JP2001269657A - Soil cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the decomposition efficiency of organic matter in treating a soil for treatment containing organic matter with hydrogen peroxide in the presence of a catalyst which is a metal ion capable of attaining >=2 kinds of valences. SOLUTION: The soil cleaning method for decomposing organic matter by treating a soil for treatment containing organic matter with hydrogen peroxide in the presence of a catalyst which is a metal ion capable of attaining >=2 kinds of valences consists of adding an assistant capable of supplying at least either of the cation which is more easily adsorbable on the cation exchange seat of the soil for treatment as compared to the catalyst described above and the cation which produces a product by more easily reacting with phosphoric acid as compared with the catalysts described above to the soil prior to the treatment by hydrogen peroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for decomposing organic matter by treating the soil to be treated with hydrogen peroxide in the presence of a catalyst which is a metal ion having two or more valences. The soil purification method.

[0002]

2. Description of the Related Art Conventionally, when decomposing organic substances contained in wastewater, a compound capable of supplying hydrogen peroxide and iron ion which is a metal ion capable of taking two or more valences as a catalyst to the wastewater ( A method of generating a hydroxyl radical (OH.) By adding ferrous sulfate heptahydrate (so-called Fenton's reagent) and reacting the radical with the organic material to oxidatively decompose the organic material. Was known. Attempts have been made to apply this method to the purification of soil containing organic matter (see JP-A-7-75772). In addition, the said organic substance mainly refers to a hardly decomposable organic substance which is difficult to be decomposed by living organisms, and is an aromatic compound contained in agrochemicals, preservatives, petroleum and its fractions, especially polycyclic aromatic hydrocarbons (Polynucleic acid).
ar Aromatic Hydrocarbon; P
AH) and chlorinated organic substances.

[0003]

However, in carrying out this soil purification method, there are the following problems. The iron ions are adsorbed and inactivated on the cation exchange sites present in the soil to be treated, and the iron ions capable of reacting with the hydrogen peroxide decrease. Accompanying this, the generation of the hydroxyl radical is reduced, and the efficiency of oxidative decomposition of the organic substance is reduced. The iron ions combine with the phosphoric acid contained in the soil to be treated to form a sparingly soluble phosphate. This deactivates the catalyst and reduces the iron ions that can react with the hydrogen peroxide. Accompanying this, the generation of the hydroxyl radical is reduced, and the efficiency of oxidative decomposition of the organic substance is reduced. Many of the organic substances are hardly soluble in water, and it is difficult to obtain an opportunity to come into contact with the hydroxyl radical. Therefore,
The progress of the reaction is slow, and the efficiency of oxidative decomposition of the organic substance is reduced. In particular, the soil in Japan has a cation exchange capacity (Cati
On exchange capacity (CEC) is relatively high in many cases, so that the amount of iron ions adsorbed on the cation exchange site is large. In addition, there are many soils having a high phosphoric acid content. In such soils, the iron ions and the phosphoric acid combine with the phosphoric acid to form a sparingly soluble phosphate. Therefore, if the conventional soil purification method is carried out, the decomposition efficiency is likely to be suppressed low by inactivation of the catalyst, so that it was necessary to add a large amount of the catalyst.

However, as a result of intensive studies, the present inventors have found that, when a large amount of an iron-containing compound is added as the catalyst and oxidative decomposition treatment is performed, biodegradable oxidative decomposition products are obtained even after biological treatment. It was revealed that decomposition was extremely suppressed. Therefore, when biodegradation of the decomposition product is expected by utilizing microorganisms originally existing in the soil to be treated or by adding microorganisms capable of decomposing the oxidative decomposition product, the amount of the catalyst added is Has to be restricted.

Accordingly, an object of the present invention is to provide a method for treating a soil to be treated containing the organic matter with hydrogen peroxide in the presence of a catalyst which is a metal ion capable of taking two or more valences in view of the above-mentioned drawbacks. It is an object of the present invention to improve the decomposition efficiency of the organic matter.

