Method for insolubilizing organic fluorine compound

Abstract

To provide a novel method for insolubilizing an organic fluorine compound.SOLUTION: A method for insolubilizing an organic fluorine compound, comprising adding (A) a magnesium compound and (B) cement and / or gypsum to soil containing the organic fluorine compound.SELECTED DRAWING: Figure 2

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 coatings on 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. 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.

[0004] Patent Document 1 discloses an in-situ remediation system for organic fluorine compounds that can purify soil and the like contaminated with organic fluorine compounds. The system includes a soil heating device that heats the soil by applying pressure to three or more electrode wells constructed in the soil and passing an electric current through the soil, and a decomposition treatment device that decomposes the organic fluorine compounds contained in the contaminated water vapor generated by heating the soil heating device. The decomposition treatment device is portable and installed on the ground, and decomposes the organic fluorine compounds by blowing ozone gas into the contaminated water that has been cooled from the contaminated water vapor and irradiating it with ultraviolet light.

[0005] Furthermore, Patent Document 2 discloses a modified clay adsorbent for adsorbing PFAS from contaminated samples, which comprises one or more polyfunctional quaternary amine compounds having three or more functional groups and clay intercalated with one or more monoquaternary amine compounds. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-30560 [Patent Document 2] Special Publication No. 2023-526607 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 intensive research to solve the above-mentioned problems, the present inventors have found that the organic fluorine compounds can be insolubilized by adding (A) a magnesium compound and (B) cement and / or gypsum to soil contaminated with the organic fluorine compounds, and have thus completed the present invention.

[0009] That is, the present invention relates to the following inventions. [1] A method for insolubilizing an organic fluorine compound, comprising adding (A) a magnesium compound and (B) cement and / or gypsum to soil contaminated with the organic fluorine compound. [2] A method for insolubilizing organic fluorine compounds, comprising adding (A) a magnesium compound, (B) cement and / or gypsum, and (C) activated carbon to soil contaminated with the organic fluorine compounds. [3] The method for insolubilizing an organic fluorine compound according to [1] or [2], wherein the magnesium compound (A) is at least one selected from the group consisting of 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. [4] The method for insolubilizing an organic fluorine compound according to [1] or [2], wherein the (B) cement is at least one selected from the group consisting of blast furnace cement type A, blast furnace cement type B, and blast furnace cement type C. [5] The method for insolubilizing an organic fluorine compound according to [1] or [2], wherein the (B) gypsum is at least one selected from the group consisting of gypsum hemihydrate, gypsum anhydrite, and gypsum dihydrate. [6] The method for insolubilizing an organic fluorine compound according to [2], wherein the activated carbon (C) is powdered activated carbon. [7] The method for insolubilizing an organic fluorine compound according to [1] or [2], characterized in that 5 to 300 g of the magnesium compound (A) is added per 1 kg of soil containing the organic fluorine compound. [Effects of the Invention]

[0010] 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 as both an on-site insolubilization method and an in-situ insolubilization method. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a graph showing the change in the amount (ng / L) of PFOS, PFOA, and PFHxS leached from soil by adding components (A) and / or (B) to simulated contaminated soil. [Figure 2] 1 is a graph showing the change in the amount (ng / L) of PFOS, PFOA, and PFHxS eluted from soil by adding components (A) to (C) to simulated contaminated soil. [Figure 3] 1 is a graph showing the change in the amount of various PFAS eluted from soil (ng / L) by adding components (A) to (C) to simulated contaminated soil. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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 when removed 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 (preparation of specimens without compaction of stabilized soil), and the unconfined compression test method can be measured in accordance with JGS0511 (unconfined compression test method for soil).

[0017] [1. Method for insolubilizing organic fluorine compounds] [1-1. Embodiment 1 of the method for insolubilizing an organic fluorine compound] The method for insolubilizing an organic fluorine compound according to this embodiment is characterized by adding (A) a magnesium compound and (B) cement and / or gypsum to soil contaminated with an organic fluorine compound.

[0018] <Organofluorine compounds> The organic fluorine compound to be insolubilized in this embodiment 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.

[0019] 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.

[0020] In the insolubilization method according to this embodiment, the organic fluorine compound is preferably a per- or polyfluoroalkylcarboxylic acid or a per- or polyfluoroalkylsulfonic acid, more preferably a per- or polyfluorooctanoic acid or a per- or polyfluorooctanesulfonic 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 or public water bodies such as rivers and lakes, and are subject to regulation.

