Method for recovering organic fluorine compound

Abstract

Provided is a method for recovering an organic fluorine compound which requires only a small amount of acid and base for recovery treatment. A metal cation is added to an aqueous phase containing an organic fluorine compound to cause a complex formation reaction with molecules of the organic fluorine compound, and an electrically neutral chemical species generated thereby is solvent-extracted into an organic phase forming a two-liquid system with the aqueous phase.

Description

Method for recovering organofluorine compounds

[0001] The present invention relates to a method for recovering an electrically neutral chemical species by solvent extraction into an organic phase that forms a two-liquid system with the aqueous phase, by adding a metal cation to an aqueous phase containing an organofluorine compound, thereby causing a complex formation reaction, an ion pair formation reaction, or both of these reactions between the anion or both generated by the dissociation of molecules or hydrogen ions of the organofluorine compound and the metal cation, and by solvent extraction of the electrically neutral chemical species produced therefrom. Furthermore, the present invention relates to a method for recovering an organofluorine compound by back-extracting the organic phase containing the extracted organofluorine compound into an aqueous phase, which is performed after the solvent extraction, by contacting the organic phase containing the extracted organofluorine compound with an aqueous phase in which the concentration of the metal cation is lower or the metal cation is not present than in the aqueous phase used during solvent extraction, an aqueous phase in which the pH is lower than that of the aqueous phase used during solvent extraction, an aqueous phase in which the pH is higher than that of the aqueous phase used during solvent extraction, or an aqueous phase containing a complexing agent which is a water-soluble organic ligand, or an aqueous phase which is an arbitrary combination thereof, thereby separating the metal cation from the organofluorine compound.

[0002] The group of organofluorine compounds known as PFAS possesses excellent chemical properties such as heat resistance, chemical resistance, light resistance, biodegradability resistance, water and oil repellency, and insulation properties. They are used in many industrial fields, including textiles and clothing, cooking utensils, semiconductors, medical equipment, automobiles, home appliances, construction, aerospace, and food, as surfactants, emulsifiers, fire extinguishing agents, coatings, antifouling agents, food packaging materials, etching agents, photoresists, anti-reflective agents, refrigerants, lubricants, and lithium-ion battery separator materials.

[0003] On the other hand, PFAS are persistent substances that accumulate easily in living organisms and can travel long distances in the environment without being broken down. Some PFAS are suspected of having various health effects, including carcinogenicity, reproductive toxicity, thyroid hormone disruption, liver dysfunction, and effects on the immune system and blood cholesterol levels. Among them, PFOS (perfluorooctanesulfonic acid) and PFOA (perfluorooctanoic acid), which have eight carbon atoms and are the most widely used, are already banned or restricted internationally.

[0004] Technologies have been developed to remove PFAS (Pervasive Fatty Acids) primarily by adsorption, targeting raw water from water sources, river water, and tap water. Activated carbon is often used as the adsorbent (for example, Patent Document 1), but desorption of PFAS from activated carbon is difficult. Therefore, a method has been proposed (Patent Document 2) to remove PFAS and regenerate activated carbon using an alcohol-containing solution and a base-containing solution.

[0005] In addition to activated carbon, other methods have been proposed for using adsorbents, such as using polymers (for example, Patent Documents 3 and 4), using metal-organic structures (Patent Document 5), and using metal-inorganic compounds (Patent Document 6).

[0006] In addition to methods using adsorbents, other methods have been proposed, such as using ion exchange resins (anion exchangers) (Patent Document 7), using membranes or membrane-like filters (Patent Document 8), using microgels (Patent Document 9), and using aquatic algae (Patent Document 10).

[0007] However, conventional methods, including the adsorption described above, are suitable for removing low concentrations of PFAS, but are unsuitable for rapidly and effectively treating wastewater containing high concentrations of PFAS. When rapidly and effectively treating high concentrations of target substances in wet separation, liquid-liquid extraction (also called solvent extraction) is generally chosen. In solvent extraction, the target substance dissolved in water is extracted into a solvent that is immiscible with water (a solvent that forms a two-phase system with water).

