JP2007301548A - Metal powder for decomposing organic halogen compound and method for cleaning soil using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal powder for decomposing organic halogen compounds, which is capable of decomposing persistent organic halogen compounds contained as pollutants in soil, underground water and the like at a high speed. <P>SOLUTION: As the metal powder for decomposing the organic halogen compounds capable of decomposing and cleaning at a high speed the persistent organic halogen compounds, such metal powder is prepared as a metal powder having an adhesion metal phase 2 in which metal particles 3 composing a metal powder 4 contain nickel as a main component and a base metal phase 1 in which iron is a main component, the metal powder 4 having an adhesion metal phase 2 containing manganese as a main component and a base metal phase 1 containing aluminum as a main component, or a metal powder composed of aluminum dross generated in an aluminum smelting process. The organic halogen compounds in an environment are decomposed and cleaned at a high speed using the methods of mixing any of the above metal powders with the soil polluted with the organic halogen compounds. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

TECHNICAL FIELD OF THE INVENTION

  The present invention relates to a metal powder for decomposing an organic halogen compound, which can decompose an organic halogen compound, which is one of pollutants contaminating the environment such as soil, river water, ground water, and air, at high speed.

Conventional technology

  In recent years, soil and groundwater by organic halogen compounds typified by organic chlorine compounds such as tetrachlorethylene (hereinafter referred to as PCE), trichlorethylene (hereinafter referred to as TCE), dichloroethylene (hereinafter referred to as DCE) and the like. Such pollution has become obvious and has been taken up as a social problem. Various methods for purifying these organic halogen compounds have been devised. For example, Patent Document 1 describes a method of aerobic or anaerobic decomposition treatment by microorganisms. Further, for example, Patent Document 2 describes a method of oxidative decomposition treatment using a photocatalyst. Further, for example, Patent Document 3 describes a reductive decomposition method using special iron powder having a spongy shape (hereinafter referred to as special iron powder).

In addition, for example, in Patent Document 4, copper-containing iron powder (hereinafter referred to as copper-containing iron powder) in which 0.2 to 20 wt% of metal copper is attached to the surface of the metal iron powder is prepared, and metal is prepared. It is disclosed that the decomposition activity of iron powder into organic halogen compounds can be enhanced.
JP 7-178395 A Japanese Patent Laid-Open No. 7-144137 Japanese Patent Application Laid-Open No. 11-235577 JP 2000-5740 A

  In order to purify the contamination of soil and groundwater by organic halogen compounds, the above-described techniques have been disclosed and proposed. However, organic halogen compounds include a wide range of compound groups. Some technologies are difficult to disassemble and require a long time for purification. For this reason, for example, in the field of soil purification, a method that can quickly purify the hardly decomposable organic halogen compound is strongly desired. The present invention has been made in the background as described above, and provides a metal powder capable of decomposing and purifying a hardly decomposable organic halogen compound contaminating the environment such as soil at a high speed. It is in.

  First, the present inventors prepared various metal powder samples, selected DCE as a hardly decomposable organic halogen compound, and conducted a DCE decomposition rate test using these metal powder samples. As a result of trial and error, the present inventors have found that two or more metal species, in particular, metal powder having a phase mainly composed of nickel and iron, and a metal having a phase mainly composed of aluminum and manganese, respectively. As a result of further research, it was found that these metal powders are metal powders that can decompose and purify DCE and other difficult-to-decompose organic halogen compounds at high speed. I came up with it. Furthermore, metal powder produced from aluminum dross produced as a by-product in the aluminum melting process in the aluminum smelting process and aluminum processed product manufacturing process is also a metal powder that can decompose and purify persistent organic halogen compounds at high speed. The present invention has been completed with this in mind.

That is, the first invention that solves the above-described problem is a metal particle that constitutes a metal powder, and each metal particle has a phase mainly composed of nickel and a phase mainly composed of iron. This is a metal powder for decomposing organic halogen compounds.

