JP2016007591A - Soil cleaning agent and method for cleaning contaminated soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-part soil cleaning agent that allows the preparation of a soil cleaning agent for an iron powder slurry capable of detoxicating contaminants such as organic halides and hexavalent chromium by efficiently reducing them directly from a soil contaminated with such contaminants, or capable of removing them after the detoxication, wherein an excellent dispersion of the iron powder can be obtained over an extended time.SOLUTION: The soil cleaning agent for cleaning a contaminated soil comprises: an iron powder aqueous suspension containing iron powder or dispersed iron powder; and a montmorillonite clay mineral aqueous suspension where a montmorillonite clay mineral as a thickener is dispersed in water. The montmorillonite clay mineral is bentonite or synthetic smectite.

Description

  The present invention relates to a soil purification agent used for decomposing and detoxifying the pollutants from soil contaminated with organic halides, hexavalent chromium and the like, and a method for purifying the contaminated soil.

  For industrial cleaning such as oil removal of machinery, organochlorine compounds such as trichlorethylene have been used in large quantities so far. At present, the use of such organochlorine compounds is regulated from the viewpoint of environmental pollution. However, a large amount of organochlorine compounds have already been used, and as a result, soil contamination or water pollution is also progressing. That is, organochlorine compounds such as trichlorethylene are stable and difficult to break down into microorganisms. Organochlorine compounds dumped in the natural environment not only contaminate the soil, but ultimately pollute rivers and groundwater, This can be a source of drinking water, which is problematic.

  Conventionally known methods for purifying soil contaminated with volatile organic compounds such as organic chlorine compounds include soil gas suction, groundwater pumping, soil excavation, and the like. 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 are 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 a purification agent used in the method capable of direct purification, for example, Patent Document 1 (International Publication No. 2001-08825) discloses a soil purification agent comprising a spherical iron fine particle slurry having a particle size of less than 10 μm. . That is, by finely pulverizing iron particles, the surface area of iron is increased to increase the processing capacity of pollutants, and in addition to atomization, the shape of the particles is made spherical to rapidly penetrate iron into the soil. Is possible.

  The iron powder slurry as described in Patent Document 1 has a problem that since the iron powder itself has a high specific gravity, it is easy to settle and it is difficult to obtain a well dispersed iron powder slurry. For this reason, in order to make an iron powder slurry into a favorable dispersion state, it is common to add a thickener. For example, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-272068), polysaccharides such as guar gum, chitosan, xanthan gum, and alginates are used as thickeners for soil purification agents.

International Publication No. 2001-08825 JP 2006-272068 A

  According to the study of the present inventor, when a polysaccharide such as guar gum described in Patent Document 2 is used in order to make the iron powder slurry in a good dispersion state, the polysaccharide deteriorates due to decay or the like during storage. It became clear that there was a problem that not only the bad smell caused by rot occurred but also the essential thickening action could not be obtained. In addition, when the thickening action cannot be obtained, there is a problem that when the cleaning agent is injected into the contaminated soil, the uniform penetration of the cleaning agent into the contaminated soil is also inhibited.

  Therefore, the object of the present invention is to remove the contaminants directly or efficiently from the soil contaminated with contaminants such as organic halides and hexavalent chromium, and to remove them after detoxification. An object of the present invention is to provide a soil purification agent containing an iron powder slurry, which can obtain a good dispersion state of iron powder over a long period of time.

  Moreover, the object of the present invention is a two-component type soil purification agent capable of preparing a soil purification agent that is an iron powder slurry soil purification agent that can obtain a good dispersion state of iron powder over a long period of time. It is to provide.

  Accordingly, an object of the present invention is to use the above-described two-component type soil purification agent to efficiently purify soil contaminated with organic halides, hexavalent chromium, etc. in situ by agitation without excavation. It is to provide a way to do.

  Therefore, the above object is a soil purifier for purifying contaminated soil, which is an iron powder aqueous suspension containing iron powder or dispersed iron powder, and montmorillonite clay as a thickener. It can be achieved by a soil purification agent comprising a montmorillonite clay mineral aqueous suspension in which a mineral is dispersed in water.

  The montmorillonite clay mineral of the present invention includes a montmorillonite group mineral and a synthetic montmorillonite group mineral.

  Preferred embodiments of the soil purification agent are listed below.

