Method for insolubilizing organic fluorine compound

Abstract

To provide a new method for insolubilizing an organic fluorine compound.SOLUTION: A method for insolubilizing an organofluorine compound, comprising adding and mixing (A) a calcium compound and / or a magnesium compound, (B) a neutral solidifying material, and (C) activated carbon to and with soil containing the organofluorine compound, wherein the pH of the soil after treatment by the insolubilization method is 6 to 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for insolubilizing an organic fluorine compound. [Background technology]

[0002] PFAS (an abbreviation for perfluoroalkyl compounds, polyfluoroalkyl compounds, and their salts), which are organic fluorine compounds, are chemically stable and have excellent heat and chemical resistance. For this reason, PFAS are widely used in industrial applications, including fire extinguishing agents and Teflon (registered trademark) coatings for frying pans.

[0003] On the other hand, organic fluorine compounds are chemically stable and persistent, so they remain in the environment for long periods of time. Furthermore, they are easily soluble in groundwater, etc. For these reasons, there is concern that organic fluorine compounds may move around the environment, accumulate in plants and animals, and have a negative impact on ecosystems.

[0004] For this reason, in April 2020, the "Water Quality Management Target Setting Items" established under the Water Supply Act were revised, and PFOS (perfluorooctane sulfonate) and PFOA (perfluorooctanoic acid), which are types of PFAS, were newly added to the water quality management items. A provisional target value of 50ng / L or less was set for the combined value of PFOS and PFOA in tap water. Furthermore, in November 2023, "PFHxS or its isomers or salts thereof" was designated as a Type 1 Specified Chemical Substance under Article 2, Paragraph 2 of the Act on the Evaluation of Chemical Substances and Regulation of Their Manufacture, etc.

[0005] Patent Document 1 discloses an invention related to the containment of PFAS, which is a method for containing PFAS in a low-permeability cementitious product, comprising forming a cementitious slurry containing cement, water, and aggregate, and hardening the cementitious slurry to thereby form a cementitious product, wherein one or more of the water and the aggregate are contaminated with PFAS, and further comprising adding one or more of a siliceous pozzolan, a plasticizer, and a crystal growth water-resistant compound in an amount sufficient to produce a cementitious product having low water permeability such that PFAS does not substantially leach out. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2023-539477 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the environmental impact of the above-mentioned organic fluorine compounds, an object of the present invention is to provide a novel method for insolubilizing organic fluorine compounds. [Means for solving the problem]

[0008] As a result of extensive research into solving the above-mentioned problems, the present inventors have discovered a method for insolubilizing organic fluorine compounds, which involves adding and mixing (A) a calcium compound and / or a magnesium compound, (B) a neutral solidification material, and (C) activated carbon to soil contaminated with organic fluorine compounds, and have discovered that the organic fluorine compounds can be insolubilized when the pH of the soil after treatment by this insolubilization method is 6 to 11, thereby completing the present invention.

[0009] The Ca(OH)2 produced from the calcium compound in component (A) and the Mg(OH)2 produced from the magnesium compound are both basic. Cement-based solidification materials are generally alkaline (approximately pH 11 or higher). In contrast, the neutral solidification material in component (B) is neutral (approximately pH 6-10). The present invention is based on the discovery that by appropriately adjusting the amounts of component (A) and component (B) added and mixing components (A) to (C) with soil contaminated with organofluorine compounds, the pH of the soil after treatment by this insolubilization method can be adjusted to 6 to 11, thereby making it possible to more effectively insolubilize the organofluorine compounds.

