JP2022183674A - Purifier for purification treatment of soil/groundwater and purification treatment method of soil/groundwater - Google Patents

Abstract

To provide a purifier for purification treatment of soil/groundwater capable of efficient and economical treatment of organic halides involved in a soil or groundwater and a purification method using the same.SOLUTION: A purifier for purification treatment of soil/groundwater comprises a water suspension involving an active ingredient comprising composite particles composed of metallic iron particulates having an average particulate diameter of 0.05-0.30 μm and a BET specific surface area of 10-60 m2/g and active carbon particulates having a BET specific surface area of 500-1400 m2/g, wherein a total pore volume of macropores of the composite particles is 0.20 mL/g or over, a blend ratio of the metallic iron particulates and the active carbon particulates at a weight ratio is 10:90-70:30, and a ratio (A)/(B) is 0.50-0.90. Here, (A) is a ratio of a pore volume of a pore size of 1 μm or over with respect to a total pore volume of macropores of the composite particles, and (B) is a ratio of a pore volume having a pore size of 1 μm or over with respect to a total pore volume of macropores of the active carbon particulates.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a soil/groundwater purification agent and a purification method for decomposing organic halogen compounds contained in soil or groundwater to purify the soil or groundwater.

Aliphatic organic halogen compounds such as trichlorethylene and tetrachlorethylene are widely used for cleaning in semiconductor factories and for degreasing of processed metals.

Dioxins, which are aromatic organic halogen compounds that are extremely toxic to the human body, are found in exhaust gas, fly ash, and bottom ash generated from garbage incinerators that incinerate municipal and industrial waste. It is included. Dioxins is a general term for compounds such as dibenzo-p-dioxin and dibenzofuran in which hydrogen is substituted with chlorine. Exhaust gas and fly ash remain around the incinerator and dioxins remain in the soil of the surrounding area.

Furthermore, PCB (polychlorinated biphenyl) is chemically and thermally stable and has excellent electrical insulation properties. Therefore, its manufacture and use are prohibited. However, no effective treatment method has been established for PCBs used in the past, and most of them are stored as they are without being treated.

Since organic halogen compounds such as aliphatic organic halogen compounds and aromatic organic halogen compounds are persistent and carcinogenic or highly toxic, environments where soil and groundwater are seriously contaminated by organic halogen compounds. it's a problem.

That is, when the organic halogen compounds are discharged, since the organic halogen compounds are persistent, they accumulate in the discharged soil and become contaminated with the organic halogen compounds, and groundwater is also contaminated with the organic halogen compounds. It will be done. Furthermore, since groundwater spreads to surrounding areas other than contaminated soil, contamination by organic halogen compounds becomes a problem over a wide area.

Since soil contaminated with organic halogen compounds cannot be reused or redeveloped, various technical means have been proposed as methods for purifying soil and groundwater contaminated with organic halogen compounds. Organic halogen compounds are difficult to decompose, and a large amount of soil and groundwater are subject to treatment, so an efficient and economical purification technology has not yet been fully established.

Methods for remediation of soil contaminated with organic halogen compounds include a method of purification using various catalysts, a method of suction removal using the volatility of organic halogen compounds, and a method of excavating and detoxifying soil through heat treatment. A decomposition method, a method using microorganisms, and the like are known. Further, as a method for purifying groundwater contaminated with organic halogen compounds, a method of extracting contaminated groundwater from the soil to render it harmless, a method of pumping groundwater to remove organic halogen compounds, and the like are known.

Among the technical means proposed as a method for purifying soil, groundwater, and wastewater contaminated with organic halogen compounds, mixing and contacting soil, groundwater, and wastewater contaminated with organic halogen compounds with a purification agent using iron-based particles. There have been proposed technical means for detoxification by detoxification (Patent Documents 1 to 11).

JP-A-2000-5740 JP-A-2002-161263 Japanese Patent Application Laid-Open No. 2003-105313 JP-A-2003-136051 Japanese Patent Application Laid-Open No. 2004-83860 JP 2006-326561 A JP 2010-194450 A JP 2010-194451 A JP 2011-26524 A JP 2011-46985 A JP 2013-208527 A

A cleaning agent capable of efficiently and economically decomposing organic halogen compounds contained in soil or groundwater is currently most demanded, but has not yet been obtained.

That is, the aforementioned Patent Document 1 discloses a technique for detoxifying organic halogen compounds in soil using iron powder containing copper. It is difficult to say that organic halogen compounds can be rendered harmless.

In addition, the aforementioned Patent Document 2 describes an iron powder for decomposition of an organic halogen compound, in which a metal selected from nickel, copper, cobalt and molybdenum is attached to the surface, and the surface other than the attached metal is covered with an iron oxide film. However, iron powder obtained on a mill scale or iron powder obtained by water atomizing molten steel is used, and from the specific surface area of the iron powder described, it seems that the particle size of the iron powder is large, and organic halogen It is difficult to say that the compounds can be sufficiently reduced.

In addition, in the aforementioned Patent Document 3, an organic halogen compound detoxifying agent composed of graphite and Fe—Ni and having a graphite content of 1 to 20% by weight and a Ni content of 0.1 to 15% by weight is disclosed. Although it is described, the particle size seems to be large, and it is difficult to say that the organic halogen compounds can be sufficiently reduced.

Further, in Patent Document 4 mentioned above, a metal powder for decomposing an organic halogen compound, which is composed of nickel-adhered iron particles having a phase containing iron as a main component as a base metal phase and a phase containing nickel as a main component as an adhering metal phase, However, the particle size is as large as 1 to 500 μm, and it is difficult to say that the amount of organic halogen compounds can be sufficiently reduced.

In addition, the aforementioned Patent Document 5 describes that iron composite particles composed of α-Fe and magnetite are used for purification treatment of soil and groundwater contaminated with organic halogen compounds. The amount added is still not sufficient for efficient decomposition in a short period of time.