[0008] Adsorption and absorption by solids such as adsorbents and ion exchange resins have a smaller capacity for recovering and removing target components compared to extraction into liquids (solvent extraction), and are also less rapid. The same applies to membrane separation. Furthermore, when the target substance is highly concentrated, adsorbents and membranes can be reused far less frequently than extractants used in solvent extraction, resulting in high consumable costs and the generation of large amounts of solid waste. Although adsorbents incorporating the functional groups of extractants have been developed, ion exchange resins, adsorbents, and membranes are based on macroscopic, rigid solids such as polymers and porous materials, and are therefore more susceptible to degradation compared to extractants, which are molecules themselves.

[0009] Thus, solvent extraction offers many advantages that wet separation techniques using solid agents (ion exchange, adsorption, membrane separation) do not possess. However, it also has fatal drawbacks, and for this reason, it has rarely been used in wastewater treatment until now. In other words, solvent extraction results in the contamination of wastewater with organic compounds such as solvents and extractants, leading to a significant environmental burden and making it unsuitable for wastewater treatment. In fact, solvent extraction is often cited as a prime example of an environmentally unfriendly technology. Moreover, the solvents (extraction solvents) chosen for the solvent extraction of highly polar PFAS are often harmful solvents such as ethyl acetate, toluene, and methyl butyl ether. On the other hand, saturated hydrocarbons (alkanes such as octane and hexane), which are nonpolar, chemically inert, almost insoluble in water, and have low toxicity, are considered unsuitable for the extraction of highly polar PFAS. Therefore, although solvent extraction may be used as a pretreatment for the rapid analysis of PFAS, there are no known examples of its use in purifying PFAS-containing wastewater (recovering and removing PFAS from wastewater). In other words, the use of solvent extraction for PFAS is currently limited to analytical applications.

[0010] Japanese Patent Publication No. 2022-93398, Japanese Patent Publication No. 2022-526919, Japanese Patent Publication No. 2011-25102, Japanese Patent Publication No. 2012-101159, Japanese Patent Publication No. 2021-137805, Japanese Patent Publication No. 2022-526606, Japanese Patent Publication No. 2019-511363, Japanese Patent Publication No. 2023-521446, Japanese Patent Publication No. 2014-231056, Japanese Patent Publication No. 2009-22887

[0011] Solvent extraction offers significantly larger capacity and faster processing for the recovery and removal of PFAS compared to adsorption / absorption to solids (adsorbents, ion exchange resins, etc.) or membrane separation. Furthermore, the extractants used in solvent extraction can be reused far more frequently than adsorbents, ion exchange resins, or membranes, resulting in extremely low consumables. Consequently, the amount of waste generated is also significantly lower. On the other hand, solvent extraction has a significant environmental impact, such as the contamination of water environments with oil in the wastewater. Therefore, currently, the use of solvent extraction for PFAS is limited to analytical applications rather than wastewater purification. Moreover, saturated hydrocarbon solvents (alkane solvents), which have low toxicity and extremely low solubility in water, and thus have minimal biological and environmental impacts, are considered unsuitable as PFAS extraction solvents. Therefore, in many cases, harmful solvents such as ethyl acetate, toluene, and methyl butyl ether are selected as extraction solvents.

[0012] PFAS (for example, carboxylic acid-based PFAS), which have the property of dissociating hydrogen ions as acids, can be extracted into alkane-based solvents as pure solvents by lowering the pH to make them electrically neutral (non-dissociated), provided they have a sufficiently large number of carbon atoms.

[0013] Alkane solvents have low toxicity and low solubility in water. Alkane solvents can be selected from linear alkanes, cyclic alkanes, or mixtures thereof; "linear" here includes both straight chains and side chains. In particular, alkane solvents with a large number of carbon atoms (for example, dodecane with 12 carbon atoms) have extremely low solubility in water and can be considered diluents with minimal biological and environmental impact.