[0010] That is, the present invention relates to the following inventions. [1] A method for insolubilizing organic fluorine compounds, comprising adding and mixing (A) a calcium compound and / or a magnesium compound, (B) a neutral solidification material, and (C) activated carbon to soil contaminated with organic fluorine compounds, The pH of the soil after treatment by the insolubilization method is 6 to 11. A method for insolubilizing organic fluorine compounds. [2] The method for insolubilizing an organic fluorine compound according to [1], wherein the (A) calcium compound and / or magnesium compound is at least one selected from the group consisting of calcium hydroxide, calcium oxide, calcium chloride, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium hydroxyapatite, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, magnesium hydrogen phosphate, magnesium borate, magnesium chloride, magnesium sulfate, magnesium acetate, magnesium nitrate, magnesium silicate, and magnesium stearate. [3] The method for insolubilizing an organic fluorine compound according to [1], wherein the (B) neutral solidification material is at least one selected from the group consisting of a gypsum-based solidification material, an aluminum-based solidification material, and a polymer-based solidification material. [4] The method for insolubilizing an organic fluorine compound according to [3], wherein the gypsum-based solidifying material is at least one selected from the group consisting of gypsum hemihydrate, gypsum anhydride, and gypsum dihydrate. [5] The method for insolubilizing an organic fluorine compound according to [1], wherein the mass ratio of the component (A) to the component (B) added is 0.6:3-8. [6] The method for insolubilizing an organic fluorine compound according to [1], wherein the activated carbon (C) is powdered activated carbon. [7] The method for insolubilizing an organic fluorine compound according to [1], characterized in that 0.5 to 150 g of the (A) calcium compound and / or magnesium compound is added per 1 kg of soil containing the organic fluorine compound. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a novel method for insolubilizing an organic fluorine compound. Furthermore, the hydraulic conductivity of treated soil that has been subjected to the method for immobilizing an organic fluorine compound according to the present invention is reduced, so that even if the organic fluorine compound is re-eluted from the treated soil, the movement of the organic fluorine compound in the environment can be restricted. Furthermore, the treated soil subjected to the method for insolubilizing an organic fluorine compound according to the present invention has a certain degree of strength, and therefore the method for insolubilizing an organic fluorine compound according to the present invention can be suitably used both as an insolubilization treatment for excavated soil (hereinafter referred to as an in-situ insolubilization treatment method) and as an in-situ insolubilization treatment method. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a graph showing the changes in the soil leaching amounts (ng / L) of PFOA, PFHpA, PFHxA, PFPeA, and PFBA caused by the addition or mixing of components (A) to (C) into simulated contaminated soil and the pH value of the simulated treated soil. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments.

[0014] As used herein, "insolubilization" refers to rendering an organofluorine compound in soil slightly soluble or insoluble in water. By insolubilizing the organofluorine compound, the amount of the organofluorine compound eluted from the soil into water can be reduced.

[0015] In this specification, the term "pollution" means that the soil is contaminated with an organic fluorine compound, that is, that the organic fluorine compound is contained in the soil.

[0016] In this specification, the term "hydraulic conductivity" refers to an index that indicates the degree of ease with which water passes through soil, and can be measured in accordance with JIS A 1218:2020.

[0017] In this specification, whether soil has a certain strength or bearing capacity can be determined by, for example, filling soil treated using a specified method for insolubilizing an organic fluorine compound into a cylindrical mold 5 cm in diameter x 10 cm in height, curing for 7 days, and then removing the soil from the cylindrical mold to confirm strength development. If the soil specimen is not self-supporting upon removal from the mold, an unconfined compression test to confirm strength development was not performed. The cylindrical mold filling method can be measured in accordance with JGS0821 (Method for preparing specimens without compaction of stabilized soil), and the unconfined compression test can be performed in accordance with JIS A 1216:2020 (Method for unconfined compression test of soil).

[0018] [1. Method for insolubilizing organic fluorine compounds] The method for insolubilizing an organic fluorine compound according to this embodiment is a method for insolubilizing an organic fluorine compound by adding and mixing (A) a calcium compound and / or a magnesium compound, (B) a neutral solidification material, and (C) activated carbon to soil contaminated with the organic fluorine compound, and is characterized in that the pH of the soil after treatment by this insolubilization method is 6 to 11.

[0019] <Organofluorine compounds> In the insolubilization method according to this embodiment, the organic fluorine compound is not particularly limited, and may be a compound in which part or all of the hydrogen atoms in a hydrocarbon have been substituted with fluorine atoms and / or a salt thereof.

