JP4433173B2 - Iron composite particle powder for purification treatment of soil and groundwater, production method thereof, purification agent containing the iron composite particle powder, production method thereof, and purification treatment method of soil and groundwater - Google Patents

Description

  The present invention relates to dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, 1,1,1-trichloroethane, 1,1,2, contained in soil or groundwater. -Efficient use of aliphatic organic halogen compounds such as trichloroethane, trichlorethylene, tetrachloroethylene and 1,3-dichloropropene, aromatic organic halogen compounds such as dioxins and PCB, heavy metals such as cadmium, lead, chromium, arsenic, selenium and cyanide It provides a cleansing agent that can be decomposed and insolubilized well, economically and economically.

  Aliphatic organic halogen compounds such as trichlorethylene and tetrachloroethylene are widely used for cleaning in semiconductor factories and for degreasing metalworking metals.

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

  In addition, PCB (polychlorinated biphenyl) is chemically and thermally stable, has excellent electrical insulation properties, and has been frequently used as an insulating oil, plasticizer, and heat medium for transformers and capacitors, but is harmful. Therefore, production and use are prohibited. However, an effective processing method for PCBs used in the past has not been established, and most of them are stored without being processed.

  Organic halogen compounds such as aliphatic organic halogen compounds and aromatic organic halogen compounds are difficult to decompose and are carcinogenic or highly toxic. Therefore, contamination by organic halogen compounds in soil and groundwater is serious. Has become a serious environmental problem.

  That is, when the organic halogen compounds are discharged, since the organic halogen compounds are hardly decomposable, the organic halogen compounds are accumulated in the discharged soil and contaminated with the organic halogen compounds. It will be contaminated by compounds. Furthermore, since groundwater spreads in surrounding areas other than contaminated soil, contamination with organic halogen compounds becomes a problem in a wide range.

  Since soil cannot be reused or redeveloped in soil contaminated with organohalogen compounds, various technical means have been proposed as a purification method for soil and groundwater contaminated with organohalogen compounds. However, since organic halogen compounds are hardly decomposable and a large amount of soil and groundwater are treated, an efficient and economical purification technology has not yet been established.

  As a purification method for soil contaminated with organic halogen compounds, a method of purification using various catalysts, a method of removing by suction using the volatility of organic halogen compounds, excavation of soil and detoxification by heat treatment There are known thermal decomposition methods and methods utilizing microorganisms. In addition, 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 removing organic halogen compounds by pumping groundwater, and the like are known. .

  Among the technical means proposed as a purification method for soil and groundwater contaminated with organohalogen compounds, soil and groundwater contaminated with organohalogen compounds and a cleaning agent using iron-based particles are mixed and contacted. Technical means for detoxification have been proposed (Patent Documents 1 to 8).

  On the other hand, soil and groundwater contamination by heavy metals has attracted attention due to recent environmental awareness improvements. In particular, since contamination with toxic substances such as cadmium, lead, chromium, arsenic, selenium, cyanide and other heavy metals is harmful to the human body or ecosystem, there is an urgent need to clean and remove the toxic substances. .

  As is well known, countermeasures for soil or groundwater contaminated with toxic substances such as heavy metals are categorized as “purification technology” and “containment”. “Excavation removal”. “In-situ purification” further includes “in-situ decomposition” in which heavy metals contained in contaminated soil and groundwater are decomposed underground (in-situ), and “in-situ removal” that removes heavy metals from extracted or excavated contaminated soil and groundwater. It is divided into “extraction”.

  “In-situ extraction” refers to “decomposition” that decomposes compounds such as cyanide and pesticides among the target substances classified as heavy metals, etc., and heavy metals concentrated by physical separation from soil and groundwater. There is "separation" to separate.

  On the other hand, “containment” is classified into “in-situ containment” and “containment after excavation and removal”. In-situ containment is a technique in which a contaminated soil is mixed with a solidifying agent and solidified, and then the contaminated soil is contained in-situ without moving on-site soil. Containment after excavation and removal is a technique in which an insolubilizing agent is mixed in the contaminated soil as a pretreatment to make it insoluble, and after excavation is performed once, the contaminated soil is contained again.

  Construction methods related to “Purification Technology” include soil washing method, thermal desorption method, etc., for example, chemical dissolution method that adds chemicals and dissolves and separates heavy metals, etc., washing and classifying soil with water , Water washing method for separating fine particles containing a lot of heavy metals, etc., cleaning contaminants adhering to the surface of soil particles with a cleaning agent, and classifying them into clean large particles and contaminant fine particles according to the size and specific gravity of the particles Examples include soil wet cleaning.

  In addition, the construction method related to “containment” is “in-situ containment”, in which there is a method of mixing a contaminated soil with a solidifying agent such as cement and containing it with an impermeable layer and a steel sheet pile, etc. There is a method in which the contaminated soil is insolubilized with a chemical to change the contaminated soil into a form in which it is difficult to elute, and is then contained by a barrier or water barrier.

  However, each processing technique is expensive and requires a long period of time, and it is difficult to say that it is a technique that efficiently and continuously reduces harmful substances such as heavy metals.

  Recently, a low-cost processing technique has been developed that mainly uses the reducing action of iron powder to reduce the valence of heavy metals and render them harmless and stable. For example, a technique using a reduction action of iron powder (reduction of metal valence) against chromium is described (Patent Document 5). Further, in Patent Document 9, when a solution containing heavy metal ions is adjusted to about pH 5-6, and iron powder is added and stirred, part of the iron powder is dissolved and ferric hydroxide precipitates, and pH It is described that goethite and rapid crosite are formed with the rise in the temperature, and in this case, a part of heavy metals are co-precipitated and most of them are adsorbed to the iron powder. It is described that it increases and the adsorption removal effect deteriorates.

Japanese Patent Application Laid-Open No. 11-235577 JP 2000-5740 A JP 2000-334063 A JP 2001-38341 A JP 2001-198567 A JP 2002-161263 A JP 2002-210452 A JP 2002-317202 A Japanese Patent Publication No. 52-45665

  Patent Document 1 discloses a technique for detoxifying organic halogen compounds in soil by adding and mixing iron powder containing 0.1% by weight or more of carbon to the soil. Although the surface area and particle size are described, it is difficult to say that the organic halogen compound can be sufficiently reduced because the particle size is large.

  In addition, Patent Document 2 discloses a technique for detoxifying organic halogen compounds in soil using iron powder containing copper. However, since it requires a long time to decompose the organic halogen compounds, efficiency is improved. It is difficult to say that organic halogen compounds can be rendered harmless.

  Patent Document 3 discloses a technique for detoxifying dioxins by bringing dioxins into contact with an acidic aqueous hydrochloric acid solution containing mill scale generated from a hot-rolled steel sheet manufacturing process at a steel mill at a temperature lower than 100 ° C. However, an aqueous hydrochloric acid solution that promotes detoxification is essential, and it is difficult to say that the decomposition reaction of the mill scale itself is sufficient.

  Moreover, although the above-mentioned patent document 4 discloses a soil purifier comprising an aqueous suspension containing iron particles having an average particle diameter of 1 to 500 μm, the particle size is large and the organic halogen compound is sufficiently decomposed. It becomes difficult.

  In addition, Patent Document 5 discloses a technique using an aqueous suspension containing spherical iron particles having an average particle diameter of less than 10 μm. The aqueous suspension containing spherical iron particles is used for steelmaking. It is a water suspension obtained by collecting exhaust gas generated during refining from an oxygen blowing converter and removing the gas, and it is difficult to say that organic halogen compounds can be sufficiently reduced.

  In addition, the aforementioned Patent Document 6 describes an iron powder for decomposing 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, the iron powder obtained by mill scale and the iron powder obtained by water atomization of the molten steel are used. From the specific surface area of the iron powder described, the particle size of the iron powder seems to be large. It is difficult to say that the compound can be sufficiently reduced.

  Further, in the above-mentioned Patent Document 7, it is described that iron powder containing S is used for purification treatment of soil / groundwater contaminated with an organic halogen compound, but the particle size is large and the organic halogen compound is sufficient. It is hard to say that it can be reduced.

  In addition, in the aforementioned Patent Document 8, it is described that the iron composite particle powder containing magnetite is used for the purification treatment of soil / groundwater contaminated with an organic halogen compound, but does not contain S, It is difficult to say that organic halogen compounds can be sufficiently reduced.

  In addition, the above-mentioned Patent Document 5 describes a detoxification and stabilization treatment method using the reduction action (valence reduction) of iron powder. However, over the years, the sustainability of the reduction action of iron powder is improved. Even if the heavy metal is harmless and has a stable valence, the valence may rise again and turn into a harmful metal, which is not a permanent measure.

In the technique described in Patent Document 9, the action of iron powder is mainly reduction or adsorption. Although there is an effect due to partial dissolution, it is a mechanism in which goethite, rapid crosite and magnetite are generated and taken in via the elution of iron powder in the acidic region, and in the processing technology using iron powder, Fe It is not a technique that actively utilizes the phenomenon of spinel ferrite formation while taking in heavy metals by dissolution of ²⁺ or Fe ³⁺ .

