JP3963722B2 - Method for producing aqueous solution containing dithiocarbamate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an aqueous solution containing a dithiocarbamate capable of accurately controlling the content of dithiocarbamate, and in particular, when a reaction product is used as a heavy metal fixing agent, the quality of the heavy metal fixing agent is guaranteed to be constant. The present invention relates to a method for producing an aqueous solution containing dithiocarbamate.
[0002]
[Prior art]
When treating incineration ash discharged from incineration plants such as industrial wastewater, municipal waste and industrial waste, fly ash collected by an electric dust collector, etc. from smoke, incineration ash In order to prevent and control the release of harmful heavy metals such as lead, chromium, cadmium, arsenic and selenium contained in fly ash into the environment, incineration ash, a method of solidifying fly ash, etc., incineration ash, There are known methods for treating fly ash and the like with acid to extract heavy metals, but there are problems such as an increase in the volume of waste and treatment of heavy metals extracted with acid. For this reason, a treatment method using a heavy metal fixing agent that does not require a special apparatus and does not require post-treatment is employed, and as such a heavy metal fixing agent, a liquid chelating agent of an amine derivative having a dithiocarboxy group as a functional group Is widely used because it has a high heavy metal collection effect and can immobilize and elute heavy metals in rainwater, etc., and diethyldithiocarbamine as a liquid chelating agent for amine derivatives having a dithiocarboxy group as a functional group. An aqueous solution containing an acid potassium salt has been suitably used (JP-A-8-332475, etc.).
[0003]
An aqueous solution containing diethyldithiocarbamate used as such a heavy metal fixing agent is mixed with an amine and an alkali hydroxide aqueous solution, and carbon disulfide is added dropwise to the mixture to cause a reaction. It is manufactured as an aqueous solution containing at least% diethyldithiocarbamate, but when the amine is volatile, when the carbon disulfide is added dropwise, the volatilized amine and carbon disulfide react in the gas phase, resulting in a reaction product. If the product adheres to the reaction vessel wall of the gas phase part and is not washed away with water or the like, it will not be contained in the reaction solvent, and the desired amount of reaction product will not be obtained in the liquid phase, and the diethyldithiocarbamate of the aqueous solution will not be obtained. There is a disadvantage that the concentration is lowered and the concentration of the product cannot be predicted. Further, when the reaction is carried out under normal pressure, there is a problem that the condenser is clogged due to the adhesion of the product.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to produce an aqueous solution containing dithiocarbamate obtained by reacting carbon disulfide with an aqueous solution of an amine and an alkali metal, even if a volatile amine is used. The reaction between carbon disulfide and amine can be prevented in the phase, and dithiocarbamate can be obtained in the expected yield, the formation of thiocarbonate can be suppressed, and an aqueous solution containing a predetermined concentration of dithiocarbamate can be obtained. It is possible to provide a method for producing an aqueous solution containing a dithiocarbamate capable of producing a product having a certain quality when the reaction product is applied as a heavy metal fixing agent as it is.
[0005]
[Means for Solving the Problems]
The present inventors produce an aqueous solution containing, as a main component, a dithiocarbamic acid metal salt obtained by reacting at least one compound having a primary amino group, carbon disulfide and a metal hydroxide in an aqueous solution. At the same time, a method for producing an aqueous solution that does not produce impurities such as thiocarbonate by adjusting the pH of the aqueous solution to a range of 10 to 14 has already been proposed (Japanese Patent Application Laid-Open No. 9-183763). In the process of further studying the method for producing an aqueous solution containing a dithiocarbamate suitable as a heavy metal fixing agent, the present inventors dropped carbon disulfide into an aqueous solution containing an amine and a metal hydroxide to add dithiocarbamine. When adding carbon disulfide to an aqueous solution containing an amine and a metal hydroxide in the reaction step of forming an acid salt, the amine vaporized in the gas phase and carbon disulfide are added under the surface of the reaction solution. Focusing on the fact that it is possible to eliminate the reaction with carbon disulfide, and found that the production amount corresponding to the expected yield of dithiocarbamate produced by the reaction of carbon disulfide, amine and metal hydroxide can be reliably obtained. The present invention has been completed.