In addition, the aforementioned Patent Document 6 describes an iron-based powder for purification in which Ni fine particles having an average particle size of 1 to 50 nm are attached to the surface of iron powder containing iron as a main component. has a large average particle size of 65 μm, and it is difficult to say that the amount of organic halogen compounds can be sufficiently reduced.

In addition, in the above-mentioned Patent Document 7, an organic A method for purifying halides is described, and the aforementioned Patent Document 8 discloses a partially alloyed powder having a partially alloyed phase of iron and nickel inside and/or on the surface of the iron powder, and for the partially alloyed powder, A process for remediation of organic halides is described in which less than 1% by weight of nickel sulfate and/or nickel chloride is admixed with organic halide-contaminated soil, wastewater or groundwater. However, the particle sizes of the iron powder and the partially alloyed powder are relatively large, and it is difficult to say that a small amount of addition can sufficiently reduce the organic halogen compounds.

In addition, the aforementioned Patent Document 9 describes a decomposing material for an organic halogen compound composed of iron powder whose surface is coated with a metal such as nickel that is more noble than iron, but the iron powder has a large particle size and is added in a small amount. It is difficult to say that organic halogen compounds can be sufficiently reduced with

In addition, in Patent Document 10 mentioned above, by pulverizing or strongly stirring iron powder and a water-soluble nickel aqueous solution, nickel is precipitated on the surface, and furthermore, organic halogen made of iron powder in which the nickel is partially alloyed with iron Although a compound-decomposing treatment agent is described, the particle size of the iron powder is large, and it is difficult to say that a small amount of addition can sufficiently reduce the amount of organic halogen compounds.

In addition, in the aforementioned Patent Document 11, iron composite particle powder composed of α-Fe and magnetite, in which Ni and/or Cu are coated and supported in the vicinity of the particle surface in a metallic state, is contaminated with an organic halogen compound. Although it is described that it is used in soil and groundwater for purification treatment, it is still difficult to say that it is sufficient for efficient decomposition in a short period of time.

An object of the present invention is to provide a soil/groundwater purification agent capable of efficiently and economically treating organic halogen compounds contained in soil or groundwater, and a purification method using the same.

The above technical problems can be achieved by the present invention as follows.
That is, the present invention provides metallic iron particles having an average particle size of 0.05 to 0.30 μm and a BET specific surface area of 10 to 60 m ² /g and activated carbon particles having a BET specific surface area of 500 to 1400 m ² /g. A cleaning agent for soil and groundwater purification treatment, which is an aqueous suspension containing composite particles consisting of The mixing ratio of the metal iron particles and the activated carbon particles is 10:90 to 70:30 by weight, and the ratio (A) of the pore volume with a pore diameter of 1 μm or more to the total pore volume of the macropores of the composite particles. and the ratio (B) of the pore volume with a pore diameter of 1 μm or more to the total pore volume of the macropores of the activated carbon particles (A)/(B) is 0.50 to 0.90. (Invention 1).

The present invention also provides metallic iron particles having an average particle diameter of 0.05 to 0.30 μm and a BET specific surface area of 10 to 60 m ² /g, and activated carbon particles having a BET specific surface area of 500 to 1400 m ² /g. , the mixing ratio of the metallic iron particles and the activated carbon particles is 10:90 to 70:30 by weight, and the total amount of the metallic iron particles and the activated carbon particles is 10 to 40% by weight with respect to the water suspension. %, and pulverized and dispersed using a wet pulverizer. , the ratio (A) of the pore volume with a pore diameter of 1 μm or more to the total pore volume of the macropores of the composite particle, and the ratio of the pore volume of the pore diameter of 1 μm or more to the total pore volume of the macropores of the activated carbon particle. A cleaning agent for cleaning soil and groundwater, characterized in that the ratio (A)/(B) to (B) is 0.50 to 0.90 (Invention 2).

In the present invention, metallic iron particles having an average particle diameter of 0.05 to 0.30 μm and a BET specific surface area of 10 to 60 m ² /g are put into water and pulverized and dispersed using a wet pulverizer. and a liquid obtained by putting activated carbon particles having a BET specific surface area of 500 to 1400 m ² /g into water and pulverizing and dispersing them using a wet pulverizer. A cleaning agent for soil/groundwater purification treatment comprising an aqueous suspension containing particles as an active ingredient and having a content of said composite particles of 10 to 40% by weight, wherein said composite particles comprise all macropores of said macropores. The ratio (A) of the pore volume with a pore diameter of 1 μm or more to the volume and the ratio (B) of the pore volume with a pore diameter of 1 μm or more to the total pore volume of the macropores of the activated carbon particles (A)/( B) is 0.50 to 0.90.

Further, in the present invention, the surface of the metal iron particles forms a magnetite phase, and in the X-ray diffraction spectrum of the metal iron particles, the diffraction intensity D110 of the (110) plane _{of α-Fe and the (} 311) The intensity ratio (D110/(D311+D110)) to the diffraction intensity D311 of the plane is 0.30 to 0.95, and the S content is 3500 to 10000 ppm. Any one of claims 1 to 3, wherein 1. The cleaning agent for cleaning soil and groundwater according to item 1 (the present invention 4).

Further, the present invention provides the soil/groundwater purification agent according to any one of claims 1 to 4 for soil contaminated with organic halogen compounds or groundwater contaminated with organic halogen compounds. (Invention 5).

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a soil/groundwater purification agent capable of efficiently and economically treating organic halogen compounds contained in soil or groundwater, and a purification method using the same.

The detailed configuration of the present invention is as follows.

The soil/groundwater purification agent according to the present inventions 1 to 4 is an aqueous suspension containing metallic iron-activated carbon composite particles as an active ingredient. First, metallic iron-activated carbon composite particles (hereinafter referred to as "metallic iron-activated carbon composite particles for purification treatment"), which is an active ingredient of a cleaning agent for soil/groundwater purification treatment, will be described. In the present embodiment, hydrodehalogenation of organic halogen compounds and decomposition of organic halogen compounds are synonymous.

