JP5911716B2 - Treatment agent and treatment method for contaminated soil - Google Patents

Description

The present invention relates to a treatment agent and a treatment method effective for soil contaminated with radionuclides and heavy metals.

The planning of effective measures for decontamination of contaminated soil and the prevention of scattered runoff by radionuclides generated in the nuclear accident is a urgent issue in Japan.
Based on the knowledge of environmental measures for many years, the inventor focused on ferric nitrate, polyferric sulfate and ferric chloride, and examined the measures.

In Patent Document 1, phosphonic acid and magnesium sulfate are mixed in a solvent that does not contain chlorine as a solidifying agent for the step of condensing harmful substances from a liquefied or muddy object, and then stirred for several minutes. A method for regenerating and purifying incinerated ash and soil containing harmful substances that has been shown to be an inorganic electrolytic flocculant administered with aluminum sulfate and polyferric sulfate and stirred for several minutes has been proposed. This is intended for treatment of substances containing harmful substances such as dioxins, PCBs, asbestos and various heavy metals, not for soil contaminated with radionuclides.

In Patent Document 2, when radioactive waste generated from a nuclear power plant is solidified using a hydraulic inorganic solidifying material, an electron scavenger having a high reaction rate with free electrons and hydrated electrons is added. A method of solidifying radioactive waste using iron scavenger as an iron nitrate with an addition amount of 0.01% or more and 5% or less based on the weight of the solidified material has been proposed, but soil contaminated with radionuclides has been proposed. It was not intended.
Non-Patent Document 1 shows the results of research on the behavior of radioactive cesium and the like in soil.

Generally, clay minerals are said to be 1: 1 type clay minerals such as kaolinite and halloysite, and 2: 1 type clay minerals such as montmorillonite and vermiculite. In the 1: 1 type clay mineral, a silicon tetrahedral layer and an aluminum octahedral layer are combined to form a unit layer, and these unit layers are overlapped. In the 2: 1 type clay mineral, three layers of a silicon tetrahedral layer, an aluminum octahedral layer, and a silicon tetrahedral layer are combined to form a unit layer, and these unit layers are overlapped. In the silicon tetrahedral layer, a space having a diameter of about 264 pm is formed by an oxygen six-membered ring constituting the Si—O atomic plane, and potassium ions and ammonium ions are said to enter and be fixed in this space. Cesium ions are similarly fixed because they are similar in chemical nature and ion diameter to potassium ions. In Non-Patent Document 1, an aqueous solution containing cesium-137 is added to a plurality of types of soil, left to stand for 1 day after shaking for 1 hour, and then the supernatant fraction obtained by centrifugation is dissolved in water. The amount of cesium-137 in the exchanged state (including the water-soluble state) and the amount of cesium-137 in the fixed state remaining in the soil were compared, and the 2: 1 type clay mineral montmorillonite Revealed that there was more cesium-137 in the stationary fraction than in the 1: 1 type clay mineral kaolinite.

Thus, cesium-137 is adsorbed by clay minerals and humus constituting the clay fraction among the soil constituents. A part of the cesium-137 descended to the soil is adsorbed on the surface of the clay mineral and humus as an exchange state, while the other is adsorbed as a fixed state on the crystalline clay mineral.

JP 2009-136812 A JP 7-128497 A

Akihito Tsumura, Misako Komamura, Hironobu Kobayashi (1984) Study on behavior of radioactive strontium and cesium in soil and soil-plant system, Agricultural Research Institute B, 36: 57-113

The present invention mainly focuses on soil contaminated with radionuclides generated in the nuclear accident, and also performs comprehensive cleaning treatment on complex contaminated soil such as heavy metals resulting from tsunami-affected sea mud. The purpose of the present invention is to provide a treatment agent and a treatment method for dealing with contaminated soil, which can be detoxified by extraction by destroying the bonding group adhering to the soil.

Moreover, this invention aims at provision of the processing agent and the processing method which enabled prevention of scattering or outflow as a countermeasure for contaminated soil.

