JP2007209825A - Purifying method of contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purifying method of contaminated soil which enables treatment of excavated soil contaminated with organochlorine compounds down to or below environmental standards. <P>SOLUTION: The method comprises supplying a metal reducing agent containing zero-valent iron powder and water to excavated soil 1 contaminated with organochlorine compounds, mixing with stirring to prepare a slurry-like mixture 15 and curing the mixture 15 in a container 4 for a specified period to convert organochlorine compounds into harmless products. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a purification technique for soil contaminated with harmful substances, and more particularly to a purification process for soil contaminated with an organic chlorine compound such as PCB (polychlorinated biphenyl).

  Soil contaminated with organochlorine compounds represented by PCB (polychlorinated biphenyl, non-volatile hydrophobic organic compound) and the like is present in the ground such as a factory site without much decomposition.

  Further, this PCB or the like is excavated from the ground for soil purification and stored in a container such as a drum can.

  In particular, the excavated contaminated soil is stored in large quantities without being subjected to purification treatment, and the purification treatment is urgently needed.

  Conventionally known methods include, for example, a thermal decomposition method, an alkali catalytic chemical decomposition method, a melt-solidification method, and an iron powder method.

  However, it is desired to develop a method in which contaminated soil is purified so as to satisfy safety standards and the number of treatment steps is small.

  Among the various processing methods, there are the following as typical solution means.

  Electrical components such as transformers and capacitors are those that contain hardly decomposed harmful substances such as PCBs, waste liquids, and waste oils as constituent members or parts thereof.

  This harmful substance is stored in various containers such as drums and boxes, charged into a melting furnace as fuel, and melted at a high temperature to thermally decompose the harmful substance (see, for example, Patent Document 1). ).

  Further, there is a method in which after excavating soil contaminated with an organic halogen compound, iron powder is mixed into the excavated soil and piled up on the ground in a pile shape and left for several days to several months.

  There is also a method of decomposing pollutants by mixing iron powder in excavated soil and backfilling it underground to convert it into hydrocarbons containing no halogen such as ethane or ethylene.

  Furthermore, there is a treatment method for preventing recurrence of contamination due to contaminants remaining in the surrounding soil (see, for example, Patent Document 2).

  Also, dioxin-contaminated solids are pulverized with a pulverizer, the atmosphere of the pulverized product is replaced with an inert gas, and a reducing metal is introduced into the pulverized material and mixed.

Thereafter, the pulverized dioxin-contaminated mixture obtained from the pulverized product and the reducing metal is transferred to a dehalogenation treatment reactor while maintaining the inert gas atmosphere, and the pulverized product is reduced with the reducing metal. Thus, the dehalogenation reaction of dioxins is performed. (For example, refer to Patent Document 3).
JP 2004-154666 A JP 2001-577 A JP 2003-190932 A

  However, what is described in Patent Document 1 is a thermal decomposition process, which requires a high-temperature incinerator, which complicates equipment and becomes large-scale.

  Hazardous substances in this thermal decomposition treatment include devices such as PCBs, waste liquids, waste oils, etc. that are difficult to decompose (hereinafter referred to as PCBs) or contaminated with PCBs, articles such as parts, PCBs, etc. Contaminated soil, contaminated water, etc. mixed with or a container such as a drum can.

  This hazardous substance is directly burned while maintaining a high temperature in a high-temperature incinerator, and the hazardous substance is thermally decomposed. The high-temperature incinerator requires a large-scale facility that considers durability, fuel for incineration, etc. The amount of energy used increases.

  There is also a problem of undecomposed dioxins by combustion.

  Next, the thing of patent document 2 mixes iron powder with excavated soil, piles up the obtained mixture in the shape of a pile (pile), hangs a sheet, and is left still for several days to several months. is there.

  When excavating this contaminated soil, the excavated material excavated from the contaminated site contains large contaminants such as stones and glass, and components having greatly different particle sizes. For this reason, when mixing iron powder with excavated soil, it is difficult to disperse | distribute iron powder uniformly in excavated soil.

