyldithiocarbamate, zinc N, N-diethyldithiocarbamate, N, Iron N-diethyldithiocarbamate, zinc N, N-dibutyldithiocarbamate, iron N, N-dibutyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, iron N-ethyl-N-phenyldithiocarbamate, 1-piperidine Zinc carbodithioate, iron 1-piperidinecarbodithioate, zinc 1-morpholine carbodithioate, iron 1-morpholine carbodithioate, zinc 1-piperazinecarbodithioate, iron 1-piperazinecarbodithioate, 1-pyrrolidinecarbodithio Zinc acid, 1-pyrrolidine Rubojichio iron can be mentioned. Many of these compounds have been conventionally used as vulcanization accelerators in the rubber industry and are currently industrially produced compounds. Dithiocarbamic acid metal salts other than these are compounds that can be synthesized by known production methods.

  As the metal salt of dithiocarbamate according to the present invention, any powder that can be obtained by an ordinary production method can be used. In the present invention, it is preferable to use a material that does not easily cause bridging when being introduced through a hopper or the like, has a large apparent specific gravity, has no adhesion, or has good fluidity.

  Examples of the surfactant according to the present invention include an anionic system such as aliphatic monocarboxylate, sodium higher alcohol sulfate, polyoxyethylene-added alkyl sulfate, alkylbenzenesulfonate, dioctylsulfosuccinate, phosphate ester, etc. Nonionic surfactants such as surfactants, long-chain alcohol polyoxyethylene adducts, polyoxyethylene fatty acid esters and sorbitan fatty acid esters, and cationic surfactants such as quaternary ammonium salts.

  The mixing ratio of the surfactant in the present invention is preferably 0.001 to 10 parts by weight, particularly preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the dithiocarbamate represented by the formula [I]. .

  Specificity is seen in the combination of dithiocarbamic acid metal salt and surfactant. When the optimal combination is selected, a high heavy metal fixing ability can be exhibited with a small amount of addition, compared to the case where the heavy metal fixing agent is used alone.

When zinc dithiocarbamate is selected as the compound represented by the formula [I], the surfactant that is an appropriate combination is:
(I) Alkyltrimethylammonium chloride salts (for example, Arcard (Lion Co., Ltd.), Katiogen (Daiichi Kogyo Seiyaku Co., Ltd.), Econol (Sanyo Kasei Co., Ltd.), Cotamine (Kao Co., Ltd.),
(B) Polyoxyethylene fatty acid esters (for example, Neugen ES (Daiichi Kogyo Seiyaku Co., Ltd.), Ionette M (Sanyo Kasei Co., Ltd.), Emar (Kao Co., Ltd.), etc.)
(C) Dioctylsulfosuccinic acid ester salt (for example, Neocor (Daiichi Kogyo Seiyaku Co., Ltd.), Sanmorin OT-70 (Sanyo Kasei Co., Ltd.), Perex OTP (Kao Co., Ltd.), etc.)
(D) Sorbitan fatty acid ester (for example, Sorgen (Daiichi Kogyo Seiyaku Co., Ltd.), Ionette (Sanyo Kasei Co., Ltd.), Hellship (Kao Co., Ltd.), etc.),
(E) Aliphatic monocarboxylate (for example, red mark needle-shaped soap (Daiichi Kogyo Seiyaku Co., Ltd.), Marcel soap (Lion Co., Ltd.) non-sar (Nippon Yushi Co., Ltd.)),
(F) Polyoxyethylene alkyl ethers (eg, Emulgen (made by Kao Corporation), Emalmine (made by Sanyo Chemical Co., Ltd.), Neugen ET and DKSNL (made by Daiichi Kogyo Seiyaku Co., Ltd.)) and polyoxyalkylene branched decyl ether (Neugen XL (Daiichi Kogyo Seiyaku Co., Ltd.) etc.) and other long chain alcohol polyoxyethylene adducts,
(G) Polyoxyethylene lauryl ether sulfate (for example, Sandet E (manufactured by Sanyo Chemical Co., Ltd.)), polyoxyethylene alkyl ether sulfate (Hitenol (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)), polyoxyethylene alkyl sulfate Polyoxyethylene-added alkyl sulfates such as salts (e.g., EMAL 20 (manufactured by Kao Corporation), etc.)
(H) Phosphoric acid ester salts such as polyoxyethylene alkyl ether phosphates (for example, Prisurf, DKS Elenon (Daiichi Kogyo Seiyaku Co., Ltd.), Phosphanol (Toho Chemical Co., Ltd.), etc.)
At least one selected from the group consisting of:

  Further, when the compound represented by the formula [I] is iron dithiocarbamate, the appropriate surfactants are (b) alkyltrimethylammonium chloride, (b) polyoxyethylene fatty acid ester, (c) ) Dioctyl sulfosuccinic acid ester salt, (d) sorbitan fatty acid ester, and (l) higher alcohol sulfate sodium (eg Sandet ONA (manufactured by Sanyo Chemical Co., Ltd.), Monogen (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Emar (Kao stock) Group), (nu) alkyl benzene sulfonate (for example, Neogen (Daiichi Kogyo Seiyaku Co., Ltd.), Neoperex (Kao Corporation), Raipon LS and PS (Lion Corporation), etc.) Including at least one selected from.

