JP2008184469A - Mixture composition and method for treating heavy metal therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to simultaneously treat cationic and anionic heavy metals even with a conventional heavy metal-treating agent alone. <P>SOLUTION: This mixture composition has an iron sulfide concentration of 1 to 50 wt.% and a dithiocarbamate of 1 to 50 wt.%, can singly treat both cationic and anionic heavy metals, has an excellent heavy metal-treating ability, and does not produce an injurious gas. The dithiocarbamate is preferably potassium piperazine-N, N'-biscarbodithioate, and the iron sulfide preferably has a mackinawite structure as a crystal structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composition suitable for use in detoxification treatment using heavy metals contained in ash, soil, or waste water, a heavy metal treatment agent using the same, and various heavy metals using the heavy metal treatment agent. It is related with the detoxification processing method of the waste containing a.

  Iron sulfide is known as an agent for treating anionic heavy metals. (For example, Patent Document 1) Iron sulfide is particularly effective with respect to As, Se, and hexavalent Cr, but has a problem that its effect is weak with respect to cationic metals such as Pb, Cd, and Hg. Moreover, in order to use effectively with respect to a contaminant, it is necessary to use as a liquid (slurry), but it was difficult to obtain a high concentration and stable thing.

  On the other hand, various amine salts such as dithiocarbamic acid heavy metal treating agents are known for treating cationic species such as Pb, Cd, and Hg. (For example, refer to Patent Document 2) However, conventional heavy metal treating agents using amine salts have low treatment effects on heavy metal ions of anionic species such as As, Se, and hexavalent Cr.

  Thus, to treat contamination with both cationic and anionic heavy metals, it was necessary to use both iron sulfide and amine salts. However, when using each separately, the container for each chemical | medical agent is needed, The chemical characteristic of each chemical | medical agent differs, and it reacted at the time of mixing, and there existed a problem that sufficient characteristic as a heavy metal processing agent was not acquired. Furthermore, depending on conditions, a toxic gas may be generated due to the decomposition of the functional group of the heavy metal treating agent.

  In addition, since iron sulfide contains iron, when iron sulfide and an amine salt are used separately, the amount of amine to be added may increase due to the reaction of the amine salt with iron depending on the conditions of heavy metal treatment. It was. In particular, since each of these drugs contains water, there is a problem that the water accompanying the drug increases depending on the object to be used.

JP 2002-326819 A Japanese Patent No. 3391173

  An object of the present invention is to provide a heavy metal treating agent that can be treated with one chemical solution for heavy metal treatment of both cationic species and anionic species, and that does not generate toxic gas in heavy metal treatment, and a heavy metal treatment method using the same. It is.

  As a result of intensive studies on treatment agents effective for heavy metals of both cationic species and anionic species, the present inventors have found that iron sulfide for anionic species, particularly iron sulfide having a makinawite structure, dithiocarbamic acid for cationic species. The mixed composition of salts, particularly piperazine-N, N'-biscarbodithioate, is excellent in the ability to treat heavy metals of both cationic and anionic species, and enables high concentration of iron sulfide and dithiocarbamate. The inventors have found that the solidification of iron sulfide is suppressed, and no toxic gas is generated during the heavy metal treatment, and the present invention has been completed.

  Hereinafter, the present invention will be described in detail.

  In the mixed composition of the present invention, the concentration of iron sulfide is 1 wt% or more and 50 wt% or less. When the iron sulfide concentration is less than 1 wt%, it is necessary to use it in a large amount when used as a heavy metal treating agent, and transportation and storage costs become great. The higher the iron sulfide concentration, the better, and it is preferably 5 wt% or more, more preferably 10 wt% or more. On the other hand, when the iron sulfide concentration is too high, the viscosity of the iron sulfide particle-containing solution becomes too high and handling becomes difficult, so the upper limit of the iron sulfide concentration is 50 wt% or less, more preferably 40 wt% or less, A concentration of 30 wt% or less is preferred.

  The mixed composition of the present invention contains dithiocarbamate in an amount of 1 wt% to 50 wt%. When the concentration of dithiocarbamate is less than 1%, it is difficult to be a high-performance treatment agent for various heavy metals. When it is too high, the viscosity tends to increase and handling becomes difficult. Precipitates easily.