[0014] However, in order to convert PFAS into an electrically neutral molecular form (non-dissociated form) and extract it in an alkane solvent, it is necessary to add a sufficient amount of acid (e.g., hydrochloric acid, sulfuric acid, or nitric acid) to the wastewater to lower the pH sufficiently. For example, a considerable amount of acid must be added to bring the pH to around 1.0, and then an equivalent amount of base (e.g., sodium hydroxide) must be added to neutralize it in order to meet the pH standards for back-extraction and discharge. In other words, if the amount of wastewater to be treated is large, the amount of acid and base required for treatment will also be large, which increases the cost of chemicals (acids and bases) as consumables and increases OPEX (operating expenses).

[0015] The inventors, taking advantage of the benefits of solvent extraction, have diligently studied to solve the above problems and have devised a method to recover the organofluorine compound by solvent extraction into an organic phase that forms a two-liquid system with the aqueous phase. This method involves adding a metal cation to an aqueous phase containing an organofluorine compound, causing a complex formation reaction, an ion pair formation reaction, or both to occur between the anion or both generated by the dissociation of the molecules or hydrogen ions of the organofluorine compound and the metal cation, and then adding a metal cation to an aqueous phase that forms a two-liquid system with the aqueous phase by solvent extraction. The inventors have also devised a method to recover the organofluorine compound by back-extracting it from the organic phase into the aqueous phase, after the solvent extraction, by contacting the extracted organic phase containing the organofluorine compound with an aqueous phase that has a lower concentration of the metal cation than the aqueous phase used during solvent extraction, an aqueous phase with a lower pH than the aqueous phase used during solvent extraction, an aqueous phase with a higher pH than the aqueous phase used during solvent extraction, an aqueous phase containing a complexing agent which is a water-soluble organic ligand, or an aqueous phase which is an arbitrary combination of these, thereby separating the metal cation from the organofluorine compound.

[0016] Specifically, all metal ions that can exist as cations are effective as metal cations. However, cations such as cadmium, mercury, and lead are highly toxic and should not be used in the method of this invention, even in very small amounts. Therefore, metal cations that have little adverse effect on the human body or the environment in very small amounts, such as rare earth elements, iron, calcium, and aluminum, are selected.

[0017] According to the method of the present invention, if a metal cation is added to wastewater containing PFAS that has the ability to coordinate to metal cations at a concentration exceeding the charge equivalent of the PFAS concentration (for example, about 10 times), the PFAS can be recovered into the organic phase by solvent extraction. In other words, if the concentration of the PFAS to be recovered is low, the concentration of the metal cation to be added can be lower accordingly. For example, if the concentration of PFAS in the wastewater is on the order of ppt or ppb, the concentration of the metal cation added to the wastewater can also be on the order of ppt or ppb. Therefore, when the concentration of the target PFAS is low (on the order of ppt or ppb), using the method according to the present invention can significantly reduce OPEX compared to a method in which acid is added to the wastewater until the pH does not cause acid dissociation of the PFAS, and then an equivalent amount of base is used for neutralization.

[0018] Furthermore, by selecting a metal cation with a higher valency as the metal cation to be added to the wastewater, the charge equivalent to PFAS will be smaller, thus reducing the amount of metal cation added. Since many PFAS dissociate into monovalent anions through acid dissociation, for example, if a trivalent metal cation is used, the charge equivalent of the trivalent metal cation will be 1 / 3 of the PFAS concentration. Therefore, in this respect, polyvalent metal cations are more advantageous than monovalent metal cations.

[0019] When PFAS does not ionize but coordinates to a metal cation as a molecule, a hydrophobic cation is generated in which the positive charge number of the metal cation is maintained, and this cation is extracted into the organic phase along with an anion as a counterion. If the wastewater contains a high concentration of electrolytes, the anions of the electrolytes can act as counterions. Also, if another PFAS coexists as an anion, this PFAS anion becomes a counterion and is extracted into the organic phase together with the other PFAS. This makes it possible to simultaneously solvent extract, recover, and concentrate different types of PFAS.

[0020] PFAS extracted into the organic phase can be back-extracted by contacting the organic phase with an aqueous phase that has a lower concentration of metal cations than during solvent extraction, or an aqueous phase that does not contain metal cations. However, this is not an effective back-extraction method for PFAS that form strong complexes with metal cations.

[0021] When PFAS is converted from an acid-dissociated anion (dissociated form) to an acid molecule (undissociated form) by lowering the pH, its ability to coordinate with metal cations is often significantly reduced by becoming an acid molecule. This eliminates complex formation with the metal cation, making back extraction into the aqueous phase possible. In other words, an aqueous phase with a lower pH than that used during solvent extraction is effective for back extraction. However, this method is not effective for back extraction if the metal cation forms a strong complex with the PFAS anion, making acidification of the PFAS difficult.

[0022] Conversely, an aqueous phase with a higher pH than that used during solvent extraction is also effective for back-extraction of PFAS. Increasing the pH causes most metal cations to precipitate as hydroxides or oxide hydrates, thus breaking down the complex between the metal cations and PFAS, and allowing PFAS to be back-extracted from the organic phase. This method is effective even when metal cations form strong complexes with PFAS.

[0023] If the complex between the metal cation and PFAS is too strong and back-extraction is difficult using any of the above methods, an aqueous phase containing a complexing agent, which is a water-soluble organic ligand, can be used for back-extraction. However, since the complexing agent is difficult to reuse, it is used as a consumable agent to increase OPEX.

[0024] Furthermore, by arbitrarily combining the back-extraction methods described above, it may be possible to more effectively back-extract organofluorine compounds from the organic phase to the aqueous phase.

[0025] In the method of the present invention, an alkane solvent can be used as the organic phase on its own, eliminating the need for other organic compounds such as extractants. Furthermore, by selecting an alkane solvent with a sufficiently large number of carbon atoms, biological and environmental impacts can be reduced to a negligible level.

[0026] Hereinafter, the present invention will be described in more detail. As specific PFASs, carboxylic acid-based PFASs will be mainly described, but the scope of the present invention is not limited thereto.

[0027] By dissolving metal inorganic salts, oxides, etc. in PFAS-containing wastewater, metal cations are added to the wastewater. In addition, the wastewater from the factory may originally contain metal cations. When PFAS coordinates with a metal cation (M ｍ＋ , ｎ ,

[0029] ), a hydrophobic cation represented by M(PFAS) ｎ ｍ＋ is generated. Here, m is the valence of the metal cation, and n is the number of PFAS molecules coordinated to the metal cation. On the other hand, when PFAS coordinates with a metal cation (M － [[ID=​​​​​​​​​​​​​​A hydrophobic cation represented by is generated. In that case, M(PFAS) ｎ ｍ＋ These are extracted into the organic phase as electrically neutral ion pairs, with anions from the electrolyte contained in the wastewater and other PFAS present in anionic form under the same conditions acting as counterions.

[0030] In the method of the present invention, an alkane solvent with a large number of carbon atoms is suitable as the organic phase for extracting PFAS. Specifically, alkanes with 11 or more carbon atoms that have extremely low solubility in water are effective. Although alkane solvents have low toxicity, from the viewpoint of reducing environmental impact, it is necessary to reduce as much as possible the amount of solvent remaining in the wastewater after solvent extraction. For example, data shows that the solubility in water of octane (8 carbon atoms) is 0.7 ppm, nonane (9 carbon atoms) is 0.2 ppm, decane (10 carbon atoms) is 0.052 ppm, undecane (11 carbon atoms) is 0.004 ppm, and dodecane (12 carbon atoms) is 0.0037 ppm. In addition, data shows that the acute aquatic environmental toxicity values, measured at 48 hours EC50 (50% effective concentration) in crustaceans (Daphnia magna), are 0.029 ppm for decane and 0.011 ppm for undecane. In other words, the impact on the aquatic environment is significantly reduced when using undecane (11 carbon atoms), whose solubility is below the value for acute aquatic environmental toxicity.

[0031] Furthermore, it must be noted that flammable solvents are typically used in solvent extraction. Especially when dealing with large volumes of wastewater requiring rapid treatment, a significant amount of organic phase is inevitably needed. Since this increases the amount of diluent used, a diluent with a lower flash point should be selected to safely recover and concentrate PFAS.