The present invention provides a treating agent for purification containing at least one of polyferric sulfate and ferric chloride, ferric nitrate, and a strong acid (mainly sulfuric acid). These preferable blending amounts are 35-50 parts by mass of at least one of ferric sulfate and ferric chloride, 11-30 parts by mass of ferric nitrate, and 0.75-0.5 of strong acid (sulfuric acid). 3 parts by mass. Furthermore, it is also possible to add at least one of sodium nitrate and calcium nitrate, preferably 5.6 to 11.2 parts by mass.

The purification treatment agent is at least one of ferric nitrate and sodium nitrate (preferably 8 to 20 parts by mass), strong acid (preferably sulfuric acid), and at least one of ethylenediaminetetraacetic acid tetrasodium. One (preferably 30 to 37.5 parts by mass) containing a pretreatment agent can be used as a two-component cleaning function agent.

This two-component cleaning function agent can clean soil contaminated with radionuclides and heavy metals by the following method. That is, a first stirring step of mixing and stirring the radionuclide-contaminated soil, water, and the pretreatment agent as a primary treatment object, and the primary treatment object that has undergone the first stirring step as a solid phase and a liquid phase A first solid-liquid separation step for substantially solid-liquid separation, a second stirring step for mixing and stirring the solid phase, water, and the purification treatment agent as a secondary treatment object, and the first stirring step. A second solid-liquid separation step of substantially solid-liquid separating the secondary processed material that has passed through into a solid phase and a liquid phase, and the solid phase obtained by the second solid-liquid separation step has been washed The soil.

Among these, for radionuclide contaminated soil, the pretreatment agent must contain the sulfuric acid and the ferric nitrate, and the purification treatment agent must contain the polyferric sulfate. To do.

Moreover, with respect to heavy metal contaminated soil, the said pretreatment agent shall contain the said ethylenediaminetetraacetic acid tetrasodium and the said sodium nitrate essentially, and the said processing agent for purification shall contain the said ferric chloride essential.

Moreover, the processing agent for purification | cleaning of this invention is an inorganic binder containing sodium polyacrylate (preferably 0.2-0.5 mass part) and sodium silicate (preferably 20-40 mass part). In combination with an aqueous solution, a two-part spillage prevention agent can also be obtained. A method for treating a radionuclide-contaminated site using the scattering spill preventive agent includes the first spraying step of spraying the binder aqueous solution to the radionuclide-contaminated site, and the radionuclide-contaminated site through the first spraying step. A second spraying step of spraying the purification treatment agent is performed.

The present invention is mainly contaminated soil due to radionuclides generated in the nuclear accident, and moreover, contaminated soil capable of performing effective cleaning treatment on contaminated soil such as heavy metals caused by tsunami-affected sea mud It was possible to provide treatment agents and treatment methods for countermeasures.

Process explanatory drawing of the purification method of the soil using the cleaning function agent of this invention. The schematic diagram of the inclined ground surface after the processing method of the radionuclide contaminated land of this invention. An illustration of Schulz Barday's law. Explanatory drawing of the experimental apparatus of the processing method of the radionuclide contaminated land of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the reference numerals after the processes are the reference numerals in FIG.
(Purification treatment of contaminated soil with a two-component cleaning function agent)
In the present invention, a two-component cleaning function agent that combines a pretreatment agent and a purification treatment agent is provided, and a method for purifying contaminated soil using this is proposed.

(Pretreatment agent)
First, the pretreatment agent will be described.
The pretreatment agent (A) contains the following (1a) and (1b), and these are mixed with (1c) water.
(1a) At least one of a strong acid (hydrochloric acid, nitric acid, etc. can be used but preferably sulfuric acid) and tetrasodium ethylenediaminetetraacetate.
(1b) At least one of ferric nitrate and sodium nitrate.

About compounding amount,
(1a) 30-37.5 parts by mass of sulfuric acid, 40-50 parts by mass of tetrasodium ethylenediaminetetraacetate are desirable, (1b) 8-20 parts by mass of ferric nitrate, and sodium nitrate 5. It is desirable to blend 6 to 11.2 parts by mass. (1c) It is appropriate to mix 30 to 50 parts by mass of water.
When treating radionuclides, it is desirable to contain (1a) sulfuric acid and (1b) ferric nitrate, and when treating heavy metals, (1a) tetrasodium ethylenediaminetetraacetate and (1b ) Sodium nitrate is preferably blended, and in the case of combined contamination of both, it is desirable to contain all of them.

