JP5439979B2 - Solid heavy metal treating agent, production method and use thereof - Google Patents

Description

  The present invention is a solid heavy metal that is excellent in transportation economy, storage stability (stable active ingredient concentration, anti-caking), safety in use (no harmful gas generation), and excellent reaction selectivity for harmful lead. A treatment agent is provided.

  Amine carbodithioate is used as an immobilizing agent for heavy metals such as fly ash, soil and wastewater. As the carbodithioate of amine as a heavy metal treating agent, an aqueous solution of about 30 to 60% is usually used, but recently, the demand for a solid (powdered) heavy metal treating agent is increasing.

  So far, solid heavy metal treating agents containing amine carbodithioate in solid excipients have been proposed. For example, a method of using 100 parts by weight of alkali hydroxide or alkaline earth hydroxide with respect to 3 to 30 parts by weight of carbodithioate (Patent Document 1), a method using calcium silicate as a carrier (Patent Document 2), A method using a carbodithioate of an insoluble transition metal (Patent Document 3), a method using a spray-dried carbodithioate solution at a high temperature (Patent Document 4), and a starch containing a chelating agent in powder form (Patent Document 5) and the like.

  However, conventional solid heavy metal treating agents have only a low active ingredient concentration in the solid. Further, when an insoluble carbodithioate salt is dispersed in water and used as a slurry when a conventional heavy metal treating agent in an aqueous solution is used, there is a problem that it is difficult to use due to clogging of piping and the like. In the method of obtaining a solid heavy metal treating agent by concentration or spray drying, a large amount of energy is required for evaporation of the aqueous solution, which is not economical. In order to avoid energy consumption in removing the solvent, the method in which the carbodithioate is included in the excipient has a problem that the performance of the drug per unit weight is low because the ratio of the formation in the heavy metal treatment agent is large. It was.

  On the other hand, piperazine-N, N′-biscarbodithioate is known as an excellent heavy metal treating agent having high heavy metal treating ability and no generation of harmful gas (see Patent Document 6). Conventional fly ash treatment using piperazine-N, N′-biscarbodithioate as an active ingredient has only been used as an aqueous solution of piperazine-N, N′-biscarbodithioate.

  Solid piperazine-N, N′-biscarbodithioate is an anhydrous form of piperazine-N, N′-biscarbodithioic acid sodium salt (solid) obtained by recrystallization in an organic solvent. Japanese hydrate (or 4.5 hydrate) or hexahydrate is only known as a reagent used for colorimetric analysis of trace metals and has not been used as a heavy metal treating agent (Non-patent Document) 1-4).

Japanese Patent No. 3895018 JP 2004-97927 A JP2003-301165A JP 2003-336035 A JP 2003-113362 A Japanese Patent No. 3391173

Meiji University research report No. 67, pp. 23-30 (1985) Meiji University research report No. 67, pp. 31-36 (1985) Spectrochemica Acta, Vol. 40A, pp 343-346, (1984) CHEMICA ANALYTYCZNA, Vol. 10, p837-844, (1965)

  The object of the present invention is excellent in transportation economical efficiency, no change in active ingredient concentration during storage, no caking, excellent storage stability, no generation of harmful gases during storage and use, and against harmful lead The object is to provide a heavy metal treating agent with high selectivity.

  As a result of intensive studies on a solid heavy metal treating agent excellent in heavy metal treating ability and handleability (economic efficiency, storage stability, safety), the present inventors have conducted piperazine-N, N′-biscarbodithio. Acid sodium salt hexahydrate has high crystallinity not found in other forms of hydrates or hydrates of the salt, has no problems of weight change and consolidation during storage, and contains heavy metals It has been found that the generation of harmful gases such as carbon disulfide when mixed directly with materials can be reduced to the limit, and that the reaction selectivity for harmful lead is particularly high, and the present invention has been completed. It is.

  The heavy metal treating agent comprising piperazine-N, N′-biscarbodithioate sodium hexahydrate according to the present invention will be described below.