[0006]

According to a first aspect of the present invention, there is provided a soil purification method comprising the steps of:
In the soil purification method of decomposing the organic matter by treating with hydrogen peroxide in the presence of a catalyst that is a metal ion capable of taking two or more valences, the treatment with the catalyst is performed before the treatment with the hydrogen peroxide. An auxiliary agent capable of supplying at least one of a cation easily adsorbed to the cation exchange site of the soil to be treated and a cation which easily reacts with phosphoric acid to produce a product as compared with the catalyst is added. Is to do. To achieve this object, the second characteristic means of the soil purification method of the present invention, as described in claim 2, is to treat the soil to be treated containing organic matter with a metal ion capable of taking two or more valences. In the soil purification method of decomposing the organic matter by treating with hydrogen peroxide in the presence of a catalyst that is, before adding the catalyst, adsorb to a cation exchange site of the treatment target soil as compared with the catalyst. The point is to add an auxiliary agent capable of supplying at least one of a cation which easily reacts with phosphoric acid or a phosphoric acid to easily produce a product. Further, as described in claim 3 in the first and second feature means, after the treatment with the hydrogen peroxide, a microorganism capable of decomposing the decomposition product of the organic substance may be further added. Preferably, the auxiliary is capable of supplying calcium ions, as described in claim 4, and further, as described in claim 5, before the treatment with the hydrogen peroxide, It is preferable to add a surfactant for solubilizing the organic substance. And these effects are as follows.

That is, as described in claim 1, the soil to be treated containing an organic substance is treated with hydrogen peroxide in the presence of a catalyst which is a metal ion having two or more valences, In the soil purification method for decomposing organic substances, before the treatment with the hydrogen peroxide (before the hydroxyl radical is generated from the hydrogen peroxide by the action of the catalyst), the soil to be treated is compared with the catalyst in a ratio of the catalyst. If a cation that can be easily adsorbed is added to the cation exchange site of the soil to be treated, the cation will be adsorbed to the cation exchange site. As described above, if the cation exchange site is filled with the cation, the catalyst has a lower affinity for the cation exchange site than the cation, so that the cation is adsorbed. The cation exchange sites are not easily displaced and adsorbed. In addition, the treatment target soil may contain metal ions having two or more valences having catalytic activity, and the cations may be converted to the metal ions by an exchange reaction. It can be released from the ion exchange site and brought into a state where it can function as a catalyst. Therefore, the hydroxyl radical can be efficiently generated from the hydrogen peroxide by causing the catalyst to be present in the soil to be treated in a state capable of exhibiting its catalytic activity. Similarly, the product easily reacts with phosphoric acid as compared with the catalyst to form a product (solid (precipitation) as a hardly soluble / hardly decomposable phosphate).
Is easily obtained. ) Is added to the soil to be treated before the treatment with the hydrogen peroxide,
Since the binding site of the phosphoric acid is blocked by the cation having a higher affinity than the catalyst, the reaction between the phosphoric acid and the catalyst is inhibited, and the catalyst can exhibit its catalytic activity. And the hydroxyl radical can be efficiently produced from the hydrogen peroxide. Therefore, at least one of a cation which is easily adsorbed to the cation exchange site of the soil to be treated as compared with the catalyst or a cation which easily reacts with phosphoric acid as compared with the catalyst to generate a product. If a compound or solution that can be supplied is added to the soil to be treated as an auxiliary and treated with the hydrogen peroxide, the catalyst exhibits activity even in a soil with a high CEC or a soil with a high phosphoric acid content. Since the state can be maintained, the hydroxyl radical can be efficiently generated, and the organic substance can be decomposed with a small amount of catalyst. The addition of the cation may cause the cation to be adsorbed to the cation exchange site or to bind to the phosphate binding site, instead of the metal ion which may be a catalyst existing in the treatment target soil. Thus, it is considered that the intrinsic catalyst can be activated to improve the efficiency of oxidative decomposition of the organic substance. Here, as the catalyst, a compound capable of supplying the iron ion can be mentioned as a typical example, and two or more compounds having an action of promoting the generation of a hydroxyl radical from the hydrogen peroxide can be mentioned. A compound that can supply a metal ion that can take a valence (metal ion such as chromium, titanium, vanadium, tin, copper, manganese, and cobalt) can also be used. Also,
It is also possible to directly supply metal ions as an electrolyte solution. In addition, the ease with which cations are adsorbed to the cation exchange site varies depending on the ionic species, and as a result of research by the inventors, ammonium ions, calcium ions, and potassium ions were compared with the catalyst. It was revealed that the cation was easily adsorbed. Similarly, the present inventors have studied cation species that easily react with the phosphoric acid as compared with the catalyst to generate a product, and as a result, have found that calcium ions and magnesium ions are applicable.

