JP4345493B2 - Soil purification agent and soil purification method - Google Patents

Description

  The present invention relates to a soil purification method for removing the pollutants from soil contaminated with organic halides, and a soil purification agent that is advantageously used for the method.

  A large amount of organic halides such as trichlorethylene has been used for industrial cleaning such as oil removal of machinery. In recent years, the use of such organic halides has been regulated from the viewpoint of environmental pollution. However, a large amount of organic halide has already been used, and as a result, soil contamination or water pollution is also progressing. That is, organic halides such as trichlorethylene are stable and difficult to be decomposed by microorganisms, and organic halides discarded in the natural environment not only contaminate the soil, but ultimately pollute rivers and groundwater, which can be used as beverages. It can become raw water, which is a problem.

  Known methods for purifying soil contaminated with volatile organic compounds such as organic halides include a soil gas suction method, a groundwater pumping method, and a soil excavation method. The soil gas suction method forcibly sucks the target substances present in the unsaturated zone. A suction well is installed in the ground by boring, and the inside of the suction well is depressurized by a vacuum pump, and the vaporized organic The compounds are collected in a suction well, guided to the underground, and treated by a method such as adsorption of organic compounds in soil gas onto activated carbon. When the contamination by the organic compound extends to the aquifer, a method is adopted in which a submersible pump is installed in the suction well and the water is pumped and treated simultaneously with the soil gas.

  The underground pumping method is a method of setting up a pumping well in soil and pumping up contaminated groundwater. Furthermore, the soil excavation method is a method in which contaminated soil is excavated, and the excavated soil is subjected to wind drying and heat treatment to remove and collect organic compounds.

  However, these methods are not methods for directly purifying soil, but methods for purifying contaminated water collected by the soil gas suction method, groundwater pumping method, etc., or contaminated water such as rivers and groundwater. The amount is extremely large, and the treatment often takes a long time. It is also a drawback that the processing steps are often complicated. For this reason, a method for directly and simply purifying soil that is a source of contamination is required.

  As described above, the conventional method for purifying soil contaminated with organic halides is to collect contaminated water from the contaminated soil and purify it, or collect the soil itself and purify the contaminated soil itself. This is not a direct and simple purification method.

  In Patent Document 1 (WO01 / 08825), by making iron particles fine, the surface area of iron is increased to increase the processing ability of pollutants, and in addition to atomization, the shape of the particles is made spherical. Thus, a soil purifier comprising a spherical iron fine particle slurry having a particle size of less than 10 μm, which enables rapid penetration of iron into the soil, is disclosed.

WO01 / 08825

  The soil purification agent for iron fine particle slurry described in Patent Document 1 is far superior in permeability to soil compared to the conventional one having a large particle size, and is contaminated by contaminants such as organic halides. This pollutant can be detoxified or removed directly from the soil after the detoxification by reducing this pollutant directly and efficiently. However, such purification requires a long period of time for processing, and therefore requires a large amount of funds. In order to shorten the processing period as much as possible, a more rapid purification method is required.

  On the other hand, according to the Soil Contamination Countermeasures Law, “the designated area where the soil remediation work was carried out is the concentration of the environmental reference substance of the land for two years after it is judged that the pollutant has dropped below the environmental standard value and the construction has been completed. Must be monitored ”. For this reason, the need for a purification agent that is short-term and sustainable is increasing.

  The reason for monitoring the environmental standard substance concentration is that even if purification in the designated area is completed, there is a possibility that contaminants may flow in from other neighboring areas due to groundwater. In addition, although it should not be the case, the preliminary contamination survey by boring or the like is inaccurate, and “clean-up site was overlooked” or “contamination concentration was actually high”. It cannot be denied that it may happen that it is insufficient from a quantitative point of view.

  The object of the present invention is to reduce the time required for detoxification or removal after detoxification by directly reducing this pollutant from soil contaminated with organic halides. An object of the present invention is to provide a soil purification agent that can be significantly shortened and that can maintain the purification effect even after the completion of the purification work.

  The present inventors have paid attention to iron exhibiting an action of reducing and decomposing organic halides (so-called dehalogenation action), and have conducted research to develop various purification methods using these. Among these, iron fine particles (hereinafter referred to as “iron fine particles S” or simply “S”) having a high decomposition rate of organic halides, and iron fine particles (hereinafter referred to as iron fine particles C or It was found that when combined with C), the soil cleansing agent has both fast-acting and long-lasting effects.

