JP2019026793A - Heavy metal stabilization agent and manufacturing method therefor, and stabilization method of heavy metal using the same - Google Patents

Abstract

To provide a heavy metal stabilization agent excellent in low temperature stability and a manufacturing method therefor, and a stabilization method of heavy metal using the same.SOLUTION: The heavy metal stabilization agent contain water and piperazine-N,N'-bisdithiocarbamate, and having specific gravity of 1.190 to 1.235. The manufacturing method of the heavy metal stabilization agent has a process for preparing a mixture containing water and piperazine-N,N'-bisdithiocarbamate, and a process for adjusting the specific gravity of the mixture to 1.190 to 1.235. The stabilization method of heavy metal has a process for mixing the heavy metal stabilization agent to a heavy metal-containing article. The stabilization method of heavy metal has a process for obtaining the heavy metal stabilization agent by the manufacturing method of the heavy metal stabilization agent and a process for mixing the heavy metal stabilization agent to the heavy metal-containing article.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heavy metal fixing agent, a production method thereof, and a heavy metal immobilization method using the same.

  Conventionally, incineration ash discharged from incineration plants such as municipal waste and industrial waste, fly ash (including molten fly ash) collected by bag filters, etc. from smoke, contaminated with factory waste water and heavy metals Soil and the like need to prevent the release of heavy metals contained in them to the environment. As the method, a method of immobilizing heavy metals using a heavy metal fixing agent composed of a carbodithioic acid (dithiocarbamic acid) salt of an amine such as diethylamine or piperazine is widely used.

  Patent Document 1 discloses a heavy metal fixing agent mainly composed of an aqueous solution containing piperazine di-N, N′-biscarbodithioate (piperazine-N, N′-bisdithiocarbamate). On the other hand, a heavy metal fixing agent characterized by containing 0.01 to 2.5% by weight or containing 0.01 to 4.5% by weight of polyamine based on the main component and not solidifying at low temperature is described. Yes.

Japanese Patent Laid-Open No. 2004-15639

  However, when piperazine or polyamine is contained in the heavy metal fixing agent, generation of ammonia gas or amine gas becomes remarkable, and an odor problem may occur when the heavy metal is fixed.

  Then, an object of this invention is to provide the heavy metal fixing agent excellent in low temperature stability, its manufacturing method, and the fixing method of heavy metal using the same.

  The heavy metal fixing agent according to the present invention contains water and piperazine-N, N′-bisdithiocarbamate and has a specific gravity of 1.190 to 1.235.

  The method for producing a heavy metal fixing agent according to the present invention comprises a step of preparing a mixture containing water and piperazine-N, N′-bisdithiocarbamate, and the specific gravity of the mixture is adjusted to 1.190 to 1.235. The process of carrying out.

  The heavy metal immobilization method according to the present invention includes a step of mixing the heavy metal fixing agent with a heavy metal-containing material.

  The method for immobilizing a heavy metal according to the present invention includes a step of obtaining a heavy metal fixing agent by the method for producing a heavy metal fixing agent, and a step of mixing the heavy metal fixing agent with a heavy metal-containing material.

  ADVANTAGE OF THE INVENTION According to this invention, the heavy metal fixing agent excellent in low temperature stability, its manufacturing method, and the fixing method of heavy metal using the same can be provided.

It is the graph showing the relationship between the specific gravity in the heavy metal fixing agent manufactured in the Example, and solid substance precipitation temperature.

  The heavy metal fixing agent according to the present invention is for fixing heavy metals in a heavy metal-containing material. Heavy metal containing materials include heavy metal containing incineration ash, heavy metal containing fly ash, heavy metal containing waste water, heavy metal containing soil, etc., but the heavy metal fixing agent according to the present invention is effective for immobilizing heavy metals in heavy metal containing fly ash. It is. Examples of the heavy metal to be immobilized include lead, mercury, chromium, cadmium, zinc, copper, nickel, arsenic, selenium, etc., but the heavy metal fixing agent according to the present invention includes lead, mercury, chromium, cadmium, zinc, It is effective for fixing copper, and particularly effective for fixing lead.

