WO2002078871A1

WO2002078871A1 - Method of purifying contaminated soil

Info

Publication number: WO2002078871A1
Application number: PCT/JP2002/002948
Authority: WO
Inventors: Hisahide Saito
Original assignee: Lion Corporation
Priority date: 2001-03-28
Filing date: 2002-03-27
Publication date: 2002-10-10
Also published as: JP4238036B2; JPWO2002078871A1

Abstract

A method of purifying contaminated soil, comprising a humus composite lowest layer disposing process (21) for placing ferrihydrite humus composite on soil near the contaminated soil, a humus soil stacking layer process (22) for placing the contaminated soil and the ferrihydrite humus composites alternately on the humus composite lowest layer (5) to form a humus soil stacked layer (11), and a humus soil stirring process (23) for stirring the humus soil stacked layer (11) to provide a humus soil mixture (12).

Description

Specification

How to clean contaminated soil

Technical field

The present invention relates to a method for purifying soil, and more particularly to a method for purifying contaminated soil containing heavy metals. Background art

In recent years, the environmental pollution of the earth has become serious, and interest in environmental problems has increased. As soil pollution, which is one of the environmental pollutions, there is a problem of soil pollution due to carcinogenic harmful chemicals such as trichlorethylene, soil pollution due to heavy metals, and composite pollution due to both.

Soil pollution is caused by factory accidents and illegal dumping of waste.However, if harmful chemicals and heavy metals exceed the soil purification capacity, it will impair soil functions and contaminate groundwater. It may cause. In addition, it takes a long time for environmental destruction due to soil pollution to take place in the form of pollution as a result of the act of polluting, making it difficult to take measures against soil pollution. In light of the worsening situation of soil contamination, environmental standards for soil have been established in Japan, and the foundation for measures against soil and groundwater contamination has been established.

In soil remediation, it is common practice to replace soil in contaminated land with non-contaminated soil, and to carry out `` soil replacement '' and transport the contaminated soil to another location for purification. .

When pollution is widespread, pumping wells and other facilities are used to pump up contaminated groundwater and purify the soil.

However, according to the conventional soil purification method as described above, there is a problem that a large-scale apparatus is required. When replacing the soil, in addition to the work of replacing the contaminated soil with the clean soil, transportation of the contaminated soil and a soil purification device were required, requiring large-scale construction and equipment. According to the purification method by pumping contaminated groundwater, a purification device such as an activated carbon adsorption device was required in addition to a pumping well, which required a large-scale device.

In many cases, it is necessary to purify a narrow range of soil.However, according to the above-mentioned conventional method, the construction requires a large amount of time. Development was desired.

The present invention has been made in view of the above problems and demands, and an object of the present invention is to provide a soil purification method that can be easily performed without using a large-scale apparatus. Disclosure of the invention

The soil purification method according to the present invention includes a humus-soil stacking step of forming a humus-soil stack by alternately placing the ferrihydrite humus complex and the contaminated soil on soil near the contaminated soil, A humus-soil stirring step of stirring the humus-soil laminate to obtain a humus-soil mixture.

The method for purifying soil according to the present invention is a method for purifying contaminated soil, wherein the step of arranging the bottom layer of the humus complex, wherein the ferrihydrite humus complex is placed on soil near the contaminated soil, A humus * soil stacking step of alternately placing the contaminated soil and the ferrihydrite humus complex on the lowermost layer of the complex to form a humus'soil stack; And a humus-soil stirring step of obtaining a mixture of humus and soil.

As described above, the use of the ferrihydrite humus complex makes it possible to efficiently purify the soil due to the unique properties of ferrihydrite contained in the soil restoration material. Ferrihydrite purifies soils containing heavy metals because its mono-OH group, which has mutational charge properties on its surface, has the property of adsorbing, chelating, fixing, and inactivating heavy metals with positive ions. It becomes possible. Furthermore, ferrihydrite has a specific surface area of 180 to ²⁰⁰ m2 Zg, which is a large area that can adsorb heavy metals.Therefore, by using a ferrihydrite humus complex containing ferrihydrite, efficient purification of heavy metal soil It is possible to do it.