[0020] Examples of the fluorine compound include: Per- or polyfluoroalkylcarboxylic acids such as perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid, 4,8-dioxa-3H-perfluorononanoic acid, perfluoro-3-methoxypropanoic acid, perfluoro-4-methoxybutanoic acid, nonafluoro-3,6-dioxaheptanoic acid, 3-perfluoropropylpropanoic acid, 3-perfluoroheptylpropanoic acid, and 2H,2H,3H,3H-perfluorooctanoic acid; perfluorobutanesulfonic acid, perfluoropentanesulfonic acid, perfluorohexanesulfonic acid (PFHxS), perfluoroheptanesulfonic acid, perfluorooctane sulfonic acid (PFOS), perfluorononanesulfonic acid, perfluorodecanesulfonic acid, perfluorododecanesulfonic acid, 1H,1H,2H,2H-perfluorohexanesulfonic acid, 1H,1H,2H,2H-perfluorooctane sulfonic acid, 1H,1H,2H,2H-perfluorodecanesulfonic acid, 9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid, 11-chloroicosafluoro-3-oxaundecane-1-sulfonic acid, perfluoro(2-ethoxyethane)sulfonic acid, and other per- or polyfluoroalkylsulfonic acids; Examples of perfluorooctane sulfonamide include perfluorooctane sulfonamide (PFOSA), N-methylperfluorooctane sulfonamide, N-ethylperfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide acetic acid, N-ethylperfluorooctane sulfonamide acetic acid, N-methylperfluorooctane sulfonamide ethanol, N-ethylperfluorooctane sulfonamide ethanol, and hexafluoropropylene oxide dimer acid. One or more of these organic fluorine compounds may be contained in the soil.

[0021] In the insolubilization method according to this embodiment, the organic fluorine compound is preferably a per- or polyfluoroalkyl carboxylic acid or a per- or polyfluoroalkyl sulfonic acid, from the viewpoints that these compounds are widely used in industrial products and daily necessities, are found in large amounts in soil, are likely to migrate into groundwater and public water bodies such as rivers and lakes, and are subject to regulation, and more preferably is a perfluoroalkyl carboxylic acid such as perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), or perfluorooctanoic acid (PFOA).

[0022] <(A) Calcium Compound and / or Magnesium Compound> The calcium compound according to the present embodiment is not particularly limited, and known and commonly used compounds can be used. Examples of calcium compounds include calcium hydroxide, calcium oxide, calcium chloride, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium hydroxyapatite, etc. These calcium compounds may be used alone or in combination of two or more.

[0023] As the calcium compound, from the viewpoint of making it difficult for organic fluorine compounds to leach out of the soil, it is preferable to use calcium hydroxide, calcium oxide, calcium chloride, or calcium carbonate, and it is more preferable to use calcium hydroxide or calcium oxide.

[0024] The magnesium compound according to the present embodiment is not particularly limited, and known and commonly used compounds can be used. Examples of magnesium compounds include magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, magnesium hydrogen phosphate, magnesium borate, magnesium chloride, magnesium sulfate, magnesium acetate, magnesium nitrate, magnesium silicate, magnesium stearate, and hydrates thereof. These magnesium compounds may be used alone or in combination of two or more.

[0025] As the magnesium compound, from the viewpoint of making it difficult for organic fluorine compounds to leach out of the soil, it is preferable to use magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, magnesium chloride, or magnesium sulfate, and it is more preferable to use magnesium oxide, magnesium hydroxide, or magnesium carbonate.

[0026] The (A) calcium compound and / or magnesium compound according to this embodiment may be at least one selected from the group consisting of calcium hydroxide, calcium oxide, calcium chloride, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium hydroxyapatite, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, magnesium hydrogen phosphate, magnesium borate, magnesium chloride, magnesium sulfate, magnesium acetate, magnesium nitrate, magnesium silicate, and magnesium stearate.

[0027] The amount of calcium compound and / or magnesium compound used in this embodiment to be added is not particularly limited and can be appropriately set depending on the type of component (A), the types and amounts of components (B) and (C), the pH value, the content of organic fluorine compounds in the soil, etc. From the viewpoint of making the organic fluorine compounds less likely to leach out of the soil, the amount of component (A) to be added is, for example, preferably 0.5 to 150 g, more preferably 1 to 100 g, and even more preferably 3 to 50 g, per 1 kg of soil containing the organic fluorine compounds.

[0028] <(B) Neutral solidifying material> The neutral solidification material according to this embodiment is not particularly limited, and any known and commonly used material can be used. Examples of neutral solidification materials include gypsum-based solidification materials, aluminum-based solidification materials, and polymer-based solidification materials. These neutral solidification materials may be used alone or in combination of two or more. As the neutral solidification material, it is preferable to use a gypsum-based solidification material or a polymer-based solidification material, and it is more preferable to use a gypsum-based solidification material, from the viewpoint of promoting the insolubilization of organic fluorine compounds and maintaining the strength of the soil.