  The heavy metal fixing agent according to the present invention contains water and piperazine di-N, N′-bisdithiocarbamate (piperazine di-N, N′-biscarbodithioate). Usually, piperazine di-N, It is the state of the aqueous solution containing N'-bisdithiocarbamate. Piperazine di-N, N'-bisdithiocarbamate is a compound having a function of immobilizing heavy metals in heavy metal-containing materials.

  As piperazine-N, N′-bisdithiocarbamate, an alkali metal salt, alkaline earth metal salt, ammonium salt, or the like of piperazine-N, N′-bisdithiocarbamate can be used. Examples of the alkali metal include lithium, sodium, and potassium. Examples of the alkaline earth metal include magnesium and calcium. Of these, a thermally stable sodium salt or potassium salt of piperazine-N, N′-bisdithiocarbamic acid is preferable. Piperazine-N, N′-bisdithiocarbamate includes piperazine, carbon disulfide, and an alkali metal compound or an alkaline earth metal compound (for example, an alkali metal hydroxide or an alkaline earth metal hydroxide). It can be synthesized by reacting in water, and by this reaction, a mixture containing water and piperazine-N, N′-bisdithiocarbamate is obtained. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. Examples of the alkaline earth metal hydroxide include magnesium hydroxide and calcium hydroxide.

  In the present invention, the content (concentration) of piperazine di-N, N′-bisdithiocarbamate in the heavy metal fixing agent is preferably adjusted to 25 to 45% by weight. By setting the content of piperazine di-N, N′-bisdithiocarbamate in the heavy metal fixing agent to 25% by weight or more, the ability to immobilize heavy metals can be enhanced. Moreover, generation | occurrence | production of an odor can be suppressed by making the content rate of piperazine di-N, N'-bisdithiocarbamate in a heavy metal fixing agent into 45 weight% or less. The content of piperazine di-N, N′-bisdithiocarbamate in the heavy metal fixing agent is more preferably adjusted to 30 to 41% by weight, and further preferably adjusted to 34 to 39% by weight.

  The heavy metal fixing agent according to the present invention may contain diethyldithiocarbamate (diethylcarbodithioate) as a compound having a function of fixing heavy metals in the heavy metal-containing material.

  As the diethyldithiocarbamate, an alkali metal salt, alkaline earth metal salt, or ammonium salt of diethyldithiocarbamic acid can be used. Examples of the alkali metal include lithium, sodium, and potassium. Examples of the alkaline earth metal include magnesium and calcium. Of these, the sodium salt or potassium salt of diethyldithiocarbamic acid which is thermally stable is preferable. Diethyldithiocarbamate is synthesized by reacting diethylamine, carbon disulfide, and an alkali metal compound or an alkaline earth metal compound (for example, an alkali metal hydroxide or an alkaline earth metal hydroxide) in water. And this reaction yields a mixture containing water and diethyldithiocarbamate. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. Examples of the alkaline earth metal hydroxide include magnesium hydroxide and calcium hydroxide.

  However, heavy metal fixatives containing diethyldithiocarbamate become prominent in the generation of harmful gases such as carbon disulfide gas, which causes a problem of odor when fixing heavy metals. That is, the heavy metal fixing agent according to the present invention preferably does not contain diethyldithiocarbamate, and even when it contains diethyldithiocarbamate, a compound (piperazine having a function of fixing heavy metals in the heavy metal-containing material). -N, N'-bisdithiocarbamate and diethyldithiocarbamate) are preferably in an amount not exceeding 5% by weight.