(Description of ingredients)
The strong acid (preferably sulfuric acid) of (1a) is considered to be excellent in metal solubility and destroy the crystal structure in the clay mineral.
Ethylenediaminetetraacetic acid tetrasodium (1a) is a metal ion chelating agent and is expected to be effective as a metal ion scavenger. In particular, a chelate compound that forms a strong soluble complex salt with a heavy metal ion and has a structure in which the metal ion is encapsulated in the center by an organic polydentate ligand has high complex salt stability.
The ferric nitrate (1b) is obtained by dissolving a metal in nitric acid, and is said to be extremely corrosive, and is used as an adsorbent for radioactive substances.
Since sodium nitrate (sodium nitrate) (1b) has a strong oxidizing power, it is used as a treatment agent for metal surfaces.

(First stirring step 1)
The pretreatment agent is mixed and stirred with soil and water added to the soil (hereinafter referred to as a primary material to be treated). The mixing ratio of soil and water is preferably 1 to 2 in terms of mass ratio. 3% by mass of the pretreatment agent (1a) (1b) (1c) is added to the primary object to be treated, and the mixture is sufficiently stirred. This is the first stirring step.

(Purpose of the first stirring step 1)
The first stirring step is to sufficiently mix and stir the soil and the pretreatment agent, and by adding the pretreatment agent, it was excellent in strong acidity and oxidizing power of pH 1.5 to 1.8 (Fe ³⁺ − SO ₄ ^2- ) ⁺¹ cleaning atmosphere, destroying silicon tetrahedrons and aluminum octahedrons adsorbed with radionuclides and heavy metals in soil clay minerals, stubborn stationary nuclides and heavy metals in water or exchanged state To migrate. That is, the strongly acidic / oxidizing atmosphere by the pretreatment agent promotes the elution of radionuclides bound to the silicon tetrahedron and destroys / dissolves the crystal structure that serves as the adsorbing group of the aluminum octahedron, so that it can be in water and exchanged state The purpose is to migrate.

(First solid-liquid separation step 2)
The first solid-liquid separation step is a step of substantially solid-liquid separation of the primary object to be processed after the first stirring step into a solid phase and a liquid phase. Specifically, the primary object to be treated is allowed to stand, and the supernatant liquid is pulled out by suction or the like, thereby substantially solid-liquid separation into a liquid phase and a solid phase that is a precipitate. Further, other solid-liquid separation means such as a cyclone separator or a thickener may be used. In addition, since complete separation between the solid phase and the liquid phase is impossible and unnecessary, it is sufficient to achieve solid-liquid separation to the extent that the supernatant is sucked and separated.

(Treatment agent for purification)
Next, the purification treatment agent will be described.
The purification treatment agent (B) contains the following (2a), (2b), and (2c), preferably (2d) added, and these are mixed with (2e) water.
(2a) At least any one of ferric sulfate and ferric chloride (preferable compounding amount 35-50 mass parts).
(2b) Ferric nitrate (preferred blending amount: 11 to 30 parts by mass).
(2c) Strong acid (hydrochloric acid, nitric acid, etc. can be used, but preferably sulfuric acid) (suitable blending amount: 0.75 to 3 parts by mass).
(2d) At least one of sodium nitrate and calcium nitrate (preferred blending amount: 5.6 to 11.2 parts by mass).
(2e) Water (preferably 13 to 19 parts by mass).
When treating radionuclides, it is desirable to contain (2a) polyferric sulfate and (2d) sodium nitrate. When treating heavy metals, (2a) ferric chloride and ( 2d) It is preferable to mix calcium nitrate, and in the case of complex contamination of both, it is desirable to contain all of them.

(Description of ingredients)
The ferric polysulfate (2a) is an iron-based inorganic polymer flocculant, and has an advantage that the metal content is higher than that of an aluminum-based material and can be used with a low addition amount. It is said that the pH is less likely to lower than ferric chloride and the effect range is wide, and the problem of corrosion is relatively small.
Ferric chloride (2a) is also an inorganic flocculant and has a metal content higher than that of aluminum and can be used at a low addition amount. However, since the pH tends to decrease, the effect range is narrow, and attention is paid to corrosion problems. It is said that it will be necessary.