Further, as described in claim 2,
A soil purification method for treating a soil to be treated containing organic matter with hydrogen peroxide in the presence of a catalyst that is a metal ion capable of taking two or more valences to decompose the organic matter,
Before adding the catalyst, if an auxiliary agent containing a cation that is easily adsorbed to a cation exchange site of the soil to be treated as compared with the catalyst is added to the soil to be treated, the cation exchange site Will be sufficiently replaced in advance by the cation. In such a state, if the catalyst is added, the catalyst is hardly displaced or adsorbed on the cation exchange site where the cation is adsorbed. Further, metal ions having two or more valencies having catalytic activity and contained in the soil to be treated can also be brought into a state capable of functioning as a catalyst. Therefore, the hydroxyl radical can be efficiently generated from the hydrogen peroxide by causing the catalyst to be present in the soil to be treated in a state capable of exhibiting its catalytic activity.
Similarly, before the addition of the catalyst, an auxiliary containing a cation which easily reacts with phosphoric acid to produce a product,
When added to the soil to be treated, the cation is sufficiently bonded to the binding site of the phosphoric acid, so that a large amount of the phosphoric acid can be converted to a hardly soluble salt form. In such a state, if the catalyst is added later, the cation is firmly bound to the phosphoric acid, so that the catalyst cannot react with the phosphoric acid. Thus, the catalyst is present in the soil to be treated in a state where it can exhibit its catalytic activity, and can efficiently generate the hydroxyl radical from the hydrogen peroxide. Here, the cation does not necessarily have to have a higher affinity for the phosphoric acid in relation to the catalyst. The reason is that even if it has a lower affinity for phosphoric acid than the above-mentioned catalyst and it is difficult to bind to phosphoric acid if it competes with the catalyst, it is hardly soluble and hardly decomposable by adding it first. This is because, if the phosphate is formed, the exchange reaction with the catalyst added later is unlikely to occur (conversely, the relationship between the cation and the catalyst is that the cation forming the phosphate is It is only necessary to have an affinity for phosphoric acid to such an extent that it does not displace the catalyst.) By doing so, the catalyst can be maintained in a state where the activity can be expressed even in a soil where the CEC is high or a soil where the phosphoric acid content is high, so that the hydroxyl radical can be efficiently generated. The organic substance can be decomposed with a small amount of catalyst. The addition of the cation may cause the cation to be adsorbed to the cation exchange site or to bind to the phosphate binding site, instead of the metal ion which may be a catalyst existing in the treatment target soil. Thus, it is considered that the intrinsic catalyst can be activated to improve the efficiency of oxidative decomposition of the organic substance.

[0009] The soil to be treated after the above-mentioned treatment can be reduced in the amount of the catalyst to be added by promoting the activation of the catalyst. The effect on microorganisms inhabiting is reduced.
Further, by performing the above treatment, the organic substance is decomposed by cleavage of the cyclic structure, removal of halogen, and the like. Here, since biodegradable products are included in the decomposition products, microorganisms capable of decomposing the decomposition products of the organic substances after the above-mentioned treatment are used as described in claim 3. If added, it can be further decomposed to low molecules and reformed to a state close to nature. In particular, when microorganisms capable of decomposing the decomposition products are not widely distributed in nature, if such microorganisms are further decomposed to low molecular weight by adding them to the soil to be treated, indigenous microorganisms can also be used. Will be able to do it.