  Therefore, the present invention is technically intended to provide a purification method using iron composite particles that can efficiently and continuously and economically treat organic halogen compounds and / or heavy metals contained in soil and groundwater. Let it be an issue.

  The technical problem can be achieved by the present invention as follows.

That is, the present invention is an iron composite particle powder comprising α-Fe and magnetite used for purification treatment of soil and groundwater contaminated with organic halogen compounds and / or heavy metals, and the X-ray of the iron composite particle powder In the diffraction spectrum, the intensity ratio (D ₁₁₀ / (D ₃₁₁ + D ₁₁₀ )) between the diffraction intensity D ₁₁₀ of the (110) plane of α-Fe and the diffraction intensity D ₃₁₁ of the (311) plane of magnetite is 0.30-0. It is an iron composite particle powder for purification treatment of soil and groundwater, characterized in that it has an Al content of 0.10 to 1.50 wt% and an S content of 3500 to 7000 ppm (this invention) 1).

In the present invention, the saturation magnetization value is 85 to 155 Am ² / kg, the BET specific surface area is 5 to 60 m ² / g, and the crystallite size of the (110) plane of α-Fe is 200 to 400 mm. The iron composite particle powder for purification treatment of soil and groundwater of the present invention 1 according to the present invention 1 having an average particle diameter of 0.05 to 0.50 μm (present invention 2).

  Further, the present invention is a soil / groundwater purification agent comprising a water suspension containing the iron / composite powder for soil / groundwater purification treatment of the present invention 1 or 2 as an active ingredient (invention 3).

  The present invention also provides a goethite particle powder having an average major axis diameter of 0.05 to 0.50 μm and an Al content of 0.06 to 1.00% by weight or an average major axis diameter of 0.05 to 0. A hematite particle powder having an Al content of 0.07 to 1.13% by weight is heat-reduced in a temperature range of 350 to 600 ° C. to obtain an iron particle powder. After cooling, the iron particle powder is It is taken out in water without forming a surface oxide film in the gas phase, and then dried after forming a surface oxide film on the particle surface of the iron particle powder in water. This is a method for producing iron composite particle powder for purification treatment of groundwater (present invention 4).

  The present invention also provides a goethite particle powder having an average major axis diameter of 0.05 to 0.50 μm, an Al content of 0.06 to 1.00% by weight, and an S content of 2200 to 4500 ppm. A hematite particle powder having an average major axis diameter of 0.05 to 0.50 μm, an Al content of 0.07 to 1.13 wt%, and an S content of 2400 to 5000 ppm is obtained at a temperature of 350 to 600 ° C. Heat reduction in the range to make iron particle powder, after cooling, the iron particle powder is taken out in water without forming a surface oxide film in the gas phase, and a surface oxide film is formed on the particle surface of the iron particle powder in water Thus, the method for producing a soil / groundwater purifier of the present invention 3 is characterized in that an aqueous suspension containing iron composite particle powder is obtained (invention 5).

Further, the present invention is a purifier obtained by preserving a purifier comprising an aqueous suspension containing the iron composite particle powder comprising α-Fe and magnetite of the present invention 3 as an active ingredient for a long period of time. The purification agent contains coarse particles having a particle size of 0.1 to 5.0 μm, and the diffraction intensity D ₁₁₀ of the (110) plane of α-Fe in the X-ray diffraction spectrum of the entire iron composite particle powder; A soil / groundwater purifier having an intensity ratio (D ₁₁₀ / (D ₁₁₀ + D ₃₁₁ )) of the diffraction intensity D ₃₁₁ of the (311) plane of magnetite between 0.20 and 0.80 ( Invention 6).

Further, the present invention provides the soil / groundwater purification agent of the invention 6, wherein the iron composite particle powder in the purification agent has a saturation magnetization value of 70 to 140 Am ² / kg, and the (110) plane of α-Fe. This is a soil / groundwater purifier having a crystallite size of 200 to 400 mm (Invention 7).

  Further, the present invention is the soil or groundwater purification agent of the present invention 6 or 7, wherein the iron composite particle powder in the purification agent has an Fe content of 65 to 80% by weight based on the total particle powder. It is a soil / groundwater purification agent characterized (present invention 8).

  In addition, the present invention is contaminated with the soil or organic halogen compounds and / or heavy metals contaminated with the iron composite particle powder for purification treatment of soil / groundwater of the present invention 1 or 2 and the organic halogen compounds and / or heavy metals. It is a method for purifying soil and groundwater, wherein the groundwater is mixed and contacted (present invention 9).

  In addition, the present invention is contaminated with soil or organic halogen compounds and / or heavy metals contaminated with the soil / groundwater purification agent of any of the present inventions 3, 6, 7 and 8 and organic halogen compounds and / or heavy metals. A method for purifying soil and groundwater, wherein the groundwater is mixed and contacted (present invention 10).

  Since the iron composite particle powder for purification treatment according to the present invention can efficiently decompose and insolubilize organic halogen compounds and / or heavy metals, it can be used as a purification agent for soil and groundwater contaminated with organic halogen compounds and / or heavy metals. Is preferred.

  The configuration of the present invention will be described in detail as follows.

  First, an iron composite particle powder for purification treatment of soil and groundwater according to the present invention 1 or 2 (hereinafter referred to as “iron composite particle powder for purification treatment”) will be described.

The constituent phase of the iron composite particle powder for purification treatment contains an Fe ₃ O ₄ phase together with the α-Fe phase. In the X-ray diffraction spectrum of the iron composite particle powder, the content of Fe ₃ O ₄ is the diffraction intensity D ₁₁₀ of the (110) plane of α-Fe and the diffraction intensity D ₃₁₁ of the (311) plane of Fe ₃ O ₄ . The intensity ratio (D ₁₁₀ / (D ₃₁₁ + D ₁₁₀ )) is 0.30 to 0.95. When the strength ratio immediately after production is less than 0.30, the abundance ratio of the α-Fe phase is low, so the purification performance of the organic halogen compounds is not sufficient, and it is difficult to easily obtain the intended effect of the present invention. Become. When the strength ratio exceeds 0.95, the abundance ratio of the α-Fe phase is sufficient, but the abundance ratio of the Fe ₃ O ₄ phase produced in the present invention is lowered, and the catalyst activity is prematurely deteriorated and sustained. Therefore, the intended effect of the present invention cannot be obtained. Preferably it is 0.32-0.95. Fe ₃ O ₄ is preferably present on the particle surface of the iron composite particle powder for purification treatment.

  The S content of the iron composite particle powder for purification treatment according to the present invention is 3500 to 7000 ppm. When the S content is less than 3500 ppm, the purification performance of the organic halogen compounds is not sufficient, and the intended effect of the present invention cannot be obtained. When it exceeds 7000 ppm, there is a purification performance of organic halogen compounds, but even if it is contained in a large amount, the effect is saturated and it is not economical. Preferably it is 3800-7000 ppm, More preferably, it is 3800-6500 ppm.

The Al content of the iron composite particle powder for purification treatment according to the present invention is 0.10 to 1.50% by weight. When the Al content is less than 0.10% by weight, it tends to be a hard granulated product due to volume shrinkage of the granulated product, and therefore labor is required when performing wet grinding. When the amount exceeds 1.50% by weight, the reduction reaction proceeds slowly and requires a long time for the reduction reaction. Also, the crystal growth cannot be sufficiently performed, the α-Fe phase becomes unstable, and a thick oxide film is formed on the particle surface, or the phase change from the Fe ₃ O ₄ phase to the α-Fe phase during the heating reduction Is insufficient, it becomes difficult to increase the abundance ratio of the α-Fe phase, and the intended effect of the present invention cannot be obtained. Preferably it is 0.20 to 1.20% by weight.

  The particle shape of the iron composite particle powder for purification treatment according to the present invention is preferably granular. In the present invention, the spindle-shaped or needle-shaped goethite particle powder or hematite particles are subjected to heat reduction treatment as they are, so that when undergoing crystal transformation to the α-Fe phase, the particle shape collapses and undergoes an isotropic growth process, so that the granular shape It becomes. On the other hand, if the particle size is the same in the spherical shape, the BET specific surface area is decreased and the catalytic activity is decreased.

The average particle diameter of the iron composite particle powder for purification treatment according to the present invention is preferably 0.05 to 0.50 μm. When the average particle size is less than 0.05 μm, the α-Fe phase is unstable, so that a thick oxide film is formed on the surface, making it difficult to increase the abundance ratio of the α-Fe phase. The effect is not obtained. If it exceeds 0.50 μm immediately after production, the abundance ratio of the α-Fe phase can be increased, but the abundance ratio of the Fe ₃ O ₄ phase is relatively lowered, leading to early deterioration of catalytic activity and deterioration of maintainability. For this reason, the object of the present invention cannot be easily solved. More preferably, it is 0.05-0.30 micrometer.

The crystallite size (α-Fe (110) plane) of the iron composite particle powder for purification treatment according to the present invention is preferably 200 to 400 mm. If it is less than 200%, it is difficult to increase the abundance ratio of the α-Fe phase, and it becomes difficult to obtain the intended effect of the present invention. If it exceeds 400%, the abundance ratio of the α-Fe phase can be increased, but it is difficult to maintain the abundance ratio of the Fe ₃ O ₄ phase produced in the present invention to such an extent that the intended effect of the present invention can be obtained. It becomes. More preferably, it is 200-350cm.