(Second stirring step 3)
The second stirring step is a step of mixing and stirring the purification treatment agent, the solid phase obtained by the first solid-liquid separation step, and water (fresh water) as a secondary treatment object.
Specifically, approximately the same amount of water (fresh water) as the liquid phase separated from the solid phase in the first solid-liquid separation step is added. 4% of the above-mentioned purification treatment agent is added to the total weight of the solid phase and the added water (fresh water). In addition, it is preferable to adjust a secondary to-be-processed object to pH 6.5-7.0, and sodium hydroxide etc. are added as needed as a pH adjuster, and are fully stirred (2nd stirring process).

(Purpose of the second stirring step)
In the second stirring step, stirring is performed in an oxidizing atmosphere, and the radionuclide remaining in the adsorbing group of the silicon tetrahedron and aluminum octahedron is still stirred in the strongly acidic atmosphere of the first stirring step described above. The purpose is to neutralize the fixed and exchanged nuclide ions with the polyvalent metal ions of the purification treatment agent, adsorb them to the iron nitrate ions, and decontaminate to the limit value. That is, in a strong oxidizing atmosphere, the radionuclide stationary ions and the metal ion of the purification treatment agent are activated, and the increase of positive ions promotes the reduction of stationary ions and at the same time, adsorption decontamination is achieved by ion exchange.

(Second solid-liquid separation step 4)
The second solid-liquid separation step is a step of substantially solid-liquid separation of the secondary processed material that has undergone the second stirring step into a solid phase and a liquid phase. Specifically, the secondary material to be processed is allowed to stand, and the supernatant liquid is pulled out by suction or the like, so that the liquid phase and the solid phase that is a precipitate are substantially solid-liquid separated. Further, other solid-liquid separation means such as a cyclone separator or a thickener may be used.

In the second stirring step, the radionuclide adsorbed on ferric sulfate or the like is dissolved in water, so the liquid phase is separated from the solid phase soil particles by the second solid-liquid separation step. Thus, decontamination of the soil can be achieved.

The cyclone separator is intended for solid-liquid separation of soil particles up to 75 μm, and fine particles under 75 μm are subjected to solid-liquid separation by a thickener as necessary. In particular, since 95% or more of the soil particles of farmland are under 75 μm, it is desirable to perform solid-liquid separation by repeating natural sedimentation by a thickener a plurality of times. In this case, the thickener stirring operation is stopped.

As described above, the radionuclide adsorbed on polyferric sulfate or the like is dissolved in water, but when left standing for a long time (3 to 6 hours or more), a sedimentation phenomenon occurs. Therefore, when performing solid-liquid separation by a thickener during the solid-liquid separation step (particularly during the second solid-liquid separation step), it is desirable to achieve sedimentation separation while maintaining a gentle flowing water. Further, depending on the properties of the soil, the connection of a plurality of sickles may be made flexible, and after the sedimentation separation is confirmed by the previous thickener, it is allowed to flow into the next connected thickener. This coupled thickener is described in more detail in the section on processing and recycling of liquid phases containing radionuclides.
The first and second stirring steps and the first and second solid-liquid separation steps can be repeated a plurality of times as necessary.

(Decontaminated soil 6)
The solid phase obtained by the second solid-liquid separation step is safe to the extent that it can be restored as decontaminated soil. Therefore, soil that has been separated by solid-liquid separation and decontaminated is, for example, piled in a mountain shape on a farmland ground and then completely dehydrated by natural dehydration, and then spread evenly on farmland. Can be returned. The sewage that has flowed out during the natural dehydration is collected by a U-shaped groove formed around the water-impervious sheet and joined to the liquid phase separated by the thickener. The above-mentioned solid-liquid separation means can be installed at any number or dozens according to the spread of the decontamination area.

(Process 7 for liquid phase containing radionuclide)
The liquid phase 5 containing the radionuclide obtained by the above-mentioned second solid-liquid separation step may be treated by an appropriate method such as a decontamination method performed today. The following method is proposed.