  Metal powders having this configuration are various hard-to-decompose organic halogen compounds such as PCE, TCE, cis-1,2-DCE, trans-1,2-DCE, such as monochlorobenzene (hereinafter referred to as MCB). 1,2-dichlorobenzene (hereinafter referred to as 1,2-DCB), 1,3-dichlorobenzene (hereinafter referred to as 1,3-DCB), dichloromethane, carbon tetrachloride, 1,2-dichloroethane (hereinafter referred to as 1,2-DCA), 1,1-dichloroethane (hereinafter referred to as 1,1-DCA), 1,1,1-trichloroethane, 1,1, Applicable to 2-trichloroethane, 1,3-dichloropropene, trihalomethane, 1,1-dichloroethylene, PCB, etc. Especially, chlorinated organic compounds are decomposed and purified at high speed. It can be. As a result, by using the metal powder according to the present invention, it is possible to purify soil, groundwater, and surface water contaminated with organic halogen compounds.

  According to a second aspect of the invention, the organic halogen compound according to the first aspect is characterized in that the phase mainly composed of nickel is scattered and adhered to the surface of the phase mainly composed of iron. It is a metal powder for decomposition.

  A third invention is the metal powder for decomposing an organohalogen compound according to the first or second invention, wherein the content of nickel in the metal powder is 20 wt% or less not including 0 wt%. .

  4th invention is the metal particle which comprises metal powder, Comprising: Each said metal particle has the phase which has manganese as a main component, and the phase which has aluminum as a main component, The organic halogen characterized by the above-mentioned It is a metal powder for compound decomposition.

  According to a fifth invention, the organic halogen compound according to the fourth invention is characterized in that the phases mainly composed of manganese are scattered and adhered to the surface of the phase mainly composed of aluminum. It is a metal powder for decomposition.

  A sixth invention is the metal powder for decomposing an organohalogen compound according to the fourth or fifth invention, wherein the content of manganese in the metal powder is 30 wt% or less not including 0 wt%. .

  The seventh invention is a metal powder produced from aluminum dross produced in the melting process of aluminum, mainly composed of aluminum oxide, C, Na, Mg, Al, Si, Ca, Mn, Fe, Co It is a metal powder for decomposing | disassembling an organic halogen compound characterized by including the phase which has at least 1 or more types of elements in any one of Ni, Cu, and Zn as a main component.

  By adopting this configuration, an effective utilization method of a by-product in the aluminum melting process called aluminum dross was found, and at the same time, an extremely low-cost metal powder for decomposing an organic halogen compound could be obtained. As a result, by using the metal powder according to the present invention, it is possible to purify soil, groundwater, and surface water contaminated with an organic halogen compound at a low cost.

  An eighth invention is a method for purifying soil and / or ground water and / or surface water, characterized in that the metal powder for decomposing an organohalogen compound according to any one of the first to seventh inventions is used.

  As described above in detail, the present invention is mainly composed of a metal powder capable of decomposing and purifying a hardly decomposable organic halogen compound at a high speed, a phase mainly composed of nickel and metal, which constitute the metal powder. A metal powder having a phase as a component, or a metal powder constituting a metal powder having a phase mainly composed of manganese and a phase mainly composed of aluminum, or produced in an aluminum melting process. It is provided as a metal powder composed of aluminum dross.

BEST MODE FOR CARRYING OUT THE INVENTION

(Components and structure of metal powder for organic halogen compound decomposition)
The metal powder for organic halogen compound decomposition (hereinafter referred to as metal powder) according to the embodiment of the present invention is at least iron (hereinafter referred to as Fe) -nickel (hereinafter referred to as Ni). A phase mainly composed of Fe, a phase mainly composed of Fe as a base metal phase, a phase mainly composed of Ni as an adhering metal phase, and the adhering metal phase as a base metal It adheres to the phase to form Ni-adhered Fe particles, and these particles are aggregated.

  Next, the metal powder according to the different embodiments of the present invention is a phase mainly composed of at least two metal elements of aluminum (hereinafter referred to as Al) -manganese (hereinafter referred to as Mn). The phase containing Al as the main component is the base metal phase, the phase containing Mn as the main component is the adhering metal phase, and the adhering metal phase adheres to the base metal phase and becomes the form of Mn adhering Al particles. These particles are aggregates.

  Furthermore, the metal powder which concerns on different embodiment of this invention is the metal powder manufactured from the aluminum dross which is by-products, such as Al smelting process.