[0021] <(A) Magnesium Compound> 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.

[0022] 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.

[0023] The amount of magnesium compound added to be used in this embodiment 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 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 magnesium compound added is, for example, preferably 5 to 300 g, more preferably 10 to 250 g, and even more preferably 20 to 200 g, per kg of soil containing the organic fluorine compounds.

[0024] <(B) Cement and / or Gypsum> (cement) The cement according to the present embodiment is not particularly limited, and known and commonly used cements can be used. Examples of cement include Portland cement (ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, etc.), blended cement (cement mixed with blast-furnace cement types A to C, silica cement, fly ash cement, etc.), ecocement, special cement (white Portland cement, alumina cement, ultra-fast hardening cement, grout cement, oil well cement, etc.). These cements may be used alone or in combination of two or more. As the cement, from the viewpoint of maintaining the strength of the soil, it is preferable to use blast furnace cement types A to C, silica cement, or fly ash cement, and it is more preferable to use blast furnace cement types A to C.

[0025] The amount of cement used in this embodiment 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 content of organic fluorine compounds in the soil, etc. From the viewpoint of maintaining soil strength, the amount of cement added is preferably 10 to 400 g, more preferably 20 to 360 g, and even more preferably 30 to 300 g, per kg of soil containing organic fluorine compounds.

[0026] (plaster) The gypsum according to the present embodiment is not particularly limited, and known and commonly used gypsums can be used. Examples of gypsum include gypsum hemihydrate, gypsum anhydrite, and gypsum dihydrate. These gypsums may be used alone or in combination of two or more. As the gypsum, it is preferable to use gypsum hemihydrate from the viewpoint of promoting the insolubilization of the organic fluorine compound and maintaining the strength of the soil.

[0027] The amount of gypsum added to be used in this embodiment 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 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 gypsum added is, for example, preferably 10 to 400 g, more preferably 20 to 360 g, and even more preferably 30 to 300 g, per kg of soil containing organic fluorine compounds.

[0028] It should be noted that cement and gypsum may be used together as component (B). Portland cement, blended cement, and the like typically contain gypsum. Cement is alkaline (approximately pH 11 or higher), while gypsum is neutral (approximately pH 6 to 8). Therefore, by using cement and / or gypsum as component (B), the insolubilizing effect can be achieved in both alkaline and neutral conditions, and the ratio of the cement and / or gypsum to be added can be adjusted appropriately depending on the properties of the soil containing organic fluorine compounds.

[0029] [1-2. Embodiment 2 of the method for insolubilizing organic fluorine compounds] In another embodiment of the method for insolubilizing an organic fluorine compound according to the present invention, activated carbon (C) may be added to soil contaminated with an organic fluorine compound in addition to the components (A) and (B).

[0030] <(C)Activated carbon> The activated carbon according to the present 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).

[0031] 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.

[0032] The amount of activated carbon (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 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 1 kg of soil containing organic fluorine compounds.

[0033] [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.

[0034] 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.

[0035] <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) and (B), or components (A) to (C), or a slurry of these with water, may be added to and mixed with excavated soil using a backhoe, a mixer, etc. 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.

[0036] 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.

[0037] In the method for insolubilizing an organic fluorine compound according to this embodiment, the magnesium compound (A) and the cement and / or gypsum (B) act together as a solidifying 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.

[0038] <In-situ insolubilization treatment method> When the method for insolubilizing organic fluorine compounds according to this embodiment is used as an in-situ insolubilization treatment method, for example, if the soil contaminated with organic fluorine compounds is located shallow from the ground surface, a backhoe or a high-speed rotating rotor or the like can be used, or if the soil is located deep from the ground surface, a rotary blender or the like can be used to add and mix components (A) and (B), or components (A) to (C), or a slurry made by adding water to these, in-situ, to produce soil that has been subjected to the in-situ insolubilization treatment method (hereinafter also referred to as "treated soil").

[0039] 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.