[0032] While non-flammable solvents (diluents) exist, almost all of them are toxic, harmful, or have a high environmental impact, and many are highly toxic, harmful, and environmentally harmful. Therefore, the use of non-flammable solvents should be restricted. Furthermore, even ionic liquids, which are said to be highly environmentally friendly, inevitably leak their constituent components into wastewater when used in solvent extraction due to the principles of ion exchange. In addition, their high cost makes them economically unfeasible.

[0033] From the perspective of flammability, alkane solvents such as octane, nonane, decane, undecane, and dodecane are all classified as flammable liquids (Class 4) under the Fire Service Act. Furthermore, in the classification of petroleum hazards determined by flash point, octane is classified as Class 1 petroleum (flash point less than 21°C at 1 atmosphere), nonane as Class 2 petroleum (flash point between 21°C and 70°C at 1 atmosphere), and decane, undecane, and dodecane as Class 3 petroleum (flash point between 70°C and 200°C at 1 atmosphere). In other words, under the Fire Service Act, octane is classified as Class 4, Class 1 petroleum, nonane as Class 4, Class 2 petroleum, and decane, undecane, and dodecane as Class 4, Class 3 petroleum. Therefore, from the perspective of flammability, alkanes with 10 or more carbon atoms (decane and above) are preferred as the organic phase.

[0034] To back-extract PFOA from the n-dodecane phase after solvent extraction (forward extraction) of C8 perfluorooctanoic acid (PFOA) to n-dodecane using a carboxylic acid-based PFAS with a metal cation, an aqueous phase with a higher pH than that used during solvent extraction is effective. By increasing the pH, the metal cation precipitates as hydroxides, the ion pair between the PFOA anion and the metal cation is resolved, and PFOA is back-extracted into the aqueous phase.

[0035] If the extraction rate of carboxylic acid-based PFAS in solvent extraction (forward extraction) is sufficiently high, the carboxylic acid-based PFAS can be recovered while being concentrated in the organic phase. If the back extraction rate in back extraction is sufficiently high, the carboxylic acid-based PFAS can be recovered while being concentrated in the aqueous phase (back extract). In this method, carboxylic acid-based PFAS can be concentrated in two stages: solvent extraction (forward extraction) and back extraction. To recover carboxylic acid-based PFAS while being concentrated in forward extraction, the amount or flow rate of the organic phase relative to the aqueous phase should be controlled (reduced). To recover carboxylic acid-based PFAS while being concentrated in back extraction, the amount or flow rate of the aqueous phase relative to the organic phase should be controlled (reduced).

[0036] In practice, when recovering PFAS from wastewater by solvent extraction, the choice of equipment is extremely important. To perform solvent extraction efficiently, the aqueous and organic phases must be mixed until an emulsion is formed. However, mixer-settlers, which achieve this, rely on gravity to naturally separate the phases, making them prone to contaminating wastewater with oil, which is undesirable from an environmental perspective. Furthermore, centrifugal extractors, which use centrifugal force to rapidly separate the phases from the emulsion, have a complex mechanism and low robustness against solid components. Also, because they require both centrifugal force and stirring force simultaneously, they have a high power load and are not suitable for large-scale processing with large-scale equipment. Using a column-type solvent extraction system (for example, a pulse column) allows for more reliable phase separation at the expense of phase mixing efficiency, but the low step efficiency necessitates a huge system.

[0037] In recent years, the emulsion flow system developed by the Japan Atomic Energy Agency (JAEA) is an innovative solvent extraction device that, by controlling the size of droplets and their vertical linear velocity, mixes the aqueous and organic phases with a step efficiency superior to that of a mixer-settler, while simultaneously achieving phase separation of the two phases in an extremely clear state. By utilizing emulsion flow for solvent extraction of PFAS from wastewater and back extraction of PFAS from the organic phase, it becomes possible to recover and concentrate PFAS from wastewater with high efficiency while avoiding secondary environmental pollution by not introducing organic phase droplets (oil droplets) into the wastewater.