  The heavy metal treating agent comprising piperazine-N, N′-biscarbodithioate sodium hexahydrate of the present invention is particularly preferably one having high crystallinity having the following main X-ray diffraction peaks.

  Piperazine-N, N'-biscarbodithioate sodium hexahydrate, which has high crystallinity, varies in content of the active ingredient (piperazine-N, N'-biscarbodithioate sodium) during storage in the atmosphere And has the feature that it is difficult to consolidate during storage.

  Piperazine-N, N'-biscarbodithioate anhydrate, dihydrate absorbs moisture in the air and changes the weight ratio of the active ingredients of the heavy metal treatment agent. It is necessary to confirm the concentration of the active ingredient. However, in the piperazine-N, N′-biscarbodithioate sodium hexahydrate of the present invention, there is no weight change due to absorption of moisture in the atmosphere. There is no need for.

  The heavy metal treating agent containing piperazine-N, N′-biscarbodithioic acid sodium salt hexahydrate of the present invention as an active ingredient has a content of piperazine-N, N′-biscarbodithioic acid sodium of 70% or more. It is preferable that When the crystal powder of the heavy metal treating agent is all hexahydrate, the content of piperazine-N, N′-biscarbodithioate is 72.3% by weight. Piperazine-N, N'-biscarbodithioate sodium hexahydrate is not a mixture of amine carbodithioate with other solid salt (carrier) like conventional solid heavy metal treating agent, Since it is a pure crystal | crystallization, the content rate of the active ingredient in a heavy metal processing agent is high. In the present invention, even if a part of the hydrate or low hydrate is contained in the hexahydrate crystal, at least the surface layer portion of the particle is composed of hexahydrate to prevent caking. The effect can be demonstrated.

  The heavy metal treating agent comprising piperazine-N, N′-biscarbodithioic acid hexahydrate of the present invention does not generate harmful gases when stored and when mixed with heavy metal-containing substances. There is nothing. Solid piperazine-N, N′-biscarbodithioate anhydrate, dihydrate, although the amount of carbon disulfide generated is increased compared to the case of using it in an aqueous solution, hexahydrate Then there is no such problem.

  Furthermore, the heavy metal treating agent comprising piperazine-N, N′-biscarbodithioate hexahydrate of the present invention has high reaction selectivity to harmful lead, and efficiently fixes harmful lead. It can be processed. For example, piperazine-N, N'-biscarbodithioate sodium hexahydrate reaction selectivity to lead (compared to copper) in heavy metal treatment of heavy metal-containing materials is the water content of total solids (fly ash + chelating agent) When the addition amount is about 20% by weight, it is five times higher than the dihydrate and anhydride. Even when the amount of water added is increased, the superiority of the reaction selectivity of hexahydrate to lead is maintained.

  The amount of water added to the total solid content of the heavy metal-containing material and heavy metal treatment agent in the heavy metal treatment using the heavy metal treatment agent of the present invention is not particularly limited, but is preferably 10% by weight to 50% by weight, particularly preferably 20% by weight or more. It is preferably 40% by weight or less. For example, in the treatment of heavy metal-containing fly ash, if the amount of water added is too large, it becomes a huge lump or slurry and it becomes difficult to handle the treated ash, so the amount of water added is usually 20 to 40% by weight based on the solid content. It is performed to be in the range. Accordingly, the heavy metal treating agent comprising piperazine-N, N′-biscarbodithioic acid hexahydrate of the present invention exhibits a high reaction selectivity to lead in the fly ash treatment with a normal water addition amount. can do.

  The heavy metal treating agent of the present invention may further contain an alkali hydroxide or an alkaline earth hydroxide for improving the stability. Since these alkali components are not used as excipients (carriers), the content thereof is 0.01 to 5% by weight, particularly 0.1% with respect to the piperazine-N, N′-biscarbodithioate sodium component. A range of ˜2% by weight is sufficient. As the alkali hydroxide to be used, sodium hydroxide and potassium hydroxide are preferable, and as the alkaline earth hydroxide, magnesium hydroxide and calcium hydroxide are preferable.