In addition, ferrihydrite has the property of chelating and aggregating with the functional group of an organic compound having a negative charge, and the property of catalyzing the decomposition of an organic compound of iron hydrated oxide. Inactivation makes it possible to purify soil containing organic compounds. Furthermore, ferrihydrite adsorptive decomposition specific surface force "1 8 0~200m ² Zg and size organic compounds, the area that can be inactivated fried wide, to the use of ferrihydrite humus complex comprising a ferrihydrite This makes it possible to efficiently purify organic soil.

In addition, since the bottom layer of the humus complex is placed on the soil first, the heavy metal and harmful organic compounds contained in the contaminated soil are prevented from migrating to the soil. Becomes possible.

Furthermore, since the contaminated soil and the ferrihydrite humus complex are alternately placed on the bottom of the humus complex to form a humus-soil laminate, a humus-soil stacking step is performed. Humus, which is a post-process, can be easily and evenly mixed with the humus complex and the contaminated soil in the soil stirring process.

At this time, after the stirring step, the lowermost layer of the humus complex in which the ferrihydrite humus complex is placed on the soil, and the lowermost layer of the humus complex obtained in the rearrangement step, A humus-mixture laminate, wherein the humus-soil mixture formed in the stirring step and the ferrihydrite humus complex are alternately placed to form a humus-mixture laminate. The humus-mixture stirring step of obtaining the humus-mixture mixture by stirring the humus-mixture laminate obtained in the process It is preferable to perform the operation repeatedly one after another.

As described above, the humus 'soil mixture obtained in the stirring process is subjected to the humus' mixture stirring process, and the ferrihydrite humus complex is further mixed, so that the polluted soil can be more completely purified. It becomes possible.

Further, after the stirring step, a lowermost layer arrangement step of placing the humus'soil mixture formed in the stirring step on soil near the contaminated soil, and a humus'soil mixture obtained in the arrangement step. A mixture-soil stacking step in which the contaminated soil and the humus'soil mixture formed in the stirring process are alternately placed on the lowermost layer to form a mixture-soil stack; and the mixture-soil It is preferable that the mixture obtained in the laminating step-the soil layered body is stirred and the mixture “mixture to obtain a mixture of soil” and the soil stirring step are repeatedly performed a predetermined number of times.

In this way, the humus-soil mixture obtained in the stirring process is used in place of the polyhydrite humus complex. And reuse of the ferrihydrite humus complex becomes possible. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory view showing an outline of an embodiment of a soil purification method of the present invention, FIG. 2 is a block diagram showing a flow of an embodiment of a soil purification method according to the present invention, and FIG. It is a block diagram showing a flow of other embodiments of a soil purification method according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The members, arrangements, and the like described below do not limit the present invention, and can be variously modified within the scope of the present invention. (Embodiment 1)

The present embodiment is a method for purifying (inactivating) heavy metal soil using a ferrihydrite humus complex.

The ferrihydrite humus complex of the present embodiment refers to a complex of amorphous ferrihydrite (hereinafter referred to as ferrihydrite) and an organic substance. The term "humus" as used herein means soil organic matter, and is synonymous with compost.

Ferri The high dry Bok (ferrihydrite), a general formula 5Fe ₂ 0 ₃ 'non AkiraTadashitetsu hydrated oxide represented by 9H ₂ 0. Generally, it is known as a low-crystalline iron mineral that is formed at an early stage in the Earth's surface.

Ferrihydrite has the property of coordinating with the OH and O ends of carboxyl groups and carbonyl groups of organic compounds and forms aggregates. Since the specific area of the organic compound is as large as about 200 (m ² Z g), it can be used for the reaction with the OH and O ends of organic compounds, so it has high catalytic ability and high ability to form aggregates. I know it.

The ferrihydrite humus complex of the present embodiment is obtained by adding a 10 to 20% by weight sulfuric acid aqueous solution to a sedimentary rock soil such as basalt and andesite to extract an acid-soluble component, and a naturally-derived ionized mineral concentrate ( It is manufactured by the following manufacturing process using Clay Extract W. W (manufactured by Rion Co., Ltd .; hereinafter, referred to as a mineral liquid) and an organic compound mixture as raw materials.