[0038] When recovering and concentrating carboxylic acid-based PFAS, using emulsion flow as the solvent extraction apparatus prevents the mixing of organic phase droplets (oil droplets) into wastewater, thus avoiding secondary environmental pollution.

[0039] The method of recovering PFAS by adding metal cations can be applied in addition to solvent extraction. For example, PFAS contained in a soft material system can be discharged and removed outside the soft material system as a complex or an ion pair or both generated by the reaction with metal cations. Soft materials are a general term for soft substances such as polymers, liquid crystals, colloids, biomembranes, and biomolecules such as proteins, and the method of the present invention can thus be considered applicable to the removal of PFAS from the body.

[0040] Next, examples of the present invention will be shown, but the present invention is not limited thereto.

[0041] Example 1 (Solvent extraction test of PFOA) As a representative carboxylic acid-based PFAS, perfluorooctanoic acid (PFOA) was selected, and a solvent extraction (positive extraction) test was conducted when trivalent iron was added. An aqueous solution with a pH of 2.7 containing 1000 ppm of PFOA and 500 ppm of trivalent iron as the aqueous phase and n-dodecane (pure solvent) as the organic phase were prepared. After both phases were put into a centrifuge tube (made of polypropylene, 50 mL) in the same volume, they were shaken for 10 minutes using a vertical shaking machine. Then, centrifugation was performed at 3000 revolutions per minute for 5 minutes using a centrifuge. After centrifugation, the aqueous phase was collected, the concentration of PFOA was measured, and based on the results, the extraction rate (positive extraction rate) of PFOA was calculated, and the result was 97.9%. Incidentally, since the charge equivalent of trivalent iron (trivalent cation with an atomic weight of 55.85) with respect to the concentration of PFOA (monovalent carboxylic acid with a molecular weight of 414.07) = 1000 ppm (= 0.002415 mol / L) is 0.0008050 mol / L (= 44.96 ppm), trivalent iron (concentration = 500 ppm) is contained at a concentration approximately 11 times the charge equivalent.

[0042] The present invention relates to a method for effectively and efficiently recovering an organic fluorine compound from industrial wastewater containing the organic fluorine compound at a high or low concentration. Here, the high concentration refers to a concentration at which economic rationality cannot be ensured in terms of efficiency and cost from the viewpoints of capacity for the organic fluorine compound, rapidity of treatment, repeatability of consumables, etc. in conventional methods such as activated carbon adsorption, ion exchange, and membrane separation. Specifically, even at a concentration in the ppb level, it is difficult to establish economic rationality by conventional methods using activated carbon adsorption, ion exchange, etc.

[0043] Organic fluorine compounds are widely used in various industries, but there are concerns about their impact on health and the ecosystem. Organic fluorine compounds are hardly decomposable, and some of them are harmful substances. They have the property of being stable in the environment for a long time and being easily diffused by long-distance movement. Therefore, in recent years, the movement to gradually restrict or abolish their use globally and rapidly has spread, unless it is proven to be essential socially. On the other hand, there are many cases where substitution is difficult for industrial or consumer use. For so-called essential uses (indispensable uses), even if their use is not abolished, strict restrictions are imposed on emissions from factories. That is, a technology capable of dealing with an aqueous solution containing an organic fluorine compound at a high concentration, such as industrial wastewater, is essential. Also, not limited to the viewpoint of the impact on health and the ecosystem, it is necessary to consider recycling and using the organic fluorine compounds targeted for essential uses in a completely closed system without discharging them outside the system at all from the viewpoints of resource circulation and carbon dioxide reduction. The present invention meets these urgent industrial needs.

Claims

1. A method for recovering an organofluorine compound, characterized by adding a metal cation to an aqueous phase containing an organofluorine compound, thereby causing a complex formation reaction, an ion pair formation reaction, or both of these reactions between the anion or both of the molecules or hydrogen ions of the organofluorine compound and the metal cation, and then solvent-extracting the electrically neutral chemical species resulting therefrom into an organic phase that forms a two-liquid system with the aqueous phase.