  The heavy metal fixing agent according to the present invention may contain components other than water, piperazine-N, N′-bisdithiocarbamate, and diethyldithiocarbamate. For example, unreacted piperazine, unreacted carbon disulfide, unreacted alkali metal compound or alkaline earth metal compound, piperazine-N, N′-bisdithiocarbamic acid, piperazine-N-dithiocarbamic acid, piperazine-N-dithiocarbamine Components derived from raw materials such as acid salts, unreacted diethylamine, and diethyldithiocarbamic acid may be included. An alkali metal compound or an alkaline earth metal compound (for example, an alkali metal hydroxide or an alkaline earth metal hydroxide) may be positively added to the heavy metal fixing agent according to the present invention. In addition, the heavy metal fixing agent according to the present invention may contain amines as a stabilizer.

  In Patent Document 1, 0.01 to 2.5% by weight of piperazine or 0.01% of polyamine is added to the main component (an aqueous solution containing piperazine-N, N′-bisdithiocarbamate). Although the low temperature stability is improved by containing ˜4.5% by weight, it is not necessary to actively contain piperazine or polyamine in the present invention. That is, the content of piperazine relative to the main component (an aqueous solution containing piperazine-N, N′-bisdithiocarbamate) in the heavy metal fixing agent according to the present invention may be less than 0.01% by weight, or 0.005% by weight. It may be less. In addition, the content of polyamine relative to the main component (an aqueous solution containing piperazine-N, N′-bisdithiocarbamate) in the heavy metal fixing agent according to the present invention may be less than 0.01% by weight, or 0.005% by weight. It may be less. The piperazine content can be more than 2.5% by weight, and the polyamine content can be more than 4.5% by weight. However, ammonia gas and amine gas are prominently generated, and heavy metal is fixed. Odor problems may occur.

  In the present invention, it is necessary to adjust the specific gravity of the heavy metal fixing agent to 1.190 to 1.235. By adjusting the specific gravity of the heavy metal fixing agent within this range, the solid precipitation temperature of the heavy metal fixing agent is lowered, and the low temperature stability is excellent. The reason for this is not necessarily clear, but if the specific gravity increases, the solid content concentration in the heavy metal fixing agent increases, so the freezing point of the heavy metal fixing agent decreases due to the freezing point depression, while if the specific gravity is too high, This is probably because the solid content concentration of the glass approaches saturation and the solid content tends to precipitate. In the present invention, the specific gravity of the heavy metal fixing agent is preferably adjusted to 1.200 to 1.232, more preferably adjusted to 1.205 to 1.230. The specific gravity of the heavy metal fixing agent can be changed by changing the contents of piperazine-N, N′-bisdithiocarbamate, which is an essential component, and other optional components (especially alkali metal compounds or alkaline earth metal compounds). Can be adjusted.

  In the present invention, it is preferable to adjust the pH of the heavy metal fixing agent to 13.0 or more. By setting the pH of the heavy metal fixing agent to 13.0 or higher, the generation of ammonia, amines, and the like can be suppressed, and the heavy metal fixing agent generates less odor. Moreover, in this invention, it is preferable that pH of a heavy metal fixing agent shall be 14.5 or less. By adjusting the pH of the heavy metal fixing agent to 14.5 or less, the amount of salt such as alkali metal hydroxide or alkaline earth metal hydroxide can be reduced, reducing the cost and fixing the heavy metal fixing agent. It can be maintained without lowering the ability. In the present invention, it is more preferable to adjust the pH of the heavy metal fixing agent to 13.4 to 14.0, and even more preferably to 13.6 to 13.8. In addition, pH said here means the value measured using the pH meter (brand name: HM-41X) by Toa DKK (it is the same below). The pH of the heavy metal fixing agent can be adjusted, for example, by changing the content of the alkali metal compound or alkaline earth metal compound.