  First, the Ni-attached Fe powder and the Mn-attached Al powder will be described with reference to FIG. FIG. 1 is an enlarged view schematically showing metal particles in the metal powder according to the present invention. In FIG. 1, reference numeral 1 denotes a base metal phase, and reference numeral 2 denotes an attached metal phase. The attached metal phase 2 adheres to the base metal phase 1 to be in the form of metal powder particles indicated by reference numeral 3. The metal powder 4 is a collection of a large number of the metal powder particles 3. Further, reference numeral 5 denotes an interface between the base metal phase 1 and the attached metal phase 2, and reference numeral d denotes an attached film thickness of the attached metal phase 2. For both the Ni-attached Fe powder and the Mn-attached Al powder, the shape of the Fe metal phase, which is the base metal phase 1, and the Al phase may be any shape such as spherical, needle-like, or sponge-like, but the specific surface area per unit weight is Larger is preferred. The Ni phase and Mn phase, which are the adhered metal phase 2, are dispersed in the surface of the base metal phase 1 without being continuous with each other and adhered in a scattered manner. preferable. That is, it is preferable that at least two phases constituting the metal powder particle 3 are exposed on the surface of the metal powder particle 3. By having this configuration, the metal powder 4 is considered to be able to efficiently decompose the surrounding organic halogen compound. However, even if a portion having a compound form such as an oxide of the base metal exists in the interface 5 between the base metal phase 1 and the adhered metal phase 2, the decomposition characteristics of the organic halogen compound are reduced. There is no major adverse effect.

  Although there is no restriction | limiting in particular in the adhesion film thickness d of the adhesion metal phase 2, When using metals, such as Ni and Mn, as an adhesion metal, it is preferable to make it as thin as possible from a viewpoint of cost.

In both the Ni-adhered Fe powder and the Mn-adhered Al powder, the particle diameter of the metal powder particles 3 is preferably 1 to 500 μm. This is because when the particle size is 1 μm or less, dispersibility in soil is excellent, but for example, groundwater flow and the like may pass through the soil particle gap and be washed away to the lower layer. On the other hand, if it exceeds 500 μm, the position in the soil is stable, but the amount of metal powder 4 used per unit soil area increases, so a particle size of 500 μm or less is preferable in terms of cost. . However, this is not the case, for example, when a metal phase having a large specific surface area such as spongy particles is used as the base metal phase 1. In the case of a metal phase having a large specific surface area, the number of effective reaction sites per unit weight of the metal phase increases, so that the amount used per unit soil area can be reduced, and the metal powder 4 having a particle size of the metal particles 3 exceeding 500 μm. However, it can be preferably used.

  In the Ni-adhered Fe powder, when the sum of the weights of the Ni element in the Ni phase and the Fe element in the Fe phase is 100 wt%, the decomposition rate of the organic halogen compound is reduced when the Ni phase adhesion amount to the Fe phase is 0 wt%. Slowly, when it becomes 10 wt% or more, the decomposition rate of the organic halogen compound is saturated. Here, since Ni is a metal with a high raw material cost, considering the decomposition rate of the organic halogen compound and the raw material cost, the Ni attached amount in the Ni attached Fe powder is preferably 20 wt% or less not including 0 wt%. Preferably, it is 5 wt% or less not including 0 wt%.

  Next, in the Mn-attached Al powder, when the sum of the weights of the Mn element in the Mn phase and the Al element in the Al phase is 100 wt%, the decomposition of the organic halogen compound occurs when the Mn adherence amount to Al is 0 wt%. When the rate is slow and becomes 30 wt% or more, the decomposition rate of the organic halogen compound is saturated. Here, since Mn is a metal having a high raw material cost, considering the decomposition rate of the organic halogen compound and the raw material cost, the Mn adhesion amount in the Mn-attached Al powder is preferably 30 wt% or less not including 0 wt%.

  From the viewpoint of the cost of constructing the above-described metal powder 4 on contaminated soil or the like, the particle diameter of the metal particles 3 is preferably 1 to 500 μm, more preferably 10 to 100 μm for both the Ni-attached Fe powder and the Mn-attached Al powder. The degree is preferred. If the particle size is 1 μm or less, the dispersibility in the soil is excellent. However, for example, it may flow through the soil particle gap to the lower layer along with the groundwater flow. On the other hand, if it exceeds 500 μm, the position in the soil will be stable, but the amount of metal powder 4 used per unit soil area will increase, so considering the construction cost, the particle size of the metal particles 3 will be 500 μm or less This is because the metal powder 4 in which the particle size of the metal particles 3 is about 10 to 100 μm is more preferable. However, this is not the case when the base metal phase 1 having a large specific surface area such as spongy particles is used. In the case of the base metal phase 1 having a large specific surface area, the number of effective reaction sites per unit weight of the base metal phase 1 is increased, so that the amount used per unit soil area can be reduced, and the particle size of the metal particles 3 can be reduced. Even metal powder 4 exceeding 500 μm can be preferably used.

