Method for purifying organofluorine compound

Abstract

To provide a novel method of purifying an organofluorine compound.SOLUTION: A method of purifying an organofluorine compound comprises a step of adding (A) an oxidant to soil and / or water containing an organofluorine compound.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a method for purifying organic fluorine compounds.

Background Art

[0002] Organic fluorine compounds (PFAS: perfluoroalkyl compounds, polyfluoroalkyl compounds, and their salts, etc.) have chemical properties such as water and oil repellency, flame retardancy, and chemical resistance. For this reason, PFAS has been widely used from industrial products such as surface treatment agents for semiconductors to daily products such as fluorine processing agents for frying pans and waxes.

[0003] On the other hand, PFAS is also known as a persistent compound with strong carbon-fluorine bonds and is resistant to oxidative decomposition, photodegradation, biodegradation, etc. And specific PFAS (for example, PFOS (perfluorooctanesulfonic acid), PFOA (perfluorooctanoic acid), etc.) have properties such as high persistence in the environment and tendency to accumulate in the body, and their production, use, import and export, etc. are regulated internationally by the Stockholm Convention.

[0004] In Japan, in April 2020, PFOS and PFOA were classified as items for setting water quality management targets, and the provisional target value was set at 50 ng / L in total for PFOS and PFOA. In recent years, worldwide, guideline values and provisional values for soil have begun to be set, and in Japan, the Ministry of the Environment has issued a notice regarding the provisional measurement method for soil elution amount / soil content.

[0005] From the above circumstances, effective decomposition methods and purification methods for PFAS are being explored. For example, in Patent Document 1, as a liquid treatment method for decomposing persistent substances such as PFAS, when electrolyzing a treatment target liquid containing a persistent substance, a liquid treatment method having an electrolysis step of aerating a gas containing at least oxygen into the treatment target liquid is disclosed.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2022-135951 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] Therefore, an object of the present invention is to provide a method for purifying a novel organic fluorine compound. [Means for Solving the Problems]

[0008] As a result of intensive studies to solve the above problems, the present inventors have found that an organic fluorine compound can be effectively purified by adding (A) an oxidizing agent to soil and / or water containing the organic fluorine compound. Further, it has been found that by additionally adding (B) an alkali metal or alkaline earth metal compound, the organic fluorine compound can be purified more effectively, and the present invention has been completed.

[0009] That is, the present invention relates to the following inventions. [1] A method for purifying an organic fluorine compound, comprising adding (A) an oxidizing agent to soil and / or water containing the organic fluorine compound. [2] The method for purifying an organic fluorine compound according to [1], wherein the (A) oxidizing agent contains a salt of peroxymonosulfuric acid and / or peroxydisulfuric acid. [3] The method for purifying an organic fluorine compound according to [2], wherein the salt of peroxymonosulfuric acid is KHSO5. [4] The method for purifying an organic fluorine compound according to [1], further comprising adding (B) an alkali metal or alkaline earth metal compound. [5] The method for purifying an organic fluorine compound according to [4], wherein the (B) alkali metal or alkaline earth metal compound is a calcium compound and / or a basic compound. [6] The purification method of the organic fluorine compound according to [5], wherein the (B) calcium compound and / or basic compound is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium oxide, calcium hydroxide, calcium chloride, calcium carbonate, and calcium hydrogen carbonate. [7] The purification method of the organic fluorine compound according to [4], wherein the mass ratio of the addition of the (A) oxidizing agent to the (B) alkali metal or alkaline earth metal compound is 1 to 4:1 to 10.

Advantages of the Invention

[0010] According to the present invention, a novel purification method of an organic fluorine compound can be provided. In particular, the purification method of the organic fluorine compound according to the present invention is simple, and can be used not only for on-site treatment of purifying excavated soil on the ground, but also for in-situ treatment methods of injecting or mixing materials into the ground without excavation. Further, by using an alkali metal or alkaline earth metal compound, the purification of the organic fluorine compound can be promoted. In particular, by using a calcium compound and / or basic compound, organic fluorine compounds such as per- or polyfluoroalkyl sulfonic acid or per- or polyfluoroalkyl carboxylic acid contained in the soil can be eluted into the aqueous solution, and the organic fluorine compound can be purified more effectively.

