JP2006247483A - Treatment method of contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of detoxifying soil contaminated by harmful and hardly decomposable organic contaminating substances easily, inexpensively, safely and environmentally friendly and, further, capable of preventing ground water contamination by detoxifying the contaminated soil. <P>SOLUTION: The treatment method of water quality contamination organic substance-containing waste is characterized in that the soil contaminated by harmful and hardly decomposable organic contaminating substances is treated by adding active carbon and metallic salt such as iron salt which have high peroxide decomposition ability and by adding an oxidizing agent such as peroxide under conditions of pH 5 or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for treating soil contaminated with persistent organic pollutants and the like.

  In recent years, organic chlorine compounds (perchloroethylene, trichloroethylene, tetrachloroethane, trichloroethane, chlorobenzenes, chloronaphthalenes, hexachlorocyclohexane, polychlorobiphenyl (PCB), etc.), aromatic compounds (phenol, toluol, catechol, biphenyl, quinoline) , Dibenzofuran, pyrene, phenanthrene, anthracene, fluorene, acenaphthene, carbazole, etc.), agricultural chemicals / preservatives (dichlorodiphenyltrichloroethane (DDT), benzenehexachloride (BHC), cresol, thiuram, simazine, isoxathione, diazinone, fenitrothion, chlorpyrifos, Trichlorphone, butahomis, propizzamide, etc.), petroleum and its fractions (crude oil, heavy oil, light oil, kerosene, lubricating oil, etc.) Harmful and soil pollution and groundwater contamination by persistent organic pollutants has become a manifest, serious social problem.

  On the other hand, various methods have been proposed and implemented, and can be broadly classified as follows: (1) a method for purifying contaminated soil in situ, (2) a method for containing contaminated soil in situ, (3) After excavating contaminated soil, it can be divided into a method of purifying and refilling in situ, and (4) a method of excavating contaminated soil, transferring it to a treatment facility, purifying it, and then disposing it by landfill.

(1) In-situ purification methods include microorganism-based methods (see Patent Documents 1 to 5), plant-based methods, and chemical decomposition methods using various drugs (see Patent Documents 6 and 7, non-patent documents). 1), decomposition using a photocatalyst or the like (see Patent Document 8), a method of sucking gas generated from soil by decompression or the like (see Non-Patent Document 1), a method of injecting activated carbon or the like (see Patent Documents 9 and 10) ), The method of injecting quicklime and volatilizing the pollutants with heat from the hydration reaction (see Non-Patent Document 1), etc. As a method of containment as it is in the original position of (2), cement and various chemicals are added and insolubilized After the excavation of (3), the method or the like (see Patent Document 11) purifies and refills in place, after excavating the contaminated soil, directly using various microorganisms that decompose using microorganisms, etc. Utilize chemical Decompose, purify the gas generated from the soil by suction removed by reduced pressure, purifying by sucking gas generated by heat treatment to decompose the contaminants by heat treatment. Alternatively, there is a method (see Non-Patent Document 1) in which after extracting contaminated soil by various methods, the extract is treated by various methods (for example, the above method). After the excavation in (4), as a method for transferring to a treatment facility, purifying, and then disposing by landfill, etc., the above method can be applied as a purification method.

  However, none of these methods can be said to be perfect methods, and development of better technology is desired. For example, although the method (1) of purifying contaminated soil in situ has the advantage that it can be purified without moving the contaminated soil, the method using microorganisms or plants is effective because the decomposition reaction proceeds slowly. It takes a long time to appear. In chemical decomposition methods using various drugs, there may be secondary contamination due to residual chemical drugs. In the decomposition method using a photocatalyst, it is necessary to irradiate light. In the method of sucking gas generated from the soil by decompression or the like, the efficiency is affected by the volatility of the pollutant, and the relatively highly volatile substance is efficiently removed, but the removal efficiency of the less volatile substance is low. In the method of injecting activated carbon, etc., it is necessary to use activated carbon that matches the adsorption capacity. The method of injecting quicklime has problems such as poor removal efficiency of substances with low volatility.