Minera Les solution 7000 to iron "! Containing about 3000 (ppm). Iron that is part of the minerals Les liquid is present in different forms by pH. In pH3 or less, iron, Fe ^{3 +,} pH ³ ~ In pH 4, Fe ^{3 +} and Fe (OH) ₂ +, the pH4 ~ pH5, Fe ^{3 +} and Fe (OH) ^{2 +} and Fe (OH) ₂ +, the pH greater than pH 5, and Fe (OH) ²⁺ Exists as Fe (OH) ₂ + and Fe (OH) ₃ .

Further, the residue obtained by extracting sulfuric acid from the soil, which is the base material of the mineral liquid of the present embodiment, contains pure iron (Fe (3+)) and amorphous goethite (Hi-FeOOH). Here, pure iron (Fe (3+)) refers to stable iron that is hard to change, and is not oxidized and does not elute. It means iron having the property of

As the organic compound mixture, organic waste such as animal dung, garbage, food waste, pruned branches and waste material chips, and septic tank sludge are used.

A method for producing a ferrihydrite humus complex will be described.

First, a pH adjusting step of the organic waste crushed by a known shredder is performed. In this step, slaked lime (calcium hydroxide: Ca (OH) ₂ ) is added to adjust the pH of the organic matter to 5 or more. By this pH adjustment step, the pH of the mixture of the organic substance and the aqueous solution of the mineral liquid becomes 5 or more in each of the steps subsequent to the step of immersing in the mineral liquid, so that ferrihydrite can be formed.

After the pH adjustment step, the organic matter adjusted to pH 5 or more is immersed in a mineral liquid dilution water tank diluted 5000 times with water, and a mineral liquid diluting water immersion step of leaving it for 5 hours or more is performed.

As described above, the mineral liquid is diluted with water because the amount of the mineral liquid is about 0.1 to 0.2, so if an organic compound is added to the mineral liquid undiluted solution, the mineral liquid is diluted during the composting process. This is because the fermenting bacterium is killed and cannot be composted in the subsequent mineral addition-fermentation process.

The mineral water dilution water is preferably adjusted to pH 5 to 7 in order to prevent bacterial killing.

Thereafter, in a known blender, a mineral liquid dilution water is added, and a primary fermentation (mineral liquid addition) step of fermenting an organic substance with stirring is performed. Here, a known fermentation aid may be added.

Next, the organic matter is taken out from the blender 11 and subjected to secondary fermentation and “ripening” (a mineral liquid addition step. In this step, the organic matter taken out of the blender is deposited in a compost plant with a roof and fermented while the mineral liquid is fermented. When the temperature of the organic material reaches 65 ° C to 70 ° C, replenish the 7000-fold diluted mineral water while turning it over using a bulldozer, excavator, etc. . Secondary fermentation-About 3 weeks after the start of the ripeness (addition of mineral liquid) process, the organic matter becomes ripe compost.

Thereafter, a mineral liquid dilution water is added to the ripe organic compost while stirring, and a post-composting mineral addition step is performed.

Thus, the ferrihydrite humus complex used in the present embodiment is completed. The amount of ferrihydrite in this ferrihydrite humus complex is 5 ppm. The CEC (cation exchange capacity) of this ferrihydrite humus complex is about 80 (meq) (measured by ammonium acetate method in fertilizer analysis).

In the present embodiment, the ferrihydrite humus complex produced by the above method is used, but the present invention is not limited to this, and a ferrihydrite humus complex produced by another method or a natural ferrihydrite humus complex may be used. Is also good.

The effect of improving the contamination of the ferrihydrite humus complex is specified by the cation exchange capacity (CEC). Cation exchange capacity refers to the maximum amount of soil capable of adsorbing cations (total amount of negative charge), and is also called base substitution capacity. The ferrihydrite humus complex used in the present embodiment may have a cation exchange capacity of 30 (meq) or more, preferably 50 (meq) or more.

Next, a soil purification method according to the present embodiment will be described.

