JP2007302779A - Mixed solution containing iron sulfide particle and method of treating heavy metal using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in the working environment when using a conventional iron sulfide slurry for treating heavy metals, wherein the slurry emits an odor depending on the treatment condition. <P>SOLUTION: Iron sulfide slurry with iron sulfide concentration of 1-50 wt.% and activated carbon concentration of 0.01-30 wt.% does not emit any odor and is user-friendly. Such the iron sulfide slurry is obtained by mixing an aqueous solution of a divalent iron salt and an aqueous solution containing sulfur ions to obtain the iron sulfide slurry and further mixing the slurry with a fine powder of activated carbon. Since iron sulfide serving as a heavy metal treating agent is in a solid state, its activity is not deteriorated by the adsorption of heavy metal components to the activated carbon. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mixed solution containing iron sulfide particles that is suitable for use in detoxification treatment by treating heavy metals contained in ash, soil, or waste water, without generating odor during heavy metal treatment.

  For solutions containing iron sulfide particles, iron sulfide colloid solutions in which iron sulfide particles are stably dispersed in a dispersion medium such as water and do not settle and separate, and iron sulfide slurries in which iron sulfide settles and separates when left standing There is. A solution containing iron sulfide particles in which iron sulfide particles are dispersed in a dispersion medium such as water is easy to mix with soil contaminated with heavy metals, incinerated ash, and the like, and is suitable as a heavy metal treatment agent.

It has been widely known that iron sulfide is mixed with heavy metal contaminants to insolubilize (detoxify) various heavy metals. For example, it contains industrial iron sulfide (pilotite structure) and iron (II) ions. There has been known a method of treating harmful heavy metals such as Pb, Cd, Cr, Hg and As in an aqueous solution by using iron sulfide produced from a solution and a solution containing sulfur ions. In particular, it has been known that iron sulfide (makinawite structure) produced from a solution containing iron (II) ions and a solution containing sulfur ions is excellent as a heavy metal treatment characteristic. (For example, see Patent Documents 1 to 3)
However, in the case of a conventional iron sulfide particle-containing solution, in a solution obtained by mixing a divalent iron salt aqueous solution and an aqueous solution containing sulfur ions, an odor may be felt depending on heavy metal treatment conditions.

  On the other hand, it has been reported that powdered carbon and a heavy metal treating agent are used in combination with heavy metal treatment such as fly ash. (Refer to Patent Documents 4 and 5) However, the conventional use of carbon is used separately from the heavy metal treating agent, and there has been no example of using carbon and the heavy metal treating agent as one agent. It has also been known that when a heavy metal treating agent and powdered carbon are used in combination, the heavy metal treating component is adsorbed on the activated carbon, and there is a problem in using it simultaneously.

Japanese Patent Laid-Open No. 52-113559 JP 52-148473 A JP 2001-121130 A JP-A-9-66275 JP 2003-117521 A

  An object of the present invention is to provide an iron sulfide particle-containing mixed solution that does not generate odor under any heavy metal treatment condition and is excellent in operability and heavy metal treatment characteristics.

  As a result of intensive studies on a solution containing iron sulfide particles used as a heavy metal treating agent, the present inventors have found that the cause of the odor is not an inorganic sulfur raw material (such as sodium hydrosulfide) but an organic sulfur compound. The present inventors have found that activated carbon is particularly effective for suppressing the odor of organic sulfur compounds, and have completed the present invention.

  Hereinafter, the present invention will be described in detail.

  The mixed solution containing iron sulfide particles of the present invention (hereinafter referred to as “iron sulfide slurry”) has a concentration of iron sulfide of 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 iron sulfide concentration is preferably as high as possible, more preferably 5 wt% or more, and further preferably 10 wt% or more. On the other hand, if the iron sulfide concentration is too high, the viscosity of the iron sulfide slurry is 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, and even 30 wt%. The following concentrations are preferred.

  The activated carbon concentration in the iron sulfide slurry of the present invention is 0.01 wt% or more and 30 wt% or less. If the activated carbon concentration is less than 0.01 wt%, the effect of suppressing odor is small, and if it is more than 30 wt%, more activated carbon than necessary is present for the odor suppression effect, which is disadvantageous in terms of cost. Furthermore, since the solid component concentration is high, the solution viscosity increases and handling becomes difficult.