[0006]
That is, the present invention provides an aqueous solution containing an amine and a metal hydroxide when an aqueous solution containing a dithiocarbamate is produced by reacting an amine, a metal hydroxide, and carbon disulfide in an aqueous solvent. The present invention relates to a method for producing an aqueous solution containing dithiocarbamate, characterized by adding carbon disulfide below the liquid level. Preferably, a supply hole is provided below the liquid level of the aqueous solution containing an amine and a metal hydroxide. Carbon disulfide is added through an introduction pipe having an aqueous solution containing dithiocarbamate according to claim 1 (claim 2), or an amine is added to carbon disulfide with respect to carbon disulfide. The present invention relates to a method for producing an aqueous solution containing a dithiocarbamate according to claim 1 or 2 (claim 3).
[0007]
DETAILED DESCRIPTION OF THE INVENTION
As a method for producing a dithiocarbamate-containing aqueous solution of the present invention, an amine, a metal hydroxide, and carbon disulfide are reacted in an aqueous solvent to produce an aqueous solution containing a dithiocarbamate. It is not particularly limited as long as it is a method of adding carbon disulfide under the liquid level of the aqueous solution containing the hydroxide, and disulfide under the liquid level of the aqueous solution containing the amine and the metal hydroxide. Examples of the method of adding carbon include, for example, a method of adding carbon disulfide via an introduction pipe having a supply hole under the surface of an aqueous solution containing an amine and a metal hydroxide, and an amine and a metal hydroxide. A method of adding carbon disulfide through a supply hole provided in the bottom or wall surface of a storage tank containing an aqueous solution, a tubular mixer, for example, a claw using a static mixer (manufactured by Noritake Co.) The addition method by using a gas system can be exemplified, but for the convenience of the apparatus, disulfide is introduced via an introduction pipe having a supply hole under the surface of an aqueous solution containing an amine and a metal hydroxide. A method of adding carbon is preferable. In this case, it is preferable to control the amount of carbon disulfide added by providing a flow rate control mechanism in the introduction pipe.
[0008]
The amine used in the method for producing a dithiocarbamate-containing aqueous solution of the present invention is not particularly limited, but preferably has a primary or secondary amino group, and is not limited to a monoamine, but includes diamine, triamine, and tetramine. And polyamines having a plurality of amino groups, such as aliphatic amines and aromatic amines. Aliphatic amines include aliphatic unsaturated amines and alicyclic amines. Can do. One or more of these compounds can be selected and mixed for use.
Specifically, such amines include, as primary monoamines, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, sec-butylamine, iso-butylamine, n-amylamine, iso-amylamine. 2-aminopentane, 3-aminepentane, neopentylamine, 1,2-dimethylpropylamine, n-hexylamine, 1,3-dimethyl-n-butylamine, n-heptylamine, n-octylamine, n- Fats such as nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, benzylamine, α-phenylethylamine, β-phenylethylamine, allylamine And aromatic amines such as aniline, aniline, o-toluidine, m-toluidine, and p-toluidine. Secondary monoamines include dimethylamine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, di-n-amylamine, diallylamine, methylaniline, ethylaniline, diphenylamine, dibenzylamine and the like. Is mentioned.
[0009]
Specific examples of the polyamine having a primary amino group include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentadiamine, 1,6-hexanediamine, , 2-propanediamine, 1,2-diamino-2-methylpropane, 2,2-dimethyl-1,3-propanediamine, 1,3-diaminopentane, 2-methyl-1,5-pentanediamine, bis ( 3-aminopropyl) -methylamine, 1,4-cyclohexanediamine, 1,3-cyclohexanediamine, 1,2-cyclohexanediamine and the like, and those having a primary amino group and a secondary amino group Specifically, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, Liethyleneimine, N- (2-aminoethyl) -1,3-propanediamine, iminobispropylamine, N-methylethylenediamine, N-ethylethylenediamine, N-isopropylethylenediamine, N-butylethylenediamine, N-methyl-1, 3-propanediamine, N-propyl-1,3-propanediamine, N-isopropyl-1,3-propanediamine, N- (2-aminoethyl) piperazine, 4- (2-aminoethyl) piperidine, 2- ( 2-aminoethylamino) ethanol and the like.