The BET specific surface area value of the metallic iron-activated carbon composite particles for purification treatment is preferably 250 to 1400 m ² /g. When the BET specific surface area value is less than 250 m ² /g, the initial decomposition rate of the organic halogen compounds is high, but the decomposition performance deteriorates early, resulting in a decrease in sustainability, which is not preferable. When the BET specific surface area value exceeds 1400 m ² /g, early deterioration of decomposition performance is small, but decomposition of organic halogen compounds takes a long time. More preferably 300 to 1300 m ² /g, still more preferably 400 to 1300 m ² /g.

The pore volume of the macropores of the metallic iron-activated carbon composite particles for purification treatment is preferably 0.20 mL/g or more. If it is less than 0.20 mL/g, the amount of metal iron particles supported in the macropores of the activated carbon particles is reduced, and the decomposition rate of organic halogen compounds is reduced. More preferably, it is 0.25 mL/g or more. Incidentally, macropores refer to pores having a diameter of 50 nm or more.

The pore volume of macropores having a pore diameter of 1 μm or more in the metallic iron-activated carbon composite particles for purification treatment is preferably 0.08 mL/g or more. If it is less than 0.08 mL/g, the ratio of the metallic iron particles supported in the macropores of the activated carbon particles to the total metallic iron particles tends to be low, and the decomposition rate of the organic halogen compounds tends to be low. More preferably, it is 0.10 mL/g or more.

The average particle size of the metallic iron particles used for the metallic iron-activated carbon composite particles for purification treatment is preferably 0.05 to 0.30 μm. If the average particle size is less than 0.05 μm, the reactivity between the metallic iron particles and water is too high, causing rapid oxidation and formation of goethite on the surface of the metallic iron particles. is not preferred because it inhibits the hydrodehalogenation reaction of If the average particle size exceeds 0.30 μm, the reactivity between the metallic iron particles and water is low, and the reaction rate of hydrodehalogenation with organic halogen compounds is low. In addition, the wet pulverization process at the time of preparation of the purifying agent makes it difficult for the metallic iron particles to invade and be carried in the macropores of the activated carbon particles. More preferably 0.05 to 0.25 μm, still more preferably 0.05 to 0.20 μm.

The BET specific surface area of the metallic iron particles used for the metallic iron-activated carbon composite particles for purification treatment is preferably 10 to 60 m ² /g. When the BET specific surface area value exceeds 60 m ² /g, the initial decomposition rate of organic halogen compounds by the metallic iron-activated carbon composite particles for purification treatment is fast, but the decomposition performance deteriorates early, and the sustainability decreases. occur. When the BET specific surface area value is less than 10 m ² /g, the decomposition performance of the organic halogen compounds by the metallic iron-activated carbon composite particles for purification treatment does not deteriorate early, but it takes a long time to decompose the organic halogen compounds. , the problem to which the present invention is directed cannot be easily solved. More preferably 10 to 50 m ² /g, still more preferably 15 to 50 m ² /g.

The shape of the metallic iron particles used in the metallic iron-activated carbon composite particles for purification treatment is not particularly limited and may be granular, spherical, scaly or the like, but preferably granular or spherical.

It is preferable that the metallic iron particles used for the metallic iron-activated carbon composite particles for purification treatment have an Fe ₃ O ₄ phase formed by oxidizing the surface of the particles in air or water.

The Fe content of the metallic iron particles used for the metallic iron-activated carbon composite particles for purification treatment is preferably 75% by weight or more, more preferably 76 to 98% by weight, and even more preferably 77% by weight relative to the metallic iron particles. ~95% by weight. In addition, in the X-ray diffraction spectrum of the metallic iron particles used for the metallic iron-activated carbon composite particles for purification treatment, the diffraction intensity D110 of the (110) plane of α-Fe and the diffraction intensity D311 of the (311) plane of Fe ₃ O ₄ and the intensity ratio (D110/(D311+D110)) is preferably 0.30 to 0.95. If the intensity ratio is less than 0.30, the purification performance of the organic halogen compounds by the metallic iron-activated carbon composite particles for purification treatment is insufficient, and the intended effect of the present invention cannot be obtained. When the intensity ratio exceeds 0.95, the particle size is extremely large or the BET specific surface area is extremely small and the particles are stable in the air, resulting in significantly inferior decomposition performance of organic halogen compounds. . It is preferably 0.40 to 0.93.

The metallic iron particles used in the metallic iron-activated carbon composite particles for purification treatment preferably contain a small amount of S, and the S content is preferably 3500 to 10000 ppm, more preferably 3500 to 7000 ppm.

The BET specific surface area value of the activated carbon particles used for the metallic iron-activated carbon composite particles for purification treatment is 500 to 1400 m ² /g. When the BET specific surface area value is less than 500 m ₂ /g, the adsorbing action of the organic halogen compounds becomes low, the volume of the macropores of the activated carbon particles becomes small, and the metallic iron particles are not supported in the macropores. it gets harder. If the BET specific surface area exceeds 1400 m ² /g, the adsorption action of organic halogen compounds is enhanced, but hydrodehalogenation by metallic iron particles is difficult to occur. More preferably 600 to 1380 m ² /g, still more preferably 700 to 1350 m ² /g.

The pore volume of the macropores of the activated carbon particles used for the metallic iron-activated carbon composite particles for purification treatment is preferably 0.30 mL/g or more. If it is less than 0.30 mL/g, the amount of metallic iron particles supported in the macropores of the activated carbon particles is reduced, and the decomposition rate of organic halogen compounds is reduced. More preferably, it is 0.35 mL/g or more.