According to a fourth aspect of the present invention, when the auxiliary agent is capable of supplying calcium ions to the soil to be treated, the calcium ions are treated more efficiently than metal ions derived from the catalyst. Since the catalyst is easily adsorbed to the cation exchange site of the target soil, it is possible to suppress the adsorption of the catalyst to the cation exchange site. Furthermore, since the calcium ion has higher reactivity to phosphoric acid than the metal ion derived from the catalyst, the calcium ion reacts with the phosphoric acid to form a sparingly soluble salt, and also binds the catalyst to the phosphoric acid. Can be inhibited. Therefore, the catalyst supplied to the soil to be treated can be maintained in a form capable of expressing a catalytic function, which is particularly suitable for increasing the efficiency of decomposing the organic matter.

According to a fifth aspect of the present invention,
Before the treatment with hydrogen oxide, the soil to be treated is
When a surfactant that solubilizes organic substances is added,
Can be solubilized, and subsequently by the action of the catalyst
That the hydroxyl radical was generated from hydrogen peroxide
The contact between the hydroxyl radical and the organic substance
Promote the oxidative decomposition of the organic matter
Can be. Here, as the surfactant, structural formula 4
− (C₈H₁₇) C₆H_FourO (CH _TwoCH_TwoO)₁₁・ CH
_TwoCH_Two“Igep,” a surfactant represented by OH
al CA-720 ”(Aldrich Chemical Can
(Available from Pany) is preferred.

[0012]

Embodiments of the present invention will be described below. As a method of adding the auxiliary agent, hydrogen peroxide (for example, hydrogen peroxide solution), and a catalyst to the soil to be treated containing organic matter, the method may be applied by spraying from the surface of the soil to be treated or by mixing with a slurry method. Is also good. Further, a supply pipe may be stretched around the soil to be treated, and the auxiliary agent, hydrogen peroxide, and catalyst may be supplied from the supply pipe. Also,
In addition, an addition method applicable to a conventional soil purification method can be applied. As the supply order of the auxiliary agent, hydrogen peroxide, and the catalyst, before the treatment with the hydrogen peroxide, that is, at the stage before generating the hydroxyl radical from the hydrogen peroxide by the action of the catalyst,
There is no particular limitation as long as the form can exhibit its activity. Therefore, the order of addition of the catalyst and the hydrogen peroxide may be simultaneous or they may be added before or after any one of them. It is necessary to add an agent to the soil to be treated. Therefore, the time required for the cations contained in this auxiliary agent to be sufficiently adsorbed to the cation exchange site or for the cations to bind to the reaction site of the phosphoric acid sufficiently to form a poorly soluble salt is reduced. In order to ensure this, it is preferable to leave the mixture for about 1 to 7 days after the addition of the auxiliary agent until the reaction between the catalyst and the hydrogen peroxide. In this case, the catalyst is present in the soil to be treated in a form capable of exerting a catalytic action, so that the hydroxyl radical can be efficiently generated from the hydrogen peroxide, and the hardly soluble organic substance is efficiently oxidized. Decomposed. In addition, it is preferable that the amount of the auxiliary added at this time is such that the cation contained in the auxiliary is 50 mM / g or more in dry soil. Here, as the cation, calcium ion has a higher affinity for the cation exchange site than the catalyst, and also easily reacts with the phosphoric acid as compared with the catalyst to have a poor solubility. It is preferable because a salt is easily formed.

The solubilized organic compound is solubilized so that the hydroxyl radical can be easily accessed.
Before the generation of the hydroxyl radical, a surfactant that solubilizes the organic matter may be added to the soil to be treated in the same manner as described above.