It is known that iron particles having an average particle size of less than 10 μm have the effect of reducing and detoxifying a halide such as trichlorethylene (WO-01 / 08825). In addition, iron fine particles having a particle size of less than 10 μm and iron fine particles having a content of zero-valent iron in the particles of 50% or more dechlorinate organic halides, and therefore can be dehalogenated at a very high speed. It became clear that we could do it.

The iron fine particles S decompose organic chlorinated substances such as trichlorethylene by a reductive dechlorination reaction. That is, it oxidizes itself. When the present inventors investigated the oxidation state of the iron fine particles S using X-ray diffraction, the composition of the fine particles before purification was about 70% Fe (zero-valent iron) and about 30% Fe ₃ O _4. It was found to contain. This aqueous slurry of iron fine particles S was used in a trichlorethylene purification experiment (5% by weight of iron fine particles S added to water with a trichlorethylene concentration of 3000 mg / l and shaken for 2 weeks), and then the fine particle residue in the test solution was filtered. The sample was taken and dried under reduced pressure, and the X-ray diffraction was measured in the same manner to examine the oxidation state of the fine particle residue. Then, Fe (zero-valent iron) existing before purification was 0%, and all was Fe ₃ O ₄ . These indicate the reactivity of iron fine particles, suggesting that the iron fine particles have very high reactivity.

On the other hand, using iron fine particles C having a particle diameter of 0.3 to 100 μm, an organic chlorination product such as trichlorethylene was shaken for two weeks in the same manner as the iron fine particles S, and changes in the oxidation state were investigated. Iron fine particles C had about 40% initial Fe, about 45% FeO, and about 15% Fe ₃ O _4, but after the decomposition experiment, about 25% Fe, about 45% FeO, and Fe ₃ O ₄ was about 25%. From these, the iron powder mother particle C is slower in the decomposition reaction than the iron fine particle S, but zero-valent iron is present even after decomposition, which is further decomposed when the organic halide is supplied. It is possible to contribute, suggesting that it is a soil cleanser with persistence.

  By mixing these iron fine particles at a predetermined ratio, the soil purification agent having a fast-acting / sustainable property that shortens the purification period, which is a problem, and maintains the purification effect even after the completion of the purification work, and soil A purification method can be proposed.

  The iron fine particles S preferably have an average particle size of less than 10 μm, more preferably less than 5 μm. From the viewpoint of the primary particle diameter, it is preferably less than 3 μm, and more preferably in the range of 1 μm to 0.1 μm. Since the aggregation tendency becomes stronger as the primary particle size becomes smaller, the dispersed particle size becomes a rather large value, but it is desirable that the dispersed particle size is less than 10 μm in the slurry state. The amorphous iron fine particles S can be obtained, for example, by converting iron sulfate into iron hydroxide, further converting it into iron oxide, and then reducing.

  The iron fine particles C preferably have an average particle size of less than 100 μm, but the primary particle size is preferably in the range of 10 μm to 0.3 μm.

  The average primary particle diameter of the iron fine particles C is preferably in the range of 0.01 to 0.9 μm, more preferably 0.02 to 0.7 μm. The shape of the iron fine particles is preferably spherical or indeterminate. A spherical product is easily obtained from an oxygen blow converter for steelmaking by collecting exhaust gas generated during refining and removing the gas. By-product can be used effectively. The dust collection is preferably performed by wet dust collection, and after the dust collection, steelmaking dust is preferably collected by sedimentation using a thickener.

  A soil purification agent for purifying soil or groundwater contaminated with an organic compound, comprising an iron fine particle slurry in which iron fine particles having an average primary particle size of 0.01 to 1 μm are dispersed in water, Hydrogen can be generated when the fine particles are oxidized, and the generated amount is 0.3 ml or more per 1 g of iron fine particles at room temperature for 24 hours. Thereafter, when simply called iron fine particles, the iron fine particles S and iron fine particles C are not particularly distinguished.

  The amount of hydrogen generated when iron fine particles are oxidized is preferably in the range of 0.3 to 3 ml, particularly 0.3 to 2 ml. This method of measuring the amount of hydrogen generation is performed by measuring the amount of hydrogen generation after a mixture of 50 g of iron fine particles and 150 g of water at room temperature for 24 hours. As described above, iron particles having a very small particle diameter and exhibiting such a hydrogen generation amount are preferable.