Brief Description of the Drawings

[0011]

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Figure 10

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[0013] [1. Method for Purifying Organic Fluorine Compounds] The method for purifying an organic fluorine compound according to this embodiment is characterized by adding (A) an oxidizing agent to soil and / or water containing the organic fluorine compound. In addition to the above component (A), (B) an alkali metal or alkaline earth metal compound may be added simultaneously or at different times.

[0014] [1-1. Organic Fluorine Compounds] The organic fluorine compound according to this embodiment is not particularly limited as long as it is a perfluoroalkyl compound, a polyfluoroalkyl compound, or salts thereof. Examples of the organic fluorine compound include per- or polyfluoroalkyl carboxylic acids such as perfluorobutanoic acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, 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, 2H,2H,3H,3H-perfluorooctanoic acid; per- or polyfluoroalkyl sulfonic acids such as perfluorobutane sulfonic acid, perfluoropentane sulfonic acid, perfluorohexane sulfonic acid, perfluoroheptane sulfonic acid, perfluorooctane sulfonic acid, perfluorononane sulfonic acid, perfluorodecane sulfonic acid, perfluorododecane sulfonic acid, 1H,1H,2H,2H-perfluorohexane sulfonic acid, 1H,1H,2H,2H-perfluorooctane sulfonic acid, 1H,1H,2H,2H-perfluorodecane sulfonic acid, 9-chlorohexadecafluoro-3-oxanonane-1-sulfonic acid, 11-chloroeicosaf luoro-3-oxaundecane-1-sulfonic acid, perfluoro(2-ethoxyethane) sulfonic acid; and perfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide, N-ethylperfluorooctane sulfonamide, N-methylperfluorooctane sulfonamide acetic acid, N-ethylperfluorooctane sulfonamide acetic acid, N-methylperfluorooctane sulfonamide ethanol, N-ethylperfluorooctane sulfonamide ethanol, hexafluoropropylene oxide dimer acid. One or more of these organic fluorine compounds may be contained in soil and / or water.

[0015] In the present embodiment, as the organic fluorine compound to be purified, from the viewpoints of being widely used in industrial products and daily products and being contained in large amounts in soil and / or water, and from the viewpoint of being a regulated target, it is preferably per- or polyfluoroalkyl carboxylic acid or per- or polyfluoroalkyl sulfonic acid, and more preferably per- or polyfluorooctane sulfonic acid or per- or polyfluorooctanoic acid.

[0016] The soil content of the organic fluorine compound is not particularly limited and can be appropriately set according to the type and amount of the oxidizing agent used, the type and amount of the alkali metal or alkaline earth metal compound used, etc. The soil content of the organic fluorine compound is preferably, for example, 100 μg / kg or less, more preferably 80 μg / kg or less, and even more preferably 50 μg / kg or less. In particular, when adding not only an oxidizing agent but also a calcium compound and / or a basic compound, although it is unclear whether it is due to the interaction between calcium and fluorine or due to the formation of CaF2 (fluorite), by promoting the purification reaction of the organic fluorine compound or increasing the elution amount of the organic fluorine compound in the soil, it is possible to purify even when the soil content of the organic fluorine compound is large. Also, the concentration of the organic fluorine compound in water is not particularly limited and can be appropriately set according to the type and amount of the oxidizing agent used, the type and amount of the alkali metal or alkaline earth metal compound used, etc. The concentration of the organic fluorine compound in water is preferably, for example, 100 μg / L or less, more preferably 80 μg / L or less, and even more preferably 50 μg / L or less.

[0017] In this specification, "purification" means that the organic fluorine compound contained in soil or water is decomposed or the like, and the elution amount or soil content or both of them are reduced. In this specification, the "soil elution amount" refers to the amount of organofluorine compounds eluted when water is added to the soil, and means the elution amount measured in accordance with the "Provisional Measurement Methods for PFOS, PFOA and PFHxS in Soil (Elution Amount Test, Content Test)" (Ministry of the Environment HP: https: / / www.Eenv.go.jp / water / dojo / pfas.html). Also in this specification, the "soil content" refers to the amount of organofluorine compounds contained in the soil, and means the content measured in accordance with the above "Provisional Measurement Methods for PFOS, PFOA and PFHxS in Soil (Elution Amount Test, Content Test)".