  Next, the metal powder manufactured from aluminum dross will be described. First, aluminum dross is a by-product containing impurities generated on the surface of the Al melt during the melting process of waste containing Al ore or Al compound in the Al refining process or the processed aluminum product manufacturing process. Almidros contains several tens wt% of Al, and conventionally, after separating and collecting the lower layer portion having a low impurity content, performing the Al smelting process again to recover the Al content, the remaining portion Was disposed of as waste. Since this high temperature heat treatment process is included in this second Al smelting process, a large amount of energy is required, and in the remaining waste, there are still about 5 to 10 wt% Al and about 10 to 50 wt%. An alumina component was contained, which was inefficient in terms of recovery and reuse of Al content.

  This aluminum dross has at least one or more of any of C, Na, Mg, Al, Si, Ca, Mn, Fe, Co, Ni, Cu, Zn, etc. in the Al oxide phase forming the base metal phase. Elements are incorporated and / or deposited in the form of alloys and / or deposited metal phases. The adhering metal phase is generally dispersed and scattered in the adhering metal phase without being continuous on the Al oxide phase.

And it is aluminum dross collect | recovered in the said smelting process, Comprising: Al content is about 0.01-70 wt%, The particle diameter is the range of 0.1-300 mm, The specific surface area is 0.1. Those in the range of ^{2 to} 120 m ² / g have a high decomposition rate of the organic halogen compound, and can be suitably used as a metal powder for organic halogen compound decomposition. The metal powder produced from the aluminum dross is also considered to decompose and purify the hardly decomposable organic halogen compound at a high speed by a mechanism similar to that of the Mn-attached Al powder.

  Of course, it is also preferable to pulverize the aluminum dross to prepare a metal powder having a particle diameter in the range of 0.1 to 80 μm. By adopting the above-described configuration, it becomes easy to add metal powder to the soil and the like, and after addition to the soil, it becomes possible to decompose and purify the hardly decomposable organic halogen compound at a high speed.

  As a result, it requires a large amount of energy for the aluminum dross reprocessing process, and it replaces the inefficient recovery and recycling process of Al, which has a large industrial merit for producing metal powder at a low manufacturing cost. The production process and beneficial use of aluminum dross can be realized.

(Decomposition characteristics of organohalogen compounds with metal powder for decomposing organohalogen compounds)
Various powders such as MCB as well as PCE, TCE, cis-1,2-DCE, trans-1,2-DCE are also available for metal powders manufactured from Ni-attached Fe powder, Mn-attached Al powder, and aluminum dross. Organic halogen compounds such as 1,2-DCB, 1,3-DCB, dichloromethane, carbon tetrachloride, 1,2-DCA, 1,1-DCA, 1,1,1-trichloroethane, 1,1,2 -Applicable to the decomposition of trichloroethane, 1,3-dichloropropene, trihalomethane, 1,1-DCE, PCB and the like, and particularly suitable for the decomposition of chlorinated organic compounds. Further, soil, groundwater, and surface water contaminated with heavy metals and organic halogen compounds can be purified by the metal powder described above. In particular, when metal powder containing Al is used, the construction environment is excellent in that it exhibits the decomposition action of the organic halogen compound regardless of whether the construction environment is weakly acidic, neutral or weakly alkaline.

  When the hardly decomposable organic halogen compound comes into contact with the surface of the metal powder particles prepared by the method as described above, if the hardly decomposable organic halogen compound is volatile, in the form of gas adsorption, if non-volatile It is thought that it contacts in the form of contact accompanying flow or mixing. The hardly decomposable organohalogen compound adsorbed or brought into contact with the surface of the metal powder particles is decomposed by the interaction between the composition / surface state of the metal powder and the constituent elements / stereostructure of the organohalogen compound. This interaction is considered to be a direct action of the metal powder on the halogen element in the organic halogen compound, an action on the double bond portion, an action of forming various complex structures, and the like.