  (1) The montmorillonite clay mineral is bentonite or synthetic smectite.

  (2) The aqueous montmorillonite clay mineral suspension further contains an additive capable of thickening the suspension. Thereby, a big thickening effect can be acquired with a small amount of bentonite. Moreover, the pH of bentonite can be shifted to a neutral range suitable for purification.

(3) The additives are FeCl ₂ (ferrous chloride), FeCl ₃ (ferric chloride), FeSO ₄ (ferrous sulfate), Fe ₂ (SO ₄ ) ₃ (ferric sulfate), FeO, At least one iron compound selected from Fe ₃ O ₄ and FeS, in particular at least one iron compound selected from FeCl ₂ , FeCl ₃ , FeSO ₄ , and Fe ₂ (SO ₄ ) ₃ .

  (4) The average particle size of the iron powder is 1 to 500 μm, particularly 10 to 200 μm. Since the iron powder is more likely to settle in the slurry as the average particle size is larger, the thickener of the present invention is particularly effective for iron powder having a relatively large particle size.

  (5) The pollutants in the contaminated soil are organic halides and / or hexavalent chromium, particularly organic halides, among which volatile organic chlorine compounds (CVOC). The reducing action of iron powder is particularly effective for pollutants and organic halides that can be reduced, but is also effective for hexavalent chromium.

  This invention exists also in the soil cleaning agent which consists of a mixture of the iron powder or the aqueous suspension of iron powder, and the montmorillonite clay mineral aqueous suspension described in the above-mentioned soil cleaning agent.

  Preferred embodiments of the soil purification agent are listed below.

  (1) The concentration of iron powder is 10 to 50% by mass, and the concentration of bentonite is 0.3 to 5% by mass. An efficient thickening effect is obtained.

  (2) The viscosity is 200 to 400 mPa · s at 25 ° C. The viscosity is suitable for pumping the iron powder suspension at a uniform concentration to a construction machine that prevents sedimentation and injects into contaminated soil.

  The present invention mixes iron powder or an aqueous suspension of iron powder and an aqueous suspension of montmorillonite clay mineral described in the two-component type soil purification agent, and permeates the mixture into contaminated soil. There is also a soil purification method consisting of

  Preferred embodiments of the soil purification method are listed below.

  (1) The soil cleaner is infiltrated by spraying the soil cleaner over substantially the entire surface of the soil.

(2) The soil purifier is infiltrated by inserting an injection tube for supplying the mixture and injecting the mixture into the injection tube. Alternatively, the soil purifying agent is permeated by supplying the mixture into the soil using a construction machine for ground improvement and stirring the mixture and the soil.

  The soil purification agent of the present invention mainly uses iron powder for removing contaminants, and uses bentonite as a thickener to obtain good dispersion stability of iron powder. This prevents the generation of bad odors and deterioration due to rot such as polysaccharides, so the soil purifier stabilized with a good viscosity can be used stably for a long time, and stable soil The effect can also be obtained for a long time. In particular, by using an acidic additive such as an iron compound to increase the thickening effect of bentonite, a thickening effect can be obtained efficiently with a small amount of bentonite, so the amount of thickening agent can be suppressed, and iron It is easy to obtain a purification effect. It is also possible to shift the pH to a neutral range suitable for purification with iron powder by using an acidic additive.

  When the soil cleansing agent stabilized to a good viscosity according to the present invention is directly injected into contaminated soil, iron powder is not only applied to sandy layers that are relatively easy to penetrate, but also to silt layers, clay layers, Kanto loam layers, etc. Since they can be introduced uniformly, it is possible to sufficiently detoxify pollutants such as organochlorine compounds.

FIG. 1 is a cross-sectional view showing an example of an embodiment of the purification method of the present invention. FIG. 2 is a graph of the viscosity with respect to the concentration of each thickener shown in Tables 1 and 2 of the Examples. FIG. 3 is a graph showing the relationship between the concentration of each additive and the viscosity when the concentration of Kunipia F in Tables 3 to 10 in the examples is 2.5 mass%. FIG. 4 shows the relationship between pH and viscosity of a montmorillonite clay mineral aqueous suspension (additive preparation) to which each additive was added when the concentration of Kunipia F in Tables 3 to 10 in the Examples was 2.5 mass%. It is a graph which shows. FIG. 5 is a graph showing the relationship between ferrous chloride concentration and viscosity when the concentration of Kunipia F in Tables 11 to 13 of the examples is 1.0 mass%, 1.5 mass%, and 2.5 mass%. is there. FIG. 6 is a graph showing the relationship between the ferrous sulfate concentration and the viscosity when the concentration of Kunipia F in Tables 14 to 16 is 1.0 mass%, 1.5 mass%, and 2.5 mass%. is there. FIG. 7 is a graph showing a change in the trichlorethylene (TCE) concentration with respect to the number of days elapsed by each of the cleaning liquids in Table 17 of the example.