  Moreover, since the lower part of the mound of the mixture of iron powder mixed with excavated soil is in contact with the ground, the mixture may leak.

  Moreover, it is difficult for the hills formed of the mixture to break down due to weathering or the like and maintain the initial shape, and the mixture is easily exposed from the sheet.

  Furthermore, the required amount of water in the mixture necessary for preventing oxidation by contact of iron powder with air and promoting reductive decomposition of the organic halogen compound cannot be maintained.

  In other words, the balance between the oxidation rate of iron powder and the reduction rate of PCB or the like changes due to the evaporation of water due to the drying of the mixture, and stable reductive decomposition of PCB or the like over a certain period is difficult.

  Furthermore, although it is a common problem of the soil purification treatment method using iron powder, hydrophobic organic chlorine compounds adhering to the soil, such as PCBs and dioxins, adhere very strongly to the soil surface.

  Even if a large amount of iron powder is mixed, as a substance, for example, the contamination concentration is halved in a relatively short period of time, but then the purification rate becomes slow and the purification process takes time.

  In particular, when the soil concentration of excavated soil is high, it becomes more difficult to completely purify the soil.

  In addition, a large amount of iron powder is required, which is not economical and has a problem of secondary contamination.

  Moreover, the thing of patent document 3 requires the grinder which grind | pulverizes a contaminated solid substance, Furthermore, the reducing metal of metallic sodium is mixed with the grind | pulverized substance grind | pulverized with the grinder, and a dehalogenation process reaction is carried out.

  At this time, an apparatus for maintaining an inert gas or a reducing atmosphere is necessary, which complicates the entire system, resulting in a problem that the operating cost increases.

  The present invention solves the above-described conventional problems, and excavated soil contaminated with PCB or the like is reliably (here, “certain” means below a reference value that conforms to environmental standards), and further iron powder. It is an object of the present invention to provide a method for purifying contaminated soil, which can reduce running costs as a result and effectively comply with environmental standards.

  The present invention is to supply a metal reducing agent containing zero-valent iron powder and water to excavated soil contaminated with an organic chlorine compound, and then stir and mix to make a slurry mixture, and the mixture is cured in a container for a certain period of time. It is made into the purification processing method of the contaminated soil characterized by making it carry out.

  According to the method for purifying contaminated soil of the present invention, a drilling soil contaminated with an organic chlorine compound typified by PCB or the like is reliably and more efficiently charged with a metal reducing agent containing zero-valent iron powder. This makes it possible to economically reduce running costs and perform processing that conforms to environmental standards.

  In the first invention, after supplying a metal reducing agent containing zero-valent iron powder and water to excavated soil contaminated with an organic chlorine compound, the mixture is stirred and mixed to form a slurry-like mixture, and the mixture is constant in a container This is a purification method for contaminated soil characterized by curing for a period of time.

  By this method, the agglomerated soil is unwound by stirring and mixing to become a slurry mixture, and the soil lump enveloping gravel and the like is separated and released and refined by stirring and mixing.

  Furthermore, it can be separated from the supplied water and eluted by the cleaning action of the water supplied with the organic chlorine compound adhering to the soil surface and the rubbing action of the soil.

  Furthermore, by supplying a metal reducing agent containing zero-valent iron powder and stirring and mixing it into a slurry-like mixture, the finely powdered metal reducing agent is uniformly dispersed among the finer soil particles having a larger specific surface area. Can do.

  Moreover, it can be made the state which a metal reducing agent contacts easily also on the surfaces, such as gravel from which the soil lump removed.

  Furthermore, the organochlorine compound eluted in water can also be brought into direct contact with the metal reducing agent to promote the decomposition reaction.

  Furthermore, a stable decomposition reaction can be maintained by curing in a sealed container.