  On the other hand, if the dithiocarbamic acid metal salt and the surfactant are selected incorrectly, the heavy metal immobilization effect may be difficult to obtain by using them in combination. For example, when polyoxyethylene alkyl ether is selected as the surfactant for diethyldithiocarbamate zinc salt, the ability to immobilize heavy metals is seen to be significantly higher than that of no addition. When added to diethyldithiocarbamate iron salt, the ability to immobilize heavy metals is greatly reduced as compared with the case of no addition. There are also cases where both zinc salts and iron salts cause a decrease in the effect, such as naphthalenesulfonate condensates. Therefore, in order to fully exhibit the heavy metal fixing ability of the metal salt of dithiocarbamate, selection of the surfactant used in combination plays an important role.

  Examples of the inorganic filler according to the present invention include activated carbon, silica, slaked lime, clay, iron oxide, iron hydroxide, and cement. Of these, activated carbon, silica and clay are particularly preferable. As the inorganic filler used in the present invention, a powder having good fluidity is preferable.

  The solid heavy metal fixing agent according to the present invention can be prepared by mixing a dithiocarbamic acid metal salt represented by the above formula [I] and a surfactant. When a solid heavy metal fixing agent containing an inorganic filler is intended, it can be prepared by mixing the dithiocarbamic acid metal salt represented by the above formula [I], a surfactant and an inorganic filler. it can.

  The incineration ash treatment method according to the present invention is characterized by kneading and treating the solid heavy metal fixing agent and the incineration ash. This treatment method includes a method in which a predetermined amount of water and the heavy metal fixing agent of the present invention are added to and mixed with incineration ash, for example, main ash and fly ash generated from a waste incinerator. Any mixing method that achieves is intended to be included within the scope of the present invention.

  The mixing ratio of the heavy metal fixing agent and incineration ash according to the present invention is 0.05 to 50% by weight, particularly preferably 0.1 to 20% by weight, based on the incineration ash. The amount of water added is preferably 5 to 60% by weight, particularly preferably 10% to 40%, based on the total weight of the incinerated ash and the heavy metal fixing agent.

  As described above, the heavy metal fixing agent according to the present invention has a sufficient potential by virtue of the optimal selection of surfactants to combine dithiocarbamic acid zinc salt and dithiocarbamic acid iron salt having a potentially high heavy metal fixing effect. Because it is a heavy metal fixing agent that is characterized by the fact that it is used in the treatment of main ash and fly ash, it can be added in a small amount compared to the conventional single use of liquid heavy metal fixing agent and solid heavy metal fixing agent. Heavy metal elution can be suppressed. As a result, the amount of processed main ash and fly ash discharged from the treatment plant can be reduced. Further, with the conventional liquid heavy metal fixing agent, it is possible to easily treat ash containing a high concentration of heavy metal, which is not easy to perform sufficiently due to its excessive amount.

  Hereinafter, the effect of the present invention will be specifically shown by examples. These claims of the present invention are not limited to the embodiments.

<Examples 1 to 23 and Comparative Examples 1 to 10>
For evaluation as a heavy metal fixing agent, lead is selected as a representative metal of harmful metals that elute from incinerated ash (treated fly ash) that has been treated with chemicals by the method described in Notification No. 13 of the Environment Agency, and the elution concentration is determined. The measurement was conducted by comparing the elution suppression effect of lead.

Table 1 shows the properties of the test incineration ash used in this experiment. The metal composition was measured by Hitachi Z-5010 polarized Zeeman atomic absorption spectrophotometer analysis.

Using a heavy metal fixing agent prepared by mixing 95% of diethyldithiocarbamate zinc salt or diethyldithiocarbamate iron salt and 5% of various surfactants, 5% heavy metal fixing agent was added to the incineration ash. The results are shown in Table 2.

  Next, based on the results shown in Table 2, various incineration ash was treated using a combination of zinc diethyldithiocarbamate-polyoxyethylene-added alkylsulfuric acid and a combination of diethyldithiocarbamate-iron-alkylsuccinate. The results are shown.