[0029] The gypsum-based solidifying material is not particularly limited, and known and commonly used materials can be used. Examples of gypsum-based solidifying materials include gypsum hemihydrate, gypsum anhydrite, and gypsum dihydrate. These gypsum-based solidifying materials may be used alone or in combination of two or more.

[0030] The aluminum-based solidification material is not particularly limited, and known and commonly used materials can be used. Examples of aluminum-based solidification materials include aluminum sulfate (aluminum sulfate), polyaluminum chloride (PAC), hydraulic alumina, etc. These aluminum-based solidification materials may be used alone or in combination of two or more.

[0031] The polymer-based solidifying material is not particularly limited, and known and commonly used materials can be used. Examples of polymer-based solidifying materials include natural polymers such as guar gum, xanthan gum, diutan gum, welan gum, carrageenan, pectin, alginate, and derivatives thereof; semi-synthetic polymers such as cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, and derivatives thereof; and synthetic polymers such as polyacrylamide, polyacrylic acid ester, polyacrylate, copolymers of acrylate and acrylamide, and derivatives thereof. These polymer-based solidifying materials may be used alone or in combination of two or more.

[0032] The (B) neutral solidification material according to this embodiment may be at least one selected from the group consisting of a gypsum-based solidification material, an aluminum-based solidification material, and a polymer-based solidification material.

[0033] The gypsum-based solidifying material according to this embodiment may be at least one selected from the group consisting of gypsum hemihydrate, gypsum anhydrite, and gypsum dihydrate.

[0034] Generally, cement-based solidification materials are alkaline (approximately pH 11 or higher), while neutral solidification materials are neutral (approximately pH 6 to 10). Therefore, by using a neutral solidification material as component (B) and adjusting the ratio of the amounts of component (B) and component (A) added, the pH can be adjusted to an appropriate range for insolubilizing the organic fluorine compounds.

[0035] The amount of neutral solidification material used in this embodiment to be added is not particularly limited, and can be appropriately set depending on the type of component (B), the types and amounts of components (A) and (C), the pH value, the content of organic fluorine compounds in the soil, etc. From the viewpoint of promoting the insolubilization of organic fluorine compounds and maintaining soil strength, the amount of neutral solidification material to be added is, for example, preferably 50 to 600 g, more preferably 100 to 500 g, and even more preferably 200 to 400 g per kg of soil containing organic fluorine compounds.

[0036] The ratio of the amounts of component (A) and component (B) added in this embodiment is preferably component (A):component (B)=0.1-0.6:3-8 by mass, more preferably 0.1-0.6:5-6, 0.6:3-8, or 0.1-0.3:3-8, and even more preferably 0.1-0.6:5.6, 0.6:4-7, or 0.1-0.3:4-7.

[0037] <(C)Activated carbon> The activated carbon (C) according to this embodiment is not particularly limited, and known and commonly used materials can be used. The raw material for the activated carbon is not particularly limited, and examples thereof include wood (waste wood, thinned wood, sawdust), coal, bark, bamboo, bagasse, rice husks, coffee beans, peat, and fruit shells (coconut and palm).

[0038] The form of activated carbon is not particularly limited, and examples thereof include granular activated carbon, powdered activated carbon, fibrous activated carbon, etc. As for the form of activated carbon, it is preferable to use powdered activated carbon from the viewpoint of a large specific surface area and good contact efficiency.

[0039] The amount of component (C) used in this embodiment is not particularly limited and can be appropriately set depending on the type of component (C), the types and amounts of components (A) and (B), the pH value, the content of organic fluorine compounds in the soil, etc. From the viewpoint of promoting the insolubilization of organic fluorine compounds, the amount of activated carbon added is, for example, preferably 0.1 to 50 g, more preferably 0.4 to 40 g, and even more preferably 0.5 to 30 g, per kg of soil containing organic fluorine compounds.

[0040] <(D)Water> In this embodiment, water (D) may be used to thoroughly mix and suspend the soil contaminated with organofluorine compounds and components (A) to (C) to form a slurry. The water is not particularly limited, and any known or commonly used water can be used. Examples of water include tap water, river water, lake water, groundwater, rainwater, distilled water, pure water, and ion-exchanged water.