  Specific examples of the dithiocarbamate include piperazine-N, N′-biscarbodithioate, thiocarbamate such as ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. Particularly, piperazine-N N'-biscarbodithioate is preferred. The cationic species of the salt is not particularly limited, but sodium salt and potassium salt are preferable.

  The iron sulfide particles in the mixed composition of the present invention have few coarse particles, and the proportion of coarse particles of 100 μm or more is preferably less than 5% with respect to all particles. According to the Stokes equation for determining the sedimentation rate of particles in a solution, the sedimentation rate of particles is proportional to the square of the particle diameter. Therefore, when coarse particles are contained in the iron sulfide particle-containing solution, even if the solution is stirred, the coarse particles settle in a portion where the rising speed of the liquid is insufficient, resulting in uneven concentration. Iron sulfide having a particle size of 100 μm or more has a sedimentation rate of about 1 cm / s or more, and not only a large amount of power and stirring equipment are required to keep it as a uniform slurry by stirring. Clogging is likely to occur in piping. In the present invention, the proportion of coarse particles of 100 μm or more is preferably less than 5%, more preferably less than 3%, still more preferably less than 1% with respect to all particles.

  Next, the crystal structure of the iron sulfide in the mixed composition of the present invention is particularly preferably a makinawite structure. In the crystal structure of iron sulfide, the pyrotite structure has a lower ability to treat heavy metals than the iron sulfide of the makinawite structure.

  The mixed composition of the present invention only needs to contain iron sulfide and dithiocarbamate as constituent components, but the remaining main component may be a liquid, particularly water. An organic solvent such as alcohol may be used or may be included, and an additive such as a surfactant may be included as long as the effects of the object of the present invention are not impaired.

  In the mixed composition of the present invention, the state of presence of the dithiocarbamate is not clear, but the mixed composition of the present invention is in a stable dispersion state, so that it is partially adsorbed on the surface of the iron sulfide particles It is estimated to be. This is considered to stabilize the dispersion of iron sulfide in the slurry.

  In addition, since dithiocarbamate is present on the surface of iron sulfide, dithiocarbamate first reacts with cationic heavy metal, and then iron sulfide reacts with anionic heavy metal, which is more efficient than mixing separately. Processing becomes possible.

  As described above, the reason why the selective competitive reaction with respect to the metal existing in the treatment system can be controlled in spite of the mixed composition is that piperazine-N, N′-biscarbodithioate is cyclic and has a low level among amine species. It seems that it is influenced by being a molecule.

  Further, by using it in a mixed state with dithiocarbamic acid, particularly piperazine-N, N′-biscarbodithioate, there is no problem of generation of toxic gas during heavy metal treatment as a synergistic effect.

  The production method of the mixed composition of the present invention is not particularly limited. For example, a divalent iron salt aqueous solution and a sulfur ion aqueous solution are mixed so as to maintain a certain pH range to obtain a slurry containing iron sulfide. The by-product salt can be removed from the slurry and then mixed with dithiocarbamate.

  A slurry containing iron sulfide can be synthesized, for example, by reacting an iron salt such as iron chloride with sodium hydrosulfide. Piperazine-N, N′-biscarbodithioate is composed of piperazine, an alkali hydroxide and carbon disulfide. Can be obtained by reacting.

  The mixed composition of the present invention is produced by mixing these reactants, but may be mixed from the beginning or may be mixed immediately before use. Since the mixed composition of the present invention is extremely stable in a mixed state and can be stored for a long time after mixing, it is preferably handled as one agent from the beginning.

  Next, heavy metal treatment using the mixed composition of the present invention will be described.

  The heavy metal treating agent comprising the mixed composition of the present invention has a treatment effect on any harmful heavy metals of the anionic species and cation types, and for the treatment of special Pb, Cd, Hg, As, Se, and hexavalent Cr. It is valid. It is possible not only to treat heavy metals individually, but also to treat those containing a plurality of these.

  The heavy metal treating agent of the present invention is particularly effective for waste such as complex contamination with cationic species such as Pb, Cd and Hg and anionic species such as As, Se and hexavalent Cr. It is possible and effective to detoxify by adding only one agent.

