JP2005131569A - Soil cleaning agent and soil cleaning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soil cleaning agent having high cleaning activity in the cleaning of soil and ground water polluted with an organohalogen compound and reduced in the elution amount of fluoride ions. <P>SOLUTION: This soil cleaning agent is used for cleaning soil or ground water polluted with the organohalogen compound and contains a calcium ion compound and/or a magnesium ion compound. The calcium ion compound and/or a magnesium ion compound is contained in an amount of 0.01-1,000 wt.% with respect to an iron powder and/or an iron oxide powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a soil purification agent and a soil purification method for detoxifying an organic halogen compound contained in soil or groundwater.

  So far, organic halogen compounds such as trichlorethylene have been used as degreasing solvents for semiconductors and metalworking products, and contamination of soil and groundwater by these leaked or dumped compounds has become a major social problem.

  Conventionally, a soil gas suction method, a soil excavation method, a groundwater pumping method, and the like have been used as purification methods for these contaminations. The soil gas suction method is a method for forcibly sucking pollutants present in the unsaturated zone, and by installing a suction well in the ground by boring and depressurizing the suction well with a vacuum pump, It is a method of collecting and removing as soil gas.

  The soil excavation method is a method in which contaminated soil is excavated, and the excavated soil is subjected to wind drying, heat treatment, and the like to recover and remove the pollutants. In the groundwater pumping method, a pumping well is installed in the soil, and the contaminated groundwater is pumped to recover and remove the pollutants.

  However, these methods have the following problems. In the soil gas suction method, when a wide range of soil is targeted, a plurality of suction wells and ground facilities are required. Moreover, when making it adsorb | suck to adsorption agents, such as activated carbon, and removing a contaminant from soil gas, the adsorption agent after a process turns into a secondary waste. In the case of the soil excavation method, if the heat treatment of the excavated soil is expensive, or if contaminants remain around the excavated area, the contaminants may diffuse and be contaminated again. In the case of the groundwater pumping method, the contaminant cannot be recovered and removed unless it is contained in saturated soil and is a compound that dissolves in water. Similarly to the soil gas suction method, when a wide range of soil is targeted, multiple pumping wells and ground facilities are required, and depending on the removal method, secondary waste is generated. Furthermore, ground subsidence can cause land subsidence.

  On the other hand, an in-situ purification method using iron has been proposed as a method for directly purifying contaminated soil. However, normally, in the purification of contaminated soil using iron, there is a problem that it takes a relatively long time to purify the contamination.

  In order to solve such a problem, Patent Document 1 discloses a technique related to a soil purifier using an iron fine particle slurry having a fine particle size. This relates to spherical iron fine particles having an average particle size of less than 10 μm, and enables rapid penetration into the soil by using fine spherical iron particles. As iron fine particles, steelmaking dust obtained by wet-collecting exhaust gas generated during refining from an oxygen blowing converter for steelmaking is used, and is used in a state of water slurry. The water of such a steelmaking dust slurry often contains an elution of a fluorite-derived fluorine compound that is used by being mixed with iron ore. Therefore, there is a possibility that secondary contamination with a fluorine compound may occur by injecting these soil purification agents into the soil.

As a technique for preventing the secondary contamination by the fluorine compound as described above, the technique of Patent Document 2 is disclosed. This relates to a refining method in which hydrotalcite is mixed with slurry of steelmaking dust and the eluted fluorine-containing ions are adsorbed and removed by hydrotalcite, and a soil purification agent produced by the method. In general, hydrotalcite has a property of exchanging anions existing between layers with anions in an aqueous solution. Because of such characteristics, even if the amount of elution of fluorine-containing ions in the steelmaking dust slurry is reduced by the above technique, there is a possibility that it is exchanged with other anions again and eluted in water. Therefore, when added to contaminated soil, it may cause secondary contamination by fluorine-containing ions.
JP 2001-198567 A JP 2003-181493 A

  An object of the present invention is to provide a soil purification agent having a high purification activity and a small amount of fluoride ion elution in purification of soil and groundwater contaminated with an organic halogen compound.