The BET specific surface area value of the iron composite particle powder for purification treatment according to the present invention is preferably 5 to 60 m ² / g. When it is less than 5 m ² / g, the contact area is small, and the catalytic activity is hardly exhibited. When it exceeds 60 m ² / g, it is difficult to increase the abundance ratio of the α-Fe phase, and it becomes difficult to obtain the intended effect of the present invention. More preferably, it is 7-55 m < ² > / g.

The saturation magnetization value of the iron composite particle powder for purification treatment according to the present invention is preferably 85 to 155 Am ² / kg (85 to 155 emu / g). When the saturation magnetization value of the iron composite particle powder for purification treatment immediately after production is less than 85 Am ² / kg, the abundance ratio of the α-Fe phase is low, and the object of the present invention is easily solved. I can't. When it exceeds 155 Am ² / kg, the abundance ratio of the α-Fe phase can be increased, but the abundance ratio of the Fe ₃ O ₄ phase obtained by the present invention should be maintained to such an extent that the intended effect of the present invention can be obtained. It becomes difficult. As a result, the abundance ratio of the Fe ₃ O ₄ phase is relatively low, leading to early deterioration of catalyst activity and a decrease in maintainability. Therefore, the object of the present invention cannot be easily solved. More preferably, it is 90-155 Am < ² > / kg (90-155 emu / g).

  The Fe content of the iron composite particle powder for purification treatment according to the present invention is preferably 75% by weight or more based on the total particle powder. When the Fe content immediately after the production is less than 75% by weight, the catalytic activity is lowered, so that it is difficult to easily obtain the intended effect of the present invention. More preferably, it is 75 to 98% by weight, and still more preferably 75 to 90% by weight.

  In the iron composite particle powder for purification treatment according to the present invention, metallic elements other than Fe, such as Pb, Cd, As, Hg, Sn, Sb, Ba, Zn, Cr, Nb, Co, and Bi, are toxic metals. Therefore, it is preferable not to contain as much as possible. In particular, when high purity and catalytic performance are taken into consideration, when the elution amount of each metal is measured by the method described later for the iron composite particle powder for purification treatment, the elution amount of cadmium is 0.01 mg / l or less, No elution was detected in cyan, lead elution amount was 0.01 mg / l or less, chromium elution amount was 0.05 mg / l or less, arsenic elution amount was 0.01 mg / l or less, and total mercury elution amount was 0. It is preferable that the elution amount of selenium is 0.01 mg / l or less, the elution amount of fluorine is 0.8 mg / l or less, and the elution amount of boron is 1 mg / l or less.

  Further, regarding the iron composite particle powder for purification treatment, when the content of each metal is measured by the method described later, the content of cadmium and its compound is 150 mg / kg or less, the content of cyanide compound is 50 mg / kg or less, lead And its compound content is 150 mg / kg or less, hexavalent chromium compound content is 250 mg / kg or less, arsenic and its compound content is 150 mg / kg or less, mercury and its compound content is 15 mg It is preferable that the content of selenium and its compound is 150 mg / kg or less, the content of fluorine and its compound is 4000 mg / kg or less, and the content of boron and its compound is 4000 mg / kg or less.

  The iron composite particle powder for purification treatment may be in the form of a granulated product.

  Next, the soil / groundwater purification agent (hereinafter referred to as “purification agent”) contaminated with the organic halogen compounds according to the third aspect of the present invention will be described.

  The purification agent according to the present invention 3 is a water suspension containing, as an active ingredient, the iron composite particle powder for purification treatment according to the first or second aspect of the present invention, in the aqueous suspension of the iron composite particle powder for purification treatment. Content can be suitably selected within the range of 0.5-50 weight part, More preferably, it is 1-30 weight part.

  When the particle size distribution of the iron composite particles constituting the purifier according to the present invention is measured using a laser diffractometer, the particle size distribution of secondary particles of the iron composite particles is preferably a single peak. When it has a plurality of peaks, the penetration rate into the contaminated soil is not uniform, and it takes a long time for purification, and it becomes difficult to obtain the intended effect of the present invention.

The median diameter of secondary particles of the iron composite particles constituting the purifying agent according to the present invention (D ₅₀ : the cumulative ratio when the cumulative ratio with respect to the particle diameter is calculated with the total volume of the iron composite particles being 100% is 50%. The particle diameter is preferably 0.5 to 5.0 μm. The median diameter (D ₅₀ ) of the secondary particles is preferably finer, but since the primary particles are fine particles and contain α-Fe, they tend to cause magnetic aggregation and are less than 0.5 μm. This is difficult industrially. When it exceeds 5.0 μm, the penetration into the contaminated soil is delayed and it is difficult to purify in a short time, and it becomes difficult to obtain the intended effect of the present invention. More preferably, it is 0.5 to 3.5 μm.

D _{90 of the} secondary particles of the iron composite particles in the purifier according to the present invention (particle diameter when the cumulative ratio to the particle diameter is 90% when the total volume of the iron composite particles is 100%) The ratio D ₉₀ / D _{10 with} D ₁₀ (particle diameter at which the cumulative ratio with respect to the particle diameter when the total volume of the iron composite particles is 100% is 10%) is 1.5 to 5.0 preferable. The smaller the distribution width, the more uniform the permeation rate into the contaminated soil and the uniform purification rate, but 1.0 is the limit industrially. If it exceeds 5.0, the rate of permeation into the contaminated soil will be uneven and purification will be delayed, and it will take a long time for purification, making it difficult to obtain the intended effect of the present invention. More preferably, it is 1.0-3.5.

Distribution width (D ₈₄ -D ₁₆ ) of secondary particles of iron composite particles in the purifier according to the present invention (D ₈₄ : Cumulative amount when the cumulative ratio with respect to the particle diameter is determined with the total volume of iron composite particles being 100%. Particle diameter at which the ratio is 84%, D ₁₆ : Particle diameter at which the cumulative ratio to the particle diameter when the total volume of the iron composite particles is 100% is 16%) is 0.5 to 5.0 μm. Is preferred. The smaller the distribution width, the more uniform the permeation rate into the contaminated soil and the uniform purification rate, but 0.5 μm is the limit industrially. If it exceeds 5.0 μm, the penetration rate into the contaminated soil becomes non-uniform, resulting in a delay in purification, and it takes a long time for purification, so the intended effect of the present invention cannot be obtained. More preferably, it is 0.5 to 3.5 μm.

  The specific gravity of the purifier according to the present invention is preferably 1.2 to 1.4. If less than 1.2, considering the transport amount of the cleaning agent and the amount added to the soil, etc., the solid content is low and not economical, and if it exceeds 1.4, the purification is performed considering the primary particle size and the secondary particle size of the present invention. The agent thickens and is difficult to manufacture industrially.

  Next, a method for producing iron composite particle powder for the purification treatment of soil and groundwater contaminated with the organic halogen compounds according to the present invention 4 will be described.

  The goethite particle powder is obtained by reacting, for example, an aqueous solution containing a ferrous salt with one or more selected from alkali hydroxide, alkali carbonate or ammonia according to a conventional method. It can be obtained by ventilating an oxygen-containing gas such as air through a suspension containing a ferrous iron-containing precipitate such as iron carbonate.

  In addition, in order to obtain the iron composite particle powder for purification processing with a small impurity content, it is preferable to use a high-purity one that reduces impurities such as heavy metals as the aqueous solution containing the ferrous salt.

  In order to reduce the amount of impurities in the aqueous solution containing the ferrous salt, for example, the steel sheet is pickled with sulfuric acid, and impurities that have precipitated on the surface layer of the steel sheet and dissolved and removed rust preventive oil are removed. There is a method using an aqueous ferrous salt solution obtained by dissolving a steel sheet with a small amount of iron. Pickling of scrap iron and scrap iron with a lot of metal impurities other than iron, steel plates with plating treatment, phosphate treatment and chromic acid treatment to improve corrosion resistance, and steel plates with anti-rust oil applied When the liquid is used, impurities remain in the iron composite particle powder, and there is a possibility that it may elute into the soil or groundwater to be purified. Also, alkali such as alkali hydroxide is added to the ferrous sulfate solution by-produced from the titanium oxide production process, etc., and titanium and other impurities are insolubilized as hydroxides by pH adjustment to remove precipitates and ultrafiltration There is a method to use it. It is preferable to use a steel plate with few impurities dissolved in sulfuric acid, and it is further preferable to remove impurities by pH adjustment. Either method has no industrial problems and is economically advantageous.

The average major axis diameter of the goethite particle powder is 0.05 to 0.50 μm, and the S content is 2200 to 4500 ppm. The particle shape may be either spindle-shaped or needle-shaped. Axial ratio is preferably from 4 to 30, more preferably from 5 to 25, BET specific surface area is preferably 20 to 200 m ² / g, more preferably 25~180m ² / g.

  In the present invention, it is important that the goethite particles contain Al or the goethite particles are coated with Al. The hardness of the granulated product can be controlled by suppressing the volume shrinkage of the granulated product by containing or coating Al. Therefore, the labor for wet pulverization can be reduced. Further, the size of the primary particles can be relatively reduced, the specific surface area is also relatively increased, and the performance is improved.