As described above, the aggregation thickener is made into two linkages, and as described above, the second solid-liquid separation step is performed in the previous thickener, and the liquid phase containing the radionuclide obtained here is agglomerated and clarified linked to the previous thickener. The above-mentioned purification treatment agent is injected into the thickener that performs the treatment while stirring continuously and gently stirred. This purifying treatment agent is automatically injected so as to have a ratio of 0.3 to 0.6% by mass with respect to the cleaning contaminated water, and at the same time, the operation of the thickener stirrer is started, and the pH adjusting agent such as caustic soda is added. Automatically adjust to pH 6.5-7 by addition.

After this mixing and stirring, an aqueous solution of a polymer flocculant (anionic) is injected. The aqueous solution of the polymer flocculant (anionic) is continuously injected so that the ratio becomes 0.8 to 1.5% by mass. As a result, harmful substances such as radionuclides and heavy metals become floc together with adsorbed components in the purification treatment agent, and are separated and precipitated from water. That is, the two continuous over waters of the two thickeners are completely clarified. It should be noted that the processing agent for purification and the addition of the pH adjusting agent can be automatically and continuously processed.

As described above, regarding the liquid phase 5 containing the above-mentioned radionuclide, the radionuclide in the liquid phase can be aggregated and precipitated as a floc. The clarified water 8 separated from the floc 9 containing the radionuclide can be flowed as it is to a river or the sea, and can be variously disposed of. As one of the disposals, the clarified water 8 can be recycled as water added in the first stirring step 1 and the second stirring step 3. Further, the floc 9 containing the radionuclide is sufficiently reduced in volume as compared with the contaminated soil before the treatment, and an optimum final disposal is awaited in the reduced form.

(Spill-out prevention treatment for contaminated land with a two-part splash-out agent)
In the above explanation, it was proposed to collect soil from contaminated land and decontaminate it. However, in the following explanation, the surface of land that is difficult to collect and decontaminate (for example, mountain slopes). We propose a method to prevent the scattering and outflow of harmful substances such as radionuclides.
Specifically, the inorganic binder aqueous solution described below and the purification treatment agent described above are sprayed onto the contaminated area.

(Inorganic binder aqueous solution)
The inorganic binder aqueous solution (3) contains the following (3a) and (3b), and these are mixed with (3c) water.
(3a) Sodium polyacrylate (preferably 0.2 to 0.5 parts by mass)
(3b) Sodium silicate (preferably 20 to 40 parts by mass)
(3c) Water (preferably 59.5 to 79.8 parts by mass)

(Description of ingredients)
(3a) Sodium polyacrylate is a kind of highly water-absorbing polymer, and incorporates a large number of water molecules into the network structure to form a gel structure.
(3b) Sodium silicate is also called water glass. In the present invention, the sodium silicate performs the following actions such as causing a catalytic reaction by contact between the silicate and the iron salt.

(Treatment agent for purification)
The purification treatment agent is as described above. In the case of processing a radionuclide contaminated site, the ferric sulfate is essential.

(Method of treating radionuclide contaminated areas)
Mow the undergrowth of contaminated mountain slopes, remove dead leaves, and perform spraying with bare ground exposed. First, an inorganic binder aqueous solution is sprayed, and then (desirably after a permeation time of 5 to 10 minutes is applied), a purification treatment agent is sprayed.

(reaction)
The inorganic binder aqueous solution adheres to and penetrates the fine clay particles and the humic fine substance on the ground surface by spraying it on the bare ground and spraying it. After applying a permeation time of 5 to 10 minutes, by spraying a purification treatment agent, a rapid catalytic reaction occurs due to contact between the silicate and the iron salt, and a silicate precipitation crystal is formed while entraining clay particles. As a result, an etrin guide that is crosslinked between clay particles with time is completed.
That is, it is entrusted to the reaction with various elements held by the ground surface clay particles, and the following crystals such as cross-linking are precipitated between the clay particles.