  As a result of intensive studies, the present inventors have found that the above problem can be solved by a soil purification agent containing iron powder and / or iron oxide powder having a fine particle size and a calcium ion compound and / or a magnesium ion compound, The present invention has been reached.

  That is, the present invention relates to the following soil purification agent and soil purification method.

  A soil purification agent for purifying soil or groundwater contaminated with organic halogen compounds, comprising iron powder and / or iron oxide powder, calcium ion compound and / or magnesium ion compound, and calcium ion compound A soil purification agent comprising 0.01% by weight to 1000% by weight of a magnesium ion compound with respect to iron powder and / or iron oxide powder.

The above-mentioned soil purification agent, wherein the iron powder and / or iron oxide powder contains 5 to 100% by weight of iron, 0 to 95% by weight of wustite (FeO), and 0 to 95% by weight of magnetite (Fe ₃ O ₄ ).

  The said soil purification agent whose shape of iron powder and / or iron oxide powder is spherical or indefinite.

  The soil purification agent, wherein the average primary particle diameter of the iron powder and / or iron oxide powder is 0.05 to 1 µm.

  The soil purification agent, wherein the iron powder and / or iron oxide powder is in a water slurry state.

  A water slurry of iron powder and / or iron oxide powder collects exhaust gas generated during refining from an oxygen blow furnace for steelmaking by wet dust collection, and the resulting steelmaking dust is coarsely fractionated and then settled by a thickener. The above-mentioned soil purification agent, which is a slurry obtained by collection.

  A soil purification method for purifying soil or groundwater contaminated with an organic halogen compound, wherein the soil or groundwater contains iron powder and / or iron oxide powder and calcium ion compound and / or magnesium ion compound simultaneously or A soil remediation method characterized by being added separately.

  The soil purification agent containing iron powder and / or iron oxide powder and calcium ion compound and / or magnesium ion compound of the present invention has high purification activity in the purification of soil and groundwater contaminated with various organic halogen compounds, By containing a calcium ion compound and / or a magnesium ion compound, fluoride ions are insolubilized and the amount of elution is reduced.

  Hereinafter, the present invention will be described in detail. The soil purification agent of the present invention is for purifying soil or groundwater contaminated with an organic halogen compound. Examples of organic halogen compounds to be purified include unsaturated halogenated hydrocarbons such as tetrachloroethylene, trichloroethylene, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, 1,1-dichloroethylene, vinyl chloride, , 1,2,2-tetrachloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,2-dichloroethane, carbon tetrachloride, chloroform, dichloromethane, and the like. The compound shown here is an example of the target substance, and the present invention is applicable to contamination by aliphatic halogenated hydrocarbons other than those described above. The soil purification agent of the present invention dehalogenates these organic halogen compounds, and finally generates harmless hydrocarbons in which all halogen atoms are replaced with hydrogen atoms.

  The method for producing iron powder and / or iron oxide powder used in the present invention is not particularly limited, but in addition to normal iron powder, electrolytic iron powder, reduced iron powder, or oxygen blowing for steelmaking. Steelmaking dust or the like obtained by collecting exhaust gas generated during refining from a furnace by wet dust collection can be used. These iron powders and / or iron oxide powders may be used as they are, or may be used in the form of a water slurry or the like as necessary.

  The soil purification agent of the present invention contains iron powder and / or iron oxide powder and a calcium ion compound and / or a magnesium ion compound. By containing a calcium ion compound and / or a magnesium ion compound, fluoride ions dissolved in the system become calcium salts and / or magnesium salts and become insoluble, so that the amount of fluoride ions eluted from the soil purification agent can be reduced. it can.

  Although the usage method of the soil purifier provided in this invention is not specifically limited, For example, a pollutant can be purified by mixing a soil purifier with the contaminated ground water collected by pumping up, the water of a river, etc. . Moreover, when using as a slurry form, it can be used also in the method of inject | pouring directly into the contaminated soil.