  Although the manufacturing method of the heavy metal processing agent containing the piperazine-N, N'-biscarbodithioic acid hexahydrate of this invention is not specifically limited, It manufactures efficiently with the following manufacturing methods. be able to.

  Piperazine-N, N'-biscarbodithioate sodium hexahydrate is prepared by reacting piperazine, carbon disulfide and sodium hydroxide in a saturated aqueous solution of piperazine-N, N'-biscarbodithioate sodium, piperazine It can be produced by precipitating -N, N'-biscarbodithioic acid sodium salt and separating the salt from the aqueous solution.

  Piperazine and piperazine-N, N′-biscarbodithioate have higher solubility in water than piperazine (piperazine is about 1.8 mol / L, piperazine-N, N′-biscarbodithioate Since the solubility is 0.9 mol / L (about 25% by weight), piperazine can be further dissolved in a saturated solution of piperazine-N, N′-biscarbodithioic acid sodium salt. Moreover, since the saturated aqueous solution of piperazine-N, N′-biscarbodithioate to be formed has low liquid viscosity, it is excellent in reactivity (handleability).

  A carbodithioate of an amine other than piperazine-N, N′-biscarbodithioate, for example, a supersaturated solution of a carbodithioate such as tetraethylenepentamine, diethylenetriamine, and polyethyleneimine, does not precipitate a solid and becomes a viscous product. Therefore, it is difficult to obtain a stable solid amine carbodithioate.

  In the method of the present invention, it is preferable to dissolve piperazine in a saturated aqueous solution of piperazine-N, N′-biscarbodithioic acid sodium salt, add carbon disulfide first, and then add sodium hydroxide later. In a saturated aqueous solution of piperazine-N, N′-biscarbodithioic acid sodium salt, a gel-like by-product is produced when piperazine and carbon disulfide are reacted in an excess of sodium hydroxide, and a continuous reaction occurs. It can be difficult.

  In the method of the present invention, piperazine is continuously obtained by dissolving piperazine in a saturated aqueous solution of piperazine-N, N′-biscarbodithioic acid salt and alternately repeating the addition of carbon disulfide and the addition of sodium hydroxide. -N, N'-biscarbodithioic acid sodium salt can be produced.

  In a particularly preferred embodiment, the piperazine is first converted to piperazine-N, N′-biscarbohydrate in the reaction of piperazine, carbon disulfide and sodium hydroxide in a saturated aqueous solution of piperazine-N, N′-biscarbodithioate. An example is a method in which after dissolving in a saturated aqueous solution of sodium dithioate, carbon disulfide is reacted with sodium hydroxide while maintaining an excess state. When carbon disulfide is reacted in excess of sodium hydroxide, solid piperazine-N, N′-biscarbodithioic acid is once precipitated, but it is more viscous than when sodium hydroxide is added first. , Low reactivity and good handling, and finally pure piperazine-N, N′-biscarbodithioate crystals are obtained. In particular, a method of adding carbon disulfide and sodium hydroxide at the same time by dividing each time into two or more portions or adding a time difference is preferable.

  In the reaction of piperazine, carbon disulfide and sodium hydroxide in an aqueous solution, in addition to piperazine-N, N′-biscarbodithioate, piperazine-sodium N-carbodithioate and thiocarbonate are by-produced or unreacted. Of piperazine may remain. Since piperazine-N-carbodithioate sodium, which has only one functional group and has a low heavy metal treatment ability, has higher solubility than piperazine-N, N′-biscarbodithioate sodium, in the method of the present invention, Only piperazine-N, N'-biscarbodithioate sodium having a high concentration can be selectively recovered as crystals.