[0041] The amount of water (D) added used in this embodiment is not particularly limited and can be appropriately set depending on the types and amounts of components (A) to (C), the pH value, the content of organic fluorine compounds in the soil, etc. From the viewpoint of thoroughly mixing and suspending the soil and each component to form a slurry, the amount of water added is, for example, preferably 50 to 800 g, more preferably 100 to 700 g, even more preferably 120 to 600 g, and even more preferably 150 to 450 g per kg of soil containing organic fluorine compounds.

[0042] <ph> The insolubilization method according to this embodiment, i.e., the insolubilization method in which the components (A) to (C) are added and mixed with soil contaminated with an organic fluorine compound, is characterized in that the pH of the soil after treatment by the insolubilization method is 6 to 11.

[0043] The pH of the soil after treatment by the insolubilization method is preferably 6 to 11.5, more preferably 6 to 11, even more preferably 6.5 to 10.8, and even more preferably 7.0 to 10.6. By adjusting the pH to within the above range, the amount of organic fluorine compounds leaching out of the soil can be reduced.

[0044] The pH after treatment by the above insolubilization method can be adjusted to fall within the above numerical range by appropriately adjusting the amounts of components (A) to (C) added.

[0045] The pH of the soil after treatment by the insolubilization method can be measured by adding and mixing the above components (A) to (C) to soil contaminated with organofluorine compounds, allowing the soil to cure for 7 days, and then measuring the pH using a commercially available pH meter in accordance with JGS0211-2000 (pH test method for soil suspensions).

[0046] [2. Use of a method for insolubilizing organic fluorine compounds] When the method for insolubilizing an organic fluorine compound according to this embodiment is applied to soil contaminated with an organic fluorine compound, the components (A) and (B) work together to impart a certain degree of strength to the soil, and therefore the method for insolubilizing an organic fluorine compound according to this embodiment can be suitably used both as an on-site insolubilization treatment method and as an in-situ insolubilization treatment method. Furthermore, the method for insolubilizing an organic fluorine compound according to this embodiment is a chemical method and can be easily used without using any special equipment or the like.

[0047] Furthermore, by applying the method for insolubilizing an organic fluorine compound according to this embodiment to soil contaminated with an organic fluorine compound, not only can the organic fluorine compound be insolubilized, but the hydraulic conductivity of the soil can also be reduced to make it less permeable to water, thereby effectively preventing the insolubilized organic fluorine compound from leaching out again via water and moving in the environment, thereby preventing the contamination from spreading. Therefore, the method for insolubilizing an organic fluorine compound according to this embodiment is also useful as a method for suppressing the spread of contamination caused by organic fluorine compounds.

[0048] <On-site insolubilization treatment method> When the method for insolubilizing an organic fluorine compound according to this embodiment is used as an on-site insolubilization treatment method, components (A) to (C) may be added to and mixed with excavated soil using a backhoe, a mixer, etc. Then, the soil that has been subjected to the on-site insolubilization treatment method (hereinafter also referred to as "treated soil") may be backfilled in the original location or another location.

[0049] When the treated soil is returned to the original location or another location, it is required that the treated soil have a certain level of strength so that it can be transported by dump truck or the like and so that the backfilled ground can be prevented from becoming poor or collapsing.

[0050] In the method for insolubilizing an organic fluorine compound according to this embodiment, the calcium compound and / or magnesium compound (A) and the neutral solidification agent (B) function together as a solidification agent. Therefore, the soil treated by the on-site insolubilization method can be transported by dump truck or the like, and has sufficient strength to be used as backfill soil as is. Therefore, the method for insolubilizing an organic fluorine compound according to this embodiment can be suitably used as an on-site insolubilization treatment method.

[0051] <In-situ insolubilization treatment method> When the method for insolubilizing an organic fluorine compound according to this embodiment is used as an in-situ insolubilization treatment method, for example, components (A) to (C) can be added and mixed in-situ using a backhoe or a high-speed rotor if the soil contaminated with an organic fluorine compound is located shallow from the ground surface, or using a rotary blender if the soil is located deep from the ground surface, to produce soil that has been subjected to the in-situ insolubilization treatment method (hereinafter also referred to as "treated soil").