[0018] Also, the "soil" is not particularly limited and includes, for example, sand, clay, silt, rock, sediment, minerals, etc., and is interpreted in a broad sense. The "water" is not particularly limited and includes, for example, tap water, groundwater, factory wastewater, sewage, river water, lake water, well water, etc., and is interpreted in a broad sense.

[0019] [1-2.(A) Oxidizing agent] The (A) oxidizing agent used in the method for purifying organofluorine compounds according to this embodiment is not particularly limited, and known and commonly used ones can be used. Examples of the oxidizing agent include persulfate, hydrogen peroxide, ozone, hypochlorous acid, etc. These oxidizing agents may be used alone or in combination of two or more.

[0020] As the oxidizing agent, it is preferable to use persulfate and hydrogen peroxide, and more preferable to use persulfate.

[0021] Examples of the persulfate include peroxymonosulfate and / or salts of peroxydisulfuric acid, etc., and these may be sodium salts, potassium salts, ammonium salts, cesium salts, thallium salts, etc. As the persulfate, sodium persulfate (SPS) or potassium persulfate, which is a kind of salt of peroxydisulfuric acid, or potassium persulfate (KHSO5), which is a kind of salt of peroxymonosulfuric acid, is preferable, and those containing potassium persulfate (KHSO5), which is a kind of salt of peroxymonosulfuric acid, are more preferable.

[0022] As the potassium persulfate, which is a kind of salt of peroxymonosulfuric acid, for example, 2KHSO5·KHSO4·K2SO4 (oxone (registered trademark)), which is a triple salt of potassium monopersulfate, potassium bisulfate, and potassium sulfate, can be used.

[0023] The addition amount of the oxidizing agent (A) used in this embodiment is not particularly limited and can be appropriately set according to the type and content of the organic fluorine compound, the type of the oxidizing agent used, the type and addition amount of the alkali metal or alkaline earth metal compound used, and the like. The addition amount of the oxidizing agent is preferably 0.1 to 25% by mass, more preferably 0.5 to 20% by mass, and even more preferably 1 to 10% by mass with respect to the soil or water containing the organic fluorine compound.

[0024] [1-3. (B) Alkali metal or alkaline earth metal compound] The (B) alkali metal or alkaline earth metal compound according to this embodiment is not particularly limited, and known and commonly used ones can be used. Examples of the alkali metal or alkaline earth metal compound include oxides of alkali metals or alkaline earth metals such as calcium oxide and magnesium oxide; hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide; halides of alkali metals or alkaline earth metals such as sodium chloride, potassium chloride, calcium chloride, and magnesium chloride; carbonates of alkali metals or alkaline earth metals such as sodium carbonate, potassium carbonate, calcium carbonate, and magnesium carbonate; hydrogen carbonates such as sodium hydrogen carbonate, potassium hydrogen carbonate, and calcium hydrogen carbonate. These alkali metal or alkaline earth metal compounds may be used alone or in combination of two or more.

[0025] (Component (B) is preferably a calcium compound and / or a basic compound. The calcium compound and / or the basic compound is not particularly limited, and examples thereof include sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide, calcium chloride, calcium carbonate, calcium hydrocarbonate, etc.)

[0026] (From the viewpoint of increasing the elution amount of per- or polyfluoroalkyl sulfonic acid or per- or polyfluorocarboxylic acid adsorbed on the soil or dissolved in the immobile water (bound water or water in isolated gaps that cannot move) of the soil as component (B), it is preferably a basic compound, and more preferably sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide, or calcium carbonate.) Also, from the viewpoint of interacting with the fluorine of the organic fluorine compound and promoting purification as component (B), it is preferably a calcium compound, and more preferably calcium hydroxide, calcium oxide, or calcium carbonate.) (Component (B) is more preferably calcium hydroxide, calcium oxide, or calcium carbonate, which is a calcium compound and a basic compound.) These calcium compounds and / or basic compounds may be used alone or in combination of two or more.)