  In the present invention, the concentration of the alkali metal compound or alkaline earth metal compound contained in the heavy metal fixing agent is preferably adjusted to 0.75 to 1.50% by weight. By setting the concentration of the alkali metal compound or alkaline earth metal compound contained in the heavy metal fixing agent to 0.75% by weight or more, the specific gravity and pH of the heavy metal fixing agent can be easily adjusted to desired values. Moreover, the ability to fix heavy metals by the heavy metal fixing agent can be maintained by setting the concentration of the alkali metal compound or alkaline earth metal compound contained in the heavy metal fixing agent to 1.50% by weight or less. In the present invention, the concentration of the alkali metal compound or alkaline earth metal compound contained in the heavy metal fixing agent is more preferably adjusted to 1.00 to 1.48% by weight, and adjusted to 1.25 to 1.45% by weight. More preferably.

  The solid precipitation temperature of the heavy metal fixing agent is preferably −11 ° C. or lower, more preferably −12 ° C. or lower, and further preferably −15 ° C. or lower. If the solid precipitation temperature of the heavy metal fixing agent is −11 ° C. or less, it can be said that the low temperature stability is excellent. In addition, the solid substance precipitation temperature of the heavy metal fixing agent in this invention is the temperature measured by the method described in the Example mentioned later.

  Although the above embodiment can be understood as an invention of a heavy metal fixing agent excellent in low-temperature stability and a method for producing the same, it can also be understood as an invention of a method for storing a heavy metal fixing agent. That is, when storing a heavy metal fixing agent containing water and piperazine-N, N′-bisdithiocarbamate, the solid gravity of the heavy metal fixing agent is precipitated by adjusting the specific gravity to 1.190 to 1.235. The temperature decreases, and it becomes possible to store stably even at low temperatures. Preferred embodiments of the heavy metal fixing agent storage method are as described above.

  The heavy metal fixing agent according to the present invention as described above can immobilize heavy metals by mixing with heavy metal-containing materials such as heavy metal-containing incineration ash, heavy metal-containing fly ash, heavy metal-containing wastewater, and heavy metal-containing soil. The amount of heavy metal fixing agent used may be appropriately adjusted depending on the type and amount of heavy metal contained in the heavy metal-containing material, but is preferably 2.8% by weight or more based on the heavy metal-containing material, 3.0% by weight. % Or more is more preferable.

  The content of heavy metal (particularly Pb) in the heavy metal-containing material is usually 300 to 10,000 mg / kg. Further, if the Pb elution amount of the heavy metal-containing material is 5 mg / L or more, the effect of the present invention is exerted greatly, preferably 10 mg / L or more, more preferably 20 mg / L or more, and further preferably 30 mg / L. L or more. The larger the amount of Pb eluted from heavy metals, the greater the effect of immobilizing heavy metals with a smaller amount of heavy metal fixing agent. Therefore, it is not a problem that the amount of Pb eluted from heavy metals is large. Usually 100 mg / L or less. The Pb elution amount of the heavy metal-containing material is, for example, based on the Environmental Agency Notification No. 13 after adding 3 g of heavy metal fixing agent and 27 g of water to 100 g of incinerated fly ash, thoroughly kneading with a mixer, and curing for 24 hours. It can be measured by conducting a Pb elution test.

<Comparative Example 1>
Piperazine (345 g) and water (1067 g) were charged into a 3 L four-necked flask equipped with a stir bar, thermometer, separatory funnel, and condenser, and completely dissolved. Furthermore, 983 g of 48.5% by weight potassium hydroxide was added, and 605 g of carbon disulfide was gently added dropwise over 2 hours while stirring. The temperature at this time was set to 35 to 40 ° C. After dripping the whole quantity of carbon disulfide, the heavy metal fixing agent (A) was obtained by continuing stirring at 40 degreeC for further 1 hour. The piperazine-N, N′-bisdithiocarbamate (PPD) concentration, specific gravity, pH, and KOH concentration of the heavy metal fixing agent (A) are shown in Table 1.