The pore volume with a pore diameter of 1 μm or more in the activated carbon particles used for the metallic iron-activated carbon composite particles for purification treatment is preferably 0.10 mL/g or more. If it is less than 0.10 mL/g, it becomes difficult for the metallic iron particles to invade into the macropores of the activated carbon particles, resulting in a decrease in the supported amount of the metallic particles and a low decomposition rate of the organic halogen compounds. Become. More preferably, it is 0.15 mL/g or more.

The mixing ratio of the metallic iron particles and the activated carbon particles used for the metallic iron-activated carbon composite particles for purification treatment is 10/90 to 70/30 by weight. If the weight ratio is less than 10/90, the metal iron particles do not decompose organic halogen compounds at a sufficient rate. If the weight ratio exceeds 70/30, the adsorption action of the organic halogen compounds by the activated carbon particles is reduced, resulting in a slow hydrodehalogenation reaction by the metallic iron particles. More preferably 10/90 to 60/40, still more preferably 10/90 to 50/50.

The metal iron-activated carbon composite particles for purification treatment have a pore volume ratio (A) with a pore diameter of 1 μm or more to the total pore volume of the macropores of the composite particle powder, and the total pore volume of the macropores of the activated carbon particles. The ratio (A)/(B) to the pore volume ratio (B) having a pore diameter of 1 μm or more is 0.50 to 0.90. When the ratio (A)/(B) is less than 0.50, the amount of organic halogen compounds adsorbed to the macropores of the activated carbon particles is small, and the metal iron particles effectively decompose organic halogen compounds. is difficult to obtain. When the ratio (A)/(B) exceeds 0.90, the amount of the metallic iron particles supported in the macropores of the activated carbon particles is small, and the metallic iron particles effectively decompose organic halogen compounds. is difficult to obtain. The ratio (A)/(B) is preferably 0.60-0.88, more preferably 0.62-0.85.

Next, the cleaning agent for soil/groundwater purification treatment (hereinafter referred to as "cleaning agent") according to the present invention will be described.

The purification agent according to the present invention is an aqueous suspension containing the metallic iron-activated carbon composite particles for purification treatment as an active ingredient, and the content of the metallic iron-activated carbon composite particles for purification treatment in the aqueous suspension is It can be appropriately selected within the range of 10 to 40% by weight, more preferably 10 to 30% by weight. If the content exceeds 40% by weight, the clarifier is thickened, so that it is difficult to transfer the mechanical load during stirring, and it is difficult to uniformly mix the clarifier, making it difficult to adjust the concentration.

The zeta potential at pH 7 of the metallic iron-activated carbon composite particles for purification treatment of the purification agent of the present invention is preferably -5 mV or less. More preferably -10 mV or less.

Next, a method for producing the cleaning agent according to the present invention will be described.

The average particle size of the metallic iron particles used in the cleaning agent according to the present invention is preferably 0.05 to 0.30 μm. If the average particle size is less than 0.05 μm, the reactivity between the metallic iron particles and water is too high, causing rapid oxidation and formation of goethite on the surface of the metallic iron particles. is not preferred because it inhibits the hydrodehalogenation reaction of If the particle size exceeds 0.30 μm, the reactivity of the metallic iron particles with water is low, and the reaction rate of hydrodehalogenation with organic halogen compounds is low. More preferably 0.05 to 0.25 μm, still more preferably 0.05 to 0.20 μm.

The BET specific surface area of the metallic iron particles used in the cleaning agent according to the present invention is preferably 10 to 60 m ² /g. When the BET specific surface area value exceeds 60 m ² /g, the initial decomposition rate of organic halogen compounds by the cleaning agent is high, but the decomposition performance deteriorates early, resulting in a decrease in sustainability. When the BET specific surface area value is less than 10 m ² /g, early deterioration of the decomposition performance of the organic halogen compounds by the cleaning agent is small, but it takes a long time to decompose the organic halogen compounds, which is not the object of the present invention. problems to be solved cannot be easily solved. More preferably 10 to 50 m ² /g, still more preferably 15 to 50 m ² /g.

The shape of the metallic iron particles used in the cleaning agent according to the present invention is not particularly limited and may be granular, spherical, scaly or the like, but preferably granular or spherical.

The metallic iron particles used in the cleaning agent according to the present invention preferably have surfaces that are oxidized in air, water, or the like to form an Fe ₃ O ₄ phase.

The Fe content of the metallic iron particles used in the cleaning agent according to the present invention is preferably 75% by weight or more, more preferably 76 to 98% by weight, and even more preferably 77 to 95% by weight relative to the metallic iron particles. %. In addition, in the X-ray diffraction spectrum of the metallic iron particles used in the cleaning agent according to the present invention, the intensity of the diffraction intensity D110 of the (110) plane of α-Fe and the diffraction intensity D311 of the (311) plane of Fe ₃ O ₄ The ratio (D110/(D311+D110)) is preferably 0.30 to 0.95. If the intensity ratio is less than 0.30, the purification performance of the organic halogen compounds by the present cleaning agent is not sufficient, and it is difficult to obtain the intended effect of the present invention. When the intensity ratio exceeds 0.95, the particle size is extremely large or the BET specific surface area is extremely small and the particles are stable in the air, resulting in significantly inferior decomposition performance of organic halogen compounds. . It is preferably 0.40 to 0.93.

The metallic iron particles used in the cleaning agent according to the present invention preferably contain a small amount of S, and the S content is preferably 3500 to 10000 ppm, more preferably 3500 to 7000 ppm.

The BET specific surface area of the activated carbon particles used in the cleaning agent according to the present invention is 500-1400 m ² /g. When the BET specific surface area value is less than 500 m ² /g, the adsorbing action of the organic halogen compounds becomes low, the volume of the macropores of the activated carbon particles becomes small, and the metallic iron particles are not supported in the macropores. it gets harder. If the BET specific surface area exceeds 1400 m ² /g, the adsorption action of organic halogen compounds is enhanced, but hydrodehalogenation by metallic iron particles is difficult to occur. More preferably 600 to 1380 m ² /g, still more preferably 700 to 1350 m ² /g.