The method (2) for containing contaminated soil as it is has the problem that it always leaves the danger of leakage because the pollutant is essentially not purified and remains on the spot. After excavation in (3), the method of purifying and backfilling in situ is more efficient than the method of purifying in situ, but it requires a process of excavating and extracting contaminated soil and requires a lot of labor. In some cases, it may be necessary to remove structures and plantations on the ground, or to install large-scale treatment facilities locally. After excavation in (4), the method of transferring to a treatment facility, purifying, and then disposing by landfill disposal is a good method for local purification if excavation is complete, but it is necessary to move contaminated soil. Therefore, there is a risk that the contamination may be spread over a wide range, and the same problems as in (1) to (3) above may occur in the purification of the contamination at the treatment plant. Furthermore, there is a risk that a serious problem such as contamination of the final landfill may occur if the final landfill is critically insufficient or the detoxification treatment is insufficient.
JP2003-116526A JP 2003-102469 A JP-A-8-80484 JP-A-8-3012 JP 10-34127 A JP 2004-321887 A Japanese National Patent Publication No. 11-500708 JP 2001-19554 A Japanese Patent Laid-Open No. 2003-164846 JP 2004-216249 A JP 2003-290757 A Taisei Corporation Pamphlet 0211.1000. Re-S

  The present invention makes it easy and low-cost, environmentally friendly and harmless to soil contamination by organic pollutants that are toxic and difficult to decompose, such as organochlorine compounds, agricultural chemicals / preservatives, petroleum and its fractions, In addition, by purifying soil contamination, it provides a new technology that can prevent groundwater contamination.

  As a result of intensive studies on the above problems, the present inventors have used activated carbon having a high ability to decompose hydrogen peroxide and a metal salt such as iron salt in combination with an oxidizing agent such as hydrogen peroxide to reduce pollutants in the soil. It was found that it can be made harmless easily at low cost, easily and safely. That is, the present invention adds a metal salt such as an iron salt and activated carbon having a high ability to decompose hydrogen peroxide in a method for purifying contaminated soil, adjusts the pH to 5 or lower if possible, and further oxidizes such as hydrogen peroxide. The present invention relates to a method for treating soil contaminated with persistent organic pollutants, characterized by adding an agent and treating the soil.

  According to the present invention, soil contaminated with a wide range of hardly decomposable organic substances can be purified in a short time, very efficiently and inexpensively under mild conditions without causing secondary pollution, etc. This is a very useful method.

A feature of the present invention resides in the use of activated carbon having a high ability to decompose hydrogen peroxide despite the use of an oxidizing agent such as hydrogen peroxide. The activated carbon used in the present invention has the ability to decompose hydrogen peroxide in an aqueous solution having a temperature of 27 ° C. and a hydrogen peroxide concentration of 0.5% by weight. Is measured by the hydrogen peroxide decomposition rate calculated by the following formula.
Hydrogen peroxide decomposition rate = (0.5−residual hydrogen peroxide concentration (%)) / 0.5 × 100

  In the present invention, activated carbon having a hydrogen peroxide decomposition rate of 5% or more, preferably 20% or more is used. The higher the hydrogen peroxide decomposing activity, the more efficiently the decomposition of pollutants in the soil proceeds, and the amount of activated carbon used is reduced, and the treatment time can be shortened. When the hydrogen peroxide decomposition rate is 5% or less, a large amount of activated carbon is required or a very long treatment time is required, and the object of the present invention cannot be achieved.