  Furthermore, the amount of the metal reducing agent containing the necessary zero-valent iron powder is minimized, and it is not necessary to use a large and complicated processing apparatus.

  By reducing the amount of the metal reducing agent containing zero-valent iron powder to a minimum (1% to 10% of the weight of the slurry-like soil), the metal reducing agent can be appropriately reduced, and excess metal The introduction of the reducing agent can be prevented, and the container storage amount in the subsequent stage becomes an appropriate amount.

  Therefore, by excavating soil contaminated with organochlorine compounds represented by PCB, etc., the iron powder oxidation reaction and slurry can be reliably treated by minimizing the amount of metal reducing agent containing zero-valent iron powder. It can act to make the reduction reaction of the gaseous mixture efficient.

  According to a second invention, in the first invention, after supplying water to the excavated soil in advance and mixing with stirring to form slurry-like soil, a metal reducing agent containing zero-valent iron powder is supplied and mixed with stirring. It is set as the purification processing method of the contaminated soil characterized by performing.

  Accordingly, the metal reducing agent can be dispersed more uniformly and in a short time in the entire soil by supplying the metal reducing agent after the refinement of the excavated soil and eluting the organic chlorine compound into the water and stirring and mixing.

  This is because, after supplying water to the excavated soil and stirring and mixing to make a slurry soil, supplying a metal reducing agent containing zero-valent iron powder and stirring and mixing, the grain system of the slurry soil is kneaded. Since it becomes fine and water is infiltrated between the soil systems, a metal reducing agent containing zero-valent iron powder will be supplied, so that hydrogen ions are likely to mobilize in the oxidation reaction between iron powder and water, and Chlorine and hydrogen ions of organic chlorine compounds such as PCB contained in the slurry-like soil facilitate the desalting reaction.

  A third invention is a method for purifying contaminated soil according to the second invention, wherein water and a metal reducing agent are mixed in advance, and then supplied to slurry-like soil and mixed by stirring to form a mixture. It is.

  As a result, oxidation and aggregation due to contact of the metal reducing agent with air can be prevented, and the metal reducing agent can be dispersed more uniformly in the entire soil in a short time.

  4th invention is set as the purification | cleaning processing method of the contaminated soil characterized by supplying the elution promoter of an organic chlorine compound to a mixture in any one of 1st-3rd invention.

  Thereby, detachment | desorption and elution of the organochlorine compound adhering to the surface of excavated soil can be accelerated | stimulated, and the decomposition efficiency by a metal reducing agent can be improved more.

  5th invention is set as the purification | cleaning processing method of the contaminated soil characterized by mixing and stirring a mixture continuously or every fixed time during the curing period in any one of 1st-4th invention.

  This prevents sedimentation of the soil with larger particle size in the mixture into the lower part of the container, aggregation of the soil, and aggregation of the metal reducing agent to uniformly disperse the metal reducing agent throughout the soil, The elution of the compound into water can be promoted to promote the contact between the metal reducing agent and the organochlorine compound, and the metal reducing agent can effectively act on the decomposition of the organochlorine compound.

  Therefore, the organochlorine compound in the excavated soil 1 can be reliably treated more economically and rendered harmless.

Hereinafter, a soil purification method according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a conceptual diagram of a method for purifying contaminated soil according to an embodiment of the present invention, and FIG. 2 is a flowchart showing processing steps corresponding to FIG. Hereinafter, description will be given based on the drawings.

  First, the basic configuration will be described with reference to the conceptual diagram of the contaminated soil purification method of FIG.

  In FIG. 1, excavated soil 1 contaminated with an organic chlorine compound such as PCB is transported to a sorting device 2 having a vibrating sieve 2a and a vessel 2b. In this sorting device 2, the mesh of the vibration sieve 2a is set to about 30 mm, for example, and a large contaminant 3 such as a relatively large stone or glass mixed in the soil remains on the vibration sieve 2a. To be separated. The excavated soil 1 passed through the vibrating screen 2a and shaken down is accommodated in the vessel 2b.