[0027] The addition amount of the alkali metal or alkaline earth metal compound (B) used in this embodiment is not particularly limited and can be appropriately set according to the type and content of the organic fluorine compound, the type and addition amount of the oxidizing agent used, the type of component (B) used, etc. The addition amount of component (B) is preferably 0.1 to 30% by mass, more preferably 0.2 to 20% by mass, and even more preferably 0.5 to 15% by mass with respect to the soil or water.)

[0028] [1-4. Addition method and addition amount ratio of component (A) and component (B)] The method of adding (A) an oxidizing agent and (B) an alkali metal or alkaline earth metal compound to soil and / or water containing an organic fluorine compound is not particularly limited and can be appropriately selected according to the purpose. As the above addition method, for example, the components (A) and / or (B) may be added to the soil and / or water containing the organic fluorine compound at once or divided into a plurality of times. When adding the components (A) and (B), the components (A) and (B) may be added simultaneously, or the component (B) may be added after adding the component (A), or the component (A) may be added after adding the component (B). When adding the components (A) and (B) simultaneously, they may be added after being mixed.

[0029] The addition amount ratio of the components (A) and (B) used in the present embodiment is not particularly limited and can be appropriately set according to the type and content of the organic fluorine compound, the type of the oxidizing agent used, the type of the component (B) used, etc. As the addition amount ratio of the components (A) and (B), for example, it is preferably 1 to 4:1 to 10, and more preferably 1 to 2:1 to 6.

[0030] [2. Use of the purification method] The method of using the purification method of the organic fluorine compound according to the present embodiment is not particularly limited, and a known and commonly used method of use can be used. Examples of the method of using the purification method of the organic fluorine compound include on-site treatment and in-situ treatment.

[0031] Examples of on-site treatment include a method of excavating soil containing an organic fluorine compound, adding and mixing the component (A), or the components (A) and (B) to the excavated soil to purify the organic fluorine compound. Also included is a method of adding and mixing the component (A), or the components (A) and (B) to the pumped groundwater containing the organic fluorine compound or the pumped well water to purify the organic fluorine compound.

[0032] As in-situ treatment, for example, when the soil containing an organic fluorine compound is in the shallow part from the ground surface, a backhoe, a high-speed rotating rotor, etc. are used, and when it is in the deep part from the ground surface, a rotary blender, etc. are used to add and mix the component (A) or the components (A) and (B) in-situ to purify the organic fluorine compound. Further, a method of injecting the component (A) or the components (A) and (B) into groundwater, well water, etc. containing an organic fluorine compound to purify the organic fluorine compound is also mentioned.

Example

[0033] [Test Example 1: Purification effect of PFOS or PFOA by sodium persulfate (SPS) and its evaluation] Soil contaminated with PFOS or PFOA (hereinafter also referred to as "simulated contaminated soil") was prepared. To this, 20% sodium persulfate (SPS: manufactured by Wako Pure Chemical Industries, Ltd.), which is a kind of salt of peroxydisulfuric acid, was added as the (A) oxidant, and the reaction was carried out at different temperatures. Then, the purification effect of PFOS or PFOA by sodium persulfate was evaluated by measuring the elution amount of PFOS or PFOA in the soil and the soil content of PFOS or PFOA. This will be described more specifically below.

[0034] <Preparation of simulated contaminated soil> The simulated contaminated soil was prepared by adding a predetermined amount of PFOS or PFOA to sandy soil (true sand). For both PFOS and PFOA, those with a purity of 95% manufactured by Fujifilm Wako Pure Chemical Corporation were used. It was prepared so that the final soil content of PFOS and PFOA in the wet soil described in Tables 1 and 2 below would be 11 μg / kg and 7.9 μg / kg, respectively. Hereinafter, they are also referred to as PFOS or PFOA simulated contaminated soil.

[0035] <Purification of PFOS or PFOA by sodium persulfate> In a plastic container (with a capacity of 250 ml), PFOS or PFOA-simulated contaminated soil and water in the amounts described in Tables 1 and 2 below were mixed to prepare moist soil. To the moist soil, 20% sodium persulfate (SPS: manufactured by Wako Pure Chemical Industries, Ltd.), which is a kind of salt of peroxydisulfuric acid, in the amounts described in Tables 1 and 2 below was added and mixed with a medicine spoon for 30 seconds. The plastic container was placed in a constant temperature water bath at the temperature described in Tables 1 and 2 below and allowed to react for 30 minutes. After the above reaction, it was cured for 2 weeks.