  The soil purification agent of the present invention preferably further contains silica fine particles. The amount of hydrogen generation is increased by the addition of silica.

  The iron fine particles preferably have alkalinity. The amount of hydrogen generation increases.

  The organic compound is generally an organic halide, and an aliphatic halide is particularly preferable.

  The solid content of the iron fine particle slurry is preferably 20 to 80% by mass. Generally, this is diluted with water and applied to the contaminated soil.

  Another object of the present invention is to inject the soil purification agent of the present invention into soil or groundwater contaminated with an organic halide and dechlorinate the organic halide with hydrogen generated when iron fine particles are oxidized. It can also be achieved by the soil remediation method characterized. The organic halide is particularly preferably an aliphatic halide.

  By the soil purification method of the present invention using the soil purification agent of the specific iron fine particle slurry of the present invention, it is detoxified or reduced after detoxification by directly reducing this pollutant from soil contaminated with organic halides. The time required for this can be greatly shortened compared to the prior art, and the purification effect can be expanded in a far wider range than the prior art by the purification treatment similar to the conventional one. Furthermore, since organic halides carried by groundwater and the like contain persistent iron fine particles, the purification ability is not deactivated and a long-term purification effect can be expected. The soil purification method of the present invention also has the advantage that purification can be performed easily and in a wide range by injecting the soil purification agent of the specific iron fine particle slurry of the present invention into the soil or the like.

  The soil purification agent of the present invention has a basic structure including an iron fine particle slurry in which iron fine particles having an average primary particle diameter of 0.01 to 1 μm and having a high hydrogen generation ability are dispersed in water.

  In the soil purification method of the present invention, the above-mentioned soil purification agent is injected and mixed into soil or groundwater contaminated with organic halides, and the organic halides are dechlorinated by hydrogen generated when iron fine particles are oxidized. It has the feature to do.

  For example, when hydrogen generated by oxidation (generally upon contact with water) reacts with trichlorethylene as an organic halide, one chlorine atom is replaced with one hydrogen atom, and dichloroethylene and hydrogen chloride are generated. Thereafter, chlorine is similarly replaced with hydrogen, which in turn becomes monochloroethylene and then harmless ethylene. That is, when a liquid containing the specific iron fine particle slurry is injected into soil or groundwater contaminated with an organic halide, the iron fine particle slurry reacts with the water by mixing by injection, and iron is oxidized. Hydrogen gas is generated. This hydrogen gas reacts with the organic halide, and as described above, the halogen is replaced with hydrogen and detoxified.

  Examples of organic halides that are pollutants to be purified according to the present invention include 1,1-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1, Examples thereof include aliphatic halides such as 1-trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, dichlorodifluoroethane, and chlorobenzene. Aliphatic halides are preferred. In addition, the soil purification agent of this invention is applicable also to organic compounds (eg, benzene) other than organic halides.

The iron fine particle slurry of the soil purification agent of the present invention has a relatively high concentration of iron fine particles before soil injection (that is, during storage and transport), and is generally in a soft cake state (soft agglomerated state) near the bottom of the slurry. ) And is less in contact with water. Further, since the surface of the iron fine particles is covered with an iron oxide film (FeO, Fe ₃ O ₄ or the like), it hardly reacts with water (ie, is not oxidized). Then, it is considered that an active site is generated on the surface of the iron fine particles and a reaction with water is started by vibration and mixing at the time of injection of the iron fine particle slurry at the time of use or by mixing of the iron fine particle slurry and the water at the time of use. .

The iron fine particles of the present invention are preferably covered with an iron oxide film (FeO, Fe ₃ O ₄ or the like), and the oxide film preferably contains at least Fe ₃ O ₄ . The ratio of iron, FeO, Fe ₂ O ₃ , and Fe ₃ O ₄ in spherical iron fine particles C to be described later, that is, pure iron: FeO: Fe ₂ O ₃ : Fe ₃ O ₄ is 10 to 40:30 to 70: 0-15: 10-30 (mass ratio) are preferable. Further, the pure iron: FeO: Fe ₂ O ₃ : Fe ₃ O ₄ of the amorphous iron fine particles S is preferably 55 to 100: 0 to 30: 0 to 15: 0 to 45 (mass ratio).

  The iron particles contained in the iron fine particle slurry of the present invention are extremely fine particles with an average primary particle diameter of 0.01 to 1 μm. For this reason, when directly applied to contaminated soil, they rapidly penetrate into the soil. The average primary particle diameter of the iron fine particles is preferably 0.01 to 0.9 μm, more preferably 0.02 to 0.7 μm.