  The activated carbon used in the present invention is not limited as long as it has hydrogen peroxide decomposing ability, and its origin is not particularly limited, but usually wood, cellulose, sawdust, charcoal, coconut husk charcoal, palm kernel charcoal, uncoated ash Using plant materials such as peat, lignite, lignite, bituminous coal, anthracite and other coal-based minerals, petroleum residue, sulfate sludge, oil carbon and other petroleum-based minerals . Those using protein as raw materials, those using protein-containing sludge or waste as starting materials, those using waste bacterial cells from fermentation production, those using polyacrylonitrile (PAN) as raw materials, etc. In particular, bituminous coal, waste cells, and PAN are preferably used. Moreover, by adding a treatment to these activated carbons, the ability to decompose hydrogen peroxide can be imparted or used.

  Further, the activated carbon used is more effective as the powder becomes finer, and the effect can be enhanced by using a fine powder of 1000 μm or less, preferably 300 μm or less. This is considered to be due to the fact that the contact area is increased by using fine powder, and the decomposition rate of hydrogen peroxide is increased. Even if the particle size is 1000 μm or more, for example, 10 mm, the object of the present invention can be achieved if it has the ability to decompose hydrogen peroxide. However, it is necessary to increase the amount of use or to increase the treatment time. In consideration of operability, it is preferably 1000 μm or less. In addition, activated carbon is industrially more advantageous to supply as a suspension in terms of dust generation suppression and operability. From the viewpoint of fluidity and operability of the suspension, 1000 μm or less, preferably It is preferable to supply it as a suspension of powder of 300 μm or less. Furthermore, activated carbon usually reduces its adsorption capacity by moisture adsorption or the like. In the present invention, activated carbon is suspended in a dispersion medium such as water. can do.

  The fine powder can be crushed like an old millstone, a rod mill that grinds with the drop impact force of the rod due to rotation of the fuselage, or a ball that grinds with the ball drop impact force due to rotation of the fuselage, etc. Type, centrifugal roller type that crushes between the roller and the tire on which centrifugal force acts, jet type that blows a jet stream into the fluidized bed of powder and crushes by collision of powder, pulverizes by moving a small ball in the centrifuge And a stirring type. In addition, a number of pulverizers that combine these have been developed by each equipment manufacturer. In some cases, a dry method of pulverizing in a dry state and a wet method of pulverizing in a state moistened with water or the like may be applied. There is no particular limitation on the method of making activated carbon into a fine powder, but a ball type or a stirring type can be suitably used in that it can be made into a finer powder and can prevent dusting during pulverization.

In the present invention, an oxidizing agent and a metal component are used together with activated carbon capable of decomposing hydrogen peroxide. These are not particularly limited as long as they are used for waste treatment by a normal oxidation treatment method. Examples of the oxidizing agent include hydrogen peroxide, peracetic acid, peracetic acid salt, percarbonate, percarbonate. Salt, persulfuric acid, persulfate, perboric acid, perborate, hypochlorous acid, hypochlorite, ozone, oxygen, chlorine, air, etc. Hydrogen oxide is preferred. As the metal component, copper, manganese, iron and the like are preferably used, but iron salts are preferable from the viewpoint of safety and economy. Examples of iron salts include ferrous sulfate, ferric sulfate, ferrous chloride, ferric chloride, iron (II) oxalate, iron (II) bromide, iron (III) bromide, iron nitrate bromide Iron (III), iron (III) fumarate, iron (III) fluoride, iron (II) gluconate, iron (III) hydroxide, iron (III) hypophosphite, iron (II) lactate, etc. However, ferrous sulfate and ferrous chloride are preferable from the viewpoint of cost and operability.

There are no particular restrictions on the amount of the oxidizer and iron salt used, and it is appropriately selected depending on the required treatment level of the waste liquid. In general, the oxidizer is converted into hydrogen peroxide and treated in the treated soil. In contrast, 0.1 to 50% by weight, iron salt is converted to ferrous sulfate, 0.01 to 5% by weight with respect to the treated soil, and activated carbon having the ability to decompose hydrogen peroxide is with respect to the treated soil. 0.01 to 5% by weight. In the treatment according to the present invention, the pH is preferably 5 or less. When the pH is high, the effect is impaired. Although there is no restriction | limiting in particular as a pH adjustment method, Although sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, etc. are mentioned, A sulfuric acid is used suitably from a price, operativity, etc.