Here, the decomposition product of the organic matter remains in the soil to be treated after the oxidative decomposition treatment, and finally, the decomposition product is a microorganism indigenous to the soil to be treated. And is converted into a compound ubiquitous in nature. In addition, among the decomposition products, compounds that are difficult to decompose by the indigenous microorganisms can be decomposed into substances that the indigenous microorganisms can assimilate by adding (spraying and mixing) microorganisms capable of decomposing the compound. (Conversion).

[0015]

Embodiments of the present invention will be described below with reference to the drawings. Example 1 5 ml of a 1: 1 mixture of acetonitrile and distilled water
100 mg of benzo (a) pyrene as the organic substance
/ L was prepared by dissolving the solution. 2g of soil with high CEC and phosphoric acid content collected in urban area
Was mixed with the above solution to obtain a simulated soil A. To this simulated soil A, ammonium ion (ammonium chloride) or calcium ion (calcium chloride) was added as the auxiliary agent so that the soil became 0 mM (conventional example) to 100 mM / g soil, and the mixture was allowed to stand for 15 hours. Thereafter, ferrous sulfate heptahydrate containing iron ions as a catalyst (FeSO ₄
7H ₂ O) was added to the simulated soil A so as to be 400 mg / L, and hydrogen peroxide solution was further added so that the hydrogen peroxide concentration became 0.3% by weight. FIG. 1 shows the result of measuring the content of the benzo (a) pyrene after leaving the simulated soil A for 24 hours. The benzo (a) pyrene was quantified by reversed-phase high performance liquid chromatography (HPLC).

As is clear from FIG. 1, in the conventional example in which the cation was not added, the benzo (a) pyrene was decomposed only by about 20%. On the contrary,
The addition of either of the two cations increases the decomposition rate of the benzo (a) pyrene dissolved (solubilized) in the solution, and in particular, the addition of calcium ions leads to the decomposition of about 60%. Rate was obtained, and it became clear that the effect was high. The improvement of the decomposition rate is hardly changed even when adding 50 mM / g soil or more in the case of adding calcium ions, and the decomposition rate is not changed even when adding 100 mM / g soil in the case of ammonium ions. Tends to increase, and further effects can be expected by adding ammonium ions at or above this concentration.

Example 2 5 ml of a 1: 1 mixture of acetonitrile and distilled water
100 mg of benzo (a) pyrene as the organic substance
/ L was prepared by dissolving the solution. 1g of soil with high CEC and phosphoric acid content collected in urban area
Was mixed with the above solution to obtain a simulated soil B. Magnesium chloride, ammonium nitrate, potassium chloride, or calcium chloride was added to the simulated soil B as the auxiliary agent to a concentration of 5 mM, and the mixture was allowed to stand for 7 hours. Thereafter, to each of the simulated soils B, the ferrous sulfate heptahydrate was added so as to have a concentration of 400 mg / L, and a hydrogen peroxide solution was further added so that the hydrogen peroxide was 0.3% by weight. Was added. In addition, as a control (conventional example), in the said simulated soil B,
What was processed similarly except not having added the said auxiliary agent was prepared. The result of measuring the content of the benzo (a) pyrene after leaving these simulated soils B for 24 hours is shown in FIG.

As apparent from FIG. 2, in the conventional example, the differentiation rate of the benzo (a) pyrene was about 33%.
On the other hand, when magnesium chloride, ammonium nitrate, potassium chloride, or calcium chloride is added as the auxiliary, the decomposition rate of the benzo (a) pyrene is 42, respectively.
The decomposition rate of the benzo (a) pyrene is improved by adding an auxiliary agent capable of supplying magnesium ions, ammonium ions, potassium ions, or calcium ions. I understand. In this example, the effect obtained by adding calcium ions was the highest.