  The iron fine particles used in the present invention preferably have the above-mentioned particle diameter and a large amount of hydrogen gas (hydrogen generation amount) generated when oxidized. This oxidation generally occurs due to contact between iron fine particles and water. The hydrogen generation amount is 0.3 ml or more per 24 hours per 1 g of iron fine particles, and is generally preferably in the range of 0.3 to 3 ml, particularly 0.3 to 2 ml.

  Since such iron fine particles S and C are ultra fine particles, when applied to contaminated soil, they penetrate into the soil very quickly and exhibit a purification action.

  In the mixed slurry of these iron fine particles S and C, the content of the iron fine particle slurry S is at least 1% by mass of the iron fine particle S in the slurry, preferably 20% by mass (one fifth of the total amount of the slurry). ) To 33% by mass (1/3 of the entire slurry). The mixing is preferably performed after conversion from the solid content of the slurry (for example, both S and C are converted to 25% by mass) and then mixing. The mixing method may be simply mixing the slurries together, but it is desirable to make them as uniform as possible using a stirrer such as a disper.

  The solid content of the mixture slurry of the iron fine particles S and C is preferably 20 to 80% by mass (particularly 30 to 50% by mass). Further, the slurry preferably contains an antioxidant. Thereby, it can maintain so that iron may not be oxidized with oxygen. In the solid content, 90% by mass or more is metallic iron and an iron-containing compound. In solid content, metal iron accounts for 30 mass% or more.

  The iron fine particle C slurry is generally obtained from an oxygen blowing furnace for steelmaking by collecting steelmaking dust (preferably wet dusting) in exhaust gas generated during refining and removing gas such as carbon dioxide. A slurry made of steelmaking dust can be used advantageously. Usually, after dust collection, the steelmaking dust is made into a slurry of iron powder sludge by a thickener. If desired, a high-grade iron powder for a specific application (eg, for toner) can be further added to the obtained steelmaking dust to form a slurry.

  In an oxygen blowing furnace for steelmaking, pig iron containing impurities such as C, Si, and P is charged and oxygen is rapidly blown from above while stirring. In this state, a reaction occurs between the impurity-containing pig iron and oxygen, C, Si, P, etc. become oxides, and pig iron becomes a rope. During this time, the exhaust gas containing fine iron powder generated by blowing oxygen is collected by wet dust collection through a gas recovery hood. In wet dust collection, a gas such as CO is sent to a gas recovery tank. Steelmaking dust obtained by collecting exhaust gas is in the form of a slurry. This slurry is coarsely divided (at 60 μm), the coarse is collected as coarse iron powder, and the fine is concentrated by a thickener. Finally, only fine particles are selected by a filter press, and fine iron powder (that is, iron fine particle slurry) can be obtained.

  The iron fine particles obtained in this way contain iron oxides in various oxidation stages, but such iron oxides are also in a reduced state in the dust trapped in the gas combustion state, and are considered to exhibit a reducing action that leads to a purification action. It is done. Therefore, even if metallic iron does not occupy 30% by mass or more, the iron fine particles can often exhibit a high reducing action.

  As described above, the iron fine particles that can be used in the method of the present invention can be obtained by using a by-product during iron refining without using a special method or apparatus for producing the iron fine particles. Simple and economical. Moreover, since it is obtained in the form of a slurry, oxidation of the iron powder particle surface can be prevented, and therefore oxidation during transportation can also be prevented. Moreover, in order to prevent the oxidation of the iron particle surface, it is preferable to add an antioxidant to the slurry. Examples of the antioxidant include organic acids (eg, ascorbic acid (vitamin C), citric acid, malic acid, particularly ascorbic acid) and salts thereof. 01-10 mass% is common, and 0.1-3 mass% is preferable. Furthermore, since it is a slurry form, when manufacturing a soil purification agent, there exists an advantage that mixing with another material is easy. Since the iron fine particle slurry is usually diluted and mixed with water at the time of use, it is considered that the action of these antioxidants is greatly reduced.

  The iron fine particles S used in the present invention can also be obtained by synthesis. For example, iron sulfate is converted into iron hydroxide, which is converted into iron oxide and further reduced to obtain iron powder. The iron fine particles obtained in this manner are generally amorphous and are ultrafine particles (generally 0.5 μm or less). The iron fine particles S are also usually obtained in a slurry state.