[0040] In the method for insolubilizing an organic fluorine compound according to this embodiment, the magnesium compound (A) and the cement and / or gypsum (B) act together as a solidifying agent. Therefore, the soil treated by the in-situ insolubilization method has the strength necessary to continue work using heavy construction machinery. Therefore, the method for insolubilizing an organic fluorine compound according to this embodiment can be suitably used as an in-situ insolubilization method. [Example]

[0041] [Test Example 1: Insolubilizing effect of components (A) to (C) on organic fluorine compounds] First, soil contaminated with PFOS, PFOA, and PFHxS (hereinafter also referred to as "simulated contaminated soil") was prepared. Next, the prepared simulated contaminated soil was mixed with the predetermined amounts of components (A) to (C) shown in Table 1 below and ion-exchanged water to prepare simulated treated soil. The simulated treated soil was cured for 7 days, and then the amounts of PFOS, PFOA, and PFHxS eluted from the simulated treated soil were measured using a predetermined method. Based on the amounts eluted from the soil, the insolubilization effect of components (A) to (C) on organofluorine compounds was evaluated.

[0042] <Preparation of simulated contaminated soil> The simulated contaminated soil was prepared using a predetermined amount of soil and PFOS, PFOA, and PFHxS reagents. The soil used was commercially available granular sand (Kagawa Prefecture, manufactured by Kanea Co., Ltd.) sieved to particles less than 2 mm. The PFOS, PFOA, and PFHxS used were all 95% or higher purity PFOS, PFOA, and PFHxS, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Water was added to the soil so that the concentrations of PFOS, PFOA, and PFHxS were all 100,000 ng / L, creating a PFOS-PFOA-PFHxS aqueous solution. 1 kg of the above soil was mixed with 10 kg of the above PFOS·PFOA·PFHxS aqueous solution and shaken for 24 hours under the conditions of the Ministry of the Environment Notification 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 simulated contaminated soil.

[0043] <Preparation of Simulated Treated Soil> To the simulated contaminated soil, the predetermined amounts of components (A) to (C) shown in Table 1 below and ion-exchanged water were added and mixed, and these were used as Control 1 and simulated treated soils (Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-6). The amount of ion-exchanged water added in Table 1 was set as the amount that could maintain the components (A) to (C) in a slurry state. Component (A): Magnesium oxide (manufactured by Ube Materials Co., Ltd.) Component (B): Blast furnace cement type B (manufactured by Taiheiyo Cement Corporation) Component (C): Powdered activated carbon GB (manufactured by Futamura Chemical Co., Ltd.)

[0044]

Table 1

[0045] <Measurement of Soil Elution Amounts of PFOS, PFOA, and PFHxS> The prepared Control 1 and simulated treated soils (Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-6) were cured for 7 days, and thereafter, the soil elution amounts of PFOS, PFOA, and PFHxS were measured in accordance with Environmental Notice No. 18. The results are shown in Table 1, Figures 1 and 2.

[0046] From the results of the control and Comparative Examples 1-1 to 1-3 in Table 1 and Figure 1, overall, as the amount of magnesium oxide added increases, the soil elution amounts of PFOS, PFOA, and PFHxS tend to decrease more. Also, it can be seen that by adding blast furnace cement type B as component (B) in addition to component (A) as in Examples 1-1 to 1-3, the soil elution amounts of PFOS, PFOA, and PFHxS are further reduced.

[0047] Furthermore, the results of the control and Examples 1-3 to 1-6 in Table 1 and Figures 1 and 2 show that the addition of activated carbon, which is component (C), significantly reduces the amount of PFOS, PFOA, and PFHxS leaching into soil.

[0048] <Hydraulic conductivity and bearing capacity of simulated contaminated soil and simulated treated soil> The prepared simulated treated soils (Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-6) 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 1-1 to 1-3 was 10 -4 ~10 -6 In contrast, the hydraulic conductivity of the simulated treated soils in Examples 1-1 to 1-6 was in the range of 10 -8 ~10 -9 Values ​​in the range of m / sec were shown.

[0049] 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 Examples 1-1 to 1-6 is small, making it more difficult for water to pass through. This shows that by adding components (A) and (B) to the simulated contaminated soil, it is possible to limit the movement of the organofluorine compounds in the environment, even if they are re-eluted from the simulated treated soil.

[0050] The prepared simulated treated soils (Comparative Examples 1-1 to 1-3 and Examples 1-1 to 1-6) were each filled into a cylindrical mold with a diameter of 5 cm and a height of 10 cm and cured for 7 days. The specimens were removed from the cylindrical molds and used to confirm strength development. If the specimens were not self-supporting when removed from the molds, an unconfined compression test to confirm strength development was not performed. The filling of the cylindrical molds was performed in accordance with JGS0821 (preparation of specimens without compaction of stabilized soil), and the unconfined compression test was performed in accordance with JGS0511 (unconfined compression test method for soil).