A ferrihydrite humus complex (hereinafter, referred to as a humus complex) 3 is previously loaded on a soil 1 in the vicinity of the contaminated soil 2 in question using a known truck vehicle. .

Next, as shown in FIG. 1 (B), the humus complex is placed on the soil 4 near the contaminated soil 2 on the premises so as to be substantially disc-shaped or substantially plate-shaped, and the lowermost layer 5 of the humus complex is formed. Step 21 for arranging the lowermost layer of the humus complex is performed. This step is performed by moving the humus complex with a known bulldozer.

In the present embodiment, the humus complex is first placed on the soil 4. If contaminated soil 2 is placed on soil 4 before the humus complex, Heavy metals and harmful organic compounds may migrate to the soil 4.

Next, as shown in FIG. 1 (B), the contaminated soil 2 is placed on the lowermost layer 4 of the humus complex so as to be substantially disc-shaped or substantially plate-shaped to form the first contaminated soil layer 6. Conduct the first layer of contaminated soil. This step is performed by moving the contaminated soil 2 with a known bulldozer.

Then, the humus' soil stacking step 22 is performed. In this step, first, the humus complex is placed on the contaminated soil first layer 6 so as to be substantially disc-shaped or substantially plate-shaped to form the humus complex second layer 7. Layer arranging step and arranging the contaminated soil 2 on the second layer 7 of the humus complex in a substantially disk or plate shape to form the second layer 8 of the contaminated soil. Perform the process.

Further, in the same procedure as the humus complex second layer disposing step, the humus complex third layer disposing step of forming the humus complex third layer 9 on the contaminated soil second layer 8 is performed. In the same procedure as the two-layer arrangement step, a contaminated soil third layer arrangement step of forming the contaminated soil third layer 10 on the humus complex third layer 9 is performed.

As described above, the humus' soil laminate 11 shown in FIG. 1 (C) is completed. The contaminated soil first layer disposing step to the contaminated soil third layer disposing step constitute the humus soil laminating step 22 of claim 2.

In this way, the humus complex bottom layer arrangement step 21 and the humus' soil layering step 22 are performed to alternately form the humus complex layers 5, 7, 9 and the contaminated soil layers 6, 8, 10 This makes it possible to easily and evenly mix the humus complex and the contaminated soil in the humus / soil stirring step 23 which is the subsequent step.

Although it depends on the amount of contaminated soil to be treated, it is preferable in terms of work efficiency that the total height of the humus-soil stack 11 be about 2 to 3 m in each humus complex arranging step.

Next, the humus-soil laminate 11 of FIG. 1 (C) was stirred using a known bulldozer. The humus-soil agitation step 23 is performed to obtain a humus-soil mixture 12 by mixing.

The humus' soil stirring step 23 is carried out in order to bring the OH groups on the ferrihydrite surface into good contact with the heavy metal cations, and to adsorb the heavy metal evenly on the ferrihydrite surface.

In the humus soil agitation step 23, heavy metals and organic substances are adsorbed to ferrihydrite contained in the humus complex. The adsorption in this case proceeds by a mechanism similar to the mechanism by which heavy metals adhere to the paper filter.

Humus' Soil agitation step 23, agitate well. The purpose is to supply sufficient oxygen to promote the activity of microorganisms in the soil or the complex. In addition, ultraviolet rays are sufficiently taken into the humus-soil mixture 12 to activate the catalytic ability of the organic compound decomposition reaction of the hull-L rehydrate.

Thereafter, as shown in FIG. 1 (D), the humus' soil mixture 12 is moved to a location different from that of the soil 4 to carry out a transfer step 24 to prepare for the next contaminated soil purification treatment.

Then, using the humus 'humus' soil mixture obtained in the soil agitation step 23 in place of the contaminated soil 2 and the new humus complex 3 using the new humus complex 3, the above-mentioned migration from the humus complex bottom layer arrangement step was performed. The same procedure as the steps up to the step is performed.

Specifically, a humus complex lowermost layer 5 rearrangement step 25 for placing the humus complex on the soil in the premises is performed.