  The Al content or the Al coating amount of the goethite particle powder is preferably 0.06 to 1.00% by weight.

  The goethite particle powder is preferably granulated according to a conventional method. By granulating, a fixed bed type reduction furnace can be used, and even when iron composite particles are used, it is possible to maintain the shape of the granulated product as it is depending on the reducing conditions. Is preferred.

  The obtained goethite particle powder is preferably a hematite particle powder that has been heat-dehydrated in a temperature range of 250 to 350 ° C.

  The hematite particle powder in the present invention uses goethite particles having a high S content in advance, or in the case of goethite particles having a low S content, by adding sulfuric acid to an aqueous suspension of the hematite particle powder, The S content of the hematite particle powder is controlled.

  The average major axis diameter of the hematite particle powder is 0.05 to 0.50 μm, and the S content is 2400 to 5000 ppm. The Al content or the Al coating amount of the hematite particle powder is preferably 0.07 to 1.13% by weight.

  The goethite particle powder or the hematite particle powder is heated and reduced in a temperature range of 350 to 600 ° C. to obtain iron particle (α-Fe) powder.

When the heating reduction temperature is less than 350 ° C., the reduction reaction proceeds slowly and takes a long time for the reduction reaction. Moreover, although the BET specific surface area can be increased, crystal growth cannot be sufficiently performed, the α-Fe phase becomes unstable, and a thick oxide film is formed on the particle surface, or from the Fe ₃ O ₄ phase. Since the phase change to the α-Fe phase is insufficient, the abundance ratio of the α-Fe phase cannot be increased. When the temperature exceeds 600 ° C., the reduction reaction proceeds rapidly, the sintering between the particles and the particles is excessively promoted, the particle diameter is increased, and the BET specific surface area is also decreased.

  In addition, although hydrogen gas, nitrogen gas, etc. can utilize the atmosphere at the time of temperature increase of a reductive reaction, hydrogen gas is preferable industrially.

  After cooling the iron particle powder after heat reduction, the iron particle powder is taken out in water without forming a surface oxide film in the gas phase, and a surface oxide film is formed on the particle surface of the iron particle powder in water, Then it is dried.

  The atmosphere during cooling may be either nitrogen or hydrogen, but is preferably switched to nitrogen finally. Moreover, when taking out in water, it is preferable to be cooled to 100 degrees C or less.

  The drying atmosphere can be selected as appropriate, such as nitrogen, air, or vacuum, but the temperature is preferably 100 ° C. or lower.

Through the above heat reduction treatment, the entire particles become iron particles composed of an α-Fe phase, and when taken out into water, the water is decomposed by the catalytic activity of α-Fe, separated into hydrogen and oxygen, and the generated oxygen produces α It is presumed that -Fe is oxidized and an oxide film composed of Fe ₃ O ₄ is formed on the particle surface.

  Next, the method for producing a soil / groundwater purification agent contaminated with an organic halogen compound according to the fifth aspect of the present invention is as follows. A purifier comprising an aqueous suspension containing

  In the cleaning agent of the present invention, it is preferable to pulverize and disperse the secondary aggregates of the iron composite particle powder.

  The iron particle powder after heat reduction is cooled and then taken out into water. After forming a surface oxide film on the particle surface of the iron particle powder in water, the iron composite particles are wet-pulverized.

  In consideration of the agglomeration state, properties (high activity), size, ability of the pulverizer (product particle size, pulverization amount) and final form of the iron composite particles, the pulverization is preferably wet pulverization.

  As a pulverizer used in the present invention, in the case of using a medium, a container-driven type such as a rolling mill (pot mill, tube mill, conical mill) or vibration mill (fine vibration mill), tower type (tower mill), stirring tank type ( Medium stirring types such as an attritor), a distribution pipe type (sand grind mill), and an annular type (annular mill) can be used. When the medium is 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.

  In general, the pulverization is performed by roughly pulverizing a raw material of 25 mm or less into powder and roughly divided into coarse pulverization, fine pulverization, and fine pulverization processes. It is generally said that coarse pulverization is pulverization from 5 mm to 20 mesh, fine pulverization is such that particles of 200 mesh or less are about 90%, and fine pulverization is such that particles of 325 mesh or less are about 90%. There are also ultra-fine pulverizers that can pulverize to a few microns. In the present invention, the iron composite particles are preferably subjected to three pulverization states of coarse pulverization, fine pulverization, and fine pulverization.

  For coarse pulverization, a low-speed rotation type, medium-speed rotation type, high-speed rotation shear type, high-low-speed rotation combination stirrer, etc., which is inserted into a stirring tank equipped with a baffle and stirred can be used. Considering the collection, a medium to high-speed rotating stirrer at 1000 to 6000 rpm is preferable. The blade shape of the stirrer includes a disk turbine, a fan turbine, an arrow blade turbine, a propeller type, and the like, but a disk turbine with an edge is preferable, for example, a homodisper manufactured by Tokushu Kika Kogyo.

  A batch type apparatus or a continuous type apparatus can be used for fine pulverization or fine pulverization, but a continuous type is preferred industrially. When using media, a ball mill, tower mill, sand grind mill, attritor or the like can be used, and when no media is used, a homomixer, a line mixer or the like can be used.

  For fine pulverization, it is possible to use a multi-stage combination of a rotor and a stator in which a plurality of slits are provided on the outer periphery and the shaft fixing surface portion is provided with cutter teeth, and the peripheral speed of the rotor is 30 m / s. A continuous shearing disperser such as the above-mentioned medialess line mixer, for example, a homomic line mill manufactured by Tokushu Kika Kogyo is particularly preferable.

  For fine crushing (finish crushing), φ1 to φ3 media are inserted into a cylindrical vessel at a filling rate of 70 to 80%, and a plurality of discs are attached to a rotating shaft installed at the center of the vessel and rotated. It is possible to use a media-type disperser such as a sand grind mill in which a rapid swirling action occurs in the media and the processed material passes from the bottom to the top, for example, a sand grinder manufactured by IMEX preferable.

  In the wet pulverization of the present invention, the crack growth of particles is prevented and recombination is suppressed, or the particles are aggregated to become granular and difficult to be pulverized, or the pulverization force is weakened by adhering to a ball or mill. In order to suppress, a grinding aid may be added as appropriate. Grinding aids include solids and liquids. Examples of solids include stearates, colloidal silica, colloidal carbon, etc., and liquids include triethanolamine and alkyl sulfonate.

  The concentration of the suspension during wet pulverization is preferably 20 to 40% by weight of iron composite particles. When the amount is less than 20% by weight, stress such as shearing is hardly applied during pulverization, and a predetermined pulverized particle size cannot be obtained or it takes a long time, and the media necessary for pulverization is significantly worn. If it exceeds 40% by weight, the aqueous suspension will thicken, and the mechanical load is large, making it difficult to produce industrially.

  Next, the purifier according to the present invention 6 to 8 will be described.

  When the cleaning agent according to the third aspect of the present invention is stored as it is, coarse particles are generated (hereinafter referred to as “cleaning agent after storage”). Even if coarse particles are present, the purification performance of organic halogen compounds and heavy metals is maintained.

  As will be described later, the coarse particles in the present invention are those obtained by measuring the particle diameter of the largest particles of iron composite particles that can be confirmed by a scanning electron micrograph. When coarse particles having a particle diameter exceeding 5.0 μm are contained, the penetration into the contaminated soil becomes extremely slow and it is difficult to purify in a short time, and it becomes difficult to obtain the intended effect of the present invention. Preferably it is 4.0 micrometers or less, More preferably, it is 3.5 micrometers or less.

  The storage agent after storage according to the present invention may contain, for example, coarse particles having a particle size of 0.10 to 0.30 μm in addition to the particles according to claim 2 after about one month after the production. After about 3 months, coarse particles having a particle size of 0.30 to 0.60 μm may be contained, and after about one year after production, coarse particles having a particle size of 1.00 to 5.00 μm are contained. Also good.

Cleaning agent after storage according to the present invention, in about 1 month later after production, the iron composite particles of the entire powder alpha-Fe in the X-ray diffraction spectrum (110) plane of the diffraction intensity D ₁₁₀ and magnetite (311) The intensity ratio (D ₁₁₀ / (D ₁₁₀ + D ₃₁₁ )) with the diffraction intensity D _{311 of the} surface may be 0.50 to 0.80, and after about 3 months after manufacture, the intensity ratio is 0.30 to 0.00. The strength ratio may be 0.20 to 0.30 after about one year after manufacture.

  The BET specific surface area value of the iron composite particle powder in the cleaning agent after storage according to the present invention varies within the above range.

In the purifier after storage according to the present invention, the saturation magnetization value of the iron composite particle powder contained in the purifier may be 100 to 140 Am ² / kg after about one month after production, and about three months after production. in a saturation magnetization value may even 90~100Am ² / kg, in after about one year after manufacture, the saturation magnetization values may be 70~90Am ² / kg.

  In the cleaning agent after storage according to the present invention, the crystallite size of the (110) plane of α-Fe of the iron composite particle powder contained in the cleaning agent may be 250 to 400 mm after about one month after production. After about 3 months after production, it may be 250 to 400 mm, and after about 1 year after production, it may be 200 to 300 mm.

  In the cleaning agent after storage according to the present invention, the Fe content of the iron composite particle powder contained in the cleaning agent may be 70 to 80% by weight after about 1 to 6 months after manufacture, and about 1 year after manufacture. Later, the Fe content may be 65-75% by weight.

  Next, a method for purifying soil and groundwater contaminated with the organic halogen compounds according to the present invention 9 or the present invention 10 will be described.

  In general, soil and groundwater purification treatment contaminated with organic halogen compounds decomposes pollutants in soil and groundwater that have been excavated or extracted, and in-situ decomposition methods that directly decompose the contained pollutants directly underground. There is an in-situ extraction method, and any method can be used in the present invention.

  In the in-situ decomposition method, a method is adopted in which the iron composite particle powder for purification treatment or the purification agent is directly permeated or introduced into the basement through a borehole using a gas such as high-pressure air, nitrogen, or water as a medium. In particular, since the purification agent of the present invention is an aqueous suspension, it can be used as it is or diluted as necessary.

  In the in-situ extraction method, the excavated soil and the iron composite particle powder or cleaning agent for purification treatment are mixed using a sand mill, Henschel mixer, concrete mixer, Nauta mixer, uniaxial or biaxial kneader mixer, etc. What is necessary is just to stir. Further, the pumped ground water can be passed through a column or the like filled with the iron composite particle powder for purification treatment.

  The amount of iron composite particle powder for purification treatment or the amount of purification agent (solid content conversion) can be selected as appropriate according to the degree of contamination of organic halogen compounds in the soil and groundwater. Usually, 0.01-20 weight part is preferable with respect to 100 weight part of soil, More preferably, it is 0.05-10 weight part. When the amount is less than 0.01 parts by weight, the intended effect 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 with respect to 100 parts by weight of the groundwater.

When the organohalogen compounds are purified using the iron composite particle powder or the purifying agent according to the present invention, the apparent reaction rate constant can be set to 0.005 h ⁻¹ or more in the evaluation method described later.

  Next, the purification method for soil and groundwater contaminated with heavy metal harmful substances according to the present invention 9 or the present invention 10 will be described.

  The method for purifying soil / groundwater contaminated with hazardous substances of heavy metals according to the present invention is a method of “containment”, and can be applied to either “in-situ containment” or “containment after excavation”.

  “In-situ containment” is a method in which a mixture or a purification agent of iron composite particle powder for purification treatment and water or a gas such as nitrogen or the like is permeated or introduced into a basement through a borehole as it is. When using a cleaning agent, since it is a water suspension, it may be used as it is or may be diluted as necessary.

  In "containment after excavation", use a sand mill, Henschel mixer, concrete mixer, nauter mixer, uniaxial or biaxial kneader type mixer, etc., for the mixture or detergent of iron composite particle powder for purification treatment and water This is a method of mixing and agitation with contaminated soil to ferritize heavy metals in the soil and then contain them. In addition, if necessary, it is possible to magnetically separate ferrite incorporating heavy metal or the like.

  The amount of iron composite particles for purification treatment or the amount of purification agent (solid content conversion) can be selected as appropriate according to the degree of contamination of hazardous substances such as heavy metals in the soil and groundwater. When doing, 0.01-20 weight part is normally preferable with respect to 100 weight part of soil, More preferably, it is 0.05-10 weight part. When the amount is less than 0.01 parts by weight, the intended effect 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 with respect to 100 parts by weight of the groundwater.

When heavy metals are purified and insolubilized using the iron composite particle powder or the purifying agent according to the present invention, the apparent reaction rate constant in the evaluation method described later is 0.01 h ⁻¹ or more in the case of arsenic, and in the case of chromium. 0.01 h ⁻¹ or more, and in the case of lead, 0.05 h ⁻¹ or more can be set.

<Action>
An important point in the present invention is that organic halogen compounds of soil and groundwater can be decomposed efficiently and economically by using the iron composite particle powder for purification treatment or the purification agent according to the present invention.

  The present inventor has not yet clarified the reason why organic halogen compounds in soil and groundwater can be effectively decomposed, but estimates as follows.

That is, in the iron composite particle powder for purification treatment according to the present invention, the α-Fe phase (zero valence) and the Fe ₃ O ₄ phase are present in a specific ratio, and part of sulfur is 0 after the heat reduction step. It is presumed that, when present in a valence state, the iron composite particles can have a high reducing action and contribute to the decomposition reaction of organic halogen compounds.

  In the present invention, the decomposition performance of organic halogen compounds could be improved by adding a specific amount of Al compound to the iron composite particle powder for purification treatment. The reason for this is not yet clear, but by containing Al, the primary particles can be made finer, and the strength of the aggregates of the iron composite particle powder becomes smaller than before, so wet grinding. Therefore, it is possible to pulverize more finely than when pulverizing in the same manner. As a result, the present inventor presumed that the iron composite particles were able to sufficiently exhibit the decomposition activity on the organic halogen compounds inherently possessed because they can easily penetrate and disperse in soil or groundwater. Yes.

  As described above, since the catalytic activity effect is high, it is possible to efficiently perform 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.

  Furthermore, the purifying agent according to the present invention contains coarse particles after long-term storage, but maintains a high purifying activity as shown in the Examples below.

  Moreover, since the iron composite particles for purification treatment according to the present invention have a fine particle size and retain high activity, α-Fe is easily dissolved at room temperature without heating, and is further contained in soil. The water or groundwater is efficiently decomposed to generate hydrogen or a hydroxyl group so that it always becomes an alkaline region locally, so that the dissolution reaction of α-Fe proceeds gradually. Next, dissolved α-Fe and heavy metals and other harmful substances are taken at the interface of the iron composite particles, and hydroxyl groups, oxygen or dissolved oxygen, etc. due to decomposition of water are taken in and spinel ferrite formation proceeds continuously, and harmful substances such as heavy metals are removed. The inventor presumes that it is insolubilized. It is also presumed that S contained in the iron composite particles also contributes to the dissolution of α-Fe locally.

  In addition, the ferritization reaction between dissolved α-Fe and toxic substances such as heavy metals can be used to efficiently insolubilize toxic substances such as heavy metals because the grains grow epitaxially with the surface layer magnetite having a spinel structure as a seed. The inventor estimates.

  In the present invention, the process of adjusting the pH by adding an acid or alkali, the heat treatment, and the forced oxidation treatment by air blowing, etc. are also unnecessary, so that harmful substances such as heavy metals can be efficiently insolubilized. is there.

  Furthermore, in this invention, as shown in an Example mentioned later, it can suppress re-elution of the insolubilized heavy metal etc., and is excellent in insolubilization over a long period of time.

  A typical embodiment of the present invention is as follows.

  The average major axis diameter and the axial ratio of the goethite particle powder were measured with a transmission electron micrograph (magnification 30000 times). The average particle diameter of the hematite particle powder and the iron composite particle powder was measured using a scanning electron micrograph (magnification 30000 times).

  The amount of Fe, Al, and the amount of As, Cr, and Pb in the filtrate after solid-liquid separation after insolubilization of heavy metals was determined by “inductively coupled plasma emission spectrometer SPS4000” (manufactured by Seiko Electronics Co., Ltd.). ).

  The S content of each particle powder was measured using “Carbon Sulfur Analyzer: EMIA-2200” (manufactured by HORIBA).

  The crystalline phase of each particle powder was identified by measuring in the range of 10 to 90 ° by X-ray diffraction.

As described above, the peak intensity ratio of the iron composite particle powder was determined by measuring the diffraction intensity D ₁₁₀ of the (110) plane of α-Fe and the diffraction intensity D ₃₁₁ of the (311) plane of magnetite from the result of X-ray diffraction. _The intensity ratio was determined as ₁₁₀ / (D ₃₁₁ + D ₁₁₀ ).

  The crystallite size (α-Fe (110) plane) of the iron composite particle powder is the size of the crystal particle measured by the X-ray diffraction method, and the crystal particle size in the direction perpendicular to the crystal plane of each particle. The thickness is expressed by a value calculated from the diffraction peak curve for each crystal plane using the following Scherrer equation.

Crystallite size = Kλ / βcosθ
Where β = half-value width (in radians) of the true diffraction peak corrected for machine width due to the device.
K = Scherrer constant (= 0.9).
λ = wavelength of X-ray (Cu Kα ray 0.1542 nm).
θ = Diffraction angle (corresponding to the diffraction peak of each crystal plane).

  The specific surface area of each particle powder was represented by a value measured by BET method using “Monosorb MS-11” (manufactured by Kantachrome Co., Ltd.).

  The saturation magnetization value of the iron composite particle powder was measured using an “vibrating sample magnetometer VSM-3S-15” (manufactured by Toei Industry Co., Ltd.) with an external magnetic field of 795.8 kA / m (10 kOe).

  The particle size distribution of the iron composite particle powder in the cleaning agent was measured using a laser scattering / diffraction method “NIKKISO MICROTRAC HRA MODEL 9320-X100” (manufactured by Nikkiso Co., Ltd.). The dispersion solvent was ethanol, the dispersant was organosilane, and the dispersion was performed for 1 minute with an ultrasonic disperser.

  Each leaching amount of cadmium, lead, chromium, arsenic, total mercury, selenium, total cyanide, fluorine and boron other than iron present in the iron composite particle powder is 1992 Environment Agency Notification No. 46 “Soil Contamination Measured based on the environmental standards.

  The contents of cadmium, lead, chromium, arsenic, total mercury, selenium, total cyanide, fluorine and boron other than iron present in the iron composite particle powder were measured based on Ministry of the Environment Notification No. 19.

<Preparation of calibration curve: Determination of organohalogen compounds>
The concentration of the organic halogen compound was prepared in advance according to the following procedure, and the concentration was calculated based on the obtained calibration curve.
Trichlorethylene (TCE: C ₂ HCl ₃ ): molecular weight 131.39
Reagent grade (99.5%), density (20 ° C.) 1.461 to 1.469 g / ml

  Trichlorethylene is made into three levels of 0.05 μl, 0.1 μl and 1.0 μl, 30 ml of ion-exchanged water is added to 50 ml of a brown vial (actual volume 68 ml), then each amount of trichlorethylene is injected, and immediately a fluororesin liner Cover with a rubber stopper and tighten it with an aluminum seal. After leaving the vial at 20 ° C. for 20 minutes, 50 μl of the headspace gas is taken with a syringe, and trichlorethylene is measured using “GC-MS-QP5050” (manufactured by Shimadzu Corporation). Assuming that trichlorethylene is not decomposed at all, the relationship between the amount added and the peak area is determined. The column at this time is a capillary column (DB-1: manufactured by J & W Scientific, liquid phase: dimethylpolysiloxane), He gas (143 l / min) is used as a carrier gas, and the temperature is maintained at 40 ° C. for 2 minutes. The gas is analyzed by raising the temperature to 250 ° C at a rate of ° C / min.

<Sample preparation for organohalogen compound measurement>
Pour 0.1 g of iron composite particle powder for purification treatment and 30 ml of ion-exchanged water into 50 ml of brown vial (actual volume 68 ml), then inject 1 μl of trichlorethylene, and immediately cover with a rubber stopper with a fluororesin liner. Tighten with aluminum seal from above.

<Evaluation method in decomposition reaction of organic halogen compound (measurement of apparent reaction rate constant)>
The vial is left at 24 ° C. The remaining amount of trichlorethylene was allowed to stand at 20 ° C. for 20 minutes, and then 50 μl of gas was collected from the headspace with a syringe. The residual concentration of trichlorethylene in a predetermined time was measured by a batch method up to a maximum of 500 hours using the “GC-MS-QP5050” (manufactured by Shimadzu Corporation).

From the obtained residual concentration, an apparent reaction rate constant kobs was calculated based on the following formula.
ln (C / Co) = − k · t
Co: Initial concentration of trichlorethylene C: Residual concentration of trichlorethylene k: Apparent reaction rate constant (h ⁻¹ )
t: Time (h)

<Evaluation method in sample preparation and insolubilization reaction for heavy metal measurement (measurement of apparent reaction rate constant)>
Extract 25 ml of 1000 ppm standard solution (manufactured by Kanto Chemical Co., Ltd.) into a 1000 ml volumetric flask so that the chromium, lead, and arsenic solutions are 25 ppm each, and add ion-exchanged water so that the total amount becomes 1000 ml. Prepared. Pour 0.06 g of iron composite particle powder for purification treatment and 30 ml of the prepared heavy metal solution into 50 ml of brown vial (actual volume 68 ml), immediately cover with a rubber stopper and leave at 24 ° C.
The solution for measuring the amount of heavy metal remaining is suction filtered through a 0.45 μm membrane filter to obtain a solution in order to separate the solution in the vial and the iron composite particle powder. In addition, the fractionation of the solution measured the residual density | concentration in predetermined time to a maximum of 336 hours by the batch method.

<Evaluation method for heavy metals>
About the obtained solution, the residual density | concentration of each heavy metal is measured using the said "inductively coupled plasma emission-spectral-analysis apparatus SPS4000" (made by Seiko Electronics Co., Ltd.). The measurement is performed by the calibration curve method, a calibration curve is created at a concentration of 4 levels or higher, and the calibration curve is measured at a correlation coefficient of 0.9999 or higher.

Assuming that the insolubilization time and the logarithm of residual heavy metal concentration / initial heavy metal concentration can be approximated by a linear expression from the obtained heavy metal residual concentration, an apparent reaction rate constant kobs was calculated based on the following equation.
ln (C / Co) = − k · t
Co: Initial concentration of heavy metal C: Residual concentration of heavy metal k: Apparent reaction rate constant (h ⁻¹ )
t: Time (h)

<Elution test of heavy metals with acid / alkali after insolubilization>
Acid addition and alkali addition dissolution tests were conducted in accordance with “Study Group Report on Stability of Insolubilized Soils Treated with Heavy Metals-Acid Addition Dissolution Test Method, Alkaline Addition Dissolution Test Method” proposed by the Soil Environment Center.

(Excerpt of proposal)
In order to evaluate the stability when insolubilized soil is exposed to acidic or alkaline water, in addition to the Environment Agency Notification No. 46 dissolution test, a sulfuric acid addition dissolution test I and a slaked lime addition dissolution test I should be conducted. suggest.
If the insolubilization technology that does not elute heavy metals in these tests, it is considered possible to actually achieve a stable insolubilization process.When the insolubilized soil is backfilled, some acid or Even if exposed to alkali, it is considered that elution of heavy metals does not occur.

<Sample preparation for elution test of heavy metals after insolubilization>
(1) Arsenic In a 50 ml brown vial (actual volume 68 ml), the purifier is injected as iron composite particle powder at 8 g / l, arsenic 20 mg / l (manufactured by Kanto Chemical Co., Inc.), and ion-exchanged water to 30 ml. did. Immediately after that, the cap was covered with a rubber plug with a fluororesin liner, and the top was firmly tightened with an aluminum seal. The vial was left at 24 ° C. and separated into solid and liquid using a 0.45 μm membrane filter batchwise, and the filtrate was obtained using an “inductively coupled plasma emission spectrometer SPS4000” (manufactured by Seiko Denshi Kogyo Co., Ltd.). Analysis, pH was measured, and the solid after solid-liquid separation was conducted only after 21 days according to the acid / alkali elution test I proposed by the Soil Environment Center.
(2) Hexavalent chromium It was carried out in the same manner as above except that the purification agent was 12 g / l as an iron composite particle powder and hexavalent chromium was 50 mg / l (manufactured by Kanto Chemical Co., Inc.).
(3) Lead It was carried out in the same manner as above except that the purifying agent was 1 g / l as an iron composite particle powder and lead was 20 mg / l (manufactured by Kanto Chemical Co., Inc.).

<Sample preparation for measuring aliphatic organic halogen compounds>
Inject 50 g of a brown vial (actual volume: 68 ml) with 1 g of iron composite particle powder for purification treatment and 30 ml of ion-exchanged water, then inject 1 μl of trichlorethylene, and immediately cover with a rubber stopper with a fluororesin liner. Tighten firmly with an aluminum seal. The vial is shaken with a paint conditioner (Red Devil) for 3 hours.

<Evaluation method of aliphatic organic halogen compound>
The residual amount of trichlorethylene is measured using the above-mentioned “GC-MS-QP5050” (manufactured by Shimadzu Corporation) by taking 50 μl of the headspace gas of the vial bottle with a syringe.

<Manufacture of iron composite particle powder and purification agent for purification treatment>
Into a reaction vessel maintained in a non-oxidizing atmosphere by flowing N ₂ gas at a rate of 3.4 cm per second, 704 l of a 1.16 mol / l Na ₂ CO ₃ aqueous solution was added, and then Fe ²⁺ 1.35 mol / l. 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 equivalent to Fe), and FeCO ₃ was produced at a temperature of 47 ° C.

In an aqueous solution containing FeCO ₃ obtained here, subsequently, while blowing _{N 2} gas at a rate per second 3.4cm, it was held 70 minutes at temperature 47 ° C., in an aqueous solution containing the FeCO _3, temperature 47 ° C. At 2.8 cm, air of 2.8 cm / second was aerated for 5.0 hours to generate goethite particles. The pH during air ventilation was 8.5 to 9.5.

To the suspension containing the goethite particles obtained here, 20 l of an aqueous solution of Al sulfate containing Al ³⁺ 0.3 mol / l was added, stirred well, then washed with a filter press, and the resulting press cake was compressed with a compression molding machine. It was extruded using a molding plate having a pore diameter of 4 mm and dried at 120 ° C. to obtain a granulated product of goethite particles.

The goethite particles contained in the granulated product thus obtained were particles having a spindle shape with 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 0.40% by weight, and the S content was 400 ppm.

  The granulated product is heated at 330 ° C. to form hematite particles and dry pulverized. Then, it is poured into water and 70% sulfuric acid is added at a rate of 10 ml / kg and stirred. Thereafter, it was dehydrated to form a press cake, extruded using a molding plate having a pore diameter of 3 mm using a compression molding machine, and dried at 120 ° C. to obtain a granulated product of hematite particles.

  The hematite particle powder constituting the granulated product obtained here was a spindle-shaped particle 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 granulated product of the goethite particle powder was introduced into a fixed bed reducing apparatus, and reduced to complete α-Fe at 450 ° C. for 180 minutes while allowing H ₂ gas to flow. Next, after switching to N ₂ gas and allowing it to cool to room temperature, 300 ml of ion-exchanged water was directly introduced into the reduction furnace, and was directly taken out as a water suspension containing about 20 wt% iron particle powder.

  The aqueous suspension was transferred to a stainless beaker equipped with a baffle, and a T.W. K homodisper type 2.5 (edge turbine blade with a diameter of 40 mmφ, manufactured by Tokushu Kika Kogyo Co., Ltd.) was inserted and stirred at a rotational speed of 3600 rpm for 30 minutes.

  Next, as a continuous shearing type disperser, a T.I. Dispersion treatment was carried out at a rotation speed of 4000 rpm using a K homomic line mill (PL-SL type, manufactured by Tokushu Kika Kogyo Co., Ltd.).

  After that, as a media-type disperser, 0.25 l of glass beads with a diameter of 2 mm were filled into a four-cylinder sand grinder (4TSG- (1 / 8G) type, manufactured by Special Machine Industries Co., Ltd.) with a power of 1.5 kW. Then, dispersion treatment was performed at a rotation speed of 500 rpm to obtain a purifying agent.

The specific gravity of the resulting cleaning agent is 1.25, the solid content concentration is 30% by weight, the particle size distribution of the cleaning agent (water suspension) by laser diffraction / scattering method is a single peak, and the median diameter (D ₅₀ ) was 1.90 μm, the D ₉₀ / D ₁₀ ratio was 1.81, and the distribution width (D ₈₄ -D ₁₆ ) was 1.10 μm.

  The iron composite particles contained in the obtained cleaning agent were observed with a scanning electron microscope (30000 times). As a result, the primary particles had a rice grain shape and an average major axis diameter of 0.09 μm. The ratio was 1.4.

  Subsequently, it filtered, and it dried in air | atmosphere for 3 hours at 40 degreeC, and obtained the iron composite particle powder for a purification process (it is set as the iron composite particle powder for a purification process).

The iron composite particles obtained here are mainly composed of α-Fe, a saturation magnetization value of 135 Am ² / kg (135 emu / g), a BET specific surface area of 27 m ² / g, a crystallite size of 295Å, and an Fe content of 83.0. % By weight and S content were 4000 ppm. As a result of X-ray diffraction, it was confirmed that α-Fe and Fe ₃ O ₄ were present. The intensity ratio D ₁₁₀ / (D ₁₁₀ + D ₃₁₁ ) between D ₁₁₀ (α-Fe) and D ₃₁₁ (Fe ₃ O ₄ ) was 0.84.

<Results of dissolution test of iron composite particle powder for purification treatment>
According to the evaluation method, the dissolution results of the obtained iron composite particle powder were as follows: the cadmium elution amount was less than 0.001 mg / l, the total cyan elution amount was not detected, and the lead elution amount was 0.001 mg / l. Less than l, chromium elution amount less than 0.01 mg / l, arsenic elution amount less than 0.001 mg / l, total mercury elution amount less than 0.0005 mg / l, selenium elution amount less than 0.001 mg / l The elution amount of fluorine is less than 0.5 mg / l and the elution amount of boron is less than 0.1 mg / l, both of which are below the detection limit of the measuring device, and all are below the standard value of the environmental standard. Met.

<Measurement result of content of iron composite particle powder for purification treatment>
In addition, Table 1 shows the content test results of the obtained iron composite particle powder. As shown in Table 1, the content of cadmium and its compound is less than 2 mg / kg, the content of cyanide is less than 5 mg / kg, the content of lead and its compound is less than 5 mg / kg, and the content of hexavalent chromium compound is Less than 5 mg / kg, arsenic and its compound content less than 1 mg / kg, mercury and its compound content less than 1 mg / kg, selenium and its compound content less than 1 mg / kg, fluorine and its compound content The amount was less than 20 mg / kg, and the content of boron and its compounds was less than 20 mg / kg. All of these values were below the detection limit of the measuring device, and all were below the standard value of the environmental standard.

<Results of organic halogen compound purification treatment (apparent reaction rate constant)>
Regarding the evaluation results (apparent reaction rate constant) in the heavy metal insolubilization reaction, graphs of the concentrations of arsenic, chromium and lead against the reaction time are shown in FIGS.

According to the evaluation method, the apparent reaction rate constant in the purification of trichlorethylene when the purification agent was used was 0.034 h ⁻¹ .

<Evaluation results in the heavy metal insolubilization reaction (apparent reaction rate constant)>
According to the evaluation method, the apparent reaction rate constant in the heavy metals in the case of using the cleaning agent, arsenic 0.0195H ^-1, chromium 0.0138H ^-1, lead was 0.0630H ^-1 .

  Regarding the evaluation results (apparent reaction rate constant) in the heavy metal insolubilization reaction, graphs of the concentrations of arsenic, chromium, and lead with respect to the reaction time are shown in FIGS.

  That is, FIG. 3 shows the case where <the evaluation method (measurement of apparent reaction rate constant) in the sample preparation for heavy metal measurement and insolubilization reaction> is performed using the iron composite particle powder obtained in the embodiment of the invention. It is a graph of the density | concentration of arsenic, chromium, and lead with respect to reaction time.

  Moreover, FIG. 4 shows the case where <the evaluation method (measurement of apparent reaction rate constant) in the sample preparation for heavy metal measurement and insolubilization reaction> is performed using the iron composite particle powder obtained in the embodiment of the invention. It is a graph of the logarithm value of the density | concentration of arsenic, chromium, and lead with respect to reaction time.

  Further, FIG. 5 shows the case where the above-described <Method for evaluating heavy metal measurement and evaluation method for insolubilization reaction (measurement of apparent reaction rate constant)> is performed using the iron composite particle powder obtained in the embodiment of the invention. It is a graph of solution pH of arsenic, chromium, and lead with respect to reaction time.

  The solution for measuring the amount of heavy metal remaining at this time was about pH 10 for both chromium and lead addition, and it was estimated that the separated iron composite particle powder remained black and did not change and became a ferrite compound with heavy metals.

  In the case of reduced iron powder and electrolytic iron powder of Comparative Examples, which will be described later, the solution for measuring the amount of heavy metal remaining is about pH 4 for chromium and about pH 6 for lead, and the iron powder separated after adding lead produces a red precipitate. It is estimated that it became an iron hydroxide compound with lead.

<Evaluation results of heavy metal re-elution test after insolubilization>
The results of the heavy metal dissolution test after insolubilization are shown in Table 2. As shown in Table 2, the leaching amounts of arsenic, chromium, and lead were below the environmental standard in the alkaline dissolution test I results, and the leaching amounts of arsenic and chromium were below the environmental standard in the acid dissolution test I results. If the insolubilization treatment technology in which heavy metals and the like are not eluted in these tests, insolubilization of heavy metals and the like is very strong, and it is considered that a stable insolubilization treatment can actually be performed. In addition, when the insolubilized soil is backfilled, it is considered that elution of heavy metals and the like does not occur even if the soil is exposed to some acid or alkali thereafter. Therefore, it can be expected that an excellent effect is exhibited even in the insolubilization treatment of heavy metals or the like in the in-situ purification.
In the acid elution test I, only lead was eluted, and the cause is not clear. However, the additive concentration of the iron composite particle powder in the arsenic and chromium insolubilization tests is 8 g / l and 12 g / l, respectively. In contrast, the concentration of lead is as low as 1 g / l. Even in this case, the purification of contaminated water was completed because part of the lead was adsorbed on the iron composite particle powder after insolubilization as a hydroxide. Therefore, when considering re-elution from the powder after insolubilization, the inventor presumes that there is a high possibility that the addition concentration is inappropriate.

  Next, examples and comparative examples of the present invention will be given.

<Goethite particles>
The goethite particles shown in Table 3 were prepared as goethite particles.

Goethite particles 1, 2, 5
A granulated product of goethite particles was obtained in the same manner as in the above-described embodiment except that the amount of the Al sulfate aqueous solution to be added was variously changed.

Goethite particles 3
12.8 l of ferrous sulfate aqueous solution containing Fe ²⁺ 1.50 mol / l and 30.2 l of 0.44-N NaOH aqueous solution (corresponding to 0.35 equivalent to Fe ^{2+ in} ferrous sulfate aqueous solution) And a ferrous sulfate aqueous solution containing Fe (OH) ₂ at a pH of 6.7 and a temperature of 38 ° C. was produced. Next, 130 l of air per minute was passed through a ferrous sulfate aqueous solution containing Fe (OH) ₂ at a temperature of 40 ° C. for 3.0 hours to generate goethite core particles.