[0036]

Table 1

[0037]

Table 2

[0038] (Soil elution amounts of PFOS and PFOA) The soil elution amounts of PFOS and PFOA were measured by the LC / MS / MS method according to the "Appendix Table 1 Measurement Methods for Perfluorooctanesulfonic Acid (PFOS) and Perfluorooctanoic Acid (PFOA)" of Environmental Protection Agency Circular No. 2005281 and Environmental Protection Agency Soil Circular No. 2005282. The results are shown in Figures 1 and 2.

[0039] From Figure 1, in Controls 1-1A to 1-3A, as the temperature increased to 20°C, 40°C, and 70°C, the soil elution amount of PFOS tended to increase. On the other hand, from Figure 1, when sodium persulfate was added to PFOS-simulated contaminated soil and water as in Examples 1-1A to 1-3A, it can be seen that the soil elution amount of PFOS decreased compared to Controls 1-1A to 1-3A.

[0040] Similarly, from FIG. 1, in Controls 1-1B to 1-3B, as the temperature was increased to 20°C, 40°C, and 70°C, the elution amount of PFOA from the soil tended to increase. On the other hand, from FIG. 2, it can be seen that when sodium persulfate was added to the PFOA-simulated contaminated soil and water, as in Examples 1-1B to 1-3B, the elution amount of PFOS from the soil decreased compared to Controls 1-1B to 1-3B.

[0041] From FIGS. 1 and 2 above, it can also be inferred that in Examples 1-1A to 1-3A and 1-1B to 1-3B, PFOS or PFOA in water was decomposed by sodium persulfate, resulting in a decrease in the elution amount of PFOS or PFOA from the soil. On the other hand, when sodium persulfate was added and reacted, in Examples 1-1A to 1-3A and 1-1B to 1-3B, the pH of the water showed acidity (about 2.7 to 2.8) in all cases. In Controls 1-1A to 1-3A and 1-1B to 1-3B, the pH of the water was in the range of about 5.6 to 6.3. Therefore, in Examples 1-1A to 1-3A and 1-1B to 1-3B, it was also considered possible that the acidity of the water caused PFOS and PFOA to adhere to the soil and the elution amount from the soil decreased.

[0042] (Soil content of PFOS and PFOA) Therefore, the soil contents of PFOS and PFOA in Control 1-1A, Example 1-1A, Control 1-1B, and Example 1-1B were measured according to the "Provisional Measurement Method for PFOS, PFOA, and PFHxS in Soil (Elution Amount Test)" (Ministry of the Environment), respectively. The results are shown in FIGS. 3 and 4.

[0043] From FIG. 3, in Example 1-1A where sodium persulfate was added to the PFOS-simulated contaminated soil and water, the soil content of PFOS only decreased by about 5% compared to Control 1-1A, indicating that most of the PFOS adhered to the soil and was present. Also, from Figure 4, in Example 1-1B where sodium persulfate was added to the PFOA-simulated contaminated soil and water, it can be seen that the soil content of PFOA decreased to less than half compared to Control 1-1B, indicating that PFOA was effectively purified.

[0044] [Test Example 2: Purification Effect of Potassium Persulfate (Oxone (registered trademark)), a Kind of Peroxymonosulfate Salt, on PFOS or PFOA and Its Evaluation] Similar to Test Example 1, when potassium persulfate (Oxone (registered trademark)), a kind of peroxymonosulfate salt, was added to the soil contaminated with PFOS or PFOA, the elution amount of PFOS or PFOA in the soil and the soil content of PFOS or PFOA were measured to evaluate the purification effect of Oxone on PFOS or PFOA.

[0045] <Preparation of Simulated Contaminated Soil> The simulated contaminated soil was prepared by adding a predetermined amount of PFOS or PFOA to sandy soil (true sand). For both PFOS and PFOA, those with a purity of 95% manufactured by Fujifilm Wako Pure Chemical Corporation were used. They were prepared so that the final soil contents of PFOS and PFOA in the wet soil described in Tables 3 and 4 below would be 3.4 μg / kg and 1.7 μg / kg, respectively.