The pore volume of the macropores of the activated carbon particles used in the cleaning agent according to the present invention is preferably 0.30 mL/g or more. If it is less than 0.30 mL/g, the amount of metallic iron particles supported in the macropores of the activated carbon particles is reduced, and the decomposition rate of organic halogen compounds is reduced. More preferably, it is 0.35 mL/g or more.

The pore volume of the activated carbon particles having a pore diameter of 1 μm or more, which is used in the cleaning agent according to the present invention, is 0.10 mL/g. If it is less than 0.10 mL/g, it becomes difficult for the metallic iron particles to invade into the macropores of the activated carbon particles, resulting in a decrease in the supported amount of the metallic particles and a low decomposition rate of the organic halogen compounds. Become. More preferably, it is 0.15 mL/g or more.

The mixing ratio of the metallic iron particles and the activated carbon particles used in the cleaning agent according to the present invention is 10/90 to 70/30 by weight. If the weight ratio is less than 10/90, the metal iron particles do not decompose organic halogen compounds at a sufficient rate. If the weight ratio exceeds 70/30, the adsorption action of the organic halogen compounds by the activated carbon particles is reduced, resulting in a slow hydrodehalogenation reaction by the metallic iron particles. More preferably 10/90 to 60/40, still more preferably 10/90 to 50/50.

The cleaning agent according to the present invention is obtained by putting the metal iron particles and the activated carbon particles into water so that the total solid content concentration is 10 to 40% by weight, and pulverizing and dispersing using a wet pulverizer. be done. By this pulverization and dispersion treatment, the metallic iron particles are impulsively invaded into and supported on the surface of the activated carbon and the macropores to form metallic iron-activated carbon composite particles in which the metallic iron particles and the activated carbon particles are combined.

As a grinding device used for wet grinding, when using media, there are container-driven types such as rolling mills (pot mills, tube mills, conical mills) and vibration mills (fine vibration mills), tower types (tower mills), stirring tank types ( Attritor), circulation tube type (sand grind mill), and annular type (annular mill) can be used. When media are not used, a shear/friction type such as a container rotation type (Ang mill) or a wet high-speed rotation type (colloid mill, homomixer, line mixer) can be used. Especially preferred is media agitation capable of mechanochemically combining metallic iron particles and activated carbon particles by causing the metallic iron particles to impactally invade and support the activated carbon surface and macropores by the shearing force and crushing force of the media. It is a type pulverizer.

The pore volume ratio (A) with a pore diameter of 1 μm or more to the total pore volume of the macropores of the metal iron-activated carbon composite particles of the cleaning agent according to the present invention, and the micropore volume to the total pore volume of the macropores of the activated carbon particles The ratio (A)/(B) to the pore volume ratio (B) having a pore diameter of 1 μm or more is 0.50 to 0.90. When the ratio (A)/(B) is less than 0.50, the amount of organic halogen compounds adsorbed to the macropores of the activated carbon particles becomes small, and the metallic iron particles efficiently adsorb organic halogen compounds. It becomes difficult to obtain the decomposition effect. When the ratio (A)/(B) exceeds 0.90, the amount of the metallic iron particles supported in the macropores of the activated carbon particles is small, and the metallic iron particles efficiently decompose organic halogen compounds. It becomes difficult to obtain the effect. The ratio (A)/(B) is preferably 0.60-0.88, more preferably 0.62-0.85.

A method for producing another cleaning agent according to the present invention will be described.

In the method for producing a purifying agent according to the present invention, metallic iron particles and activated carbon particles are put into water, and the metallic iron particles and activated carbon particles are pulverized and dispersed using a wet pulverizer in a state where they coexist. However, here, the metallic iron particles and the activated carbon particles are separately put into water, and they are separately pulverized and dispersed using a wet pulverizer, and then these two liquids are mixed to obtain a purifying agent. . The properties of the purifying agent thus obtained and the metallic iron-activated carbon composite particles, which are the active ingredients of the purifying agent, are obtained by putting the metallic iron particles and activated carbon particles together into water, and The characteristics are basically the same as those of the purifying agent obtained by pulverizing and dispersing the activated carbon particles in the presence of them using a wet pulverizer and the metallic iron-activated carbon composite particles that are the active ingredient of the purifying agent. .

Next, a method for purifying soil contaminated with organic halogen compounds or groundwater contaminated with organic halogen compounds using the cleaning agent according to the present invention will be described.

Purification of soil contaminated with organic halogen compounds or groundwater contaminated with organic halogen compounds is generally preferably carried out using an in situ decomposition method in which the contained contaminants are decomposed directly underground. .

In the in-situ decomposition method, the purifying agent is introduced into the ground through a boring hole or a borehole using high-pressure air, a gas such as nitrogen, or water as a medium, or a purifying agent and contaminated soil are separated by using an excavation agitating mixer. A method of stirring and mixing is adopted. Since the cleaning agent of the present invention is an aqueous suspension, it may be used as it is or diluted as necessary.

The cleaning agent according to the present invention is preferably diluted so that the solid content concentration of the metallic iron-activated carbon composite particles for cleaning treatment is 0.01 to 10% by weight when used for cleaning treatment.

The amount of the cleaning agent (in terms of solid content) to be added can be appropriately selected according to the degree of contamination of the organic halogen compounds in the soil and groundwater. is preferably 0.01 to 20 parts by weight, more preferably 0.05 to 10 parts by weight. If the content is less than 0.01 part by weight, the intended effects of the present invention cannot be obtained sufficiently. If it exceeds 20 parts by weight, the purification effect is improved, but it is not economical. When contaminated groundwater is targeted, it is preferably added in an amount of 0.01 to 20 parts by weight, more preferably 0.05 to 10 parts by weight, per 100 parts by weight of groundwater.