重金属固定剤：
ＰＤＣ ：56％ジエチルジチオカルバミン酸カリウム水溶液
Ｚｎ ：ジエチルジチオカルバミン酸亜鉛
Ｚｎ-Ｓ１：ジエチルジチオカルバミン酸亜鉛（95％）、ポリオキシエチレン付加アルキル硫酸塩（1％）およびシリカ（4％）の混合物
Ｆｅ ：ジエチルジチオカルバミン酸鉄
Ｆｅ-Ｓ２：ジエチルジチオカルバミン酸鉄（90％）、アルキルコハク酸塩（１％）およびシリカ（9％）の混合物 Table 3 summarizes the amount of heavy metal fixing agent necessary to satisfy the dissolved lead concentration of 0.3 mg / L, which is the landfill standard value (Prime Minister's Ordinance No. 5).

Heavy metal fixative:
PDC: 56% potassium diethyldithiocarbamate aqueous solution Zn: zinc diethyldithiocarbamate Zn-S1: a mixture of zinc diethyldithiocarbamate (95%), polyoxyethylene-added alkyl sulfate (1%) and silica (4%) Fe: diethyl Iron dithiocarbamate Fe-S2: Mixture of iron diethyldithiocarbamate (90%), alkyl succinate (1%) and silica (9%)

  From the results in Table 2, it can be seen that the heavy metal capturing ability varies greatly depending on the type of surfactant used. Some surfactants inhibited the immobilization of heavy metals compared to no addition. In addition, the combination of the metal salt of dithiocarbamic acid and the surfactant shows specificity.

  Therefore, based on the results in Table 2, Table 3 shows the results of the chemical treatment test using a surfactant that improves the ability to capture heavy metals and is inexpensive and easy to handle.

  It can be seen that the amount of drug added necessary to immobilize lead is reduced to 1/2 to 1/3 compared to the case where no surfactant is added or a general-purpose liquid heavy metal fixing agent. Since the reduction in the amount of chemicals added directly leads to a reduction in the amount of processed fly ash discarded, general-purpose liquids such as fly ash B and E (Comparative Examples 15, 16 and 19, Examples 18 and 23, 24). The heavy metal fixing agent is particularly effective for lead-rich fly ash such as molten fly ash in which a large amount of conventional chemicals must be added.

From the above results, the heavy metal fixing agent composed of the dithiocarbamic acid metal salt-surfactant mixture according to the present invention can be obtained by selecting an appropriate combination as described above. It was shown to have an effect of 1.5 to 3 times. Therefore, by using the present invention, the amount of heavy metal fixing agent used can be reduced, and as a result, the total amount of treated fly ash can be reduced, which is useful in the waste incineration industry.

Claims (5)

A solid heavy metal fixing agent comprising a dithiocarbamic acid metal salt represented by the following formula [I] and a surfactant.

[In Formula [I], R ¹ and R ² each independently represent an alkyl group having 1 to 8 carbon atoms, a benzyl group, or a cyclohexyl group. In addition, when ^one of R ¹ and R ² is an ethyl group, the other one can be a phenyl group, and R ¹ and R ² are bonded to each other to form a pentamethylene group, an oxydiethylene group, An iminodiethylene group or a tetramethylene group may be formed. Y represents Zn or Fe, and X represents an integer of 2 or 3. ]   The solid heavy metal fixing agent according to claim 1, comprising at least one inorganic filler selected from the group consisting of activated carbon, silica, slaked lime, clay, iron oxide, iron hydroxide, and cement. Dithiocarbamic acid metal salt and alkyltrimethylammonium chloride represented by the above formula [I] wherein Y is Zn, polyoxyethylene fatty acid ester, dioctylsulfosuccinic acid ester salt, sorbitan fatty acid ester, aliphatic monocarboxylate, long chain alcohol The solid heavy metal fixing agent according to claim 1 or 2, comprising at least one surfactant selected from the group consisting of polyoxyethylene adducts, polyoxyethylene addition alkyl sulfates, and phosphate ester salts. Dithiocarbamic acid metal salt and alkyltrimethylammonium chloride represented by the above formula [I] wherein Y is Fe, polyoxyethylene fatty acid ester, dioctylsulfosuccinic acid ester salt, sorbitan fatty acid ester, sodium higher alcohol sulfate, alkylbenzene sulfonate The solid heavy metal fixing agent according to claim 1 or 2, comprising at least one surfactant selected from the group consisting of:   A method for treating incineration ash, comprising mixing and treating the solid heavy metal fixing agent according to any one of claims 1 to 4 and incineration ash.