  The soil purification agent of the present invention includes iron powder or an aqueous suspension of iron powder in which iron powder is dispersed in water, and an aqueous montmorillonite clay mineral suspension in which bentonite as a thickener is dispersed in water. And a mixture of these iron powder or iron powder aqueous suspension and montmorillonite clay mineral aqueous suspension. That is, the soil purification agent of the present invention is generally prepared with a montmorillonite clay mineral aqueous suspension, and when used, iron powder is added to the montmorillonite clay mineral aqueous suspension and mixed, Alternatively, an iron powder aqueous suspension and a montmorillonite clay mineral aqueous suspension are prepared and mixed when used. For this reason, montmorillonite clay minerals are generally stored as aqueous suspensions before use. Since this thickener is an inorganic substance, it does not rot even after long-term storage and the thickening effect does not decrease. The soil purifier of the present invention is also useful for detoxifying or removing the pollutant from the contaminated soil by reduction or the like after the decontamination from the contaminated soil, because the thickener can easily obtain the purifying effect by iron. It is also excellent in performance.

  Examples of the contamination source to be purified according to the present invention include organic halides, hexavalent chromium, and cyanide. Organic halides and hexavalent chromium are suitable, and organic halides are particularly suitable. Examples of organic halides include vinyl chloride, 1,1-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, dichloromethane, carbon tetrachloride, 1,2-dichloromethane, 1,1,1-trichloroethane, 1,1 , 2-trichloroethane, 1,1,2,2-tetrachloroethane, dichlorodifluoroethane and the like. These organic halides are considered to be removed from the soil by losing halogen to the corresponding hydrocarbons due to the dehalogenation action (reduction action) of iron. The organic halide is particularly effective for organic chlorides (especially volatile organochlorine compounds (CVOC)). Hexavalent chromium can be efficiently reduced to trivalent chromium by an effective iron reducing action over a long period of time, and then removed from the soil as necessary. Furthermore, cyanide (cyanide ions) is detoxified by forming a complex with iron ions.

  Any iron powder can be used as the iron powder contained in the slurry used in the soil purification agent of the present invention. The average particle size of the iron powder is generally 1 μm or more, preferably 1 to 500 μm, more preferably 10 to 500 μm, and particularly preferably 10 to 200 μm. Such iron powder can improve its detergency as the average particle size is smaller, but it is difficult to handle due to the danger of dust explosion, etc., and it is more expensive as it is smaller. In view of this, it is preferable that it is somewhat large, particularly 10 to 200 μm. In this range, the thickener of the present invention is particularly effective.

Moreover, the content of iron powder in the iron powder aqueous suspension of the soil purification agent of the present invention is preferably 10 to 70 mass%, particularly preferably 20 to 50 mass%. The content of iron powder in the iron powder aqueous suspension (that is, the liquid at the time of pouring into soil) after mixing with the montmorillonite clay mineral aqueous suspension is 0.1 to 50 mass%, particularly 5 to 30 mass%. % Is preferred. Although iron powder has metal iron and an iron containing compound as a main component, it is preferable that metal iron accounts for 50 mass% or more among iron powder. The iron-containing compound is mainly iron oxide such as Fe ₂ O ₃ , FeO, and FeO ₂ . The iron powder may contain a small amount of sulfur, CaO, SiO ₂ or the like as other components.

  Any iron powder can be used as long as it satisfies the above average particle diameter and the like. As iron powder which can be used, various commercially available iron powders can be used. Examples thereof include iron powders sold by JEF Mineral Co., Ltd., Kobe Steel Co., Ltd., DOWA Ecosystem Co., Ltd., etc., particularly iron powders for soil purification. The aqueous iron powder suspension can be generally obtained by dispersing the above iron powder (iron powder) in water (which may contain the following additives if desired).