  Note that the sorting device 2 may use a jumping screen that wave-moves the screen mat surface, or a multilayer screen that gradually becomes finer. The sorting device 2 may use a means for fixing the vibration sieve 2a and moving the excavated soil 1 on the sieve or a means for applying vibration to the soil.

  The sorting device 2 is not limited to the above-described configuration, and various types of vibration sieve devices and rotary sieve devices (trommel) that have already been put into practical use may be used.

  The size of the mesh of the sorting device 2 may be set to an optimum condition as appropriate according to the type and characteristics of the excavated soil 1 and the size of the contaminants. Further, depending on the state of the excavated soil 1, visual selection may be performed.

  Further, the large contaminants 3 may be removed and the particle size of the excavated soil 1 may be selected, whereby the work efficiency of the subsequent purification treatment step and the decomposition efficiency of the organic chlorine compound can be improved.

  The selection processing of the excavated soil 1 may be adopted depending on the condition of the excavated soil 1, and is omitted if the particle size is relatively constant with no large contaminants 3 such as large stones and glass. do it.

  Thus, the excavated soil 1 is classified and put into the container 4.

  Next, the apparatus of the purification method of the present invention will be described.

  It has a container 4 for storing excavated soil 1 from which large-sized contaminants 3 such as stone and glass are removed, and a lid 5 for the container 4, and the lid 5 is rotationally driven by a motor 6 that is a stirring and mixing means. The agitating blade 7 is fixed, and a supply pipe 8 having an on-off valve 8a for supplying water into the container 4 is opened and connected.

  The container 4 and the lid 5 are configured to be detachable, and the lid 5 and the supply pipe 8, the lid 5, the motor 6, and the stirring blade 7 are configured to be detachable from each other.

  Further, a storage container 9 for mixing and storing a metal reducing agent containing zero-valent iron powder and water is provided. The storage container 9 has a metal reducing agent supply port 10, a water supply pipe 11, and a motor which is a stirring and mixing means. 12 has a stirring blade 13 driven to rotate.

  Further, a supply pipe 14 having an on-off valve 14 a for supplying the metal reducing agent and water mixed from the storage container 9 to the container 4 is provided. The lid 5 and the supply pipe 14 are configured to be detachable from each other. According to the basic configuration, the excavated soil 1 is stored in the container 4, and a metal reducing agent and water are further stirred and mixed to form a mixture 15.

  Next, the operation of the purification method apparatus of the present invention will be described.

  An organic solvent (ethanol) or a surfactant which is an organic chlorine compound elution accelerator is supplied into the container 4 as required. The elution promoter is supplied together with water from the supply pipe 8 or 11 and is made into a mixture 15 of excavated soil 1, metal reducing agent, water, and elution promoter in the container 4.

  In order to make this mixture 15, the motor 6 and the stirring blade 7 in the container 4 operate.

  Thereby, detachment | desorption and elution of the organochlorine compound adhering to the surface of the excavation soil 1 can be accelerated | stimulated, and the decomposition efficiency by a metal reducing agent can be improved more.

  The elution promoter is not particularly limited as long as it is water-soluble or water-dispersible. Examples of the surfactant include nonionic, anionic, cationic, and amphoteric surfactants.

  Nonionic surfactants are susceptible to the effects of hydrogen ion concentration of water in the container 4 and zero-valent iron powder with ionic surfactants, and are less susceptible to these effects with nonionic surfactants. Is particularly preferred.

  As an elution accelerator, an organic solvent such as acetone or ethanol can also be used. The elution promoter may be supplied directly to the mixture 15, but is preferably supplied after being dissolved in water at a constant concentration in order to uniformly disperse the mixture 15 in a short time.

  Moreover, as the container 4, it is preferable to use, for example, a stainless material or a resin-coated inner surface, and the mixture 15 may be accommodated through a resin bag attached to the inner surface of the container 4.