  Similarly, piperazine and thiocarbonate remain in the aqueous solution because of their high water solubility, and can be separated from piperazine-N, N′-biscarbodithioate sodium. In the method of concentration or organic solvent extraction, there is a problem that piperazine-N-carbodithioic acid sodium, piperazine and thiocarbonate precipitate simultaneously with piperazine-N, N′-biscarbodithioic acid sodium. Then, it is possible to selectively obtain a sodium piperazine-N, N′-biscarbodithioate component having a high ability to treat heavy metals as crystals.

  In the present invention, the method for drying the precipitated crystals is not particularly limited as long as it is a method for obtaining hexahydrate. Even if the crystallinity is lowered by drying the precipitated crystals, it is further contained in an atmosphere containing moisture. It can be recrystallized by hydrating with, and it can be made into crystals of piperazine-N, N′-biscarbodithioate hexahydrate. Crystallization by hydration after drying is preferably performed in pulverization and / or forced flow.

  The heavy metal treatment agent comprising piperazine-N, N′-biscarbodithioate sodium hexahydrate according to the present invention is mixed with soil, waste water, waste, incinerated ash, etc. containing heavy metal, Elution can be prevented. The method of using the heavy metal treatment agent of the present invention in the heavy metal immobilization treatment can be applied in the same manner as other normal heavy metal treatment agents, such as water, alkali hydroxide or iron chloride as required for the heavy metal treatment agent. You may mix and use suitably with a pH adjuster.

  Piperazine-N, N'-biscarbodithioate sodium hexahydrate may be used after being dissolved in water and mixed with a heavy metal-containing material, but it is preferable to mix directly with water, particularly direct mixing. It is preferable to add water after use.

  The piperazine-N, N′-biscarbodithioate sodium hexahydrate heavy metal treating agent of the present invention has a high content of components having heavy metal treating ability, and there is no problem of weight change or solidification during storage. It is excellent in transportability and storage stability, can be treated with heavy metals by direct mixing with heavy metal containing materials, does not generate harmful gases during storage and use, and has high reaction selectivity to harmful lead.

2 shows X-ray diffraction patterns of anhydrous piperazine-N, N′-biscarbodithioate, dihydrate and hexahydrate. In the figure, the horizontal axis (X axis) represents 2θ values (unit: deg) in X-ray diffraction, the vertical axis (Y axis) represents peak intensity in X-ray diffraction, and the scale is arbitrary. Hexahydrate has high crystallinity. Piperazine-sodium N, N'-biscarbodithioate hexahydrate, dihydrate and anhydrous, lead chloride and pure water (lead chloride and piperazine-N, N'-biscarbodithioate water It is the figure which evaluated the production | generation of the lead complex at the time of mixing 20 weight% with respect to the total solid of a Japanese thing by X-ray diffraction. Piperazine-N, N'-bisdithiocarbamate sodium hexahydrate, dihydrate and anhydrous, copper chloride and pure water (copper chloride and piperazine-N, N'-biscarbodithioate hydrated It is the figure which evaluated the production | generation of the copper complex at the time of mixing 20 weight% with respect to the total solid of a thing by X-ray diffraction.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

Example 1
After dissolving 61.01 g of piperazine in 212.4 g of pure water at 40 ° C., 106.77 g of carbon disulfide and 119.82 g of 48% sodium hydroxide were added dropwise in four portions alternately while stirring in a nitrogen stream. did. After completion of the dropping, a slurry solution in which sodium piperazine-N, N′-biscarbodithioate was precipitated was obtained.

  The precipitated piperazine-N, N′-biscarbodithioic acid sodium salt was filtered off, and the attached moisture was removed by a vacuum dryer and dried.

  The obtained sodium piperazine-N, N′-biscarbodithioate was a hexahydrate as a result of thermal analysis, and the X-ray diffraction pattern had high crystallinity as shown in FIG.