  Examples of the object to be treated with the heavy metal treating agent of the present invention include waste incineration ash and fly ash containing heavy metal. Waste incineration ash and fly ash are concentrated with heavy metals contained in various types of waste and require detoxification (heavy metal insolubilization). Fly ash and molten fly ash are classified into alkaline fly ash, neutral fly ash, alkaline molten fly ash, neutral molten fly ash, etc., depending on the structure and operation method of the incinerator, and the type of garbage to be incinerated. Although the kind and content of heavy metals contained vary greatly depending on the type, the heavy metal treating agent of the present invention can be used for any ash.

  The addition amount of the heavy metal treating agent of the present invention differs depending on the type and total amount of heavy metals contained in the waste incineration ash and fly ash, but cannot be defined unconditionally. 0.1 to 50 wt%, preferably 0.5 to 30 wt%. Further, it is preferable to sample the waste incineration ash and fly ash in advance and obtain the addition amount by a lab test, and obtain the optimum addition amount in consideration of the variation in the amount of heavy metals contained in the waste incineration ash and fly ash.

  Although the amount of water added to the heavy metal treating agent of the present invention varies depending on the properties of the waste incineration ash and fly ash, it is usually 10 to 40 wt% with respect to the amount of the waste incineration ash and fly ash. The method and time for kneading are not particularly limited, and may be those conventionally known.

  The heavy metal treating agent of the present invention is also effective for treating soil containing heavy metals. The heavy metal treating agent of the present invention and, if necessary, water can be added to the soil containing heavy metals and kneaded.

  Although the amount of the heavy metal treating agent of the present invention added to the soil varies depending on the total amount of heavy metals contained in the soil, it cannot be defined unconditionally. For example, 0.1 to 20 wt% is exemplified with respect to the amount of soil to be treated. Can do. Further, it is preferable to sample the soil in advance and obtain the minimum addition amount by a laboratory test, and add an amount that is slightly excessive in consideration of safety. When the moisture contained in the soil is small, it varies depending on the type of soil, but it is preferable to add water as necessary so that the amount of moisture contained in the soil is usually 10 to 60 wt%. The kneading method and time are not particularly limited, and a conventionally known method can be used.

  The heavy metal treating agent of the present invention can also be applied to the treatment of waste water containing heavy metals. The amount of heavy metal treatment agent added to the wastewater also varies depending on the total amount of heavy metals contained in the wastewater, but it cannot be specified unconditionally. However, the wastewater is sampled in advance and the minimum amount added is determined by a laboratory test. It is preferable to do.

  In such applications, when the pH of wastewater is low, iron sulfide is decomposed and hydrogen sulfide may be generated. However, in the present invention, such a problem is caused by using a mixed composition with dithiocarbamate. Absent. The mixing method and time are not particularly limited, and a conventionally known method can be used.

  As the heavy metal treating agent of the present invention, the mixed composition of the present invention is used as a single agent. However, even if the mixed composition is mixed from the beginning, it can be mixed at the treatment site immediately before the heavy metal treatment. . In addition, an inorganic coagulant precipitating agent usually used in the coagulation / precipitation treatment, for example, ferric chloride, polyaluminum chloride, a sulfuric acid band or the like is used in combination, or a polymer coagulant that accelerates the aggregation rate is used in combination. It may be used.

  The mixed composition of the present invention can treat both anionic and cationic heavy metals at the same time, and can treat the heavy metals such as incineration ash, soil, wastewater, etc. with one agent, and can simplify the treatment equipment, Excellent operability and no generation of harmful gases during heavy metal processing.

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

Example 1
With an effective internal volume of 750 mL, the reaction vessel is maintained at 50 ° C. at the top, while stirring, an aqueous solution of iron (II) chloride (35.0 wt%) is 600 g / h, and an aqueous sodium hydrosulfide solution (10.0 wt%) is 880 g / h In addition, the aqueous solution of sodium hydroxide (48.0 wt%) was continuously added while controlling the flow rate so that the slurry pH in the reaction vessel was kept at 9.5 ± 0.5, and the produced macina wite structure The iron sulfide slurry was recovered.

  The obtained iron sulfide slurry contained 9.5 wt% iron sulfide and 12.7 wt% sodium chloride. The resulting slurry was then filtered to remove excess mother liquor containing sodium chloride. Water and piperazine-N, N′-biscarbodithioic acid potassium were added to the iron sulfide cake after filtration, and after stirring and repulping, the mixture was further crushed to obtain a mixed composition.