  As a result, leakage of the mixture 15 due to corrosion can be prevented. As the container 4, for example, a drum can having a volume of about 200 liters is used.

  The size of the container 4 is generally easy to obtain, is high in industrial productivity, and is easy to transport.

  In order to cut off the oxygen source, which is an impediment to the decomposition action of the pollutant by the metal reducing agent, it is desirable to seal the mixture 15 so that it does not come into contact with the outside air. Further, the inert gas or reducing gas is contained in the container 4 and the lid 5. It is preferable to fill the upper space part.

  If the amount of water supplied to the excavated soil 1 in the vessel 4 is too small, it will not be able to be refined and the soil mass that has wrapped gravel will not be released, and if it is too large, the total amount will increase. Absent. The amount of water supplied may be adjusted according to the water content of the excavated soil 1.

  In other words, the optimum mixing ratio of soil and water varies depending on the moisture content of the soil. For example, for soil having a moisture content of 60%, the slurry-like soil can be obtained by supplying 1.5 times the weight ratio of water. It turns out that it is obtained.

  Moreover, with respect to the soil whose water content exceeds 85%, slurry-like soil can be obtained by supplying water at a weight ratio of 1 times.

  Furthermore, for soil having a moisture content of 15% or less, slurry-like soil can be obtained by supplying water three times as much by weight. Moreover, what is necessary is just to use general water, such as tap water, river water, and groundwater, as water used for supply water.

  As the metal reducing agent, zero-valent fine particle iron powder is used as a base. For example, the iron powder is made into fine particles having an average particle size of about 70 μm, and the decomposition reactivity of the organic chlorine compound can be improved by forming the iron powder with a large surface area. Further, nickel alloy, carbon-coated iron powder or the like may be used in combination, and the present invention is not limited to these including the particle diameter.

  Moreover, the supply amount of the metal reducing agent to the excavated soil 1 is about 1 to 10% by weight with respect to the soil, and when the addition amount is less than 1% by weight, the decomposition rate is remarkably reduced. When a large amount of addition is 10% by weight or more, iron powder that does not undergo oxidation reaction increases, which is economically wasteful.

  The supply amount is set according to the particle size of the excavated soil 1, the contamination concentration, and the like. For example, when the particle size is small and / or the contamination concentration is high, the supply amount is increased.

  The amount of water mixed with the metal reducing agent in the storage container 9 is equal to or greater than the amount of saturated water of the metal reducing agent, and is fluidized in a slurry state. This prevents oxidation and agglomeration due to contact of the metal reducing agent with the air, and enables uniform mixing with the slurry-like soil in the container 4 in a shorter time, so that the metal reducing agent is uniformly dispersed throughout the soil. be able to.

  In addition, when stirring and mixing are performed at regular intervals during the curing period, the motor 6 and the stirring blade 7 may be removed from the lid 5 when stirring and mixing are not performed, and may be mounted only when stirring and mixing. As a result, the motor 6 and the stirring blade 7 can be sequentially attached to the lid 5 of the plurality of containers 4 to be stirred and mixed.

  Thus, the total number of containers 4 is provided with the lid body 5, the motor 6, and the stirring blades 7 of the containers 4 as many as the number of containers 4 that need to be stirred and mixed, even though the lid body 5, the motor 6, and the stirring blades 7 are not provided. Just do it.

  In other words, it can be reused sequentially.

  Next, processing steps of the soil purification processing method will be described with reference to FIGS. 1 and 2. First, the excavated soil 1 is removed of large contaminants such as stone and glass by the sorting device 2 (S101). The excavated soil 1 from which the large contaminants have been removed is stored in the container 4 (S102), and a lid 5 is attached to the upper opening of the container 4. Next, after opening the on-off valve 8a for a certain period of time and supplying a certain amount of water from the supply pipe 8 into the container 5, the motor 6 is energized and the agitating blade 7 is rotated to agitate and mix the excavated soil 1 and water ( S103). Thus, the excavated soil 1 from which the large contaminants 3 have been removed is forcibly moistened and kneaded to obtain slurry-like soil.