  The iron fine particle slurry can be used in combination with metals other than iron, such as Mn, Mg, Zn, Al, and Ti, which have a reducing action. These metals also preferably have an average primary particle size as small as possible.

  Examples of the method for producing the iron powder and other metal fine particles used in the present invention include the following methods. Atomization method, melt spinning method, rotating electrode method, grinding process as mechanical process, crushing method, mechanical alloying method, oxide reduction method, chloride reduction method, wet metallurgy method, carbonyl reaction method, electroanalysis as chemical process For example, the method of going out. Among these methods, the oxide reduction method and the carbonyl reaction method are particularly preferable because fine and high-quality fine metal particles can be obtained.

    The fine iron powder used in the present invention has a large surface area and is easily oxidized (passivated). Therefore, in the present invention, a hydrophilic binder and / or a metal halide may be used in combination to prevent this. preferable.

Examples of the metal halide include NaCl, KCl, MgCl ₂ and CaCl ₂ , and NaCl is particularly preferable. Metal halides have the function of reducing iron hydroxide and oxide to metallic iron. The amount used is generally 0.5 to 200% by mass, preferably 0.5 to 50% by mass, based on the iron fine particles.

  The hydrophilic binder has a function of covering the surface of the iron fine particles and protecting the organic halide from being oxidized before exhibiting a reducing action. Examples of hydrophilic binders include disaccharides such as sucrose, sucrose derivatives (eg, sucrose higher fatty acid esters), monosaccharides such as glucose, alginic acid; pullulan, PVA (polyvinyl alcohol), CMC (carboxyl methylcellulose), polyacrylamide, Mention may be made of water-soluble resins such as guar gum, methylcellulose and hydroxyethylcellulose. Pullulan (particularly preferred because of low viscosity when made into an aqueous solution), hydroxyethyl cellulose, sucrose, glucose, and PVA are preferred. The use of a biodegradable polymer as the hydrophilic binder is particularly effective against secondary environmental pollution. The amount used is generally 0.01 to 200% by mass, preferably 0.01 to 100% by mass, based on the iron fine particles.

  The soil purification agent of the present invention preferably contains silica fine particles. As such silica fine particles, amorphous silica is preferable, and powder silica (generally wet method silica or dry method silica) or colloidal silica which is synthetic silica is generally used. Natural amorphous silica can also be used, and the average primary particle size is generally large and is about 0.1 to 10 μm. The average primary particle diameter of powdered silica or colloidal silica, which is a synthetic amorphous silica, is about 1 to 100 nm. In the present invention, synthetic silica is preferred. In the present invention, the average primary particle diameter of the silica fine particles is generally in the range of 1 nm to 10 μm, more preferably in the range of 5 nm to 1 μm, and particularly preferably in the range of 5 to 100 nm. Colloidal silica may be added when the iron fine particle slurry and water are dispersed, or may be added at the time of injection after the iron fine particle slurry and water are dispersed.

The shape of the silica fine particles is spherical, hollow, porous, rod-like, plate-like, fibrous, or indefinite, and preferably spherical. The specific surface area of the silica fine particles is 0.1 to 3000 m ² / g, preferably 10 to 1500 m ² / g. These silica fine particles can be used in a dry state, or in a state of being dispersed in water or an organic solvent (preferably water), and a dispersion of fine silica particles known as colloidal silica is directly used. Can be used.

As the powdered silica, Aerosil 130, Aerosil 200 (specific surface area = 200 m ² / g), Aerosil 300, Aerosil 380 (specific surface area = 380 m ² / g), Aerosil TT600 and Aerosil OX50, manufactured by Nippon Aerosil Co., Ltd., Asahi Glass Co., Ltd. Sildex H31, H32, H51, H52, H121, H122, Nippon Silica Kogyo Co., Ltd. E220A, E220 Fuji Silysia Co., Ltd. Silicia 470, Nippon Sheet Glass Co., Ltd. -Can be mentioned.