(Enforcement method of metal powder for organic halogen compound decomposition)
When the above-described metal powder is used to purify soil, groundwater, gas, etc. contaminated with various organic halogen compounds, for example, the following method is preferable. First, when soil purification treatment is performed, there is a method of mixing metal powder into excavated soil using a heavy machine such as a soil conditioner or a backhoe. Next, there is a method in which the soil excavated in equipment such as a vibration mill and a rotary mill, metal powder, and pulverized media are added and a stirring and mixing process is performed. Furthermore, a method in which a place where the metal powder for decomposing the organic halogen compound is locally mixed is appropriately disposed in the contaminated soil, and a method of decomposing while diffusing and moving the volatile organic halogen compound can be applied. .

Moreover, when purifying groundwater, it is preferable to create a reaction wall containing metal powder that allows groundwater to penetrate in the ground. At this time, the reaction wall built in the ground is arranged so that the groundwater is in contact with the metal powder. For this purpose, the reaction wall is located so as to cover the easily permeable layer of the groundwater deep in the contaminated soil and below the easily permeable layer. It is preferable to arrange the reaction wall so that the lower end portion of the reaction wall is disposed up to the hardly permeable layer or to be embedded. Furthermore, it is preferable to adjust the water permeability of the reaction wall in a good state so that the water permeability coefficient of the reaction wall is equal to or higher than that of the surrounding soil. Therefore, for example, it is preferable to form the reaction wall with a material in which metal powder is uniformly or non-uniformly dispersed in a high sandy soil or the like in a range of about 0.1 to 50 wt%.

(Method for producing metal powder for organic halogen compound decomposition)
Both the Ni-attached Fe powder and the Mn-attached Al powder can be produced by a chemical production method and a physical production method. The chemical manufacturing method is a method in which the base metal powder is immersed in a solution in which the attached metal is dissolved with an acid, etc., and the attached metal phase is attached to the base metal phase using the difference in ionization tendency of both metals. is there. At this time, it is possible to control the adhesion state of the adhesion metal phase to the base metal phase, the adhesion film thickness, and the like by controlling the concentration of the solution of the adhesion metal and the immersion time. This method is a preferable method in that a metal powder having uniform characteristics can be easily prepared.

  A physical production method is a method in which particles containing a base metal phase granulated in advance and particles containing an adhering metal phase are mixed with a mixer or the like, and the collision pressure accompanying the contact between the particles generated during the mixing is used. This is a method of adhering an adhering metal phase to a base metal phase. As a result of observing the metal powder prepared by this method with an electron microscope, there is no alloy layer at the interface between the base metal phase and the adhered metal phase, and the metal phases are directly joined to each other at the interface. It has been found. Furthermore, since it was observed that the adhered metal phase was deformed as it was subjected to pressure, it is considered that the adhered metal phase was pressure-bonded to the base metal phase. According to this method, it is not necessary to consider the ease of dissolution by acid and the difference in ionization tendency. Therefore, it is a preferable method when considering a wide range of metal combinations as the base metal phase and the adhered metal phase. Here, when the adhesion metal phase includes a high-cost metal such as Ni or Mn, the mixing ratio of the particles including the matrix metal phase and the particles including the adhesion metal phase is the ratio of the particles including the matrix metal phase. It is good also as a structure which makes a ratio high. When this configuration is adopted, particles containing the base metal phase occupy most of the metal powder, and the particles containing the high-cost attached metal phase are scattered and attached to the surface of the particles containing the base metal phase. This is preferable from the viewpoint of taking a structure and reducing the manufacturing cost of the metal powder.

  As described above, the metal powder produced from Almidros can be obtained by recovering aluminum dross from the Al smelting step and appropriately pulverizing it as necessary. Furthermore, at least one element of any one of C, Na, Mg, Al, Si, Ca, Mn, Fe, Co, Ni, Cu, Zn, etc. is added to the crushed powder of aluminum dross in the attached metal phase. It is good also as a structure added in the form. If this structure is taken, the metal powder manufactured from aluminum dross is preferable because the rate of decomposing the organic halogen compound can be further increased. Here, as a method for adding the adhered metal phase to the pulverized powder of aluminum dross, the above-described physical production method used when producing the Ni-adhered Fe powder or the like can be suitably applied.