In the soil/groundwater purification method using the purification agent according to the present invention, the adsorption action of the organic halogen compounds by the activated carbon and the hydrodehalogenation reaction by the metallic iron particles occur almost simultaneously on the surface of the activated carbon particles and in the macropores. , soil and groundwater contamination are purified more quickly and reliably than metal iron particles alone. Efficient mass transfer of metallic iron particles to organic halogen compounds, which was rate-limiting in purification by metallic iron particles, is eliminated by the adsorption action of organic halogen compounds on activated carbon particles by compositing with activated carbon particles. and the hydrodehalogenation reaction by the metallic iron particles is rapidly realized.

<Action>
An important point in the present invention is that organic halogen compounds in soil and groundwater can be efficiently and economically decomposed by using the cleaning agent according to the present invention.

Although the reason why organic halogen compounds in soil and groundwater can be effectively decomposed is not yet clear, the inventor presumes as follows.

That is, in the soil/groundwater purification agent and the soil/groundwater purification method using the agent according to the present invention, the adsorption of organic halogen compounds by activated carbon and the hydrodehalogenation by metallic iron particles Reactions occur almost simultaneously on the surface of the activated carbon particles and inside the macropores, and soil and groundwater contamination are purified more quickly and reliably than with metallic iron particles alone. Efficient mass transfer of metallic iron particles to organic halogen compounds, which was rate-limiting in purification by metallic iron particles, is eliminated by the adsorption action of organic halogen compounds on activated carbon particles by compositing with activated carbon particles. It is thought that the hydrodehalogenation reaction by the metallic iron particles proceeds rapidly.

As described above, by combining the metallic iron particles and the activated carbon particles, the mass transfer of the metallic iron particles to the organic halogen compounds and the decomposition rate of the organic halogen compounds are accelerated. It is possible to carry out purification treatment in a short period of time, and it is particularly suitable for purification of soil and groundwater contaminated with high-concentration organic halogen compounds.

A representative embodiment of the invention is as follows.

<Embodiment of the present invention>
The average major axis diameter and axial ratio of the goethite particle powder were measured using a "transmission electron microscope: JEM-F200" (manufactured by JEOL Ltd.) with a photograph at a magnification of 30,000. The average particle size of the hematite particle powder and the metallic iron-activated carbon composite particle powder for purification treatment was measured using a photograph at a magnification of 30,000 times with a "scanning electron microscope: S-4800" (manufactured by Hitachi High-Tech).

The Fe content and Al content of the metallic iron-activated carbon composite particles for purification treatment were measured using an "inductively coupled plasma atomic emission spectrometer SPS4000" (manufactured by Seiko Electronics Industry Co., Ltd.).

The S content of each particle powder was measured using a “carbon/sulfur analyzer: EMIA-920V2” (manufactured by Horiba, Ltd.).

The specific surface area of each particle powder is shown as a value measured by the BET method using a "specific surface area measuring device: Multisorb 16" (manufactured by Quantachrome).

The crystal phase of each particle powder was identified by measuring in the range of 10 to 90° with an "X-ray diffractometer: NEW D8 ADVANCE" (manufactured by Bruker AXS).

As for the peak intensity ratio of the metallic iron-activated carbon composite particles for purification treatment, the diffraction intensity D110 of the (110) plane of α-Fe and the diffraction intensity D311 of the (311) plane of magnetite are obtained from the results of X-ray diffraction as described above. The intensity ratio was calculated as D110/(D311+D110).

The pore size distribution of macropores (50 nm or more) of each particle powder was measured using a "pore size distribution measurement device: Autopore V9620" (manufactured by Micromeritics).

<Purification treatment evaluation of organic halogen compounds in simulated groundwater and wastewater>
<Preparation of Calibration Curve: Quantification of Organic Halogen Compounds>
Concentrations of organic halogen compounds were calculated based on the obtained calibration curve, which was prepared in advance using the following procedure.
Trichlorethylene (TCE: _C2HCl3 ): molecular weight _131.39
Reagent special grade (99.5%), density (20°C) 1.461-1.469 g/mL
Three levels of trichlorethylene, 1.0 μL, 2.0 μL, and 3.5 μL, were added to 100 mL of brown vial bottle with 40 mL of ion-exchanged water, then trichlorethylene was injected into each level, and immediately covered with a rubber stopper with a fluororesin liner. and firmly tighten it with an aluminum seal. After allowing the vial to stand at 30° C. for 20 minutes, 0.5 mL of the gas in the headspace is taken with a syringe, and trichlorethylene is measured using “SRI8610C” (manufactured by SRI). Assuming that trichlorethylene is not decomposed at all, the relationship between the added amount and the peak area is obtained. The column at this time is a capillary column (Ultra Alloy-624: manufactured by Frontier Laboratories, liquid phase: cyanopropylphenylmethylpolysiloxane), He gas (25 mL / min) is used as the carrier gas, and the temperature is maintained at 50 ° C. for 1 minute. After that, the temperature is raised to 120° C. at a rate of 10° C./min, and the gas is analyzed.

<Sample preparation for measuring organic halogen compounds>
Into a 100-mL brown vial, 0.132 g of a purifying agent as the metal iron-activated carbon composite particles for purification treatment and an amount of ion-exchanged water, including the water content in the purifying agent, of 40.0 mL were injected. Next, 1.3 μL of trichlorethylene is injected, immediately covered with a rubber stopper with a fluororesin liner, tightly tightened with an aluminum seal, and left to react.

<Evaluation Method for Decomposition Reaction of Organic Halogen Compounds (Measurement of Trichlorethylene Decomposition Rate)>
The vial was allowed to stand at 30° C., and after a predetermined reaction time, 0.5 mL of gas was collected from the headspace in the vial with a syringe. In addition, the fractionation of the gas is performed by measuring the residual concentration of trichlorethylene at a predetermined time by the batch method using the above "SRI8610C" (manufactured by SRI), and the decomposition rate of trichlorethylene (1 - (concentration after reaction / before reaction Concentration at <0 hours after standing>)) was calculated.