Thereafter, the humus-soil mixture 12 formed in the stirring step and the humus complex are alternately placed on the lowermost layer 5 of the humus complex obtained in the rearrangement step 25, and the humus-mixture laminate is placed. 11. Perform humus' mixture lamination step 26 to form 1.

Next, a humus-mixture stirring step 27 of stirring the humus-mixture laminate 11 obtained in the humus-mixture stacking step 26 to obtain a humus-mixture mixture 12, and a humus-mixture mixture 12 The moving step 28 for moving is performed.

Thereafter, the lowermost layer of the humus complex, the humus' mixture laminating step, the humus-mixture stirring step, and the moving step are sequentially repeated a predetermined number of times, for example, about 2 to 4 times. Step 29 is repeated. It should be noted that the predetermined number of times includes a plurality of times of two or more times and one time.

After that, the amount of heavy metals in the purified soil after soil purification is determined by atomic absorption spectrometry. The pH is measured by the glass electrode method.

After confirming that the heavy metals have been deactivated, neutralized, or become weakly acidic, return the purified soil to the location of the original contaminated soil 2 and perform the return process 30 to complete the soil purification .

After that, if necessary, the newly contaminated soil 2 is subjected to the soil purification process shown in FIG.

In the present embodiment, the soil is purified by the method according to claim 3 shown in FIG. 2, but only the moving step 24 from the bottom layer arrangement step 21 of the humus complex in FIG. It may be a soil purification method.

The amount of the ferrihydrite humus complex used in the present embodiment varies depending on the quantity and quality of the contaminated soil to be treated. Should be set to 0.2 to 0.5 t, preferably about 0.4 t. The reason why the amount of the ferrihydrite humus complex with respect to the contaminated soil It was set to 0.5 t or less is that if the amount exceeds 0.5 t, the amount of the mixture that cannot be accommodated in the original place in the subsequent return step 30 increases. Because it is too much.

Therefore, for example, when only the lowermost layer arrangement step 21 of FIG. 2 and the movement step 24 are performed, as described above, the total height of the laminate 11 is 2 to 3 m. The composite layers 5, 7, and 9 have a thickness of about 20 to 30 cm, and the contaminated soil layers 6, 8, and 10 have a thickness of about 50 to 80 cm.

In general, the ferrihydrite humus complex is preferably mixed with the contaminated soil It so that the ferrihydrite capacity is about 1 to 5 g.

Instead of performing the humus complex bottom layer rearrangement step 25, the humus / mixture laminating step 26, and the humus / mixture stirring step 27, the purification method according to claim 4 shown in FIG. As described above, a mixture bottom layer arrangement step 35, a mixture / soil layering step 36, and a mixture-soil stirring step 37 may be performed. The humus-soil mixture 12 obtained in the humus-soil stirring step 23 is used in place of the humus complex 3, and the new humus complex The same procedure as the steps from the lower layer arrangement step 21 to the moving step 24 is performed.

Specifically, a mixture bottom layer arrangement step 35 of placing the humus'soil mixture formed in the stirring step 23 on soil near the contaminated soil 2 in the premises is performed.

Thereafter, on the lowermost layer of the mixture obtained in the disposing step 35, the contaminated soil 2 and the humus-soil mixture formed in the stirring step 23 are alternately placed, and a mixture forming a mixture-soil laminate is obtained. Perform soil layering process 36.

Next, the mixture 'the mixture obtained in the soil layering step · the mixture obtained by agitating the soil layered body to obtain a mixture-soil mixture 混合 the soil stirring step 移動 37 and the moving step 38for moving this mixture-soil mixture をDo.

Thereafter, a repetition step 39 is performed in which the mixture lowermost layer arrangement step 35, the mixture “soil stacking step 36, the mixture-soil stirring step 37, and the movement step 38 are sequentially repeated a predetermined number of times, for example, about 2 to 4 times. The predetermined times include two or more times and one time.

After that, quantitative determination of heavy metals and measurement of pH were performed, and after confirming that heavy metals were inactivated, neutralized, or weakly acidic, the purified soil was returned to the original location of contaminated soil 2. Complete the soil purification.

In the purification method shown in FIG. 3, the lowermost layer of the mixture is placed after the transfer step 24, but the lowermost layer of the mixture may be placed after the return step 30.