  One of the features of the present invention is that activated carbon is selected to suppress the odor of the iron sulfide slurry. Conventionally, since iron sulfide is produced by a reaction of an inorganic compound, an inorganic compound such as hydrogen sulfide is mainly assumed as an odor component. If hydrogen sulfide or the like is an odor source, it is generally known that an increase in alkali concentration or an odor prevention technique by adding an amine is effective. However, these techniques have not been able to achieve special odor control as in the present invention. This is because the main cause of the odor of the iron sulfide slurry is a very small amount of organic sulfur compound such as dimethyl disulfide.

  In the present invention, since the heavy metal treatment agent is an iron sulfide slurry, that is, a solid material, it is also important that the heavy metal treatment component is not adsorbed on the activated carbon and the treatment activity is not lowered. Activated carbon can also be expected to act as a heavy metal adsorption aid.

  The crystal structure of iron sulfide used in the iron sulfide slurry of the present invention is particularly preferably a makinawite structure. Although it is not impossible to prepare the iron sulfide particle-containing mixed solution of the present invention by wet-pulverizing iron sulfide having a pyrotite structure, a large cost is required for pulverization. Since the iron sulfide having a makinawite structure has a high heavy metal treatment capability, it is particularly suitable for use as a heavy metal treatment agent which is an object of the present invention.

  The iron sulfide particles used in the iron sulfide slurry 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, if coarse iron sulfide particles are contained in the mixed solution containing iron sulfide particles, even if the solution is stirred, the coarse particles are likely to settle in a portion where the rising speed of the liquid is insufficient and unevenness in concentration tends to occur. Iron sulfide having a particle size of 100 μm or more has a sedimentation speed 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 and the like. In the present invention, the proportion of coarse particles of 100 μm or more is less than 5%, more preferably less than 3%, and even more preferably less than 1% with respect to all particles.

  The activated carbon used in the present invention preferably has a particle size of 150 μm or less. As described above, in the present invention, in order to obtain a high concentration iron sulfide slurry, the particle size of iron sulfide is preferably 100 μm or less. Here, when the particle size of the activated carbon is too large, iron sulfide and activated carbon are separated, and the effect of suppressing odor tends to be non-uniform. In the present invention, by using 150 μm or less as the particle size of the activated carbon, uniformity in the iron sulfide slurry having good fluidity can be maintained.

  Next, the manufacturing method of the iron sulfide slurry of this invention is demonstrated.

  Although it does not specifically limit about the manufacturing method of the iron sulfide of this invention, For example, it manufactures by mixing the aqueous solution containing a bivalent iron salt and the aqueous solution containing a sulfur ion so that a fixed pH range may be maintained, and making it an iron sulfide slurry. be able to.

  In the present invention, activated carbon is added to the iron sulfide slurry prepared by the above method. Although it does not specifically limit as an addition method, It is preferable to add, after preparing an iron sulfide slurry and removing excess mother liquor and by-product salt. Moreover, after adding activated carbon, in order to homogenize the mixed solution containing iron sulfide particles, it is preferable to perform an operation such as stirring to make the mixed solution as uniform as possible.

  Next, heavy metal treatment using the iron sulfide slurry of the present invention will be described.

  The iron sulfide slurry of the present invention can be used as a heavy metal treating agent, and is particularly effective for the treatment of Cr, As, and Se as the heavy metal to be treated. 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 (hereinafter referred to as “heavy metal treating agent”) containing the iron sulfide slurry of the present invention is not only used alone, but also used in combination with an organic chelating agent that reacts with Pb or Cd. Also good. Among them, it is effective to detoxify the waste that is complexly contaminated with Pb, Cd and hexavalent Cr, As, and Se using the heavy metal treating agent and the organic chelating agent of the present invention.

  The object to be treated with the heavy metal treating agent of the present invention is not particularly limited, and examples thereof include waste incineration ash and fly ash containing heavy metal. The waste incineration ash and fly ash are concentrated with heavy metals contained in various types of waste and need to be detoxified. 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, and thus cannot be defined unconditionally. Examples thereof include 1 to 50 wt%, preferably 0.5 to 30 wt%. Furthermore, it is preferable to sample the waste incineration ash and fly ash in advance and obtain the addition amount by a lab test, and to obtain the optimum addition amount in consideration of fluctuations 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 also varies depending on the total amount of heavy metals contained in the soil, it cannot be defined unconditionally, but 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. At this time, if the pH of the wastewater is low, iron sulfide may decompose and hydrogen sulfide may be generated. Therefore, it is preferable to adjust the pH of the wastewater in advance, in which case the pH of the wastewater is 3.0 or more. More preferably, it should be 6.0 or more. The mixing method and time are not particularly limited, and a conventionally known method can be used. Ordinarily, inorganic coagulant precipitants used in the coagulation precipitation process, for example, ferric chloride, polyaluminum chloride, sulfuric acid band, etc. are used in combination, or polymer coagulants that increase the coagulation rate are used in combination. Is also possible.