  The iron powder aqueous suspension (iron powder slurry) collects steelmaking dust in the exhaust gas generated during refining (preferably wet dust collection) from an oxygen blow furnace for steelmaking, for example, carbon dioxide gas A slurry made of steelmaking dust obtained by removing the gas can be advantageously used. Usually, after dust collection, the steelmaking dust is made into a slurry of iron powder sludge by a thickener.

  In the iron powder of the present invention, it is preferable to add an antioxidant to the iron powder aqueous suspension in order to prevent oxidation of the iron particle surface. 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.

  The aqueous iron powder suspension or soil purification agent of the present invention can be used in combination with metals other than iron as long as Mn, Mg, Zn, Al, Ti, etc. are metals having a reducing action.

  The iron powder aqueous suspension (iron powder slurry) of the present invention is obtained by suspending or dispersing the above iron powder slurry by adding an antioxidant, a metal halide or a water-soluble polymer, if desired. It is. Further, water can be appropriately added to obtain a desired concentration. If necessary, a surfactant can be used at the time of dispersion.

  The montmorillonite clay mineral aqueous suspension used by mixing with the iron powder or iron powder aqueous suspension of the present invention is a known montmorillonite clay mineral water (optionally containing the above-mentioned additives). ) To be dispersed. The content of the montmorillonite clay mineral in the aqueous suspension of montmorillonite clay mineral is preferably 0.5 to 10% by mass, particularly 1 to 4% by mass. The content of the montmorillonite clay mineral in the iron powder aqueous suspension after mixing with the montmorillonite clay mineral aqueous suspension (that is, the liquid at the time of pouring into the soil) is 0.3 to 5% by mass, particularly 0. 5-3.5 mass% is preferable.

  The montmorillonite clay mineral of the present invention contains a montmorillonite group mineral or a synthetic montmorillonite group mineral. Examples of the montmorillonite mineral include montmorillonite (montmorillonite), beidellite, saponite (sapphire), hectorite and the like. Bentonite containing montmorillonite, hectorite, and montmorillonite as main components, particularly bentonite is preferred. Moreover, as a synthetic montmorillonite group mineral, synthetic smectite and synthetic saponite are preferable.

Montmorillonite, which is a main component such as bentonite, is a clay mineral classified as smectite, a kind of layered silicate mineral, and its crystal structure is 3 of silicate tetrahedral layer-alumina octahedral layer-silicate tetrahedral layer. The layers are stacked, and the unit layer has a very thin plate shape with a thickness of about 10 mm (1 nm) and a spread of 0.1 to 1 μm. A portion of Al, which is the central atom of the alumina octahedron layer, is replaced with Mg, resulting in a lack of positive charge, and each crystal layer itself is negatively charged, but Na ⁺ · K ⁺ · Ca ² between the crystal layers. By sandwiching cations such as ⁺ · Mg ²⁺ , neutralization of charge shortage is achieved, and montmorillonite becomes stable. For this reason, montmorillonite exists in a state in which a number of crystal layers are overlapped. The specific properties of montmorillonite are exhibited by the negative charge on the surface of the layer and the interlayer cations causing various effects. In the present invention, this is used for thickening the iron powder aqueous suspension.

  As the commercially available bentonite, Kunipia F manufactured by Kunimine Kogyo Co., Ltd. can be exemplified. As the commercially available synthetic saponite, smecton SA manufactured by Kunimine Kogyo Co., Ltd. can be exemplified, which is preferable. Smecton SA is a synthetic inorganic polymer having a saponite structure.

  The average particle size of the montmorillonite clay mineral is preferably 10 to 100 μm, particularly preferably 20 to 40 μm. An effective thickening effect is easily obtained within this range.

The aqueous montmorillonite clay mineral suspension of the present invention preferably further contains an additive capable of thickening the suspension. Thereby, a big thickening effect can be acquired with a small amount of bentonite. Also, the pH of bentonite can be shifted to a neutral range where the iron powder purification ability is increased. Suitable additives include FeCl ₂ (ferrous chloride), FeCl ₃ (ferric chloride), FeSO ₄ (ferrous sulfate), Fe ₂ (SO ₄ ) ₃ (ferric sulfate), FeO, FeS can be mentioned, and one or more of these can be used in combination. In particular, FeCl ₂ , FeCl ₃ , FeSO ₄ , and Fe ₂ (SO ₄ ) ₃ are preferable, and among them, FeCl ₂ and FeSO ₄ are preferable.