  The iron powder and / or iron oxide powder used in the soil purification agent of the present invention is preferably in a water slurry state. The water slurry can be prepared by adding and mixing iron powder and / or iron oxide powder to water. The kind of water used here is not particularly limited, and any water can be used as long as it does not contain a lot of impurities, such as ion exchange water, distilled water, tap water, and well water. The mixing method is not particularly limited, and any stirrer that is usually used for mixing liquids may be used. Moreover, it is also possible to perform a dispersion | distribution process with dispersing machines, such as a sand mill, as needed. When iron powder and / or iron oxide powder is finally obtained as a slurry when it is produced, it may be used as it is without being dried. When preparing these slurries, the pH may be adjusted with various pH adjusters. When used in a method of directly injecting the soil purification agent of the present invention into contaminated soil, the soil purification agent is preferably in the form of a slurry, and the slurry-like soil purification agent prepared as described above is in a slurry state. Therefore, it can be directly injected into the soil and allows the soil purifier to penetrate into the soil. Furthermore, when adding additives other than iron powder or iron oxide powder, it is possible to mix them easily.

  In this invention, when using iron powder and / or iron oxide powder as a slurry form, it is preferable that the density | concentration of iron powder and / or iron oxide powder is 0.5 to 60 weight% in a slurry. A more preferred concentration is 3 to 30% by weight. If it is less than 0.5% by weight, a very large amount of slurry must be used to add the amount of iron powder and / or iron oxide powder necessary for the purification of contaminated groundwater or soil, which is inefficient . Moreover, when using it by the method of inject | pouring directly into the contaminated soil, if a large amount of slurry is inject | poured, a ground may loosen after injection | pouring and a safety problem will also generate | occur | produce. On the other hand, when the concentration is higher than 60% by weight, the fluidity of the slurry is remarkably lowered, and uniform mixing becomes difficult. Moreover, when using by the method of inject | pouring directly into the contaminated soil, since rapid penetration | penetration to soil becomes difficult, it is unpreferable.

  Any calcium ion compound and / or magnesium ion compound contained in the soil purification agent of the present invention can be used as long as it can release calcium ions and / or magnesium ions and form a pair with fluoride ions. Is possible. Examples include calcium chloride, calcium bromide, calcium iodide, calcium oxide, calcium hydroxide, calcium sulfate, calcium phosphinate, calcium phosphonate, calcium phosphate, calcium monohydrogen phosphate, calcium dihydrogen phosphate, calcium diphosphate. , Calcium metaphosphate, calcium carbonate, calcium thiocyanate, calcium tetraborate, calcium formate, calcium acetate, calcium oxalate, calcium lactate, calcium citrate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium oxide, magnesium hydroxide , Magnesium sulfate, magnesium phosphinate, magnesium phosphonate, magnesium hydrogen phosphate, magnesium phosphate, magnesium pyrophosphate, magnesium carbonate, Magnesium hydroxide, magnesium thiocyanate, and the like magnesium metaborate. These may be used alone or in combination of two or more compounds. By adding these compounds, the fluoride ions eluted in the system become insoluble calcium fluoride or magnesium fluoride, and the amount of fluoride ions eluted is reduced.

  These calcium ion compounds or magnesium ion compounds may be used in the form of crystals or powder, and when they are water-soluble, those dissolved in water in advance may be used. For example, when purifying contaminated water collected by pumping water, it is possible to purify the contaminated water by adding iron powder and / or iron oxide powder and calcium ion compound and / or magnesium ion compound, or an aqueous solution thereof. Moreover, when using iron powder and / or iron oxide powder as a slurry, you may use it, adding a calcium ion compound and / or a magnesium ion compound previously to a slurry. After the addition, the slurry is mixed uniformly to obtain a constant concentration. The mixing method is not particularly limited, and can be performed by various stirring methods usually used for mixing liquids.

  As described above, when the calcium ion compound and / or the magnesium ion compound are added to the slurry of iron powder and / or iron oxide powder in advance and used, after adding the calcium ion compound and / or the magnesium ion compound, It is preferable to use after stirring for a certain time. By using it in such a manner, fluoride ions eluted in the soil purification agent can be reduced. The stirring time is preferably as long as possible, but usually 10 minutes to 1 hour is sufficient. When transporting the slurry-like soil purification agent to a place where it is actually used with a tank lorry, etc., after adding calcium ion compound and / or magnesium ion compound to the slurry of iron powder and / or iron oxide powder and mixing them uniformly It is also effective to transport and react fluoride ions during transport.