<Comparative example 2>
A heavy metal fixing agent (B) was prepared by mixing 4.4 parts of water with 100 parts by weight of the heavy metal fixing agent (A). Table 1 shows the PPD concentration, specific gravity, pH, and KOH concentration of the heavy metal fixing agent (B).

<Example 1>
A heavy metal fixing agent (C) was prepared by mixing 7.6 parts of water with 100 parts by weight of the heavy metal fixing agent (A). Table 1 shows the PPD concentration, specific gravity, pH, and KOH concentration of the heavy metal fixing agent (C).

<Example 2>
A heavy metal fixing agent (D) was prepared by mixing 11.9 parts of water with 100 parts by weight of the heavy metal fixing agent (A). Table 1 shows the PPD concentration, specific gravity, pH, and KOH concentration of the heavy metal fixing agent (D).

<Example 3>
A heavy metal fixing agent (E) was prepared by mixing 17.1 parts of water with 100 parts by weight of the heavy metal fixing agent (A). Table 1 shows the PPD concentration, specific gravity, pH, and KOH concentration of the heavy metal fixing agent (E).

<Comparative Example 3>
A heavy metal fixing agent (F) was prepared by mixing 25.8 parts of water with 100 parts by weight of the heavy metal fixing agent (A). Table 1 shows the PPD concentration, specific gravity, pH, and KOH concentration of the heavy metal fixing agent (F).

<Comparative example 4>
A heavy metal fixing agent (G) was prepared by mixing 40.0 parts of water with 100 parts by weight of the heavy metal fixing agent (A). Table 1 shows the PPD concentration, specific gravity, pH, and KOH concentration of the heavy metal fixing agent (G).

<Solid matter precipitation temperature>
The solid precipitation temperature of the obtained heavy metal fixing agents (A) to (G) was measured. Specifically, 100 g of each heavy metal fixing agent was weighed into four screw tubes and stored for 1 day using a portable low-temperature refrigerator-freezer to confirm the presence or absence of solid matter precipitation. The temperature in the portable low-temperature refrigerator-freezer was lowered from −8 ° C. by 1 ° C., and the temperature at which solid precipitation was confirmed in two of the four screw tubes was defined as the solid precipitation temperature. While showing a result in Table 1, the graph showing the relationship between the specific gravity of a heavy metal fixing agent and solid substance precipitation temperature is shown in FIG.

  As described above, it can be seen that the heavy metal fixing agent according to the present invention has a solid precipitation temperature of −11 ° C. or lower and is excellent in low-temperature stability.

Claims (10)

A heavy metal fixing agent containing water and piperazine-N, N′-bisdithiocarbamate and having a specific gravity of 1.190 to 1.235. The heavy metal fixing agent according to claim 1, wherein the pH is 13.0 or more. The heavy metal fixing agent according to claim 1 or 2, wherein the concentration of the piperazine-N, N'-bisdithiocarbamate is 25 to 45% by weight. The heavy metal fixing agent according to any one of claims 1 to 3, wherein the solid precipitation temperature is -11 ° C or lower. Preparing a mixture containing water and piperazine-N, N′-bisdithiocarbamate;
And a step of adjusting the specific gravity of the mixture to 1.190 to 1.235. The manufacturing method of the heavy metal fixing agent of Claim 5 which further has the process of adjusting pH of the said mixture to 13.0 or more. The method for producing a heavy metal fixing agent according to claim 5 or 6, further comprising a step of adjusting the concentration of the piperazine-N, N'-bisdithiocarbamate contained in the mixture to 25 to 45% by weight. The method for producing a heavy metal fixing agent according to any one of claims 5 to 7, wherein a solid matter precipitation temperature of the heavy metal fixing agent is -11 ° C or lower. The heavy metal immobilization method which has the process of mixing the heavy metal fixing agent of any one of Claims 1-4 with a heavy metal containing material. Obtaining a heavy metal fixing agent by the method according to any one of claims 5 to 8,
And a step of mixing the heavy metal fixing agent with a heavy metal-containing material.

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