  The additive is 0.01-0.5% by mass (further 0.01-0.2% by mass, especially 0.02-0.1% by mass) in the montmorillonite clay mineral aqueous suspension. It is preferable to add to.

For example, the viscosity of a 2.5% aqueous suspension of Kunipia F is about 20 mPa · s (25 ° C.), but when FeCl ₂ as a thickening additive is added to 0.05 mass%, The temperature rises to about 250 mPa · s (25 ° C.), and the pH is also about 6, showing a large thickening effect and a high purification effect (see Examples described later).

  In the method for purifying contaminated soil of the present invention using a soil purifier, the iron powder or a mixture of the iron powder aqueous suspension and the montmorillonite clay mineral aqueous suspension (soil purifier) is contaminated with an organic halide. It is performed by giving so as to penetrate into the soil (ground). Preferably, the method (1) for infiltrating the soil purification agent by spraying the soil purification agent; inserting an injection pipe for supplying the soil purification agent into the soil contaminated with the organic halide, Method (2) comprising injecting the soil purification agent into the injection pipe, and supplying the soil purification agent into the soil with a construction machine for ground improvement, stirring and mixing the soil purification agent and the soil The method (3) which consists of doing can be mentioned.

  The method (2) can be performed as follows, for example, as shown in FIG.

  Contaminated soil generally consists of a gravel layer (permeable layer) 1 and a clay layer (impervious layer) 2 below it, and a soil purification agent 3 is supplied to the contaminated soil by boring the surface contaminated with organic halides. An injection hole 4 is provided. A plurality of injection holes 4 can be provided at intervals as needed. A soil cleaner is pressed into the injection hole 4 by a pump. The soil purifier is injected into the contaminated soil in the direction of the arrow from the many holes provided around the injection hole 4, and the iron powder penetrates into the contaminated soil and gradually comes into contact with the organic halide to remove the organic halide. Decompose and remove.

  Before injecting through the injection hole 4, groundwater may be discharged from the injection hole 4, and then a soil purification agent may be injected. The soil surface may be covered with a water-impermeable sheet (eg, bentonite sheet) so that the injected solution does not overflow from the soil surface. Alternatively, a sheet may be embedded in the soil.

  In the purification treatment, for example, water is drained through the injection hole 4, the cleaning agent of the present invention is injected from the injection tube, and the pressure is reduced as necessary to remove substances generated by the diffusion of the cleaning agent and the reducing action of iron. be able to.

  As in the above method, it is preferable to cover the surface of soil contaminated with organic halides with a non-breathable sheet (generally, the cover of the sheet is installed after the injection of the cleaning agent), and if necessary, a breathable columnar shape. Part (useful for removal of the generated substance) can be provided.

  Soil contaminated with contaminants other than organic halides can be performed in the same manner as described above. In addition, contaminated soil (especially soil contaminated with hexavalent chromium) can be treated with the soil purification agent of the present invention by introducing the excavated soil into a reaction tank or the like by the soil excavation method. It may be advantageous to remove chromium compounds and the like.

As described above, the concentration of the iron powder in the soil purifier to be injected into the soil is 0.1 to 50% by mass, and preferably 5 to 30% by mass. Moreover, generally the injection amount is 5-250 kg of iron powder per 1 m < ³ > of soil, and 10-150 kg is preferable.

  Further, the injection of the soil purification agent may be performed separately by injection of an aqueous suspension of iron powder and injection of an aqueous suspension containing a hydrophilic binder or the like used as desired.

[Example 1]
(A) Montmorillonite clay mineral aqueous suspension As the montmorillonite clay mineral, Kunipia F (Kunimine Kogyo Co., Ltd.) and Smecton SA (Kunimine Kogyo Co., Ltd.) are used, and the concentrations shown in Tables 1 and 2 below. (Mass%) was added to 500 ml of distilled water while stirring with a magnetic stirrer to prepare an aqueous suspension of montmorillonite clay mineral.
The viscosity of the obtained aqueous suspension was measured at 25 ° C. using a B-type viscometer (BMII, manufactured by Toki Sangyo Co., Ltd., rotation speed: 60 rpm).

  A graph of the viscosity with respect to the concentration of each thickener shown in Table 1 and Table 2 is shown in FIG.