Aluminates tricalcium 3CaO · Al ₂ O _2, aluminate tetracalcium iron lime _{4C 2 O · Al 2 O 3} · Fe 2 O 3 reacts with water, crystals of cubic system of _{3CaO · Al 2 O 2 · 6H} 2 O The body is deposited one after the other, and the stable insoluble iron calcium silicate crystal by the conversion of the ethrin guide by the hydrate of iron silicate lime and porous ethrin guide 2Ca ₃ SiO ₅ + Fe ₂ O ₃・ 6H ₂ O, etc. will be completed, and a mesh net of micrometer units will be built on the ground surface such as an inclined surface (see Fig. 2).

(Purpose and effect)
The purpose of the treatment method for radionuclide contaminated sites is to prevent the scattering of fine clay particles to which radionuclides adhere and the outflow of rivers, lakes, and water paths, taking into account the case where mountain slopes are exposed to wind and rain. The main purpose is to prevent inflow.
That is, the silica-based porous crystal structure has no power to attach and restrain radioactive substances, but as described above, the restraining force between clay particles exhibits an unparalleled excellent ability, and at the same time, the above-mentioned purification treatment agent is used. When used in combination, the increase in ions peculiar to inorganics occurs, and while neutralizing each ion by colliding with the different charges of clay particles and ionic collisions while taking on their respective characteristic roles, the hydrophilic groups of the constrained water molecules are destroyed. Adhesive water scatters from between the particles. As a result, in accordance with Schulz-Bardy's law, an attraction reaction (hydrogen bonding) occurs between the clay particles, and grows into the aggregate particles in FIG. On the other hand, ferric nitrate Fe (NO ₃ ) ₃ exhibits excellent ability to adsorb radionuclides, as used in adsorbents for radioactive substances.

Hereinafter, in order to enhance the understanding of the present invention, examples will be shown, but the present invention should not be understood to be limited to these examples.

(Example 1) Pretreatment agent (A) for purification treatment of radionuclide-contaminated soil with a cleaning function agent
(1a) Sulfuric acid: 33.75 parts by mass (ie, 75% sulfuric acid aqueous solution: 45 parts by mass)
(1b) Ferric nitrate: 15 parts by mass (1c) Water (fresh water): 40 parts by mass were mixed to prepare one liquid pretreatment agent (A).
Treatment agent for purification (B)
(2a) Polyferric sulfate ... 39.4 parts by mass (2b) Ferric nitrate ... 14.8 parts by mass (2c) Sulfuric acid ... 1.5 parts by mass (ie 75% sulfuric acid aqueous solution ... 2.0 parts by mass) )
(2d) Sodium nitrate: 8.61 parts by mass (ie, sodium nitrate 70% aqueous solution: 12.3 parts by mass)
(2e) 31.5 parts by mass of water was mixed to prepare one liquid purification treatment agent (B).

First stirring step: Soil (site soil of Iidate Village Public Hall in Fukushima Prefecture: Table 1 shows the measurement results of radiation dose) and water are mixed in a mass ratio of 1: 2, and the pretreatment is performed on this mixture. 3% by mass of agent (A) was added and stirred for 15 minutes by a sand pump.

First solid-liquid separation step: After passing through the first stirring step, the mixture was allowed to stand overnight and separated into a solid phase and a liquid phase, and then the supernatant liquid as a liquid phase was sucked with a pump and pulled out. The extracted liquid phase was further added to the solid phase by sedimentation silt of fine soil particles settled by solid-liquid separation. The liquid phase was cleaned by agglomeration treatment with a polymeric flocculant such as polyferric sulfate, and the precipitated floc containing the radionuclide was dehydrated by natural drying.

Second stirring step: The same amount of water (fresh water) as the supernatant liquid sucked out by the above-mentioned pump was added to the solid phase after the first solid-liquid separation step, and these solid phases were added. 4% of the above-described purification treatment agent (B) was added to the total weight of water (fresh water), and the mixture was stirred for 15 minutes by a sand pump.

Second solid-liquid separation step: After passing through the second stirring step, the mixture was allowed to stand for 24 hours to separate into a solid phase and a liquid phase. The supernatant liquid phase was sucked with a pump and pulled out. About the soil after the purification process which is the said solid-phase, the radiation dose was measured about the soil of 75 micrometers sieve up. The results are shown in Table 2. Moreover, the elution liquid for 500 years of elution was created from the soil after the said purification process, and the radiation dose was measured. The results are shown in Table 3.