[0010]
The amine is preferably used in an excess of 0.01 to 10 mol% with respect to carbon disulfide. If the amount of carbon disulfide is the same or excessive with respect to the amine, if the amine has volatility, the amount of amine actually supplied to the reaction due to volatilization tends to decrease from the amount added. It becomes more excessive and the production of thiocarbonate is promoted. When the excess ratio of amine to carbon disulfide is 0.01 mol% or more, the formation of thiocarbonate can be prevented, and when the excess ratio is 10 mol% or less, in the case of a low boiling point amine. Even if unreacted amine remains in the aqueous solution after the reaction, it can be removed by nitrogen bubbling. In the case of a high boiling point amine, there is no problem of crystal precipitation due to an increase in freezing point.
[0011]
The carbon disulfide used in the present invention reacts with an amine to form dithiocarbamic acid, and the reaction between the carbon disulfide and the amine is easily influenced by the reaction temperature, the pH of the solvent, etc. Since carbon disulfide combines with metal hydroxide to form reddish brown thiocarbonate as a by-product, the temperature of carbon disulfide, the reaction solution Adjustment of temperature and pH is controlled, and the reaction proceeds. The temperature range of the reaction solution and carbon disulfide is a temperature range in which carbon disulfide does not vaporize because the boiling point of carbon disulfide is 46 ° C., and the temperature range is 0 to 40 ° C., particularly 35 ° C. or less. In terms of temperature, carbon disulfide is preferred because it selectively binds to amines. Moreover, since the reaction with an amine is accelerated | stimulated when the pH of a reaction solvent is the range of 10-14, it is preferable. When the reaction is carried out at a temperature higher than 35 ° C., or when the reaction is carried out at a pH outside the range of 10 to 14, carbon disulfide does not selectively bind to the amine and reacts with the metal hydroxide. Thiocarbonate will be produced.
[0012]
The metal hydroxide used in the production method of the present invention forms a metal salt of dithiocarbamic acid, and an aqueous solution containing the dithiocarbamate that is the reaction product of the present invention can be directly applied as a heavy metal fixing agent. As described above, since an aqueous solution containing an alkali metal salt of dithiocarbamic acid is preferable as the heavy metal fixing agent, specifically, the metal hydroxide is preferably an alkali metal hydroxide such as potassium, sodium or lithium. In addition to these aqueous solutions, these metal hydroxides can be used in any form such as powder, granule, or mass. The concentration of metal hydroxide in the case of using an aqueous solution of metal hydroxide depends on the amount of water used as a solvent to be used, but in order to produce a high concentration dithiocarbamate, for example, metal hydroxide It is preferred that the product is in the range of 20-55% by weight, preferably 30-50% by weight.
[0013]
In the reaction solvent used in the present invention, when the reaction product is used as a heavy metal fixing agent, the reaction system containing dithiocarbamate is preferably an aqueous solution, and the resulting reaction product is used as a heavy metal fixing agent as it is. Water is used so that it can be used. If the reaction system containing the obtained dithiocarbamate is an aqueous solution, it is applied to a heavy metal fixing agent, and even if the heavy metal contained in the object to be processed is in the form of an inorganic compound or an organic compound, It can easily bind to the contained dithiocarbamic acid to form a chelate complex, and can fix and elute heavy metals. In addition to water added as solvent water, water as a solvent can be used as a solvent when the metal hydroxide is mixed with an aqueous solution. The amount of water used as a solvent is sufficient when the obtained aqueous solution is used as a heavy metal fixing agent, and the dithiocarbamate, which is a product that is easily decomposed by heating, does not perform an operation such as concentration, and the heavy metal has a sufficient fixing effect. For example, the amount is preferably such that the concentration is such that 30% by weight or more of dithiocarbamate is contained so as to be contained in the aqueous solution at a high concentration as obtained.