Hereinafter, the present invention will be described in more detail based on examples.
Example 1
(Preparation of metal powder sample)
Using Ni as the main component of the base metal phase and Ni as the main component of the adhered metal phase, a Ni-coated Fe powder sample was prepared as follows using a dry co-grinding (mechanochemical) method of the physical method.

First, Fe powder having an average particle diameter of 50 μm and Ni powder having an average particle diameter of 0.3 μm were prepared as another metal. After mixing and mixing the Fe powder at 95 wt% and Ni powder at 5 wt%, 500 g is weighed and put into a 2 L capacity grinding pot. Further, 5 kg of 20 mm-diameter ZrO ₂ balls were added to the pulverization pot as a pulverization medium and placed in a rotary mill. And the rotation speed of the mill was set to 100 rpm, and the grinding process was performed for 5 minutes, and the Ni adhesion Fe powder sample was prepared.

(Observation of the prepared sample)
When the prepared sample was observed with an electron microscope, it was found that Ni metal was directly bonded to the surface of the Fe metal phase, and no alloy phase was present at the boundary interface. did.

(Decomposition test of organohalogen compounds using prepared samples)
Next, a decomposition test of the organic halogen compound was performed using the prepared Ni-adhered Fe powder. First, a test contaminant solution containing cis-1,2-DCE at a concentration of 25.6 mg / L as an organic halogen compound in ion-exchanged water was prepared. Add 0.5g of Ni powder Fe powder sample to a 100ml vial, pour 50ml of the test contaminant solution into it, seal, shake, and sample the gas in the headspace of the vial at regular intervals. Then, this gas is qualitatively and quantitatively analyzed with a GC-MS (gas chromatograph-mass spectrometer), and from the organic chlorine compound concentration in the headspace gas and the stirring and shaking treatment time, The half-life of degradation was measured.

  From this measurement result, it was found that the half life of cis-1,2-DCE degradation by the Ni-adhered Fe powder sample was 1.1 days.

(Example 2)
In Example 1, the result of this measurement was performed in the same manner except that the organic halogen compound was 1,2-DCA and the content was 25 mg. From this measurement result, the half-life of 1,2-DCA decomposition by the Ni-attached Fe powder sample was 3. It turned out to be 1 day.

(Example 3)
In Example 1, Al powder with an average particle size of 50 μm is used as one metal particle, and Mn powder with an average particle size of 30 μm is used as another metal, and the mixing ratio is 80 wt% for Al powder and 20 wt% for Mn powder. A cis-1,2-DCE decomposition test was conducted in the same manner as in Example 1 except that the above was changed. As a result, it was found that the half life of cis-1,2-DCE degradation by the Mn-attached Al powder sample was 1.9 days.

(Comparative Example 1)
300 mL of 1 M aqueous solution of copper sulfate was prepared, 20 wt% of Fe powder having an average particle size of 50 μm was added and stirred as a slurry for 5 minutes, and this copper-containing iron powder sample was used as in Example 1 to obtain cis-1,2 -A DCE degradation test was performed. From this test result, it was found that the half-life of cis-1,2-DCE degradation by the copper-containing Fe powder sample was 3.2 days.

Example 4
In the smelting process of the Al-based waste material, the aluminum dross separated on the surface of the molten metal was recovered, cooled, and then pulverized to obtain metal powder having an average particle diameter of 1 to 50 μm. As a result of qualitative analysis by X-ray diffraction on the metal powder produced from this aluminum dross, the metal powder includes a base metal phase mainly composed of aluminum oxide, Al, C, Na, Mg, Al, Si, Ca, Mn, Fe, Co, Ni, Cu, and Zn were contained.

  Using the metal powder produced from this aluminum dross, a decomposition test for TCE was performed as follows. In a vial with a capacity of 124 ml, 50 ml of ion-exchanged water, 1 μl of TCE, and 0.5 g of crushed powder of aluminum dross were charged and sealed with a butyl rubber septum with a silicon liner and an aluminum seal. From the time of sealing, the TCE concentration in the vial was analyzed and evaluated over time, and the half-life of the TCE concentration was determined to be 4.2 days.