Example 3 1 g of soil having a high content of CEC and phosphoric acid collected in an urban area was mixed with 1 benzo (a) pyrene as the organic substance.
Simulated soil C was obtained by adsorbing so as to obtain a weight%. 5 ml of distilled water was added to the simulated soil C, followed by 0 to 1.0% by weight of Igepal CA-720 (manufactured by Aldrich Chemical Company) as a surfactant. Thereafter, to each of the simulated soils C, the ferrous sulfate heptahydrate was added so as to have a concentration of 400 mg / L, and hydrogen peroxide solution was further added so that the hydrogen peroxide was 0.3% by weight. Was added. The results of measuring the content of the benzo (a) pyrene after leaving these simulated soils C for 3.5 days are as follows:
As shown in FIG.

As apparent from FIG. 3, when the surfactant was not added, the decomposition rate of the benzo (a) pyrene was only about 3%. This is considered to be because the benzo (a) pyrene is hardly soluble in water, so that contact with a hydroxyl radical hardly occurs. On the other hand, when the surfactant was added, the decomposition rate of the benzo (a) pyrene increased to 44%. This indicates that when the organic substance is a substance that is hardly soluble in water such as an aromatic compound, the decomposition efficiency is improved by solubilization with the surfactant.

Example 4 A simulated soil D was obtained by adsorbing tar as an organic substance at a concentration of 1% by weight on the soil having a high CEC and phosphoric acid content collected in an urban area. The simulated soil D is 5
0 g of this, 0-100 g / kg soil calcium chloride dihydrate and 10% by weight of the above Igepal CA-
After adding 2 ml of a solution containing 720 and stirring well,
It was left for 4 hours. Thereafter, to each of the simulated soils D, the ferrous sulfate heptahydrate was added so as to be 3% by weight, stirred well, and 5 ml of 30% by weight hydrogen peroxide solution was further added. FIG. 4 shows the result of measuring the content of the tar after leaving the simulated soil D for 10 days. In addition,
The tar contains 10 kinds of Ps in which 3 to 6 aromatic rings are condensed.
HA was contained as an organic substance, and its content was analyzed by reverse-phase HPLC, and the results were summarized for each ring number.

As shown in FIG. 4, as the amount of the calcium chloride added increases, the decomposition rate of the PAH increases, and in the case of a three-ring PAH, about 25% (no addition) to 4%.
For 5% (100 g / kg soil), 4, 5, and 6-ring PAH, 3% (no addition) to 33% (100 g / kg soil)
Soil). In particular, it was found that the 5- or 6-ring PAH was difficult to decompose by the conventional method, but could be efficiently removed by applying the soil purification method according to the present invention.

From the results of Examples 1 to 4, the soil purification method according to the present invention is effective for the soil having a high CEC and phosphoric acid content, which is difficult to obtain the effect by the conventional method. It can be seen that organic substances can be decomposed and removed.

Example 5 Sixteen kinds of PAHs contained in the EPA standard prepared by the United States Environmental Protection Agency (EPA) were mainly placed on the soil having a high CEC and phosphoric acid content collected in an urban area.
Simulated soil E was prepared by adding the group to about 3700 mg / kg soil. To this simulated soil E, ferrous sulfate as the catalyst was added so as to be 0 to 560 g / kg soil, and oxygen (air) and nutrients were supplied to promote PAH degradation by indigenous microorganisms. Cultured for 3 weeks. FIG. 5 is a graph showing the relationship between the amount of ferrous sulfate added and the rate of degradation of the PAH group by the microorganism.

As shown in FIG. 5, as the concentration of ferrous sulfate added as a catalyst increases, the biodegradation of the PAH group is suppressed, and when the added amount exceeds 280 g / kg soil, almost no microorganisms are added. It was clarified that decomposition did not progress. In the conventional soil purification method, the amount of the catalyst added had to be increased in order to increase the decomposition efficiency of organic substances.However, biological decomposition of oxidative decomposition products of the organic substances was suppressed, and There was a risk of remaining inside. However, in the present method, by reducing the amount of the catalyst added, a biological treatment can be introduced as a post-treatment of oxidative decomposition of an organic substance by a hydroxyl radical, and the oxidative decomposition product is further reduced in molecular weight. It can be decomposed into organic substances or carbon dioxide and nitrogen gas that are present universally, and the soil properties can be highly modified.