  There are no particular restrictions on the method of mixing contaminated soil with metal salts such as iron salts and activated carbon capable of decomposing hydrogen peroxide. Usually, however, these agents are first capable of decomposing metal salts and hydrogen peroxide. Activated carbon, preferably a pH adjuster is mixed. As a method of mixing these into the soil, for example, a solid drug is sprayed in the form of particles or powder, and further, a method of swallowing, a method of spraying these drugs in an aqueous solution or slurry, Examples include a method of press-fitting into the soil in the form of an aqueous solution or slurry, a method of digging up the soil, and mixing into the soil using a mixer, etc., but any other method may be used, and it is preferable to mix as evenly as possible. However, even if it is somewhat non-uniform, the object is sufficiently achieved. In addition, if there is a large amount of pollutants that are difficult to dissolve in water such as oil, in order to perform the treatment more efficiently, soils that do not contain pollutants or have low concentrations of pollutants, or carriers such as diatomaceous earth Can be added to improve the dispersion of pollutants and improve the efficiency of the purification process.

In general, hydrogen peroxide is then mixed in. Examples of the method include a method of spraying hydrogen peroxide solution, a method of press-fitting hydrogen peroxide solution into soil, and the like. Also, there are a method of spraying or press-fitting a predetermined amount at a time, a method of spraying or press-fitting a predetermined amount into several times, a method of spraying or press-fitting a predetermined amount continuously over a certain time, etc. Specifically, more efficient purification treatment can be performed in the order of continuous method, division method, and batch method. Another effective method is to circulate a solution of hydrogen peroxide added to the leachate from the soil. Furthermore, according to this method, activated carbon that has the ability to decompose hydrogen peroxide is used, so even if hydrogen peroxide remains, hydrogen peroxide is decomposed by activated carbon that has the ability to decompose hydrogen peroxide. There is no risk of remaining. Furthermore, it is also possible to return the soil to neutrality by spraying and mixing an appropriate alkaline agent such as sodium hydroxide or slaked lime as a solid or as an aqueous solution after the hydrogen peroxide addition treatment.

  Moreover, this invention can process the contaminated soil carried out from the contaminated area in another processing plant, and can also purify it in its original position without carrying out the contaminated soil. By purifying in-situ, there is no need to carry out a large amount of contaminated soil, the transportation cost and the like are reduced, and further, problems related to the movement and transportation of contaminated soil can be avoided.

  Hereinafter, the present invention will be described in detail with reference to examples. In addition, this invention is not limited to the following Example.

Reference Example 1: Type of activated carbon Ethanol diluted to 500 ppm was used as a model waste solution, and after adjusting pH to 2.7 with sulfuric acid for 1 L, ferrous sulfate heptahydrate and activated carbon shown in Table 1 were used. In addition, hydrogen peroxide shown in Table 1 was added dropwise over 8 hours. The concentration of each component in the table is the value for the model waste liquid. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with calcium hydroxide, a part was filtered off, and the TOC (total organic carbon) measurement was performed on the filtrate. At the same time, the same experiment was performed without adding hydrogen peroxide, and TOC measurement was performed. The TOC decomposition rate was calculated from the ratio of the TOC measurement value of the hydrogen peroxide addition experiment to the TOC measurement value of the hydrogen peroxide non-addition experiment. The results are shown in Table 1.

Reference Example 2: Activated charcoal Particle size of dimethyl sulfoxide (DMSO) diluted to 500 ppm was used as a model waste liquid, except that 3000 ppm of 20 wt% water slurry liquid of waste fungal activated carbon with various average particle diameters was used as activated carbon. The experiment was conducted in the same manner as in Example 1. The results are shown in Table 2.