The qualitative analysis of the decomposition products was carried out using the aforementioned "SRI8610C" (manufactured by SRI) and "GC-2014" (manufactured by Shimadzu Corporation). "Porapak Q" (manufactured by Waters) was used as the GC filler of "GC-2014".

<Production of Metallic Iron Particle Powder 1>
After adding 704 L of 1.16 mol/L Na ₂ CO ₃ aqueous solution into a reaction vessel maintained in a non-oxidizing atmosphere by flowing N ₂ gas at a rate of 3.4 cm/s, Fe ²⁺ 1.35 mol/ 296 L of ferrous sulfate aqueous solution containing L was added and mixed (the amount of Na ₂ CO ₃ corresponds to 2.0 times the equivalent of Fe) to generate FeCO ₃ at a temperature of 47°C.

Into the aqueous solution containing FeCO ₃ obtained here, continuously, while blowing N ₂ gas at a rate _of 3.4 cm per second, the temperature was kept at 47 ° C. for 70 minutes. 2.8 cm/s of air was passed through the chamber for 5.0 hours to form goethite particles. The pH during air ventilation was 8.5 to 9.5.

To the obtained suspension containing goethite particles, 20 L of an Al sulfate aqueous solution containing 0.3 mol/L of Al ³⁺ was added, thoroughly stirred and then washed with water using a filter press. The powder was extruded with a molding plate having a hole diameter of 4 mm and dried at 120° C. to obtain granules of goethite particle powder.

The goethite particles contained in the obtained granules were spindle-shaped particles having an average major axis diameter of 0.30 μm and an axial ratio (major axis diameter/minor axis diameter) of 12.5. The BET specific surface area was 85 m ² /g, the Al content was 0.13% by weight, and the S content was 400 ppm.

The granules are heated at 300° C. to form hematite particles and dry pulverized. After that, water is encountered and 70% sulfuric acid is added at a rate of 10 mL/kg and stirred. Thereafter, the cake was dehydrated to obtain a press cake, extruded using a compression molding machine through a molding plate having a hole diameter of 3 mm, and dried at 120° C. to obtain granules of hematite particle powder.

The hematite particles constituting the obtained granules were spindle-shaped particles having an average major axis diameter of 0.24 μm and an axial ratio (major axis diameter/minor axis diameter) of 10.7. The S content was 3300 ppm.

100 g of the granules of the hematite particle powder was introduced into a fixed bed reduction apparatus and reduced to complete α-Fe at 450° C. for 180 minutes while passing H ₂ gas. Next, after switching to N ₂ gas and cooling to room temperature, the oxygen partial pressure was gradually increased to the same ratio as air to form a stable oxide film on the particle surface, and metallic iron particle powder 1 was obtained. The metallic iron particle powder 1 obtained here is mainly composed of α-Fe, and has an average particle diameter of 0.09 μm, a BET specific surface area of 25 m ² /g, an Fe content of 87.2 wt%, an Al content of 0.22 wt%, The S content was 4000 ppm. X-ray diffraction confirmed the presence of α-Fe and Fe ₃ O ₄ . The intensity ratio D110/(D110+D311) between D110 (α-Fe) and D311 (Fe ₃ O ₄ ) was 0.90.

<Production of Metallic Iron Particle Powder 2>
12.8 L of ferrous sulfate aqueous solution containing 1.50 mol/L of Fe ²⁺ and 30.2 L of 0.44-N NaOH aqueous solution (corresponding to 0.35 equivalents to Fe ²⁺ in the ferrous sulfate aqueous solution) were mixed to produce a ferrous sulfate aqueous solution containing Fe(OH) ₂ at pH 6.7 and temperature 38°C. Then, air was passed through the ferrous sulfate aqueous solution containing Fe(OH) ₂ at a temperature of 40° C. at a rate of 130 L/min for 3.0 hours to generate goethite core particles.

7.0 L of 5.4N Na ₂ CO ₃ aqueous solution (remaining ferrous sulfate 1.5 equivalents to Fe ²⁺ in the aqueous iron solution) was added, and air was passed at 130 L/min for 4 hours at a pH of 9.4 and a temperature of 42° C. to generate goethite particles. To the obtained suspension containing goethite particles, 0.96 L of an Al sulfate aqueous solution containing 0.3 mol/L of Al ³⁺ was added, thoroughly stirred, washed with water using a filter press, and the obtained press cake was compressed. Using a molding machine, the product was extruded with a molding plate having a hole diameter of 4 mm and dried at 120° C. to obtain granules of goethite particle powder.

The goethite particles contained in the obtained granules were acicular particles with an average major axis diameter of 0.33 μm and an aspect ratio (major axis diameter/minor axis diameter) of 25.0. The BET specific surface area was 70 m ² /g, the Al content was 0.42% by weight, and the S content was 4000 ppm.

After heating the goethite granules at 330° C. to form hematite particles, 100 g of the _hematite granules were introduced into a fixed bed reduction apparatus, and completely α- It was reduced to Fe. Next, after switching to N ₂ gas and cooling to room temperature, the oxygen partial pressure was gradually increased to the same ratio as air to form a stable oxide film on the particle surface, and metal iron particles 2 were obtained. The metallic iron particles 2 obtained here are mainly composed of α-Fe, and have an average particle diameter of 0.11 μm, a BET specific surface area of 20 m ² /g, an Al content of 0.68 wt%, an Fe content of 85.9 wt%, S The content was 5500 ppm. X-ray diffraction confirmed the presence of α-Fe and Fe ₃ O ₄ . The intensity ratio D110/(D110+D311) between D110 (α-Fe) and D311 (Fe ₃ O ₄ ) was 0.88.