  Next, a metal reducing agent containing zero-valent iron powder and water are supplied into the storage container 9, and are agitated and mixed by the agitating blade 13 that is rotationally driven by the motor 12 that is agitating and mixing means (S104). Further, a predetermined amount of the metal reducing agent stirred and mixed with water is supplied from the supply pipe 14 to the slurry soil in the container 4 by opening the on-off valve 14a for a predetermined time.

  After that, the rotary drive of the stirring blade 7 is continued in the container 4 for a certain period of time, and the excavated soil 1 contaminated with the organochlorine compound, the metal reducing agent containing zero-valent iron powder, and water are stirred and mixed to form a slurry mixture. 15 (S105).

  Further, after the slurry-like mixture 15 is formed, the mixture 15 is cured in the container 4 for a certain period (for example, several months) (S106). During the curing period, the energization to the motor 6 is controlled to stir and mix the mixture 15 in the container 4 at regular intervals (S107, S108, S109). In addition, although it was made every fixed time, you may make it stir-mix continuously.

  During the curing period, the organochlorine compound is treated within the container 4 to a value below the environmental standard value by a dechlorination reaction. The organochlorine compound receives (reduces) electrons on the surface of the metal reducing agent containing zero-valent iron powder, and is converted into a compound containing no chlorine.

  By confirming the end of decomposition of the chlorine compound, it can be backfilled or reused for concrete or the like.

  As described above, by supplying water to the excavated soil 1 and stirring and mixing it into a slurry-like soil, the massive soil is unraveled, and the soil mass enveloping gravel and the like is detached and unraveled to be refined. Furthermore, it can be separated from the supplied water and eluted by the cleaning action of the water supplied with the organic chlorine compound adhering to the soil surface and the rubbing action of the soil.

  Furthermore, by supplying a metal reducing agent containing zero-valent iron powder to the slurry-like soil, stirring and mixing the mixture, the iron powder having a large surface area processed into a finely powdered metal reducing agent between the refined soil particles Can be uniformly dispersed.

  Furthermore, it can be made the state which a metal reducing agent contacts easily also on the surfaces, such as gravel from which the soil lump removed. Moreover, the organochlorine compound eluted in water can be brought into direct contact with the metal reducing agent to promote the decomposition reaction.

  Further, even when the metal reducing agent and water are supplied to the excavated soil 1 almost simultaneously and mixed with stirring to form a slurry mixture, the above-described effects can be obtained. , Thoroughly agitate and mix to make slurry soil, refine the soil, elute the organic chlorine compound into water, supply metal reducing agent and continue stirring and mixing to make a mixture more metal reduction The agent can be dispersed uniformly throughout the soil in a short time.

  As a reason, when the content of PCB or the like is high, the decomposition treatment with zero-valent iron powder is difficult to promote, and the low-concentration contaminated soil after elution into water or the like is decomposed with this zero-valent iron powder. This is because the processing is extremely high.

  Furthermore, the amount of the metal reducing agent containing the necessary zero-valent iron powder is suppressed to an appropriate amount, and it is not necessary to use a large and complicated processing apparatus. Therefore, the excavated soil 1 contaminated with an organic chlorine compound typified by PCB or the like can be reduced to an environmental standard value or less.

  Moreover, after mixing with water and a metal reducing agent beforehand, it supplies to slurry-like soil, stirs and mixes to make a mixture, thereby preventing oxidation and aggregation due to contact of the metal reducing agent with the air and the metal reducing agent to the soil. It can be dispersed more uniformly and in a short time.

  Moreover, by making it cure in the sealed container 4, the leakage of the mixture 15 can be prevented and a stable decomposition reaction can be continued.

  Moreover, it is preferable to stir and mix the mixture 15 in the container 4 at regular intervals by controlling energization to the motor 6 during the curing period.