Discussion: As is clear from the comparison between Table 1 before treatment and Table 2 after treatment, the radiation dose from the soil is reduced to about 26 times. As can be seen from the above, the risk of elution from the treated soil could be judged to be a negligible amount that can be substantially ignored.
In addition, the measurement of Table 1-Table 3 was performed by requesting the Kanto environmental technology center in Japan and overseas Technos of Chiba-shi, Chiba.
For reference, Table 4 shows provisional regulation values for radioactive substances.

(Example 2) As an object of purification treatment of radionuclide-contaminated fly ash with a cleaning function agent, fly ash and molten fly ash collected in Sakai City, Chiba Prefecture were used in place of the soil of Example 1.
Except for changing the object to be processed, the same processing as in Example 1 was performed, and the results are shown in Table 5.

(Example 3) As an object of purification treatment of heavy metal-contaminated soil with a cleaning function agent, a test soil prepared by mixing lead and benzene in soil not containing heavy metal is used instead of the soil of Example 1. It was.
Except for changing the object to be processed, the same processing as in Example 1 was performed, and the results are shown in Table 6.

(Example 4) Sendai Subway excavation soil was used in place of the soil of Example 1 as an object of purification treatment of heavy metal-contaminated soil with a cleaning function agent.
Except for changing the object to be processed, the same processing as in Example 1 was performed, and the results are shown in Table 7.

(Example 5) As an object of purification treatment of heavy metal-contaminated soil by a cleaning function agent, instead of the soil of Example 1, the sea mud sand of Sodegaura City, Chiba Prefecture and the soil of a farm pond were used.
Except for changing the object to be processed, the same processing as in Example 1 was performed, and the results are shown in Table 8.

(Example 6) Treatment method for radioactive nuclide-contaminated land Purification agent (B)
(2a) Polyferric sulfate ... 39.4 parts by mass (2b) Ferric nitrate ... 14.8 parts by mass (2c) Sulfuric acid ... 1.5 parts by mass (ie 75% sulfuric acid aqueous solution ... 2.0 parts by mass) )
(2d) Sodium nitrate: 8.61 parts by mass (ie, sodium nitrate 70% aqueous solution: 12.3 parts by mass)
(2e) 31.5 parts by mass of water was mixed to prepare one liquid purification treatment agent (B).
Binder aqueous solution (C)
(3a) Sodium polyacrylate (preferably 0.4 parts by mass)
(3b) Sodium silicate (preferably 30 parts by mass)
(3c) Water (preferably 69.6 parts by mass)
Were mixed to prepare a binder aqueous solution (C).

Experimental device: A 45-degree slope plate 11 was created assuming an inclined surface of a mountain, and an experimental device (i) (b) was prepared by kneading the site soil of the Iidate Village Public Hall in Fukushima Prefecture to a thickness of about 2 cm. A container 12 for receiving spray water is disposed at the lower end of the slope plate 11.

Experimental method: In the experimental apparatus (A), 500 g of the purification treatment agent (B) was sprayed, and then 500 g of the aqueous binder solution (C) was sprayed. The experimental apparatus (b) did not spray anything as a control. River water was sprayed intermittently three times a day on the experimental devices (a) and (b). The spray amount was 100 cc each time. The radiation dose was measured for the water accumulated in the container 12 during the experiment.

Measurement result:
Contamination concentration of raw soil ... Average 3.716 μSv (Measurement of contact with surface of kneaded ground soil is performed 7 times, average of 5 measurements excluding top and minimum values)
Experimental apparatus (I): 0.080 μSv (Indirect contact measurement with respect to water accumulated in the container 12 of the experimental apparatus (I) (measurement element was covered with a synthetic resin film and contacted with water) was performed once.)
Experimental device (b) 2.916 μSv (Measurement of indirect contact with water accumulated in the container 12 of the experimental device (b) was performed once (the probe was covered with a synthetic resin film and contacted with water).)
Measuring instrument: US made SEREALNER 51324
Unit of measurement: μSv

From the above measurement results, it is considered that the radionuclide-contaminated land treatment method according to the present invention provides a useful treatment method for preventing water system contamination by rainwater such as Abukuma River contaminated water.