  It is also preferable to use colloidal silica instead of powdered silica. When the dispersion solvent of colloidal silica is water, the hydrogen ion concentration is in the range of 2 to 10 as a pH value, and acidic colloidal silica having a pH of 3 to 7 is preferably used. When the colloidal silica dispersion solvent is an organic solvent, methanol, isopropyl alcohol, ethylene glycol, butanol, ethylene glycol monopropyl ether, methyl ethyl ketone, methyl isobutyl ketone, toluene are used as the organic solvent. In addition, a solvent such as xylene and dimethylformamide, an organic solvent compatible with these solvents, or a mixture with water may be used. Preferred dispersing solvents are methanol, isopropyl alcohol, methyl ethyl ketone, and xylene. As a commercial product of silica fine particles, for example, as colloidal silica, Snowtex S, methanol silica sol, IPA-ST, MEK-ST, NBA-ST, XBA-ST, DMAC-ST manufactured by Nissan Chemical Industries, Ltd. and ST-UP, ST-OUP, ST-20, ST-40, ST-C, ST-N, ST-O, ST-50, ST-OL and the like can be mentioned. The above-mentioned Aerosil and Snowtex are generally spherical.

  As a compounding quantity of a silica particle, 0.01-10 mass% is common with respect to the whole iron fine particle slurry, and 0.1-1 mass% is preferable.

  If desired, an antioxidant, a metal halide or a water-soluble polymer, or a metal halide and a hydrophilic binder may be added to the soil purification agent, and suspended or dispersed. Further, water can be appropriately added to obtain a desired concentration. If necessary, a surfactant can be used at the time of dispersion. Use of a biodegradable polymer (eg, biodegradable polycaprolactone) instead of the hydrophilic binder is particularly effective against secondary environmental pollution.

  The soil purification agent preferably further contains a metal sulfate (particularly ferrous sulfate) as a reducing agent. Since this reacts with oxygen in the air, it is possible to prevent the surface of the metal iron fine particles from being oxidized.

  The soil purification agent can further contain an inorganic carbonate or a carbonate-based mineral. Examples of these include calcium carbonate, precipitated calcium carbonate, magnesium carbonate, fossil limestone, limestone, and dolomite, and precipitated calcium carbonate is particularly preferable.

  The above-mentioned soil purification agent is obtained by adding a water-soluble polymer and silica to an iron fine particle slurry, if desired, and suspending or dispersing it. At this time, in order to promote the generation of hydrogen, an acid such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, preferably hydrochloric acid is mixed. As water used for mixing and dispersing, it is preferable to use reducing electrolyzed water (preferably pH = 7 to 12) from the viewpoint of suppressing iron oxidation as much as possible.

In the following examples, the details of the iron fine particle slurry used will be described. The primary particle size, the dispersed particle size (D50 value), the solid content, and the oxidation state of the iron powder (Fe (0)) of the iron fine particle slurry C that is non-reduced iron powder particles and the iron fine particle slurry S that is reduced iron powder particles. ), FeO, Fe ₂ O ₃ , Fe ₃ O ₄ are as follows.

State of dispersion slurry Primary particle size (μm) Dispersion particle size (μm) Solid content (%)
Iron fine particle slurry C 0.3-1.0 2.54 25.0
Iron fine particle slurry S 0.1-0.5 7.66 25.0

Oxidized state constituent ratio Fe (zero valent) FeO Fe ₂ O ₃ Fe ₃ O ₄
Iron fine particle slurry C 40% 45% 15% 0%
Iron fine particle slurry S 70% 0% 0% 30%

[Examples 1 to 3] [Comparative Examples 1 to 3]
<Purification of simulated contaminated soil>
A purification experiment of simulated contaminated soil was conducted with the formulation shown in Table 1. In Examples 1 to 3 and Comparative Examples 1 to 3, the number of measurement days was prepared for each sample. The measurement days were 0 days (Example 1 only), 1 day, 7 days, 14 days, 28 days, 56 days, and 84 days.

<Soil purification solution>
Iron fine particle C 25% by mass
(Average primary particle size: about 0.6 μm, shape: spherical)
Iron fine particle S 25% by mass
(Average primary particle size: about 0.2 μm, shape: irregular)

<Test soil>
Horticultural soil Akadama soil Horticultural soil Shiba Meso After drying these soils at 140 ° C, they are crushed in a mortar, removed pebbles, grass fragments, etc., and mixed with Akadama 50 / Shibame 50. A soil for testing was used.

  In the test, an aluminum seal vial was used as a container, and after adding soil, purified water, and TCE standard solution, they were shaken and mixed by hand. Further, a soil purification solution was added, sealed with a septum, shaken and mixed again by hand, used as a test sample, and stored in a dark place.