[0052] After in-situ insolubilization treatment, the treated soil is required to have a certain level of strength in order to continue work using heavy construction machinery such as pile drivers and rotary blenders in the treated soil or in its vicinity.

[0053] In the insolubilization treatment method for organic fluorine compounds according to this embodiment, the calcium compound and / or magnesium compound (A) and the neutral solidification material (B) function together as a solidification material. Therefore, the treated soil subjected to the in-situ insolubilization treatment method has the strength necessary to continue work using heavy construction machinery. Therefore, the insolubilization treatment method for organic fluorine compounds according to this embodiment can be suitably used as an in-situ insolubilization treatment method. [Example]

[0054] [Test Example 1: Insolubilizing effect of components (A) to (C) on organic fluorine compounds] <Preparation of simulated contaminated soil> Soil contaminated with the above PFASs (hereinafter also referred to as "simulated contaminated soil") was prepared using a solution containing fire extinguishing agents containing various PFASs (e.g., PFOA, PFHpA, PFHxA, PFPeA, PFBA, etc.). The soil used was commercially available granite soil (produced in Kagawa Prefecture by Kanea Co., Ltd.) sieved to particles less than 2 mm. Additionally, a solution containing fire extinguishing agents containing various PFASs was diluted with water to create a PFAS solution. 1 kg of the above soil was mixed with 10 kg of the above PFAS solution and shaken for 24 hours under the conditions of the Ministry of the Environment Notice No. 18 (March 6, 2003) (hereinafter also referred to as "Environmental Notice No. 18"). Thereafter, centrifugation (1000 G, 5 minutes) was performed to separate the soil and the liquid, and the separated soil was used as the simulated contaminated soil.

[0055] <Preparation of Simulated Treated Soil> The predetermined amounts of components (A) to (D) shown in Table 1 below were added to and mixed with the simulated contaminated soil to obtain simulated treated soil (Comparative Examples 1 and 2, and Examples 1 to 6). The addition amount of ion-exchanged water as component (D) in Table 1 was set as the amount that could maintain the slurry state of the simulated contaminated soil and components (A) to (C). Component (A): Slaked lime (manufactured by Ube Materials Co., Ltd.) Magnesium oxide (manufactured by Ube Materials Co., Ltd.) Others: Blast furnace cement type B (manufactured by Taiheiyo Cement Corporation) Component (B): Hemihydrate gypsum (manufactured by Yoshino Gypsum Co., Ltd.) Component (C): Powdered activated carbon GB (manufactured by Futamura Chemical Co., Ltd.) Component (D): Ion-exchanged water

[0056]

Table 1

[0057] <Measurement of Soil Elution Amounts of PFOA, PFHpA, PFHxA, PFPeA, and PFBA> The simulated treated soil (Comparative Examples 1 and 2, and Examples 1 to 6) was cured for 7 days. Thereafter, the pH of the simulated treated soil was measured using a commercially available pH meter in accordance with JGS0211-2000 (pH test method for soil suspension). The results are shown in Table 2. Also, using the simulated treated soil after the 7-day curing, the soil elution amounts of PFOA, PFHpA, PFHxA, PFPeA, and PFBA were measured in accordance with Environmental Notice No. 18. The results are shown in Table 2 and Figure ①.

[0058]

Table 2

[0059] The results of Comparative Example 1 and Examples 1 to 3 in Table 2 and Figure 1 show that the amount of PFOA, PFHpA, PFHxA, PFPeA, and PFBA leaching into the soil is reduced when the pH of the simulated treated soil is set to 8.1 to 10.6 using slaked lime and hemihydrate gypsum as component (B) as in Examples 1 to 3, compared to when the pH of the simulated treated soil is set to 12.1 using slaked lime and blast-furnace cement type B as in Comparative Example 1. Furthermore, from the results of Examples 1 to 3 in Table 2 and Figure 1, it can be seen that if the amount of slaked lime added as component (A) is too large, the pH of the simulated treated soil becomes high, so by adjusting the amount of slaked lime added in relation to components (B) and (C), etc., even a small amount can efficiently insolubilize the organic fluorine compounds.