Example 1
To 100 g of oil-contaminated soil sampled from a gas station site, ferrous sulfate heptahydrate and 20 wt% water slurry of bituminous coal-based activated carbon (average particle size 100 μm) were added and mixed at the concentrations shown in Table 3. Then, after adjusting the pH to 2.7 with sulfuric acid, the hydrogen peroxide shown in Table 3 was mixed while dropping at the time shown in Table 3. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with sodium hydroxide, and the odor and TPH (Total Petroleum Hydro Carbon) were measured on the soil remaining after filtration. The results are shown in Table 3. A significant reduction in odor and decomposition of TPH were observed.

Comparative Example 1
For 100 g of the same oil-contaminated soil used in Example 1, ferrous sulfate heptahydrate and 20 wt% water slurry liquid of bituminous coal-based activated carbon (average particle size 100 μm) as necessary are shown in Table 4. After adding and mixing at the indicated concentrations and adjusting the pH to 2.7 with sulfuric acid, water or hydrogen peroxide shown in Table 4 was added dropwise at the times shown in Table 4. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with sodium hydroxide, and the odor and TPH were measured on the soil remaining after filtration. The results are shown in Table 4. Compared to Example 1, no significant reduction in odor or decomposition of TPH was observed.

Example 2 Examination of Amount of Oxidizing Agent 10 g of A heavy oil was added to 10 kg of horticultural culture soil adjusted to a moisture content of 16% to prepare simulated contaminated soil. To 100 g of this model oil-contaminated soil, ferrous sulfate heptahydrate and 20 wt% water slurry of bituminous coal-based activated carbon (average particle size 100 μm) were added and mixed at the concentrations shown in Table 5, and sulfuric acid was used. After adjusting the pH to 2.7, the hydrogen peroxide shown in Table 5 was mixed dropwise at the time shown in Table 5. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the mixture was filtered and the remaining soil was measured for odor and TPH. The results are shown in Table 5. A significant reduction in odor and decomposition of TPH were observed.

Comparative Example 2
For 100 g of the same oil-contaminated soil used in Example 2, ferrous sulfate heptahydrate and 20 wt% water slurry liquid of bituminous coal-based activated carbon (average particle size 100 μm) as necessary are shown in Table 6. After adding and mixing at the indicated concentrations and adjusting the pH to 2.7 with sulfuric acid, water or hydrogen peroxide shown in Table 6 was added dropwise at the times shown in Table 6. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the mixture was filtered and the remaining soil was measured for odor and TPH. The results are shown in Table 6. Compared to Example 2, no significant reduction in odor or decomposition of TPH was observed.

Example 3: Type of activated carbon raw material 10 g of A heavy oil was added to 10 kg of horticultural culture soil adjusted to a moisture content of 16% to prepare simulated contaminated soil. To 100 g of this model oil-contaminated soil, ferrous sulfate heptahydrate and various activated carbon (average particle size 100 μm) powders were added and mixed at the concentrations shown in Table 7, and the pH was adjusted to 2.7 with sulfuric acid. Then, the hydrogen peroxide shown in Table 7 was mixed while being dropped at the time shown in Table 7. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with slaked lime, followed by filtration, and the remaining soil was measured for odor and TPH. The results are shown in Table 7. A significant reduction in odor and decomposition of TPH were observed.

Comparative Example 3
For 100 g of the same oil-contaminated soil used in Example 3, ferrous sulfate heptahydrate and, if necessary, powder of bituminous coal-based activated carbon (average particle size 100 μm) were added at the concentrations shown in Table 8. After mixing and adjusting the pH to 2.7 with sulfuric acid, water or hydrogen peroxide shown in Table 8 was added dropwise for the time shown in Table 8. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with slaked lime, followed by filtration, and the remaining soil was measured for odor and TPH. The results are shown in Table 8. Compared to Example 3, no significant reduction in odor or decomposition of TPH was observed.