[Another Embodiment] Another embodiment will be described below. In order to more effectively perform the soil modification using the soil treatment method according to the present invention, as a pretreatment, oxygen and nutrients are supplied to the indigenous microorganisms to activate them, or a specific substance capable of decomposing some organic substances is provided. Microbial treatment such as addition of the above microorganism may be performed. Thereby, the amount of organic substances to be subjected to the oxidative decomposition treatment can be reduced, and the decomposition efficiency of the organic substances can be further improved. For the same purpose, a microbial treatment can be performed before and after the oxidative decomposition treatment.

In the above embodiment, as the organic substance,
Although tar containing benzo (a) pyrene and PAH has been exemplified, any organic substance which can be subjected to oxidative decomposition treatment with the catalyst and hydrogen peroxide is decomposed by applying the soil purification method according to the present invention. It is possible. The amounts of the catalyst, hydrogen peroxide, cations, and surfactants added to the soil to be treated are not limited to those in the above-described embodiment. It is preferable to determine in consideration of the content.

In the above embodiment, ferrous sulfate was used as a compound capable of supplying iron ions as a catalyst. However, as long as the compound or solution can supply the iron ions, the supply source is limited. Not something. here,
Compounds capable of supplying metal ions such as chromium, titanium, vanadium, tin, copper, manganese, and cobalt as the metal ions having two or more valences can also be used as the supply source of the catalyst.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of added cations and the decomposition rate of organic substances.

FIG. 2 is a graph showing the relationship between the added cationic species and the decomposition rate of organic substances.

FIG. 3 is a graph showing the relationship between the amount of surfactant added and the decomposition rate of organic substances.

FIG. 4 is a graph showing the relationship between the amount of calcium added and the decomposition rate of hardly decomposable PAH.

FIG. 5 is a graph showing a relationship between a catalyst addition amount and a PAH decomposition rate.

Continued on front page F-term (reference) 2E191 BA11 BA12 BB01 BC01 BC05 BD11 BD13 BD20 4D004 AA41 AB05 AB06 CA15 CA18 CA34 CA36 CA47 CC05 CC09 CC11 CC12 4G069 AA02 BA36A BB10A BB10B BC22A BC31A BC50A BC54A BC58 CA67CABCA13

Claims (5)

[Claims] 1. A soil purification method for treating a soil to be treated containing organic matter with hydrogen peroxide in the presence of a catalyst which is a metal ion capable of taking two or more valences to decompose the organic matter, Prior to treatment with hydrogen peroxide, a cation that is easily adsorbed to the cation exchange site of the soil to be treated as compared with the catalyst or a cation that easily reacts with phosphoric acid as compared to the catalyst to produce a product A soil purification method comprising adding an auxiliary agent capable of supplying at least one of the above. 2. A soil purification method for treating a soil to be treated containing organic matter with hydrogen peroxide in the presence of a catalyst which is a metal ion capable of taking two or more valences to decompose the organic matter, Before adding the catalyst, at least one of a cation which easily reacts with phosphoric acid or a phosphoric acid which easily reacts with phosphoric acid at a cation exchange site of the soil to be treated as compared with the catalyst to produce a product is supplied. A soil purification method with the addition of possible auxiliaries. 3. The soil purification method according to claim 1, wherein after the treatment with the hydrogen peroxide, a microorganism capable of decomposing the decomposition product of the organic substance is further added. 4. The soil purification method according to claim 1, wherein the auxiliary is capable of supplying calcium ions. 5. The soil purification method according to claim 1, wherein a surfactant that solubilizes the organic matter is added to the soil to be treated before the treatment with the hydrogen peroxide.