[0051] When the simulated treated soils of Comparative Examples 1-1 to 1-3 were removed from the cylindrical molds filled with them, they were not self-supporting. In contrast, when the simulated treated soils of Examples 1-1 to 1-6 were removed from the cylindrical molds filled with them, they were all self-supporting.

[0052] Therefore, it can be seen that adding components (A) and (B) to the simulated contaminated soil gives the simulated treated soil a certain degree of strength.

[0053] [Test Example 2: Insolubilizing effect of organic fluorine compounds] <Preparation of simulated contaminated soil> The simulated contaminated soil was prepared using a solution containing a predetermined amount of soil and fire extinguishing agents containing various PFASs (e.g., PFHxA, PFBA, PFPeA, PFHpA, 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. 10 kg of the above PFAS solution was mixed with 1 kg of the above soil and shaken for 24 hours under the conditions of Environmental Notification No. 18. Then, the soil was centrifuged (1000 G, 5 minutes) to separate the soil and liquid, and the separated soil was used as simulated contaminated soil.

[0054] <Preparation of simulated treated soil> The simulated contaminated soil was mixed with the predetermined amounts of slaked lime, magnesium oxide, blast furnace cement type B, hemihydrate gypsum, powdered activated carbon, and ion-exchanged water shown in Table 2 below, and the resulting mixture was used as control 2 and simulated treated soil (comparative example 2 and example 2). The amount of ion-exchanged water added in Table 2 was set to an amount that would allow the additives to maintain a slurry state. Slaked lime (Ube Material Industries, Ltd.) Magnesium oxide (Ube Material Industries, Ltd.) Hemihydrate gypsum (manufactured by Yoshino Gypsum Co., Ltd.) Powdered activated carbon GB (Futamura Chemical Co., Ltd.)

[0055] [Table 2]

[0056] <Measurement of soil leaching amounts of various PFAS> The prepared Control 2 and simulated treated soils (Comparative Example 2 and Example 2) were cured for 7 days, and then the amounts of PFHxA, PFBA, PFPeA, and PFHpA leaching from the soil were measured in accordance with Environmental Notification No. 18. The results are shown in Table 3 and FIG.

[0057] [Table 3]

[0058] Comparing the results of Comparative Example 2 and Example 2 in Table 3 and Figure 3, although the amount of slaked lime added in Comparative Example 2 was 0.6g while the amount of magnesium oxide added in Example 2 was 1.2g, which is large, the amount of PFAS eluted from soil in Comparative Example 2 was 18000ng / L while the amount of PFAS eluted from soil in Example 2 was 13300ng / L, which is approximately two-thirds. From this, it can be seen that Example 2, in which magnesium oxide was added, has approximately the same effect of reducing the amount of PFAS eluted from soil, even compared to Comparative Example 2, in which slaked lime was added. Although the mechanism by which the addition of magnesium compounds produces the above-mentioned effects is unclear, it is thought that by combining magnesium compounds with cement and / or gypsum, the magnesium compounds affect the solidification of the cement and / or gypsum, thereby enhancing the insolubilization effect of PFAS.

Claims

1. A method for insolubilizing an organic fluorine compound, comprising adding (A) a magnesium compound and (B) cement and / or gypsum to soil contaminated with the organic fluorine compound.

2. A method for insolubilizing organic fluorine compounds, comprising adding (A) a magnesium compound, (B) cement and / or gypsum, and (C) activated carbon to soil contaminated with the organic fluorine compounds.

3. 3. The method for insolubilizing an organic fluorine compound according to claim 1 or 2, wherein the magnesium compound (A) is at least one selected from the group consisting of 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.

4. 3. The method for insolubilizing an organic fluorine compound according to claim 1, wherein the cement (B) is at least one selected from the group consisting of blast furnace cement type A, blast furnace cement type B, and blast furnace cement type C.

5. 3. The method for insolubilizing an organic fluorine compound according to claim 1 or 2, wherein the gypsum (B) is at least one selected from the group consisting of gypsum hemihydrate, gypsum anhydrite, and gypsum dihydrate.

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

7. 3. The method for insolubilizing an organic fluorine compound according to claim 1, wherein the magnesium compound (A) is added in an amount of 5 to 300 g per 1 kg of soil containing the organic fluorine compound.

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