[0060] The results of Comparative Example 2 and Examples 4 to 6 in Table 2 and Figure 1 show that the amounts of PFOA, PFHpA, PFHxA, PFPeA, and PFBA eluted from soil are all reduced when the pH of the simulated treated soil is adjusted to 9.0 to 9.8 using magnesium oxide and hemihydrate gypsum as component (B) as in Examples 4 to 6, compared to when the pH of the simulated treated soil is adjusted to 11.6 using magnesium oxide and blast-furnace cement type B as in Comparative Example 2. Furthermore, the results of Examples 4 to 6 in Table 2 and Figure 1 show that even when the amount of magnesium oxide added as component (A) is small, controlling the pH of the simulated treated soil within an appropriate range allows efficient insolubilization of organofluorine compounds.

[0061] [Test Example 2: Hydraulic conductivity and bearing capacity of simulated contaminated soil and simulated treated soil] The prepared simulated treated soils (Comparative Examples 1 and 2, and Examples 1 to 6) were each cured for 7 days, after which the hydraulic conductivity of the simulated treated soils was measured in accordance with JIS A 1218:2020. As a result, the hydraulic conductivity of the simulated treated soils of Comparative Examples 1 and 2 and Examples 1 to 6 was 10 -8 ~10 -9 Values ​​in the range of m / sec were shown.

[0062] The permeability coefficient of ordinary granite is 10 -7 m / sec, it can be seen that the hydraulic conductivity of the simulated treated soils of Comparative Examples 1 and 2 and Examples 1 to 6 is small, making it more difficult for water to pass through. This shows that by adding components (A) to (C) to the simulated contaminated soil, even if the organofluorine compounds are re-eluted from the simulated treated soil, the movement of the organofluorine compounds in the environment can be restricted.

[0063] The prepared simulated treated soils (Comparative Examples 1 and 2, and Examples 1 to 6) were each filled into a cylindrical mold measuring 5 cm in diameter and 10 cm in height and cured for 7 days. The specimens were removed from the cylindrical molds and used to confirm strength development. The filling of the cylindrical molds was performed in accordance with JGS0821 (method for preparing specimens of stabilized soil without compaction), and the unconfined compression test was performed in accordance with JIS A 1216:2020 (method for unconfined compression test of soil).

[0064] When the simulated treated soils of Comparative Examples 1 and 2 and Examples 1 to 6 were removed from the cylindrical molds filled with them, they all had self-supporting properties. Therefore, it is clear that adding components (A) to (C) to the simulated contaminated soil gives the simulated treated soil a certain degree of strength.< / ph>

Claims

1. A method for insolubilizing organic fluorine compounds, comprising adding and mixing (A) a calcium compound and / or a magnesium compound, (B) a neutral solidification material, and (C) activated carbon to soil contaminated with the organic fluorine compounds, The pH of the soil after treatment by the insolubilization method is 6 to 11. A method for insolubilizing organic fluorine compounds.

2. 2. The method for insolubilizing an organic fluorine compound according to claim 1, wherein the calcium compound and / or magnesium compound (A) is at least one selected from the group consisting of calcium hydroxide, calcium oxide, calcium chloride, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium hydroxyapatite, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, magnesium hydrogen phosphate, magnesium borate, magnesium chloride, magnesium sulfate, magnesium acetate, magnesium nitrate, magnesium silicate, and magnesium stearate.

3. 2. The method for insolubilizing an organic fluorine compound according to claim 1, wherein the (B) neutral solidification material is at least one selected from the group consisting of a gypsum-based solidification material, an aluminum-based solidification material, and a polymer-based solidification material.

4. 4. The method for insolubilizing an organic fluorine compound according to claim 3, wherein the gypsum-based solidifying material is at least one selected from the group consisting of gypsum hemihydrate, gypsum anhydride, and gypsum dihydrate.

5. 2. The method for insolubilizing an organic fluorine compound according to claim 1, wherein the mass ratio of the component (A) to the component (B) added is 0.6:3 to 0.6:

8.

6. 2. The method for insolubilizing an organic fluorine compound according to claim 1, wherein the activated carbon (C) is powdered activated carbon.

7. 2. The method for insolubilizing an organic fluorine compound according to claim 1, wherein 0.5 to 150 g of the calcium compound and / or magnesium compound (A) is added per 1 kg of soil containing the organic fluorine compound.

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