[0014]
The reaction of amine, metal hydroxide, and carbon disulfide in the above aqueous solvent is carried out by adding carbon disulfide under the surface of an aqueous solution containing the amine and metal hydroxide. Is obtained. As for the mixing of the amine, the metal hydroxide or the aqueous solution of the metal hydroxide, and the aqueous solvent, the whole amount can be mixed by stirring. The temperature at the time of mixing is not specifically limited, It can carry out suitably in the range of 0-40 degreeC.
[0015]
The reaction of adding carbon disulfide to the mixed solution of amine and metal hydroxide of the present invention is performed by supplying carbon disulfide below the surface of the reaction solution. As a method of supplying carbon disulfide below the liquid level of the mixed solution of amine and metal hydroxide, introduction is provided below or on the bottom of the liquid level on the side wall of the reaction vessel charged with amine and metal hydroxide. Even if carbon disulfide is supplied from the mouth, it can also be added via an introduction pipe inserted into the liquid phase from the gas phase above the reaction vessel. When adding through the introduction port or the introduction pipe, carbon disulfide may be press-fitted as necessary. The introduction tube may have any shape as long as it has a supply hole below the liquid level, and may simply be tubular. A closed system using a Tiku mixer (manufactured by Noritake Co.) may be used. Also, an L-shaped or T-shaped tube inserted into the liquid phase at right angles to the liquid level of the reaction vessel and bent along the bottom surface, and a plurality of supply ports are provided in the portion along the bottom surface It may be. Further, such a tube may be connected to a rotating mechanism to be rotatable so that carbon disulfide can be supplied into the reaction solution and the reaction solution can be added while stirring.
[0016]
The addition of carbon disulfide may be performed immediately after the addition of amine and metal hydroxide, or may be performed simultaneously. Carbon disulfide may be added in an open system under a nitrogen atmosphere, but is preferably added in a closed system. The addition is preferably performed under a temperature condition of 35 ° C. or less, and the pH of the mixed solution is preferably 10-14. Within this range, generation of thiocarbonate can be suppressed, and generation of carbon disulfide can be suppressed as a heavy metal fixing agent during the heavy metal fixing process during the storage period.
[0017]
The addition time of carbon disulfide is not particularly limited. Even if it is added at once, it is divided over a long time or continuously, for example, over about 30 minutes to 20 hours. It may be added. Moreover, after adding a part of carbon disulfide used for reaction to the aqueous solution containing amine, an aqueous solution containing a metal hydroxide or a metal hydroxide is added, or an aqueous solution containing an amine, When adding a metal hydroxide or an aqueous solution containing a metal hydroxide, a part of carbon disulfide used for the reaction may be added simultaneously, and then the remaining carbon disulfide may be added. In this way, a part of carbon disulfide used for the reaction is added in advance to the amine-containing aqueous solution prior to the addition of the metal hydroxide or the metal hydroxide aqueous solution, or the metal hydroxide or the metal water. By adding simultaneously with the oxide aqueous solution, the mixed solution containing amine avoids becoming strongly alkaline, prevents precipitation of amine metal salt crystals, and the reaction solution becomes highly viscous. Can be prevented, and stirring can be performed easily.
Aging may be performed after the addition of carbon disulfide, and the aging is preferably performed in a temperature range of 5 to 45 ° C. for 1 to 24 hours.
[0018]
The end point of the reaction is determined by confirming with NMR or the like using the time point when the carbon disulfide particles dispersed in the aqueous solution disappear as a guide, but after the reaction is completed, unreacted carbon disulfide or excess amine May be present in the aqueous solution, and unreacted carbon disulfide and the like are separated from the aqueous solution by heating the heavy metal fixing agent, fluctuation of the hydrogen ion concentration, etc., and the unreacted amine is a source of odor. Therefore, it is desirable to perform nitrogen bubbling treatment of the aqueous solution. By bubbling treatment, unreacted carbon disulfide and amine can be removed from the aqueous solution. Moreover, it is preferable to store the aqueous solution at a pH of 10 or higher after the reaction, because generation of carbon disulfide can be suppressed during the storage period. In order to preserve the aqueous solution of the reaction product at a pH of 10 or higher, 0.01 to 200 moles of dithiocarbamate can be added, such as a metal hydroxide or an aqueous solution of a metal hydroxide.