In the humus-soil stacking step 22, the above-mentioned mineral solution dilution water adjusted to pH 5 or more may be sprayed onto the contaminated soil 6, 8, 10 or the humus-soil mixture 12 to carry out. Humus-soil agitation step 23 May be. The mineral water dilution is applied while maintaining the pH of the contaminated soil 6, 8, 10 or humus' soil mixture 12 at 5 or higher. This makes it possible to form a new ferrihydrite using the mineral liquid dilution water and the organic matter contained in the contaminated soil 6, 8, 10 or the humus-soil mixture 12 as raw materials. Also, in the humus 'mixture laminating step 26, the mixture' soil laminating step 36, the humus 'mixture stirring step 27, the mixture' soil mixing step 37, and the repetition steps 29 and 39, the pH of the soil etc. was set to 5 or more, and the mineral Liquid dilution water may be sprayed.

Further, before the humus complex lowermost layer arranging step 21, the above-mentioned mineral liquid dilution water adjusted to pH 5 or more in advance may be sprayed on the soil 2 on which the humus' soil laminate 11 is arranged. This makes it possible to place contaminated soil as the first layer below the bottom layer 5 of the humus complex.

Further, before all the steps, the diluted mineral water may be sprayed on the contaminated soil 2 in advance, or the diluted mineral water may be sprayed while excavating the contaminated soil 2.

In the soil purification method of the present embodiment, since the ferrihydrite humus complex is used as the soil restoration material, the soil can be efficiently purified by the ferrihydrite-specific properties contained in the soil restoration material. It becomes possible.

Ferrihydrite has the property that its mono-OH group, which has mutated charge properties on its surface, adsorbs, chelate-bonds, fixes and inactivates heavy metals with positive ions, so it purifies soils containing heavy metals. It is possible to do. Furthermore, ferrihydrite has a specific surface area of 180 to ²⁰⁰ m2 Zg, which is a large area capable of adsorbing heavy metals.Thus, by using a ferrihydrite humus complex containing ferrihydrite, it is possible to efficiently purify heavy metal soil. It is possible to do it.

In addition, ferrihydrite has a property of chelating and aggregating with a functional group of a negatively charged organic compound and a property of catalyzing the decomposition of an organic compound of iron hydrated oxide, so that the adsorption and decomposition of the organic compound can be prevented. , Soil containing organic compounds by inactivation It is possible to purify the soil. Furthermore, ferrihydrite adsorptive decomposition specific surface force 1 8 0~200m ² Z _g and sizes organic compound, the area that can be inactivated fried wide, to the use of ferrihydrite humus complex comprising a ferrihydrite This makes it possible to efficiently purify organic soil.

(Example 1)

Hereinafter, an embodiment in which contaminated soil is purified by the soil purification method shown in FIG. 2 will be described.

In this example, the contaminated soil on the land adjacent to the waste disposal site was purified. Contaminated soil It containing 280 ppm of heavy metal cadmium (Cd) and 350 ppm of copper (Cu) was used as the contaminated soil.

The procedure of the purification method of this example will be described.

The humus complex was placed flat on a soil near the contaminated soil with a bulldozer to a height of 1 Ocm, and the contaminated soil was mounted on the soil to a height of 50 cm. After that, the humus complex and the contaminated soil are sequentially laminated on the contaminated soil so that the height of the composite layer is less than 10 cm and the height of the contaminated soil layer is 50 cm. Body 11 formed. As a whole, three layers of humus complex and three layers of contaminated soil were used, for a total of six layers. The total humic complex was 0.2 t and the total amount of contaminated soil was 1 t.

Thereafter, the humus' soil laminate 11 was stirred in place using a bulldozer to obtain 1.2 t of a humus-soil mixture 12.

The humus' soil mixture 12 was moved several meters to prepare for the next soil purification treatment. The humus complex was then laid flat again on a bulldozer to a height of 1 Ocm. A portion of the humus-soil mixture 12 was placed on it to a height of 60 cm. The humus complex and the humus-soil mixture are then placed on top of this humus 'soil mixture, with a humus complex layer height of 10 cm and a humus' soil mixture layer height of 60 cm. The humus 'mixture laminate 11' was formed so as to have a total of six layers. The humus' soil mixture 12 used here was 1.2 t and the humus complex was 0.2 t.