  This prevents sedimentation of the soil with a larger particle size in the mixture 15 to the lower part of the container 4, prevents the soil from agglomerating, and further prevents the metal reducing agent from agglomerating, thereby uniformly dispersing the metal reducing agent in the soil and The elution of the organic chlorine compound into water is promoted, the contact between the metal reducing agent and the organic chlorine compound is promoted, and the metal reducing agent can effectively act on the decomposition of the organic chlorine compound.

  Therefore, the organochlorine compound in the excavated soil 1 can be treated to an environmental standard value or less.

  In addition, the excavated soil 1, a metal reducing agent containing zero-valent iron powder, and water are stirred and mixed in the container 4 to form a slurry-like mixture 15, and the mixture 15 is cured in the same container 4. Thus, the processing steps can be simplified. Further, a stirring blade 7 that is rotationally driven by a motor 6 that is stirring and mixing means is fixed to the lid 5 of the container 4, and a supply pipe 8 having an on-off valve 8 a that supplies water into the container 4 is opened and connected. I'm allowed. The container 4 and the lid 5 are configured to be detachable, and the lid 5 and the supply pipe 8, and the lid 5, the motor 6 and the stirring blade 7 are configured to be detachable from each other. Can be simplified.

As described above, according to the method for purifying contaminated soil of the present invention, after supplying the metal reducing agent containing zero-valent iron powder and water to the excavated soil contaminated with the organic chlorine compound, the mixture is stirred and mixed. By making the mixture into a uniform slurry and curing the mixture in a container for a certain period of time, organochlorine compounds such as PCB contained in the slurry mixture are released by the oxidation reaction of a metal reducing agent containing zero-valent iron powder. Dechlorination reaction with hydrogen ions can reduce excavated soil contaminated with PCB, etc. to below the environmental standard. In addition, large and complex by introducing an appropriate amount of metal reducing agent containing zero-valent iron powder. It is not necessary to use a simple processing device. Therefore, excavated soil contaminated with organochlorine compounds typified by PCB and the like can be treated to environmental standards or below.

  It can be applied to a wide range of uses that require purification of soil contaminated with harmful substances.

The conceptual diagram of the soil treatment system of one Example of this invention Flow chart showing processing steps corresponding to FIG.

Explanation of symbols

1 Excavated soil 2 Sorting device 2a Vibrating sieve 2b Vessel 3 Stone, glass (large contaminants)
4 Container 5 Lid 6 Motor (stirring means)
7 Stirring blade (stirring means)
8 Supply pipe 8a On-off valve 9 Storage container 10 Metal reducing agent supply port 11 Supply pipe 12 Motor (stirring means)
13 Stirring blade (stirring means)
14 Supply pipe 14a On-off valve 15 Mixture

Claims (6)

After supplying a metal reducing agent containing zero-valent iron powder and water to excavated soil contaminated with organochlorine compounds, the mixture is stirred and mixed to form a slurry mixture, and the mixture is cured in a container for a certain period of time. Purification method for contaminated soil. The method for purifying contaminated soil according to claim 1, wherein the supply amount of water is adjusted according to a moisture content of excavated soil. A slurry-like soil is prepared by previously supplying water to the excavated soil and stirring and mixing, and then the slurry-like mixture is generated by supplying and stirring and mixing a metal reducing agent containing zero-valent iron powder. The method for purifying contaminated soil according to claim 1. The method for purifying contaminated soil according to claim 3, wherein the water and the metal reducing agent are mixed in advance, and then supplied to the slurry-like soil and mixed with stirring to form the slurry-like mixture. The method for purifying contaminated soil according to claim 1, wherein at least an organochlorine compound elution accelerator is supplied to the slurry mixture. 2. The method for purifying contaminated soil according to claim 1, wherein the slurry mixture is subjected to a drying step, and the dried slurry mixture is stirred and mixed at least continuously or for a fixed time during a curing period.

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