Example 4 Particle Size of Activated Carbon 10 g of A heavy oil was added to 10 kg of horticultural culture soil adjusted to a moisture content of 16% to prepare simulated contaminated soil. To 100 g of this model oil-contaminated soil, ferrous sulfate heptahydrate and bituminous charcoal activated carbon powder having the average particle size shown in Table 9 were added and mixed at the concentrations shown in Table 9, and the pH was adjusted with sulfuric acid. After adjusting to 2.7, the hydrogen peroxide shown in Table 9 was mixed while being dropped at the time shown in Table 9. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with slaked lime, followed by filtration, and the remaining soil was measured for odor and TPH. The results are shown in Table 9. The smaller the average particle size, the greater the reduction in odor and the decomposition of TPH.

Comparative Example 4
To 100 g of the same oil-contaminated soil used in Example 4, ferrous sulfate heptahydrate and bituminous coal-based activated carbon powder having the average particle size shown in Table 10 were added and mixed at the concentrations shown in Table 10 Then, after adjusting the pH to 2.7 with sulfuric acid, the water shown in Table 10 was mixed while being dropped at the time shown in Table 10. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with slaked lime, followed by filtration, and the remaining soil was measured for odor and TPH. The results are shown in Table 10. Compared to Example 4, no significant reduction in odor or decomposition of TPH was observed.

Example 5: Metals 10 g of heavy oil A was added to 10 kg of horticultural soil adjusted to a moisture content of 16% to prepare simulated contaminated soil. To 100 g of this model oil-contaminated soil, a metal salt or metal powder shown in Table 11 and a 20 wt% water slurry solution of bituminous coal-based activated carbon (average particle size 100 μm) are added and mixed at the concentrations shown in Table 11. After adjusting the pH to 2.7 with sulfuric acid, the hydrogen peroxide shown in Table 11 was mixed while being dropped for the time shown in Table 11. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with sodium hydroxide, followed by filtration, and the remaining soil was measured for odor and TPH. The results are shown in Table 11. Significant reduction and TPH degradation was observed.

Comparative Example 5
After adding and mixing the metal salt or metal powder shown in Table 12 in the concentration shown in Table 12 to 100 g of the same oil-contaminated soil used in Example 5, the pH was adjusted to 2.7 with sulfuric acid. The hydrogen peroxide shown in Table 12 was mixed while being dropped at the time shown in Table 12. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with sodium hydroxide, followed by filtration, and the remaining soil was measured for odor and TPH. Compared to Example 5, no significant reduction in odor or decomposition of TPH was observed.

Example 6: pH
10 g of heavy oil A was added to 10 kg of horticultural culture soil adjusted to a moisture content of 16% to prepare simulated contaminated soil. To 100 g of this model oil-contaminated soil, ferrous sulfate heptahydrate and bituminous charcoal-based activated carbon (average particle size 100 μm) 20 wt% water slurry liquid were added and mixed at the concentrations shown in Table 13, After adjusting the pH to the value shown in Table 13, the hydrogen peroxide shown in Table 13 was mixed while dropping at the time shown in Table 13. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with slaked lime, followed by filtration, and the remaining soil was measured for odor and TPH. The results are shown in Table 13. Significant reduction and TPH degradation was observed.

Comparative Example 6
For 100 g of the same oil-contaminated soil used in Example 6, ferrous sulfate heptahydrate and 20 wt% water slurry liquid of bituminous coal-based activated carbon (average particle size 100 μm) at the concentrations shown in Table 13 The mixture was added and mixed, and the pH was adjusted to the value shown in Table 13 with sulfuric acid, and then the hydrogen peroxide shown in Table 13 was added dropwise at the time shown in Table 13. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the pH was neutralized with slaked lime, followed by filtration, and the remaining soil was measured for odor and TPH. The results are shown in Table 14. Compared to Example 6, no significant reduction in odor or decomposition of TPH was observed.