[0019]
The aqueous solution containing the dithiocarbamate obtained by the present invention contains the dithiocarbamate at the intended concentration, and the aqueous solution containing the dithiocarbamate obtained by the present invention is used as a heavy metal fixing agent as it is. Even if applied, it has a certain quality as a heavy metal fixing agent, and a certain concentration of dithiocarbamic acid contained in the heavy metal fixing agent binds to heavy metals such as lead, mercury, chromium, cadmium, arsenic, selenium, etc. Chelate complexes are formed, and heavy metals are efficiently fixed and insolubilized.
[0020]
【Example】
Hereinafter, the present invention will be specifically described with reference to the drawings. However, the scope of the present invention is not limited to these examples.
As shown in FIG. 1, the dithiocarbamate production apparatus includes a reaction vessel 1, a carbon disulfide introduction pipe 2, and a stirring device 3 that stirs the reaction solution. The carbon disulfide introduction tube 2 is a circular tube, and is bent substantially perpendicularly in the vicinity of the bottom surface of the reaction vessel 1 and a vertical portion 2a inserted perpendicularly to the liquid level of the reaction solution charged in the reaction vessel 1. The supply unit 2b is provided with a plurality of supply holes 2c having a diameter corresponding to the supply amount of carbon disulfide.
In such a reaction vessel 1 of an apparatus for producing dithiocarbamate, 220 g of diethylamine (manufactured by Junsei Chemical Co., Ltd .: purity 99.9%) and 48% potassium hydroxide (manufactured by Nippon Soda Co., Ltd .: purity 48) 7%) 366 g, the temperature of the aqueous solution is cooled to 15 ° C. or lower, and with stirring, 228 g of carbon disulfide (manufactured by Junsei Chemical Co., Ltd .: purity 100.0%) is placed at 15 ° C. below the surface of the aqueous solution. The following were added and added in 2 hours. After aging at 30 ° C. for 1 hour, a yellow-green potassium diethylbisdithiocarbamate aqueous solution was obtained. The yield was 99.7%, and the potassium diethylbisdithiocarbamate concentration in the aqueous solution was 56.2%.
Comparative Example Reaction was carried out under the same conditions as in Example except that diethylamine and potassium hydroxide were charged in the same manner as in Example and carbon disulfide was dropped from above the aqueous solution. The yield of the obtained potassium diethylbisdithiocarbamate aqueous solution was 94.2%. The main cause of this decrease in yield is that diethyldithiocarbamic acid or diethylammonium salt, which is a direct reaction of diethylamine and carbon disulfide, adheres to the inner wall of the reaction vessel as white crystals.
[0021]
【The invention's effect】
An aqueous solution containing a dithiocarbamate obtained by the present invention reacts with carbon disulfide in the gas phase in the production process, even if the amine is volatile, and produces a side reaction product on the wall of the reaction vessel. Therefore, the thiothiocarbamate can be obtained in the expected yield, and an aqueous solution containing the intended concentration can be obtained. For this reason, even if the aqueous solution containing the dithiocarbamate obtained by the present invention is applied as a heavy metal fixing agent, a certain quality can be maintained as the heavy metal fixing agent.
[Brief description of the drawings]
FIG. 1 is a diagram showing the configuration of a production apparatus for producing a dithiocarbamate-containing aqueous solution of the present invention.

Claims (3)

In producing an aqueous solution containing a dithiocarbamate by reacting an amine, a metal hydroxide, and carbon disulfide in an aqueous solvent, the aqueous solution containing the amine and the metal hydroxide is submerged under the surface of the aqueous solution. A method for producing an aqueous solution containing a dithiocarbamate, characterized by adding carbon sulfide. 2. The dithiocarbamate-containing aqueous solution according to claim 1, wherein carbon disulfide is added through an introduction pipe having a supply hole below the surface of the aqueous solution containing an amine and a metal hydroxide. Production method. The method for producing an aqueous solution containing a dithiocarbamate according to claim 1 or 2, wherein the amine is used in an excess of 0.01 to 10 mol% with respect to carbon disulfide.

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