  In addition, when a soil cleaner is used by directly injecting it into the soil, an aqueous solution or suspension of calcium ion compound and / or magnesium ion compound is injected, and then calcium ion compound and / or magnesium ion compound is not supplied from the same injection tube. The slurry of the added iron powder and / or iron oxide powder may be poured into the soil and used in a method of contacting with the iron powder and / or iron oxide powder when penetrating into the soil.

  In the present invention, the concentration of the calcium ion compound and / or the magnesium ion compound varies depending on the amount of the eluted fluoride ions and the amount of iron powder and / or iron oxide powder to be used. It is preferable that it is 0.01 to 1000 weight% of range with respect to iron powder. A more preferable concentration is 0.3% by weight to 200% by weight with respect to iron powder and / or iron oxide powder. The standard for elution of fluorine in the Soil Contamination Countermeasures Law is set at 0.8 mg / l or less, and the concentration is very low. Therefore, elution occurs when the concentration of calcium ion compound and / or magnesium ion compound is below the above range. Fluoride ions cannot be removed below the amount standard.

  In the present invention, when iron powder and / or iron oxide powder is used as a water slurry, the amount of calcium ion compound and / or magnesium ion compound used varies depending on the concentration of eluted fluoride ions. Is preferably 0.1% by weight to 30% by weight in the slurry. A more preferable usage amount is 0.3 wt% to 10 wt% in the slurry.

The iron powder and / or iron oxide powder of the present invention is mainly composed of iron or a mixture of iron and iron oxide, iron is 5 to 100% by weight, wustite (FeO) is 0 to 95% by weight, magnetite (Fe ₃ O). ₄ ) is preferably contained in an amount of 0 to 95% by weight. If it is the range of the said composition, the composition ratio of each component will not be specifically limited. When using steelmaking dust in which exhaust gas generated during refining from an oxygen blow furnace for steelmaking as iron powder and / or iron oxide powder is collected by wet dust collection, usually a small amount of nickel, lead, manganese, Zinc, copper, fluorine, boron, etc. are contained. In the present invention, other elements may be mixed as impurities as long as the content of iron and iron oxide is in the above range. In addition, iron is usually oxidized by dissolved oxygen in water to produce iron oxide (III) (Fe ₂ O ₃ ) and iron oxide hydroxide (FeO (OH)). May be contained.

  As the iron powder and / or iron oxide powder contained in the soil purification agent of the present invention, those having various particle sizes can be used, but those having a spherical shape or an irregular shape are particularly preferred. With such a shape, uniform dispersion in the slurry is facilitated, and the fluidity of the slurry is improved. Moreover, when it uses by the method of inject | pouring directly into soil, the penetration | infiltration into soil becomes easy.

  The average primary particle diameter of the iron powder and / or iron oxide powder contained in the soil purification agent of the present invention is particularly preferably 0.05 to 1 μm. When the average primary particle diameter is less than 0.05 μm, it is difficult to disperse in a uniform state. Even if it can be dispersed, the dissolution of iron proceeds rapidly with the generation of hydrogen, and the effect as a soil purification agent is reduced. On the other hand, when it is larger than 1 μm, the surface area of the iron powder and / or iron oxide powder that can contribute to the purification of the pollutant is reduced, so that the effect as a purification agent is reduced. Moreover, when purifying by the method of injecting directly into the soil, since rapid penetration into the soil becomes difficult, the range of soil that can be purified is narrowed, and as a result, the effect as a purifying agent is reduced.

  As a slurry of the iron powder and / or iron oxide powder of the present invention, exhaust gas generated during refining from an oxygen blow converter for steelmaking is collected by wet dust collection, and the resulting steelmaking dust is subjected to coarse particle fractionation, A slurry obtained by sedimentation collection with a thickener can be used. According to this method, a special process is not required, and an iron powder and / or iron oxide powder slurry can be prepared economically and easily.