Example 7: Addition of carrier 1 g of A heavy oil and horticultural culture soil shown in Table 15 (adjusted to a moisture content of 16%) were mixed to prepare simulated contaminated soils having various oil concentrations. To this model oil-contaminated soil, ferrous sulfate heptahydrate and bituminous charcoal-based activated carbon (average particle size 100 μm) 20 wt% water slurry solution are added and mixed at the concentrations shown in Table 15, and pH is adjusted with sulfuric acid. After adjusting to 2.7, the hydrogen peroxide shown in Table 15 was mixed dropwise at the time shown in Table 15. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, the mixture was filtered and the remaining soil was measured for odor and TPH. The results are shown in Table 15. For the same amount of oil, a greater reduction in odor and decomposition of TPH was observed as the amount of culture soil increased.

Comparative Example 7
Add 1 g of A heavy oil to 1 g of ferrous sulfate heptahydrate and 20 wt% water slurry of bituminous coal-based activated carbon (average particle size 100 μm) at the concentrations shown in Table 16, and adjust the pH to 2 with sulfuric acid. After adjusting to 0.7, the hydrogen peroxide shown in Table 16 was mixed while being dropped for the time shown in Table 16. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, odor and TPH were measured. The results are shown in Table 16. Compared to Example 7, no significant reduction in odor or decomposition of TPH was observed.

Example 8: Circulation of leachate 10 g of A heavy oil was added to 10 kg of horticultural culture soil adjusted to a moisture content of 16% to prepare simulated contaminated soil. To 100 g of this model oil-contaminated soil, ferrous sulfate heptahydrate and 20 wt% water slurry of bituminous coal-based activated carbon (average particle size 100 μm) were added and mixed at the concentrations shown in Table 5, and sulfuric acid was used. After adjusting the pH to 2.7, the liquid is circulated in such a manner that a cylindrical container with a diameter of 3 cm filled with glass wool at the bottom is poured, 100 g of water is poured from the top, and water that has come out from the bottom is poured again from the top. It was. The circulation speed at that time was 0.1 L / hour. Hydrogen peroxide shown in Table 17 was added to this circulating water for the time shown in Table 17. The treatment temperature was 20 ° C. After completion of the dropwise addition of hydrogen peroxide, sodium hydroxide was added to the solution to neutralize the pH, the solution was removed, and the remaining soil was measured for odor and TPH. The results are shown in Table 17. Even without mixing the soil, a significant reduction in odor and decomposition of TPH was observed.

Comparative Example 8
In the same experimental system as in Example 8, a test was conducted using the same amount of water instead of 35 wt% hydrogen peroxide. The results are shown in Table 18. Compared to Example 8, no significant reduction in odor or decomposition of TPH was observed.

Claims (8)

  A method for treating contaminated soil, comprising adding a metal salt, activated carbon having an ability to decompose hydrogen peroxide, and an oxidizing agent to soil contaminated with a hardly decomposable organic matter.   The method for treating contaminated soil according to claim 1, wherein the metal is iron, copper or manganese.   The method for treating contaminated soil according to claim 1, wherein the oxidizing agent is hydrogen peroxide.   The method for treating contaminated soil according to claim 1, wherein the pH at the start of treatment is adjusted to 5 or less.   In an aqueous solution with an activated carbon temperature of 27 ° C. and a hydrogen peroxide concentration of 0.5% by weight, the hydrogen peroxide decomposition rate after 5 minutes of addition of 0.5% by weight of activated carbon is 5% or more. The method for treating contaminated soil according to claim 1, comprising:   The method for purifying contaminated soil according to claim 1, wherein the activated carbon is made from bituminous coal, waste cells or polyacrylonitrile.   The method for treating contaminated soil according to claim 1, wherein the activated carbon is a fine powder of 1000 μm or less.   2. The method for treating contaminated soil according to claim 1, wherein the activated carbon is a suspension of fine powder of 1000 μm or less.