(Calculation of decomposition reaction rate constant)
The reaction rate of TCE decomposition by the metal powder produced from the aluminum dross of the present invention is as follows. The initial concentration of TCE in the vial is C ₀ (eg, mg / kg), the elapsed time is t (day), and t (day ^-1 ). ) Assuming that the concentration of TCE in the vial afterwards is C (example: mg / kg), it was found that the pseudo-first order reaction equation shown in the following equation 1 is followed.
ln (C / C ₀ ) = − k · t (Formula 1)
Here, k (day ⁻¹ ) is referred to as a decomposition reaction rate constant, and can be used as an index representing the TCE decomposition performance of the metal powder produced from the aluminum dross of the present invention.

(Example 5)
TCE was mixed with 50 g of silty soil at a ratio of 1 μl to prepare a simulated contaminated soil having a TCE concentration of 29.4 mg / kg. To this simulated contaminated soil, 1.0 wt% of metal powder produced from aluminum dross described in Example 4 is added, mixed for 1 minute with a powder mixing device with stirring blades, and kept in a sealed container for 20 days. Then, the TCE content in the soil was measured. As a result, the TCE concentration after treatment was 7.2 mg / kg, which was greatly reduced from the initial concentration of 29.4 mg / kg. The decomposition reaction rate constant was 0.07 day ⁻¹ .

(Example 6)
1 wt% of Fe powder is mixed with the metal powder produced from aluminum dross described in Example 4, and then charged into a pulverization pot having a capacity of 2 L. Further, 5 kg of 20 mm-diameter ZrO ₂ balls were added to the pulverization pot as a pulverization medium and placed in a rotary mill. The mill was rotated at 100 rpm for 20 minutes to adhere the Fe phase to the metal powder. A TCE decomposition test in simulated contaminated soil similar to that described in Example 5 was performed using the metal powder to which the Fe phase was adhered. As a result, the TCE concentration after treatment was 5.4 mg / kg, which was greatly reduced from the initial concentration of 29.4 mg / kg. The decomposition reaction rate constant was 0.08 day- ¹ .

(Comparative Example 2)
Using an iron powder containing 0.1 wt% of C and having an average particle diameter of 50 μm, the same decomposition test for TCE as in Example 3 was performed to determine the half-life of the TCE concentration and the decomposition reaction rate constant. As a result, the half-life was 11.6 days, and the decomposition reaction rate constant was 0.06 day ⁻¹ .

It is the enlarged view which represented typically the metal particle in the metal powder which concerns on this invention.

Explanation of symbols

1. Base metal phase 2. Adhered metal phase Metal particles 4. 4. Metal powder Interface between base metal phase and adhering metal phase d. Adhering film thickness of adhering metal phase

Claims (7)

Metal particles constituting metal powder, each metal particle has a metal phase mainly composed of nickel and a metal phase mainly composed of iron,
A metal powder for decomposing an organic halogen compound, characterized in that the metal phase mainly composed of nickel is scattered and adhered to the surface of the metal phase mainly composed of iron.   2. The organic halogen according to claim 1, wherein the metal phase containing nickel as a main component is bonded to the surface of the metal phase containing iron as a main component by a collision pressure and is scattered and adhered. Metal powder for compound decomposition.   The metal phase mainly composed of nickel is bonded to the surface of the metal phase mainly composed of iron, and the two alloy phases are scattered and adhered to the boundary interface. The metal powder for decomposing an organohalogen compound according to claim 1 or 2.   4. The metal powder for decomposing an organic halogen compound according to claim 1, wherein the content of nickel in the metal powder is 20 wt% or less not including 0 wt%.   4. The metal powder for decomposing an organohalogen compound according to claim 1, wherein a nickel content in the metal powder is 5 wt% or less not including 0 wt%. A method for producing a metal powder for decomposing an organohalogen compound according to any one of claims 1 to 5,
For organic halogen compound decomposition, characterized in that iron particles having a particle diameter of 1 to 500 μm and nickel particles having a smaller particle diameter are mechanically mixed and brought into contact with each other and both particles are joined by a collision pressure. A method for producing metal powder.   A method for purifying soil and / or ground water and / or surface water, wherein the metal powder for decomposing an organic halogen compound according to any one of claims 1 to 5 is used.

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