The obtained piperazine-N, N′-biscarbodithioate hexahydrate was dissolved in pure water and subjected to ¹³ C-NMR measurement. As a result, piperazine and piperazine-sodium N-biscarbodithioate were detected. There wasn't.

Example 2
In addition, 250 g of piperazine-N, N′-biscarbodithioate filtered in Example 1 (saturated aqueous solution of piperazine-N, N′-biscarbodithioate) (250 g) and 42.57 g of piperazine and 50. 73 g was added, dissolved at 40 ° C., and 74.50 g of carbon disulfide and 82.19 g of 48% sodium hydroxide were alternately added in two portions while stirring in a nitrogen stream. After completion of the dropping, a slurry solution in which sodium piperazine-N, N′-biscarbodithioate was precipitated was obtained.

  It was confirmed that piperazine-N, N′-biscarbodithioate was obtained by repeatedly using the saturated solution.

Comparative Example 1
The hexahydrate of Example 1 was further dried at 50 ° C. in a dryer and 100 ° C. in a dryer to obtain a dihydrate and an anhydride, respectively.

  The X-ray diffraction pattern is shown in FIG. The dihydrate and anhydride were low in crystallinity.

Comparative Example 2
The same operation as in Example 1 was conducted except that piperazine was changed to tetraethylenepentamine, and 88.11 g of tetraethylenepentamine, 128.11 g of pure water, 127.50 g of carbon disulfide, and 156.28 g of 48% sodium hydroxide were used. However, a solid carbodithioate was not obtained.

(Storage stability evaluation 1 Change in weight)
The piperazine-N, N′-biscarbodithioate hexahydrate, dihydrate and anhydrous obtained in Example 1 and Comparative Example 1 were allowed to stand in the air, and the change in weight over time was changed. It was measured. The results are shown in Table 2.

  The non-hydrate and dihydrate changed in weight over time, but the hexahydrate did not change in weight and was confirmed to be stable during storage in the atmosphere.

  After standing in the air, the hexahydrate was not consolidated, but the dihydrate and the anhydride were found to have decreased fluidity and adhered to the container.

(Heavy metal treatment test)
Piperazine-N, N′-biscarbodithioate sodium hexahydrate of Example 1 is 0.5 parts (anhydrous equivalent) 25 parts by weight of water based on 50 parts by weight of fly ash A (Pb = 2500 ppm) Then, 0.5 parts of hexahydrate (anhydrous equivalent) was directly added to the ash, and then 25 parts by weight of water was added to the ash and kneaded. Thereafter, a dissolution test was conducted according to the Environmental Agency Notification No. 13 test.

  The elution of lead was less than 0.05 ppm and met the environmental standards.

(Gas measurement 1)
2.74 g of piperazine-N, N′-biscarbodithioate hexahydrate (equivalent to 2 g in terms of piperazine-N, N′-biscarbodithioate) in a Tedlar bag (volume 1 L), 500 mL of air Loaded and left at room temperature and 65 ° C. for 1 hour. After standing, the carbon disulfide concentration in the head space in the Tedlar bag was measured with a detector tube.

  For comparison, piperazine-N, N′-biscarbodithioate sodium dihydrate and anhydrate were loaded (each equivalent to piperazine-N, N′-biscarbodithioate sodium hexahydrate). ) And the carbon disulfide concentration was measured. The results are shown in Table 3.

  Generation of carbon disulfide was observed in the dihydrate and anhydride, but there was no generation (ND) or significantly less in the hexahydrate.

(Gas measurement 2)
In a Tedlar bag (volume 1L), 0.74% by weight of 35% pure water and piperazine-N, N′-biscarbodithioate hexahydrate per 30 g of fly ash B (Pb = 2700 ppm) After mixing, 500 mL of air was charged and heated at 65 ° C. for 1 hour. After heating, the hydrogen sulfide and carbon disulfide concentrations in the head space in the Tedlar bag were measured with a detector tube.