  A method for producing an iron powder and / or iron oxide powder slurry obtained by coarse-particle fractionation and sedimentation collection of the steelmaking dust will be described with reference to FIG. In addition, the manufacturing method shown below is an example and this invention is not limited to this.

  A raw material such as pig iron containing impurities such as carbon, silicon and phosphorus is put into an oxygen blowing furnace for steel making, and oxygen is rapidly blown from above while stirring. By doing so, the raw material reacts with oxygen, carbon, silicon, phosphorus, etc. become oxides and pig iron becomes a rope. Exhaust gas containing fine iron powder or iron vapor generated by blowing oxygen is collected as steelmaking dust by wet dust collection through a gas recovery hood. At that time, gas such as CO is sent to the gas recovery tank. The steelmaking dust slurry is coarsely fractionated and the coarse one is recovered as coarse iron powder. Fine particles can be concentrated with a thickener to obtain a slurry of iron powder and / or iron oxide powder. Alternatively, the slurry may be filtered by a filter device such as a filter press to remove water and water-soluble impurities, and the filtered iron powder and / or iron oxide powder may be used as a slurry again. At that time, the filtered iron powder and / or iron oxide powder can be used after drying, or the water-containing cake after the filtering can be used as a slurry as it is.

The iron powder and / or iron oxide powder obtained by the above production method contains iron oxides in various oxidation stages, and the main components are iron, wustite (FeO), and magnetite (Fe ₃ O ₄ ).

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

  In evaluating the average primary particle diameter and particle shape of the iron powder and / or iron oxide powder, the particles were observed at a magnification of 50,000 times with a transmission electron microscope (hereinafter referred to as TEM). In the present invention, the primary particle diameter is defined as the distance obtained by connecting two longest parallel lines in contact with the observed particle outline at right angles. Moreover, the primary particle diameter of the particle | grains within the fixed visual field range selected at random was averaged, and it was set as the average primary particle diameter.

  The composition analysis of the iron powder and / or iron oxide powder was performed by the X-ray diffraction method. Sodium chloride was used as an internal standard substance, calibration curves were prepared from the main peak areas of iron, magnetite, and wustite, and each component contained in the iron powder and / or iron oxide powder was quantified.

  Quantification of fluoride ions eluted in the soil purification agent was performed by measuring the supernatant obtained by filtering the soil purification agent by ion chromatography.

  Quantification of the organic halogen compound and its decomposition product was performed by a headspace-gas chromatograph method according to JIS K 0125. GC-8610 manufactured by JEOL Datum Co., Ltd. was used as the gas chromatograph, capillary column NBW-310SS30 manufactured by the same company was used as the column, and a hydrogen flame ionization detector was used as the detector. In the purification experiment, the headspace gas sampled at regular intervals was analyzed, and the remaining amount of the substrate was quantified from the calibration curve.

[Example 1]
Sodium hydroxide aqueous solution was added to the steelmaking dust slurry to adjust the pH to 12.0. Further, this was diluted 5 times by weight with ion-exchanged water to obtain a steelmaking dust slurry A. The ratio of steelmaking dust contained in the slurry was 5% by weight. As a result of TEM observation, the particle shape of the steelmaking dust was a mixture of a spherical shape and an irregular shape, and the average primary particle size was 0.6 μm. As a result of X-ray diffraction, the composition of the steelmaking dust contained 35% by weight of iron, 50% by weight of wustite and 15% by weight of magnetite.

  In a beaker, 50 g of steelmaking dust slurry A and 2 g of calcium chloride were weighed and stirred with a disper for 1 hour to prepare a soil purifier. The soil purification agent was filtered off and the fluoride ion concentration in the supernatant was measured and found to be less than 0.1 mg / l.

  To a 125 ml glass vial, 52 g of the soil purification agent prepared above was added and sealed with a (registered trademark) -coated butyl rubber septum and an aluminum seal. Subsequently, 0.5 mg of trichlorethylene was added with a micro syringe. The glass vial was reciprocally shaken in a constant temperature room controlled at 25 ± 2 ° C. to conduct a trichlorethylene purification experiment. A reciprocating shaker with an amplitude of 25 mm was used for reciprocal shaking, and shaking was performed at a shaking speed of 200 times / minute.