[0046] <Purification of PFOS or PFOA by Oxone> In Test Example 2, the test was conducted in the same manner as in Test Example 1, except that potassium persulfate (Oxone (registered trademark: 2KHSO5·KHSO4·K2SO4, manufactured by Fujifilm Wako Pure Chemical Corporation)), a kind of peroxymonosulfate salt, was added in the predetermined amounts described in Tables 3 and 4 and mixed.

[0047]

Table 3

[0048]

Table 4

[0049] (Soil elution amounts of PFOS and PFOA) The soil elution amounts of PFOS and PFOA were measured by the LC / MS / MS method in the same manner as in Test Example 1. The results are shown in FIGS. 5 and 6.

[0050] From FIG. 5, it can be seen that even when the temperature is increased to 20°C and 70°C for Controls 2-1A and 2-2A, the soil elution amount of PFOS does not change much. As a reason for the different tendency shown by Controls 2-1A and 2-2A compared to the cases of Controls 1-1A to 1-3A, it is considered that in Controls 2-1A and 2-2A, the final soil content of the PFOS-simulated contaminated soil is set to be 1 / 3 or less lower than that of Controls 1-1A to 1-3A. In general, perfluoroalkyl compounds are known to have strong molecular linearity, and when the number of carbon atoms is 7 or more, the strong dipolar phases are aligned, and they can form a strong lipid membrane-like structure. Therefore, it is speculated that the reason for the above phenomenon is that when the soil content of PFOS is set higher, the amount of PFOS that can form a lipid membrane-like structure and elute into water increases compared to when the soil content of PFOS is set lower. Also from FIG. 5, it can be seen that in Examples 2-1A and 2-2A, the soil elution amount of PFOS is relatively slightly increased compared to Examples 1-1A to 1-3A.

[0051] From FIG. 6, for Controls 2-1B and 2-2B, when the temperature is increased to 20°C and 70°C, the soil elution amount of PFOA slightly increases with the higher temperature. Also, in Examples 2-1B and 2-2B, it can be seen that the soil elution amount of PFOS is relatively slightly increased compared to Examples 1-1B to 1-3B.

[0052] (Soil contents of PFOS and PFOA) The soil contents of PFOS and PFOA in Control 2-1A, Example 2-1A, Control 2-1B, and Example 2-1B were measured according to the "Provisional Measurement Method for PFOS, PFOA, and PFHxS in Soil (Elution Test, Content Test)" (Ministry of the Environment website). The results are shown in Figures 7 and 8.

[0053] From Figure 7, in Example 2-1A where oxone was added to the PFOS-simulated contaminated soil and water, the soil content of PFOS decreased by about 30% compared to Control 2-1A. From this, it can be seen that in Example 2-1A with the addition of oxone, the purification of PFOS progressed more effectively compared to Example 1-1A with the addition of sodium persulfate. Also from Figure 8, in Example 2-1B where oxone was added to the PFOA-simulated contaminated soil and water, the soil content of PFOA decreased by about 40% compared to Control 2-1B. From this, it can be seen that in Example 2-1B with the addition of oxone, the purification of PFOA progressed to a similar extent compared to Example 1-1B with the addition of sodium persulfate.

[0054] [3. Purification Effect of PFOS by Oxidizing Agent and Alkali Metal or Alkaline Earth Metal Compound and Its Evaluation] In Example 1-1A of Test Example 1, sodium persulfate only slightly decreased the soil content of PFOS (Figure 3). In contrast, under the same conditions, the effect of adding an alkali metal or alkaline earth metal compound on the purification effect of PFOS was evaluated. This will be described more specifically below.

[0055] [Preparation of Simulated Contaminated Soil] The simulated contaminated soil was prepared by adding a predetermined amount of PFOS to sandy soil (true sand). PFOS with a purity of 95% manufactured by Fujifilm Wako Pure Chemical Corporation was used. It was prepared so that the final soil content of PFOS was 11 μg / kg in the moist soil described in Table 5 below.