[Example 2]
(A) Montmorillonite clay mineral aqueous suspension A montmorillonite clay mineral aqueous suspension of 2.5% by mass was prepared using Kunipia F (Kunimine Kogyo Co., Ltd.) as the montmorillonite clay mineral. To this suspension, the additives shown in Tables 3 to 10 below were added and mixed so as to be the mass% in the following Tables 3 to 10 to prepare an aqueous montmorillonite clay mineral suspension containing the additives.

  The pH and viscosity of the obtained aqueous suspension were measured. The pH was measured at 25 ° C. using a pH meter (D-50, manufactured by Horiba, Ltd.) and the viscosity was measured using a B-type viscometer (BMII, manufactured by Toki Sangyo Co., Ltd., rotation speed: 60 rpm).

  A graph showing the relationship between the concentration of each additive and the viscosity when the concentration of Kunipia F in Tables 3 to 10 is 2.5% by mass is shown in FIG.

  FIG. 4 is a graph showing the relationship between pH and viscosity of a montmorillonite-based clay mineral aqueous suspension to which each additive is added (when the additive is prepared) when the concentration of Kunipia F in Tables 3 to 10 is 2.5% by mass. Shown in

  As is apparent from FIGS. 3 and 4, ferrous chloride, ferric chloride, and ferrous sulfate are excellent in both the thickening effect and the pH lowering effect, and hydrochloric acid and sulfuric acid are pH. Is not preferred because it greatly decreases with increasing viscosity.

[Example 3]
(A) Montmorillonite-based clay mineral aqueous suspension As a montmorillonite-based clay mineral, Kunipia F (manufactured by Kunimine Industries Co., Ltd.) is used, and 1.0 mass%, 1.5 mass%, and 2.5 mass% montmorillonite-based suspension. An aqueous clay mineral suspension was prepared. To this suspension, ferrous chloride was added and mixed so as to be the mass% of the following Tables 11 to 13, and an aqueous montmorillonite clay mineral suspension containing additives was prepared. In addition, ferrous sulfate was added and mixed so as to be the mass% of the following Tables 14 to 16 to prepare an aqueous montmorillonite clay mineral suspension with additives.

  The pH and viscosity of the obtained aqueous suspension were measured. The pH was measured at 25 ° C. using a pH meter (D-50, manufactured by Horiba, Ltd.) and the viscosity was measured using a B-type viscometer (BMII, manufactured by Toki Sangyo Co., Ltd., rotation speed: 60 rpm).

  The graph which shows the relationship between the density | concentration of ferrous chloride and a viscosity in the density | concentration of Kunipia F of said Table 11-13 in 1.0 mass%, 1.5 mass%, and 2.5 mass% is shown in FIG.

  The graph which shows the relationship between the density | concentration of ferrous sulfate and the viscosity in the density | concentration of Kunipia F of said Table 14-16 in 1.0 mass%, 1.5 mass%, and 2.5 mass% is shown in FIG.

  As is clear from FIGS. 5 and 6, a particularly excellent thickening effect can be obtained when the concentration of Kunipia F is 1.5 mass% or more.

[Example 4]
(A) Iron powder aqueous suspension Iron powder (trade name: iron, powder—150 μm, 99.9%; particle size: 99.9% is 150 μm or less, manufactured by Wako Pure Chemical Industries, Ltd.) 1 L was added and stirred to obtain a 40% by mass iron powder aqueous suspension.

  A sample was prepared as follows using the iron powder aqueous suspension and the suspension of Kunipia F or Kunipia F and additives.