Thereafter, the humus' soil laminate 11 was stirred in place using a bulldozer to obtain 1.4 tons of the humus' soil mixture 12 ', and the soil purification was completed.

When the amount of heavy metals in the humus-soil mixture 12 'that had been subjected to this soil purification treatment was measured, cadmium was 1 Oppm and copper was 8 ppm.

Based on the measurement results, it was judged that the amount of heavy metals in the soil was below the target value, and 1 t of 1.4 t of humus 'soil mixture 12' was returned to the place where the original contaminated soil was.

Thus, the soil purification process has been completed.

Thus, according to the soil purification method of the present example, it was found that the amount of heavy metals in the soil was reduced and heavy metals were inactivated.

The remaining 0.4 t of the humus 'Soil mixture 12' was used for purification of other contaminated soil.

In addition, purification of contaminated soil on other land adjacent to the waste disposal site was conducted. Contaminated soil containing 0.1 to 0.2 ppm of lead (Pb), a heavy metal, was used as the contaminated soil. The same procedure as in Example 1 was performed. When the amount was measured, it was 0.014-0.020 ppm.

Thus, according to the soil purification method of the present example, it was found that the amount of heavy metals in the soil was reduced and heavy metals were inactivated. Industrial applicability

As described above, according to the present invention, since the ferrihydrite humus complex is used as the soil restoration material, it is possible to efficiently purify the soil due to the unique properties of ferrihydrite contained in the soil restoration material. It becomes possible. Ferrihydrite has the property that its mono-OH group, which has mutated charge properties on its surface, adsorbs, chelates, fixes, and inactivates heavy metals with positive ions, thus purifying soil containing heavy metals. It is possible to do. Furthermore, ferrihydrite has a large specific surface area of 180-200 m ² Zg and a large area capable of adsorbing heavy metals. Therefore, the use of ferrihydrite-containing humus complex containing ferrihydrite enables efficient purification of heavy metal soil. It is possible to do.

Claims

The scope of the claims

1. A humus-soil stacking step of forming a humus-soil stack by alternately placing a polyhydrite humus complex and the contaminated soil on soil near the contaminated soil; A method for purifying contaminated soil, comprising performing a humus-soil stirring step of stirring a soil stack to obtain a humus-soil mixture.

2. A humus complex bottom layer laying step of placing the ferrihydrite humus complex on soil near the contaminated soil;

A humus-soil stacking step of alternately placing the contaminated soil and the ferrihydrite humus complex on the bottom of the humus complex to form a humus' soil stack;

A method for purifying contaminated soil, comprising the steps of: performing the humus' humus' soil stirring to obtain a humus' soil mixture by stirring the soil laminate.

3. After the stirring step,

A step of rearranging the bottom layer of the humus complex in which the ferrihydrite humus complex is placed on the soil;

On the lowermost layer of the humus complex obtained in the rearrangement step, the humus-soil mixture formed in the stirring step and the ferrihydrite humus complex are alternately placed to form a humus-mixture laminate. Forming a humus-mixture laminating step;

3. The humus-mixture stirring step of stirring the humus-mixture laminate obtained in the humus-mixture stacking step to obtain a mixture of the humus-mixture, which is sequentially and repeatedly performed a predetermined number of times. How to clean contaminated soil.

4. After the stirring step,

Placing the humus' soil mixture formed in the stirring step on the soil near the contaminated soil;

The contaminated soil and the humus' soil mixture formed in the stirring step are alternately placed on the lowermost layer of the humus-soil mixture obtained in the disposing step, and the mixture-soil volume is placed. A layer-forming mixture-soil stacking process;

The mixture according to claim 2, characterized in that the step of `` mixing the mixture obtained in the soil layering step and the step of mixing the soil layered body to obtain a mixture of mixture and soil '' and the step of `` soil stirring '' are repeated a predetermined number of times. How to clean contaminated soil.