[0056] [Purification of PFOS or PFOA by Sodium Persulfate] In a plastic container (capacity: 250 ml), PFOS-simulated contaminated soil and water in the amounts shown in Table 5 below were mixed to prepare moist soil. To the moist soil, 20% sodium persulfate (SPS, manufactured by Wako Pure Chemical Industries, Ltd.), which is a kind of salt of peroxydisulfuric acid in the amount shown in Table 5 below, and quicklime or slaked lime were added, and the mixture was stirred with a medicine spoon for 30 seconds. The plastic container was placed in a constant temperature water bath at the temperature shown in Table 5 below and allowed to react for 30 minutes. After the above reaction, the mixture was cured for 2 weeks.

[0057]

Table 5

[0058] (PFOS soil elution amount) The PFOS soil elution amount was measured by LC / MS / MS method in accordance with "Appendix 1 Measurement Methods for Perfluorooctanesulfonic Acid (PFOS) and Perfluorooctanoic Acid (PFOA)" of Kankyo Taishui Fa No. 2005281 and Kankyo Daito Fa No. 2005282. The results, along with the results of the above Controls 1-1A to 1-3A and Examples 1-1A to 1-3A, are compared and shown in Figure 9.

[0059] Comparing Example 3-1A (SPS + quicklime + 20°C) and 3-4A (SPS + slaked lime + 20°C) in Figure 9 with Example 1-1A (SPS + 20°C), it can be seen that by adding quicklime or slaked lime, the amount of PFOS eluted into water increases compared to the case of using only sodium persulfate. On the other hand, in Examples 3-1A to 3-3A where sodium persulfate and quicklime were added, the PFOS soil elution amount tended to decrease with the increase in temperature and the amount of quicklime added. In addition, in Examples 3-4A to 3-6A where sodium persulfate and slaked lime were added, the PFOS soil elution amount tended to decrease with the increase in the amount of slaked lime added.

[0060] (PFOS soil content) The soil contents of PFOS in Control 1-1A, Example 1-1A, Example 3-3A, and Example 3-6A were measured according to the "Provisional Measurement Method for PFOS, PFOA, and PFHxS in Soil (Elution Amount Test)" (Ministry of the Environment). The results are shown in Figure 10.

[0061] From Figure 10, when PFOS was contained at a high concentration of 11 μg / kg, sodium persulfate alone could not effectively purify PFOS in the soil (Example 1-1A), whereas in Example 3-3A or Example 3-6A where quicklime or slaked lime was added in addition to sodium persulfate, the soil content of PFOS decreased, indicating that it was more effectively purified. It is presumed that by adding quicklime or slaked lime to soil and water containing PFOS, the purification reaction is promoted due to the binding of calcium ions and fluorine, and the elution amount of PFOS in the soil can be increased by making the pH in the water basic, etc., so that the purification of PFOS proceeds more effectively.

[0062] From the above, when (A) sodium persulfate or oxone is added as an oxidizing agent to soil and water containing PFOS or PFOA, an effect of purifying PFOS or PFOA contained in the soil and water is recognized. In particular, oxone was recognized to have an effect of effectively purifying both PFOS and PFOA. In addition to the above (A) oxidizing agent, an effect of further promoting the purification of PFOS and PFOA was recognized by adding (B) quicklime or slaked lime as an alkali metal or alkaline earth metal compound.

Claims

1. A method for purifying an organofluorine compound, characterized in that an oxidizing agent (A) is added to soil and / or water containing the organofluorine compound.

2. The method for purifying an organofluorine compound according to Claim 1, wherein the oxidizing agent (A) contains a salt of peroxymonosulfuric acid and / or peroxydisulfuric acid.

3. The salt of peroxymonosulfuric acid is KHSO ５ The method for purifying an organic fluorine compound according to claim 2, wherein the salt is KHSO

4. The method for purifying an organofluorine compound according to Claim 1, further characterized in that an alkali metal or alkaline earth metal compound (B) is added.

5. The method for purifying an organofluorine compound according to Claim 4, wherein the alkali metal or alkaline earth metal compound (B) is a calcium compound and / or a basic compound.

6. The method for purifying an organofluorine compound according to Claim 5, wherein the calcium compound and / or basic compound (B) is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium oxide, calcium hydroxide, calcium chloride, calcium carbonate, and calcium hydrogen carbonate.

7. The method for purifying an organofluorine compound according to Claim 4, wherein the mass ratio of the addition of the oxidizing agent (A) to the alkali metal or alkaline earth metal compound (B) is 1 to 4:1 to 10.

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