(1) TCE (trichloroethylene) 5 mg / L,
(2) TCE 5 mg / L + iron powder 50 g / L (Made 8 ml of TCE 50 mg / L and 10 ml of iron powder aqueous suspension and make up to 80 ml)
(3) TCE 5 mg / L + Kunipia F 4.3 g / L (8 ml of TCE 50 mg / L and 10 ml of Kunipia F 35 g / L (viscosity (25 ° C.) 210 mPa · s) are mixed and made up to 80 ml)
(4) TCE 5 mg / L + Iron powder 50 g / L + Kunipia F 4.3 g / L (8 ml TCE 50 mg / L and 10 ml iron powder 400 g / L + Kunipia F 35 g / L (viscosity (25 ° C.) 260 mPa · s)) To make up to 80ml
(5) TCE 5 mg / L + iron powder 50 g / L + Kunipia F 3.1 g / L + ferrous chloride 0.038 g / L (8 ml TCE 50 mg / L, 10 ml iron powder 400 g / L + Kunipia F25 g / L + ferrous chloride 0 .3g / L (Mixed with viscosity (25 ° C) 350mPa · s) and made up to 80ml.)
(6) TCE 5 mg / L + iron powder 50 g / L + Kunipia F 3.1 g / L + ferric chloride 0.031 g / L (8 ml of TCE 50 mg / L, 10 ml of iron powder 400 g / L + Kunipia F25 g / L + ferric chloride 0 .25 g / L (viscosity (25 ° C.) 300 mPa · s) mixed and made up to 80 ml)
(7) TCE 5 mg / L + iron powder 50 g / L + Kunipia F 3.1 g / L + ferrous sulfate 0.0625 g / L (8 ml TCE 50 mg / L, 10 ml iron powder 400 g / L + Kunipia F25 g / L + ferrous sulfate 0 (8) TCE 5 mg / L + iron powder 50 g / L + Kunipia F 3.1 g / L + ferric sulfate 0. 5 g / L (viscosity (25 ° C.) 290 mPa · s) 0625g / L (8ml TCE 50mg / L and 10ml iron powder 400g / L + Kunipia F25g / L + ferric sulfate 0.5g / L) (viscosity (25 ° C) 275mPa · s) To make)

  The graph which shows the change with respect to the elapsed days of the TCE density | concentration by each purification liquid of the said Table 17 is shown in FIG.

  From the results of Table 17 and FIG. 7, the combination of the iron powder of the present invention and the montmorillonite clay mineral shows a purification action excellent in TCE, and the addition of an additive further improves the purification action. Recognize.

1 Gravel layer (permeable layer)
2 Clay layer (impermeable layer)
3 Soil cleaner 4 Injection hole

Claims (15)

  A soil purification agent for purifying contaminated soil, wherein iron powder or an iron powder aqueous suspension containing dispersed iron powder and a montmorillonite clay mineral as a thickener are dispersed in water. A soil purification agent comprising a montmorillonite clay mineral aqueous suspension.   The soil purifier according to claim 1, wherein the montmorillonite clay mineral is bentonite or synthetic smectite.   The soil purification agent according to claim 1, wherein the montmorillonite clay mineral aqueous suspension further contains an additive capable of thickening the suspension. The soil purifier according to claim 2, wherein the additive is at least one iron compound selected from FeCl ₂ , FeCl ₃ , FeSO ₄ , and Fe ₂ (SO ₄ ) ₃ .   The soil purifier according to any one of claims 1 to 4, wherein the average particle size of the iron powder is 10 to 200 µm.   The soil purifier according to any one of claims 1 to 5, wherein the viscosity of the aqueous montmorillonite clay mineral suspension is 200 to 400 mPa · s at 25 ° C.   The soil purification agent according to any one of claims 1 to 6, wherein the pollutant in the contaminated soil is an organic halide and / or hexavalent chromium.   The soil purification agent according to any one of claims 1 to 7, wherein the pollutant in the contaminated soil is an organic halide.   A soil purification agent comprising a mixture of iron powder or an iron powder aqueous suspension and a montmorillonite clay mineral aqueous suspension described in the soil purification agent according to any one of claims 1 to 8.   The content of iron powder is 10-50 mass%, and the content of a montmorillonite clay mineral is 0.3-5 mass%.   The soil purifier according to claim 9 or 10, which has a viscosity of 200 to 400 mPa · s at 25 ° C.   The iron powder or iron powder aqueous suspension and the montmorillonite clay mineral aqueous suspension described in the soil purification agent according to any one of claims 1 to 8 are mixed, and the mixture is mixed with contaminated soil. A soil purification method comprising infiltration.   The soil purification method according to claim 12, wherein the soil purification agent is permeated by spraying the soil purification agent over substantially the entire surface of the soil.   The soil purification method according to claim 12, wherein the soil purification agent is permeated by inserting an injection pipe for supplying the mixture and injecting the mixture into the injection pipe.   The soil purification method according to claim 12, wherein the soil purification agent is permeated by supplying the mixture into soil with a ground improvement construction machine and stirring the mixture and the soil.

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