  The obtained mixed composition had an iron sulfide concentration of 15 wt%, a piperazine-N, N′-biscarbodithioate potassium concentration of 20 wt%, and the viscosity immediately after adjustment measured with a B-type viscometer was 530 mPa · S. The fluidity was good.

  When this iron sulfide particle-dispersed solution was allowed to stand for one week and then stirred, a uniform dispersed slurry was easily obtained. At this time, the viscosity was 550 mPa · S, and the fluidity was good.

Example 2 (performance evaluation)
Using alkaline fly ash containing hexavalent chromium and lead, the processing characteristics of heavy metals were examined using the mixed composition of Example 1. The mixed composition was added to 100 parts by weight of alkaline fly ash, and water was further added so as to be 30 parts by weight of water + treatment agent, followed by kneading and heavy metal treatment. For the treated fly ash, the Environmental Agency (current Ministry of the Environment) Notification No. 13 dissolution test (1973) was conducted. The hexavalent Cr contained in the eluate was measured by the diphenylcarbazide method, and lead and total Cr were measured by the ICP issuance analysis method. The results are shown in Table 1.

  For comparison, a slurry equivalent to 7.2 wt% of iron sulfide without any coexisting salt and a 20 wt% piperazine-N, N′-biscarbodithioate single solution were added separately (Comparative 1). Iron sulfide was equivalent to Example 1, piperazine Evaluation was carried out in the same manner as in Example 1 except that no potassium N, N′-biscarbodithioate was added (Comparative 2).

表１の結果より明らかなように、本発明の混合組成物では、少ない添加量で６価Ｃｒの処理及びＰｂ処理が可能であった。一方、共存塩のない分散性の悪い硫化鉄スラリーとジチオカルバミン酸塩を別々に混合した場合（比較例１）には、重金属の処理能が不十分であり、硫化鉄だけ（比較例２）ではＰｂの処理は不十分であった。

As is clear from the results in Table 1, the mixed composition of the present invention was able to treat hexavalent Cr and Pb with a small addition amount. On the other hand, when the iron sulfide slurry with poor dispersibility without coexisting salt and dithiocarbamate are mixed separately (Comparative Example 1), the ability to treat heavy metals is insufficient, and only with iron sulfide (Comparative Example 2). The treatment of Pb was insufficient.

Example 3
A mixed composition prepared in Example 1 for four types of model wastewater including a solution containing 1 ppm of mercury, a solution containing 10 ppm of hexavalent chromium, a solution containing 10 ppm of trivalent arsenic, and a solution containing 10 ppm of tetravalent selenium. 0.2 part by weight was added to treat heavy metals. After adding the mixed composition to the model wastewater, the mixture was mixed for 30 minutes, filtered through glass filter paper (GS-25 manufactured by Advantech Toyo), and the amount of each component contained in the filtrate was measured. The results are shown in Table 2.

表２の結果から明らかなように、本発明における混合組成物では重金属類の含有量は大きく削減され、鉛、カドミウム、水銀、六価クロム、砒素は排水基準以下まで処理可能であった。

As is apparent from the results in Table 2, the content of heavy metals was greatly reduced in the mixed composition of the present invention, and lead, cadmium, mercury, hexavalent chromium, and arsenic could be processed to below the wastewater standard.

Claims (7)

A mixed composition comprising an iron sulfide concentration of 1 wt% to 50 wt% and a dithiocarbamate salt of 1 wt% to 50 wt%. The mixed composition according to claim 1, wherein the crystal structure of iron sulfide is a makinawite structure. The mixed composition according to claim 1 or 2, wherein the dithiocarbamate is piperazine-N, N'-biscarbodithioate. The mixed composition according to claims 1 to 3, wherein the piperazine-N, N'-biscarbodithioate is a sodium salt or a potassium salt. The heavy metal treating agent comprising the mixed composition according to claim 1, wherein the heavy metal is at least one selected from the group consisting of Pb, Cd, Hg, As, Se, and hexavalent Cr. The heavy metal processing method which adds and knead | mixes the heavy metal processing agent of Claims 1-5 to any 1 or more types of refuse incineration ash, fly ash, heavy metal containing soil, and heavy metal containing wastewater. A heavy metal treatment method comprising: mixing an iron sulfide slurry and a dithiocarbamate solution at a site where the heavy metal treatment agent according to claim 1 is treated with incineration ash, fly ash, heavy metal-containing soil, and heavy metal-containing wastewater. .