As a test method, the following method was adopted as a quantitative analysis of volatile organic compounds (VOCs).
Measuring method: JIS K 0125 5.2 Headspace gas chromatography
Graph mass spectrometry apparatus: AUTOMASS-150 type manufactured by JEOL Ltd. MS conditions: ionization method EI
Ionization voltage 70eV
Ion source temperature 200 ° C
GC condition: Column AQUATIC 60m × 0.25mmΦ
Column temperature 40-180 ° C (6 ° C / min)
Carrier gas He 1mL / min
Sample introduction: Model 7000 headspace autosampler manufactured by Tekmer
Introduced into GC / MS by equipment.

  The results are shown in Table 2.

[Examples 4 to 6] [Comparative Examples 4 to 6]
<Purification of simulated contaminated water>
A purification experiment of simulated contaminated water was conducted with the formulation shown in Table 3. Samples of Examples 4 to 6 and Comparative Examples 4 to 6 were prepared. The measurement days were 0 days, 3 days, 7 days, 14 days, 28 days, and 42 days.

  The sample bottle used for the test was a brown glass aluminum sealed vial, which was sealed with a septum. After sample preparation, it was shaken well by hand and stored in the dark.

The test was a headspace method. The air in the upper part of the sample bottle containing the test solution was weighed with a gas tight syringe and introduced into a gas chromatograph to measure the concentration of remaining trichlorethylene.
Equipment: GC-8610 manufactured by NRI
GC condition: Column NBW-310SS30
Column temperature 40-100 ° C (6 ° C / min)
Carrier gas He 5mL / min
Detector PID

  The results are shown in Table 4.

[Examples 7 to 9] [Comparative Examples 7 to 9]
<Purification cycle test>
A purification cycle test was conducted to determine how long the fine iron powder for purification lasts. In the simulated contaminated water experiment, the residual concentration of TCE was measured 10 days after the start of the experiment, and then the TCE of the same concentration as the initial stage was added, measured 10 days later (total 20 days later), and then the same concentration of TCE was added. The purification cycle experiment was conducted until day later. Table 5 shows formulation examples.

  The sample bottle used for the test was a brown glass aluminum sealed vial, which was sealed with a septum. After sample preparation, it was shaken well by hand and stored in the dark.

  The test was a headspace method. The air in the upper part of the sample bottle containing the test solution was weighed with a gas tight syringe and introduced into a gas chromatograph to measure the concentration of remaining trichlorethylene.

  After the measurement, the trichlorethylene standard solution was weighed with a syringe, and the needle was inserted into the sample bottle without removing the septum. After this, it was shaken well by hand and stored in the dark. This operation was repeated 10 days, 20 days, and 30 days after the start of the test, and the experiment was completed with the measurement on the 40th day. The results are shown in Table 6.

  From the results of these experiments, the soil purification agent has a fast-acting characteristic against contamination such as trichlorethylene by mixing iron fine particles S having a rapid effect in its decomposition characteristics and iron fine particles C having a long-lasting effect. It became clear that there was a certain purification time.

  In addition, the environmental standard concerning the soil contamination of TCE is 0.03 mg or less per 1 L of the test solution (the environmental standard value for protecting human health is 0.03 mg / L or less). It can be seen that the soil remediation method of the present invention can greatly reduce such a value.

Claims (5)

A soil purification agent comprising S, which is an iron fine particle covered with iron fine particles or an iron oxide film, and C, which is an iron fine particle covered with an iron oxide film. 100 weight percent, 30 weight percent iron oxide (II) is 0, iron sesquioxide from 0 15 percent by weight and iron oxide black Ri 45% by mass from 0, C 0-valent iron from 10 40 weight percent, 70 weight percent iron oxide (II) is 30, soil purifying agent and said that it is a 30 weight percent ferric oxide is from 0 15 percent by weight and iron oxide black is from 10. The soil purification agent according to claim 1, wherein the particle diameter of the iron fine particles S covered with the iron fine particles or the iron oxide film is 10 µm or less. The soil purification agent according to claim 1 or 2, wherein the particle diameter of the iron fine particles C covered with the iron oxide film is 0.3 µm to 100 µm. The soil purifier according to any one of claims 1 to 3, wherein at least 1 mass% is iron fine particles S covered with iron fine particles or an iron oxide film. A soil purification method comprising injecting the soil purification agent according to any one of claims 1 to 4 into soil or groundwater contaminated with an organic compound.