  The iron sulfide slurry of the present invention can be used as a heavy metal treatment agent in the treatment of heavy metals such as incineration ash, soil, waste water, etc., has a high treatment capacity for heavy metals, has no odor generation regardless of the conditions used, and has a working environment. There is no problem to worsen. Activated charcoal works as an adsorption aid for heavy metal treatment without reducing the heavy metal treatment activity of iron sulfide, and the iron sulfide slurry of the present invention in which these components are used as one agent is also extremely suitable in terms of processing operability. It is a thing.

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

Example 1
A stainless steel continuous reaction vessel having an effective internal volume of 750 mL and an overflow port at the top is kept at 50 ° C., and while stirring, an aqueous solution of iron (II) chloride (35.0 wt%) is added at 600 g / h with an aqueous solution of sodium hydrosulfide (10 0.0 wt%) continuously at 880 g / h, and while controlling the flow rate of the aqueous sodium hydroxide solution (48.0 wt%) so that the slurry pH in the reaction vessel is maintained at 9.5 ± 0.5, And the produced iron sulfide slurry having a makinawite structure was recovered from the overflow port.

  The resulting 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 powdered activated carbon were added to the iron sulfide cake after filtration and stirred and repulped, and then pulverization was performed to obtain an iron sulfide slurry.

  The obtained iron sulfide slurry had an iron sulfide concentration of 15 wt% and an activated carbon concentration of 1.0 wt%. The viscosity immediately after adjustment measured with a B-type viscometer was 510 mPa · S, and the fluidity was good.

  When this iron sulfide slurry was kept standing for one week, sedimentation occurred, and a transparent layer of about 10% of the height of the container was observed from the top. Although the state of the sedimentation portion was observed, it was a very soft sediment, and when it was stirred with a stirring blade, it became a uniform dispersed solution within 1 minute. At this time, the viscosity was 520 mPa · S and the fluidity was good.

  The obtained iron sulfide slurry was put in a vial and the gas generated in the head space after being left for one day was analyzed by gas chromatogram. However, no clear peak was observed, and the sensory test was almost odorless.

Comparative Example 1
Except not adding activated carbon, operation similar to Example 1 was performed and the iron sulfide slurry was obtained. The obtained iron sulfide slurry was put in a vial and the gas generated in the headspace after being left for one day was analyzed by gas chromatogram. The largest peak observed was dimethyl disulfide. Moreover, as a result of inspecting the odor as a sensory test, a sulfur-based odor was felt.

Example 2
Using waste containing hexavalent chromium, the processing characteristics of heavy metals were examined using the iron sulfide slurry of Example 1 and Comparative Example 1. The iron sulfide particle-containing mixed solution was added to 100 parts by weight of the waste, and water was further added so as to be 40 parts by weight of water + treatment agent, followed by kneading and heavy metal treatment. For the waste, the Environmental Agency (now 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 the total Cr was measured by the ICP issuance analysis method. The results are shown in Table 1.

表１の結果より明らかなように、本発明の硫化鉄スラリーは、重金属処理能力においては従来のスラリーと比較し、同等の特性を有していた。

As is clear from the results in Table 1, the iron sulfide slurry of the present invention had equivalent characteristics in terms of heavy metal processing capacity compared to conventional slurries.

Claims (5)

An iron sulfide particle-containing mixed solution having an iron sulfide concentration of 1 wt% to 50 wt% and an activated carbon concentration of 0.01 wt% to 30 wt%. The mixed solution containing iron sulfide particles according to claim 1, wherein the crystal structure of iron sulfide is a makinawite structure. 3. The iron sulfide particle-containing mixed solution according to claim 1, wherein the activated carbon has a particle size of 150 μm or less. The heavy metal processing agent which comprises the iron sulfide containing mixed solution of Claims 1-3. The heavy metal processing method using the iron sulfide particle containing solution of Claims 1-3 as a heavy metal processing agent.