[Example 2]
50 g of steelmaking dust slurry A and 0.5 g of calcium chloride were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Example 3]
50 g of steelmaking dust slurry A and 10 g of calcium chloride were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Example 4]
50 g of steelmaking dust slurry A and 2 g of calcium hydroxide were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Example 5]
50 g of steelmaking dust slurry A and 2 g of calcium carbonate were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Example 6]
50 g of steelmaking dust slurry A and 2 g of calcium formate were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Example 7]
50 g of steelmaking dust slurry A and 2 g of calcium acetate monohydrate were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Example 8]
50 g of steelmaking dust slurry A and 2 g of magnesium chloride were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Example 9]
50 g of steelmaking dust slurry A and 2 g of magnesium hydroxide were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Comparative Example 1]
An experiment was conducted in the same manner as in Example 1 except that 50 g of slurry A of steelmaking dust was used as a soil purification agent. The fluoride ion concentration in the supernatant obtained by filtering the steelmaking dust slurry A was 5 mg / l.

[Comparative Example 2]
50 g of steelmaking dust slurry A and 2 g of hydrotalcite were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was 3 mg / l.

[Comparative Example 3]
50 g of slurry A of steelmaking dust and 0.0001 g of calcium chloride were mixed to prepare a soil purification agent. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was 3 mg / l.

[Comparative Example 4]
2.5 g of commercially available magnetite (average primary particle size 0.5 μm, amorphous) and 47.5 g of ion-exchanged water were mixed to prepare a soil purifier. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

[Comparative Example 5]
2.5 g of commercially available iron powder (average primary particle diameter 20 μm, plate-like) and 47.5 g of ion-exchanged water were mixed to prepare a soil purifier. The other experiments were performed in the same manner as in Example 1. After stirring for 1 hour with a disper, the fluoride ion concentration in the supernatant was less than 0.1 mg / l.

  Table 1 shows the results of purification experiments in Examples 1 to 9 and Comparative Examples 1 to 5. The trichlorethylene concentrations before purification and after one week of shaking were shown, respectively, and the greater the difference between the two, the higher the purification ability for trichlorethylene.

It is the flowchart which showed an example of the apparatus used in order to manufacture the slurry of the iron powder and / or iron oxide powder which were obtained from steelmaking dust.

Claims (7)

A soil purification agent for purifying soil or groundwater contaminated with an organic halogen compound, comprising iron powder and / or iron oxide powder, calcium ion compound and / or magnesium ion compound, and calcium ion compound A soil purification agent comprising 0.01% by weight to 1000% by weight of a magnesium ion compound with respect to iron powder and / or iron oxide powder. The soil purification according to claim 1, wherein the iron powder and / or iron oxide powder contains 5 to 100% by weight of iron, 0 to 95% by weight of wustite (FeO), and 0 to 95% by weight of magnetite (Fe ₃ O ₄ ). Agent. The soil purifier according to claim 1 or 2, wherein the iron powder and / or iron oxide powder has a spherical shape or an irregular shape. The soil purifier according to any one of claims 1 to 3, wherein the average primary particle diameter of the iron powder and / or iron oxide powder is 0.05 to 1 µm. The soil purification agent according to any one of claims 1 to 4, wherein the iron powder and / or iron oxide powder is in a water slurry state. A water slurry of iron powder and / or iron oxide powder collects exhaust gas generated during refining from an oxygen blow furnace for steelmaking by wet dust collection, and the resulting steelmaking dust is coarsely fractionated and then settled by a thickener. The soil purification agent according to claim 5, which is a slurry obtained by collection. A soil purification method for purifying soil or groundwater contaminated with an organic halogen compound, wherein the soil or groundwater contains iron powder and / or iron oxide powder and calcium ion compound and / or magnesium ion compound simultaneously or A soil remediation method characterized by being added separately.

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