2. The method for recovering an organofluorine compound according to claim 1, characterized in that a linear, cyclic, or mixture of alkane solvents is used as the organic phase for solvent extraction.

3. The method for recovering an organofluorine compound according to claim 1, characterized in that an alkane solvent having 11 or more carbon atoms is used as the organic phase for solvent extraction.

4. A method for recovering organofluorine compounds according to claim 1, characterized in that at least one of the organofluorine compounds contained in the aqueous phase has the ability to coordinate to a metal cation as a molecule, an anion obtained by dissociating a hydrogen ion, or both.

5. A method for recovering an organofluorine compound according to claims 1 to 4, characterized in that the organofluorine compound is concentrated in the organic phase while solvent extraction is performed by controlling the amount or flow rate of the organic phase relative to the aqueous phase.

6. A method for recovering an organofluorine compound according to claims 1 to 5, characterized in that the solvent extraction of the organofluorine compound is performed using an emulsion flow mechanism.

7. A method for recovering an organofluorine compound, characterized by back-extracting the organofluorine compound from the organic phase to the aqueous phase by contacting an organic phase containing an organofluorine compound, which has been solvent-extracted from the aqueous phase by any of the methods of claims 1 to 6, with an aqueous phase in which the concentration of the metal cation is lower than that of the aqueous phase in which the organofluorine compound was solvent-extracted, or which does not contain the metal cation.

8. A method for recovering an organofluorine compound according to claim 7, characterized in that the organofluorine compound is concentrated in the aqueous phase while being back-extracted by controlling the amount or flow rate of the aqueous phase relative to the organic phase.

9. A method for recovering an organofluorine compound according to claim 7, characterized in that the back extraction of the organofluorine compound is performed using an emulsion flow mechanism.

10. A method for recovering an organofluorine compound, characterized by back-extracting the organofluorine compound from the organic phase to the aqueous phase by contacting an organic phase containing an organofluorine compound, which has been solvent-extracted from the aqueous phase by any of the methods of claims 1 to 6, with an aqueous phase having a lower pH than the aqueous phase used to solvent-extract the organofluorine compound.

11. A method for recovering an organofluorine compound according to claim 10, characterized in that the organofluorine compound is concentrated in the aqueous phase while being back-extracted by controlling the amount or flow rate of the aqueous phase relative to the organic phase.

12. A method for recovering an organofluorine compound according to claim 10, characterized in that the back extraction of the organofluorine compound is performed using an emulsion flow mechanism.

13. A method for recovering an organofluorine compound, characterized by back-extracting the organofluorine compound from the organic phase to the aqueous phase by contacting an organic phase containing an organofluorine compound, which has been solvent-extracted from the aqueous phase by any of the methods of claims 1 to 6, with an aqueous phase having a pH higher than the aqueous phase in which the organofluorine compound was solvent-extracted.

14. A method for recovering an organofluorine compound according to claim 13, characterized in that the organofluorine compound is concentrated in the aqueous phase while being back-extracted by controlling the amount or flow rate of the aqueous phase relative to the organic phase.

15. A method for recovering an organofluorine compound according to claim 13, characterized in that the back extraction of the organofluorine compound is performed using an emulsion flow mechanism.

16. A method for recovering an organofluorine compound, characterized by back-extracting the organofluorine compound from the organic phase to the aqueous phase by contacting an aqueous phase containing a complexing agent which is a water-soluble organic ligand with an organic phase containing an organofluorine compound that has been solvent-extracted from the aqueous phase by any of the methods of claims 1 to 6.

17. A method for recovering an organofluorine compound according to claim 16, characterized in that the organofluorine compound is concentrated in the aqueous phase while being back-extracted by controlling the amount or flow rate of the aqueous phase relative to the organic phase.

18. The method for recovering an organofluorine compound according to claim 16, characterized in that the back extraction of the organofluorine compound is performed using an emulsion flow mechanism.

19. A method for recovering organofluorine compounds, characterized by the addition of a metal cation to discharge or remove the organofluorine compounds contained in a soft material system from the soft material system as complexes, ion pairs, or both, formed by the reaction with the metal cation.