Claims (9)

At least one of polyferric sulfate and ferric chloride, at least one of sodium nitrate and calcium nitrate, ferric nitrate, strong acid,
Treatment agent for radioactive nuclide-contaminated soil, various radioactive contaminated fly ash and heavy metal-contaminated soil . 35-50 parts by mass of at least one of polyferric sulfate and ferric chloride;
11-30 parts by mass of ferric nitrate,
0.75-3 parts by mass of sulfuric acid,
At least one of sodium nitrate 5.6 to 11.2 parts by mass and calcium nitrate 5.6 to 11.2 parts by mass ;
Treatment agent for radioactive nuclide-contaminated soil, various radioactive contaminated fly ash and heavy metal-contaminated soil . A pretreatment agent containing at least one of ferric nitrate and sodium nitrate, and a strong acid ;
The purification treatment agent according to claim 1 or 2 ,
A two-component cleaning function agent for radionuclide-contaminated soil, radiation-contaminated fly ash, and heavy metal-contaminated soil . At least one of 8-20 parts by mass of ferric nitrate and 5.6-11.2 parts by mass of sodium nitrate, 30-37.5 parts by mass of sulfuric acid,
A pretreatment agent containing
The purification treatment agent according to claim 2 ,
A two-component cleaning function agent for radionuclide-contaminated soil, radiation-contaminated fly ash, and heavy metal-contaminated soil . A method for cleaning radionuclide contaminated soil using the cleaning functional agent according to claim 4 ,
A first stirring step of mixing and stirring the pretreatment agent essentially containing the sulfuric acid and the ferric nitrate, soil and water contaminated with radionuclides as primary objects to be treated;
A first solid-liquid separation step for substantially solid-liquid separation of the primary workpiece subjected to the first stirring step into a solid phase and a liquid phase;
A second stirring step of mixing and stirring the processing agent for purification containing the ferric polysulfate essential, the solid phase, and water as a secondary object to be treated;
Performing a second solid-liquid separation step for substantially solid-liquid separation of the secondary workpiece after the first stirring step into a solid phase and a liquid phase;
A method for washing radionuclide-contaminated soil, wherein the solid phase obtained by the second solid-liquid separation step is used as washed soil. An inorganic binder aqueous solution containing sodium polyacrylate and sodium silicate;
The purifying treatment agent according to claim 1 or 2 , comprising the polyferric sulfate,
A two-component anti-scattering agent for radioactive nuclides contaminated soil, various radioactive contaminated fly ash and heavy metal contaminated soil . An inorganic binder aqueous solution containing 0.2 to 0.5 parts by mass of sodium polyacrylate and 20 to 40 parts by mass of sodium silicate;
The purifying treatment agent according to claim 2 , comprising the polyferric sulfate.
A two-component anti-scattering agent for radioactive nuclides contaminated soil, various radioactive contaminated fly ash and heavy metal contaminated soil . Ferric polysulfate, a ferric nitrate, and purifying treatment agent containing a strong acid,
A method for treating a radionuclide-contaminated site using a two-part splash spill inhibitor combined with an inorganic binder aqueous solution containing sodium polyacrylate and sodium silicate,
A first spraying step of spraying the binder aqueous solution to a radionuclide contaminated area;
A method for treating a radionuclide-contaminated site, comprising: performing a second spraying step of spraying the purification agent on the radionuclide-contaminated site that has undergone the first spraying step. 35-50 parts by mass of polyferric sulfate ,
11-30 parts by mass of ferric nitrate,
0.75-3 parts by mass of sulfuric acid,
A treating agent for purification,
A method for treating a radionuclide-contaminated site using a two-part splash spill inhibitor combined with an inorganic binder aqueous solution containing sodium polyacrylate and sodium silicate,
A first spraying step of spraying the binder aqueous solution to a radionuclide contaminated area;
A method for treating a radionuclide-contaminated site, comprising: performing a second spraying step of spraying the purification agent on the radionuclide-contaminated site that has undergone the first spraying step.

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