The ferrous sulfate aqueous solution containing the goethite core particles (the amount of the goethite core particles corresponds to 35 mol% with respect to the produced goethite particles) was added to 7.0 l of 5.4N Na ₂ CO ₃ aqueous solution (residual ferrous sulfate 1.5 equivalents of Fe ²⁺ in the aqueous iron solution) was added, and 130 liters of air was aerated for 4 hours at a pH of 9.4 and a temperature of 42 ° C. to produce goethite particle powder. 0.96 l of an aqueous solution of Al sulfate containing Al ³⁺ 0.3 mol / l was added to the suspension containing the goethite particles obtained here, and after sufficient stirring, the mixture was washed with a filter press and the resulting press cake was compressed. Extrusion molding was performed with a molding plate having a hole diameter of 4 mm using a molding machine and dried at 120 ° C. to obtain a granulated product of goethite particles.

The goethite particle powder contained in the granulated product thus obtained was a needle-like particle having an average major axis diameter of 0.33 μm and an axial 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.

Goethite particles 4
A granulated product of goethite particle powder was obtained in the same manner as the goethite particles 3 except that the amount of the Al sulfate aqueous solution to be added was changed.

Iron composite particle powder and purification agent for purification treatment: Examples 1 to 6, Comparative Examples 1 to 7;
Except for various changes in the type of goethite particles, the temperature of heat dehydration, the presence or absence of addition of sulfuric acid to the suspension containing hematite particles, and the temperature of heat reduction, the same as in the embodiment of the invention. An iron composite particle powder and a purification agent for purification treatment were obtained.

  The production conditions at this time are shown in Table 4, and the properties of the obtained iron composite particle powder for purification treatment and the purification agent are shown in Table 5.

In Comparative Example 2, 100 g of the granulated product of the goethite particle powder 1 was introduced into a rolling reduction device, and reduced to completely Fe ₃ O ₄ at 300 ° C. for 180 minutes while allowing H ₂ gas to flow. It is a magnetite particle powder containing no α-Fe. Comparative Example 3 is reduced iron powder, and Comparative Example 4 is electrolytic iron powder. Comparative Examples 5 and 6 are carbonyl iron powder, and Comparative Example 7 is sponge iron powder.

<Measurement of apparent reaction rate constant>
Examples 7-12, Comparative Examples 8-14;
The apparent reaction rate constant was measured by changing the type of the iron composite particle powder for the purification treatment and the type of the purification agent.

  Table 6 shows the processing conditions and measurement results at this time.

  In Comparative Examples 12 to 14, since the decomposition of trichlorethylene hardly occurred, the apparent reaction rate constant could not be obtained.

<Measurement of apparent reaction rate constant in heavy metal insolubilization>
Comparative Examples 15-18;
The apparent reaction rate constant was measured by varying the type of iron composite particle powder for purification treatment, the type of heavy metal to be insolubilized, and the addition concentration.

  Table 7 shows the processing conditions and measurement results at this time.

Examples 13-16
Table 8 shows the characteristics of the iron composite particle powder for purification treatment after storage and the purification agent. In Examples 13 to 16, the cleaning agent (solid content concentration 30%) containing the iron composite particles of Example 1 was stored in an open system for 1, 3, 6, and 12 months.

<Results of purification of aliphatic organic halogen compounds>
Examples 17-21, comparative examples 19-20;
Various types of the iron composite particle powder for purification treatment were changed, and purification treatment was performed according to the above <Preparation of Aliphatic Organic Halogen Compound Measurement Sample> and <Method for Evaluation of Aliphatic Organic Halogen Compound>. Table 9 shows the measurement results.

Since the iron composite particle powder for purification treatment according to the present invention can efficiently decompose and insolubilize organic halogen compounds and / or heavy metals, it can be used as a purification agent for soil and groundwater contaminated with organic halogen compounds and / or heavy metals. Is preferred.

It is a graph of reaction time and trichlorethylene residual rate when the purification treatment of trichlorethylene is performed using the iron composite particle powder obtained in the embodiment of the present invention (●: iron composite particle powder of the embodiment). FIG. 3 is a graph of logarithm of residual concentration / initial concentration of trichlorethylene with respect to reaction time when trichloroethylene purification treatment is performed using the iron composite particle powder obtained in the embodiment of the present invention (●: embodiment) Iron composite particle powder). Arsenic with respect to the reaction time when the above <preparation method for heavy metal measurement and evaluation method in insolubilization reaction (measurement of apparent reaction rate constant)> is performed using the iron composite particle powder obtained in the embodiment of the invention It is a graph of the concentration of (◇), chromium (□), and lead (△). Arsenic with respect to the reaction time when the above <preparation method for heavy metal measurement and evaluation method in insolubilization reaction (measurement of apparent reaction rate constant)> is performed using the iron composite particle powder obtained in the embodiment of the invention It is a graph of logarithmic values of the concentration of (◇), chromium (□), and lead (△). Arsenic with respect to reaction time when the above <preparation method for heavy metal measurement and evaluation method in insolubilization reaction (measurement of apparent reaction rate constant)> is performed using the iron composite particle powder obtained in the embodiment of the invention It is a graph of solution pH of (◇), chromium (□), and lead (Δ). It is a scanning electron micrograph (magnification 30000 times) of the coarse particle produced | generated with the cleaning agent after a preservation | save.

Claims (10)

An iron composite particle powder composed of α-Fe and magnetite used for purification treatment of soil and groundwater contaminated with organic halogen compounds and / or heavy metals, and in the X-ray diffraction spectrum of the iron composite particle powder, α-Fe The intensity ratio (D ₁₁₀ / (D ₃₁₁ + D ₁₁₀ )) of the (110) plane diffraction intensity D ₁₁₀ and the magnetite (311) plane diffraction intensity D ₃₁₁ is 0.30 to 0.95, and contains Al. An iron composite particle powder for purification treatment of soil and groundwater, having an amount of 0.10 to 1.50% by weight and an S content of 3500 to 7000 ppm. The saturation magnetization value is 85 to 155 Am ² / kg, the BET specific surface area is 5 to 60 m ² / g, the crystallite size of the (110) plane of α-Fe is 200 to 400 mm, and the average particle size is 0 The iron composite particle powder for soil / groundwater purification treatment according to claim 1, wherein the powder is 0.05 to 0.50 μm. A soil / groundwater purification agent comprising a water suspension containing the iron / particle composite powder for soil / groundwater purification treatment according to claim 1 or 2 as an active ingredient. A goethite particle powder having an average major axis diameter of 0.05 to 0.50 μm, an Al content of 0.06 to 1.00% by weight , and an S content of 2200 to 4500 ppm , or an average major axis diameter of 0. A hematite particle powder having a 0.05 to 0.50 μm Al content of 0.07 to 1.13 wt% and an S content of 2400 to 5000 ppm is heated and reduced in a temperature range of 350 to 600 ° C. After cooling, the iron particle powder is taken out in water without forming a surface oxide film in the gas phase, and then dried after forming a surface oxide film on the particle surface of the iron particle powder in water. A method for producing an iron composite particle powder for purification treatment of soil and groundwater according to claim 1 or 2.
A goethite particle powder having an average major axis diameter of 0.05 to 0.50 μm, an Al content of 0.06 to 1.00 wt%, and an S content of 2200 to 4500 ppm, or an average major axis diameter of 0 A hematite particle powder having an Al content of 0.07 to 1.13 wt% and an S content of 2400 to 5000 ppm is heated and reduced in a temperature range of 350 to 600 ° C. After cooling to iron particle powder, the iron particle powder is taken out in water without forming a surface oxide film in the gas phase, and a surface oxide film is formed on the particle surface of the iron particle powder in water to form an iron composite particle powder. 4. A method for producing a soil / groundwater purifier according to claim 3, wherein a water suspension containing water is obtained. A purification agent obtained by preserving for a long time a purification agent comprising an aqueous suspension containing the iron composite particle powder comprising α-Fe and magnetite according to claim 3 as an active ingredient, comprises coarse particles having a particle diameter of 0.1~5.0μm to, and iron composite particles of the entire powder alpha-Fe in the X-ray diffraction spectrum (110) plane of the diffraction intensity _{D 110} and magnetite (311) A soil / groundwater purifier having an intensity ratio (D ₁₁₀ / (D ₁₁₀ + D ₃₁₁ )) to the diffraction intensity D _{311 of the} surface of 0.20 to 0.80. The soil / groundwater purification agent according to claim 6, wherein the iron composite particle powder in the purification agent has a saturation magnetization value of 70 to 140 Am ² / kg and a crystallite size of (110) plane of α-Fe. A soil and groundwater purification agent characterized by being 200 to 400 mm. The soil / groundwater purification agent according to claim 6 or 7, wherein the iron composite particle powder in the purification agent has a Fe content of 65 to 80 wt% with respect to the total particle powder. Groundwater purification agent. The iron composite particle powder for purification treatment of soil and groundwater according to claim 1 or claim 2 and soil contaminated with organic halogen compounds and / or heavy metals or ground water contaminated with organic halogen compounds and / or heavy metals A method for purifying soil and groundwater, wherein the soil and groundwater are in contact with each other. The soil or groundwater purification agent according to any one of claims 3, 6, 7, and 8 and soil contaminated with organic halogen compounds and / or heavy metals or contaminated with organic halogen compounds and / or heavy metals. A method for purifying soil and groundwater, characterized by mixing and contacting with groundwater.