  The same gas measurement was performed by adding 20% by weight of pure water and 3.0% by weight of piperazine-N, N′-biscarbodithioic acid hexahydrate to Fly Ash C (Pb = 9800 ppm).

  For comparison, anhydrous piperazine-N, N′-biscarbodithioate and dihydrate were added to the same fly ash (6 piper in terms of piperazine-N, N′-biscarbodithioate, respectively). The same amount as the hydrate) and the gas concentration was measured. The results are shown in Tables 4 and 5.

  In all cases, hydrogen sulfide was not generated. However, the carbon disulfide generation was less than 1 ppm in the hexahydrate, but the carbon disulfide generation was observed in the dihydrate and the anhydride.

(Reactivity selectivity for lead)
8. Piperazine-N, N′-biscarbodithioate sodium hexahydrate, dihydrate and anhydrate are each converted to piperazine-N, N′-biscarbodithioate sodium component, 10 g each of lead chloride. 8 g and 4.8 g of copper chloride and pure water (20 wt% and 30 wt% based on the total solid content of lead chloride or copper chloride and piperazine-N, N′-biscarbodithioate hydrate) After mixing, the formation of each metal complex after mixing was measured by X-ray diffraction.

  Lead complex, copper complex and piperazine-N, N′-biscarbodithioate sodium diffraction angle 9.4 ° (peak (a) derived from lead complex), 12.9 ° (peak (b) derived from copper complex) And 21.3 ° (peak (c) derived from the piperazine-N, N′-biscarbodithioate component) (a / c is the lead reactivity (1), and b / c is the copper The reactivity (2) was set, and the ratio (1) / (2) was set to lead selectivity (3). Tables 6 and 7 show the results when the water content is 20% by weight and 30% by weight.

  Hexahydrate has higher selectivity to lead than dihydrate and anhydrate, and the tendency is more marked when the moisture content in the heavy metal-containing material (including the chelating agent) is smaller.

  The heavy metal treating agent of the present invention can be used for immobilizing heavy metals in a heavy metal-containing material, and particularly suitable for treating heavy metals in fly ash containing a large amount of lead.

Claims (10)

A heavy metal treating agent comprising piperazine-N, N′-biscarbodithioate sodium hexahydrate. The heavy metal treating agent according to claim 1, comprising piperazine-N, N'-biscarbodithioate sodium hexahydrate having crystallinity of the X-ray diffraction pattern of Table 1.

The heavy metal treating agent according to claim 1 or 2, comprising 70% or more of piperazine-N, N'-biscarbodithioate sodium. The heavy metal treating agent according to any one of claims 1 to 3, further comprising an alkali hydroxide and / or an alkaline earth hydroxide. Piperazine, carbon disulfide, and sodium hydroxide are reacted in a saturated aqueous solution of piperazine-N, N′-biscarbodithioic acid sodium salt to precipitate piperazine-N, N′-biscarbodithioic acid sodium salt, The method for producing a heavy metal treating agent according to any one of claims 1 to 4, wherein the process is separated. 6. The carbon disulfide is added first in a saturated aqueous solution of piperazine-N, N′-biscarbodithioic acid sodium salt in which piperazine is dissolved, and sodium hydroxide is added later. Manufacturing method. The production method according to claim 5 or 6, wherein the addition of carbon disulfide and the addition of sodium hydroxide are alternately repeated in a saturated aqueous solution of piperazine-N, N'-biscarbodithioic acid sodium salt in which piperazine is dissolved. The heavy metal processing agent which mixes the heavy metal processing agent in any one of Claims 1 thru | or 4 with a heavy metal containing material directly.   The heavy metal treatment method according to claim 8, wherein the amount of water added to the total solid content of the heavy metal-containing material and the heavy metal treatment agent according to any one of claims 1 to 4 is 10 wt% or more and 50 wt% or less. The heavy metal processing agent in any one of Claims 1 thru | or 4 is melt | dissolved in water, The processing method of the heavy metal which mixes the said aqueous solution and a heavy metal containing material.

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