<Metal iron particle powder 3>
Scaly pieces having an average particle size of 75 μm and a BET specific surface area of 0.88 m ² /g were used, which were obtained by mechanically pulverizing pure iron lathe chips with a ball mill.

<Activated carbon particle powder>
Activated carbon particle powders (commercial products) 1 and 2 having properties shown in Table 1 below were used. Charcoal particle powder was used as the activated carbon particle powder 3 .

<Production of cleaning agent 1>
First, 125 g of metal iron particle powder, 164 g of activated carbon particle powder, and 226 g of ion-exchanged water were first mixed in a jar tester for 1 minute, and then the mixture was passed through a vertical batch-type wet bead mill (manufactured by Imex, effective volume Purification agent 1 containing 28% by weight (solid content concentration) of composite metal iron-activated carbon composite particles for purification treatment was prepared by performing pulverization and mixing treatment for 60 minutes with 800 mL of pulverization media (2 mm diameter glass beads). Purification agent 1 was subjected to solid-liquid separation using 5C filter paper (manufactured by Advantech, pore size 1 μm), dried at 40° C., and metallic iron-activated carbon composite particles for purification treatment were taken out and evaluated for structure and physical properties.

<Production of purification agents 2 to 11>
Except for varying the type of metallic iron particle powder, the type of activated carbon particle powder, the mixing ratio of the metallic iron particle powder and the activated carbon particle powder, and the content of the metallic iron-activated carbon composite particles for purification treatment in the purification agent, the above-mentioned A cleaning agent was obtained in the same manner as in the embodiment of the invention.

Table 2 shows the production conditions at this time, and Table 3 shows various characteristics of the obtained cleaning agent.

<Evaluation results for purification treatment of organic halogen compounds in simulated groundwater and wastewater>
Usage example 1
According to the evaluation method, when the cleaning agent 1 was used, the decomposition rate of trichlorethylene was 99.9% after 2 days and 100.0% after 7 days. Ethylene was confirmed as the main decomposition product by the reaction.

Usage Examples 2-4, Comparative Usage Examples 1-7
As in Use Example 1, using the cleaning agents of Examples 2 to 4 and Comparative Examples 1 to 7, the trichlorethylene decomposition rate was measured after 2 days and 7 days.

Table 4 shows the processing conditions and measurement results at this time. In Comparative Use Examples 1, 3, 5 and 6, 1,2-dichloroethylene (DCE), which is a harmful by-product, was detected. In Comparative Example 7, no decomposition products were detected (only trichlorethylene adsorption).

Claims (5)

Composite particles composed of metallic iron particles having an average particle diameter of 0.05 to 0.30 μm and a BET specific surface area of 10 to 60 m ² /g and activated carbon particles having a BET specific surface area of 500 to 1400 m ² /g are effective. A cleaning agent for soil and groundwater purification treatment comprising a water suspension containing as a component,
The total pore volume of the macropores of the composite particles is 0.20 mL/g or more,
The mixing ratio of the metallic iron particles and the activated carbon particles is 10:90 to 70:30 by weight,
The ratio (A) of the pore volume with a pore diameter of 1 μm or more to the total pore volume of the macropores of the composite particles, and the ratio of the pore volume of the pore diameters of 1 μm or more to the total pore volume of the macropores of the activated carbon particles ( A cleaning agent for cleaning soil and groundwater, wherein the ratio (A)/(B) to B) is 0.50 to 0.90. Metallic iron particles having an average particle size of 0.05 to 0.30 μm and a BET specific surface area of 10 to 60 m ² /g, and activated carbon particles having a BET specific surface area of 500 to 1400 m ² /g, are combined with the metallic iron particles. and the activated carbon particles in a weight ratio of 10:90 to 70:30, and the total amount of the metallic iron particles and the activated carbon particles is 10 to 40% by weight with respect to the water suspension. A cleaning agent for soil and groundwater purification treatment comprising an aqueous suspension containing composite particles as an active ingredient obtained by pulverizing and dispersing using a wet pulverizer,
The ratio (A) of the pore volume with a pore diameter of 1 μm or more to the total pore volume of the macropores of the composite particles, and the ratio of the pore volume of the pore diameters of 1 μm or more to the total pore volume of the macropores of the activated carbon particles ( A cleaning agent for cleaning soil and groundwater, wherein the ratio (A)/(B) to B) is 0.50 to 0.90. Metallic iron particles having an average particle diameter of 0.05 to 0.30 μm and a BET specific surface area of 10 to 60 m ² /g are put into water and pulverized and dispersed using a wet pulverizer. Composite particles obtained by mixing a liquid and a liquid obtained by putting activated carbon particles having a BET specific surface area of 500 to 1400 m ² /g into water and pulverizing and dispersing them using a wet pulverizer as an active ingredient. A cleaning agent for soil/groundwater purification treatment comprising an aqueous suspension containing the composite particles in an amount of 10 to 40% by weight,
The ratio (A) of the pore volume with a pore diameter of 1 μm or more to the total pore volume of the macropores of the composite particles, and the ratio of the pore volume of the pore diameters of 1 μm or more to the total pore volume of the macropores of the activated carbon particles ( A cleaning agent for cleaning soil and groundwater, wherein the ratio (A)/(B) to B) is 0.50 to 0.90. The surface of the metal iron particles forms a magnetite phase, and in the X-ray diffraction spectrum of the metal iron particles, the diffraction intensity D110 of the (110) plane of α-Fe and the diffraction of the (311) plane of Fe ₃ O ₄ The intensity ratio (D110/(D311+D110)) to the intensity D311 is 0.30 to 0.95, and the S content is 3500 to 10000 ppm. purification agent for soil and groundwater purification treatment. Purification of soil contaminated with organic halogen compounds or groundwater contaminated with organic halogen compounds using the cleaning agent for soil/groundwater purification treatment according to any one of claims 1 to 4. A method for purifying soil and groundwater, characterized by: