Method for recovering organic fluorine compound

Abstract

The present invention addresses the problem of how to effectively and efficiently extract, separate, and recover high-concentration PFAS contained in water regardless of the type of PFAS. An organic fluorine compound is converted to a chemical species having a negative charge on the basis of ionization by acid dissociation of the organic fluorine compound, molecularization of protonation-type hydrophobic cations, or both of these items, the distribution of the organic fluorine compound to an aqueous phase is promoted, and the organic fluorine compound is recovered.

Description

Method for recovering organic fluorine compounds

[0001] The present invention relates to a method for recovering an organic fluorine compound, in which the organic fluorine compound is extracted from the aqueous phase to an organic phase (forward extraction) by changing the pH of the aqueous phase in solvent extraction, and then back-extracted from the organic phase to the aqueous phase, thereby recovering the organic fluorine compound in the aqueous phase.

[0002] A group of organic fluorine compounds known as PFAS (perfluoroalkyl compounds) possess excellent chemical properties, such as heat resistance, chemical resistance, light resistance, biodegradability, water and oil repellency, and insulating properties. They are used in many industrial fields, including textiles and clothing, cookware, semiconductors, medicine, automobiles, home appliances, construction, aviation, and food, for applications such as surfactants, emulsifiers, fire extinguishing agents, coating agents, antifouling agents, food packaging agents, etching agents, photoresists, antireflective agents, refrigerants, lubricants, and lithium-ion battery separator materials.

[0003] On the other hand, PFAS are substances that are persistent, easily accumulate in living organisms, and travel long distances in the environment without being decomposed. Concerns have been raised about various health effects of some PFAS, including carcinogenicity, reproductive toxicity, thyroid hormone disruption, liver dysfunction, and effects on the immune system and blood cholesterol levels. Among these, the most widely used PFAS, PFOS (perfluorooctane sulfonic acid) and PFOA (perfluorooctanoic acid), both of which have eight carbon atoms, have already been banned or restricted in use internationally.

[0004] Technologies for removing PFAS from raw water sources, river water, tap water, etc., have been developed, primarily using adsorption. Activated carbon is often used as an adsorbent (see, for example, Patent Document 1). However, it is difficult to desorb PFAS from activated carbon. Therefore, a method for removing PFAS and regenerating activated carbon using an alcohol-containing solution and a base-containing solution has been proposed (see, for example, Patent Document 2).

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

[0006] In addition to the method using an adsorbent, a method using an ion exchange resin (anion exchanger) (Patent Document 7), a method using a membrane or membrane-like filter (Patent Document 8), a method using a microgel (Patent Document 9), a method using aquatic algae (Patent Document 10), etc. have also been proposed.

[0007] However, while conventional methods such as the adsorption method described above are suitable for removing low concentrations of PFAS, they are not suitable for quickly and effectively treating wastewater containing high concentrations of PFAS. When it is desired to quickly and effectively treat high concentrations of target substances in wet separation, liquid-liquid extraction (also known as solvent extraction) is generally selected. In solvent extraction, target substances dissolved in water are extracted into a water-immiscible solvent (a solvent that forms a two-liquid phase system with water).

[0008] Adsorption and absorption into solids, such as adsorbents and ion exchange resins, have a smaller recovery and removal capacity and are less rapid than extraction into liquids (solvent extraction). The same is true for membrane separation. Furthermore, when the target substance is highly concentrated, adsorbents and membranes can be reused far less frequently than the extractants used in solvent extraction, resulting in high consumable costs.

[0009] On the other hand, solvent extraction imposes a heavy environmental burden due to the contamination of wastewater with oil, and is therefore rarely used for wastewater treatment. Furthermore, highly polar PFAS are difficult to extract with saturated hydrocarbons (alkanes such as octane and hexane), which are non-polar, chemically inert, and have little biological impact, and the solvents (extraction solvents) chosen for solvent extraction are often harmful solvents such as ethyl acetate and toluene. In fact, while solvent extraction is sometimes used for pretreatment aimed at rapid PFAS analysis, there are no known cases where it has been used to purify PFAS-containing wastewater (recover and remove PFAS). In other words, the use of solvent extraction for PFAS is currently limited to analytical applications.

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

[0011] Compared with adsorption / absorption onto solids (such as adsorbents or ion exchange resins) or membrane separation, solvent extraction offers a significantly larger capacity for PFAS recovery and removal, and allows for rapid processing. Furthermore, the extractants used in solvent extraction can be reused far more frequently than adsorbents or membranes, resulting in lower consumable costs. On the other hand, solvent extraction imposes a significant environmental burden, such as contamination of the aquatic environment due to the inclusion of oil in wastewater. Therefore, the use of solvent extraction for PFAS is currently limited to analytical applications, not wastewater purification. Furthermore, saturated hydrocarbons, which have little biological impact, are considered unsuitable as extraction solvents for PFAS, so harmful solvents such as ethyl acetate and toluene are often chosen as extraction solvents. Furthermore, distillation, which requires a high energy load, has traditionally been used to recover PFAS from extraction solvents.

[0012] The present inventors have conducted extensive research to solve the above-mentioned problems by taking advantage of the advantages of solvent extraction (large capacity for PFAS, rapid processing, low consumable costs). As a result, they have found that even when a saturated hydrocarbon is used as the extraction solvent, PFAS can be effectively and efficiently extracted (forward extracted) from the aqueous phase into the organic phase (extraction solvent phase) by lowering the pH of the PFAS-containing aqueous solution (aqueous phase) and converting PFAS into an electrically neutral chemical species (molecule or ion pair). The saturated hydrocarbon can be linear, cyclic, or both. Note that "linear" as used herein includes both straight and branched chains.

[0013] Conversely, we have found that by increasing the pH of the PFAS-containing aqueous solution and converting PFAS into an electrically negative (negatively charged) chemical species (dissociated anions), we can effectively and efficiently strip PFAS from the organic phase into the aqueous phase. This discovery has eliminated the need for conventional distillation, which requires a large energy load.

[0014] The method for recovering organic fluorine compounds according to the present invention is characterized in that, for example, in a two-liquid-phase system consisting of an aqueous phase, which is an aqueous solution containing organic fluorine compounds, and an organic phase, the pH of the aqueous phase is lowered to convert the organic fluorine compounds to electrically neutral chemical species, the organic fluorine compounds are solvent-extracted from the aqueous phase into the organic phase, and then the organic phase from which the organic fluorine compounds have been extracted is contacted with an aqueous phase whose pH is higher than the pH at which the organic fluorine compounds were solvent-extracted from the aqueous phase into the organic phase, to convert the organic fluorine compounds solvent-extracted into the organic phase into electrically negative chemical species, and the organic fluorine compounds are stripped into the aqueous phase.

[0015] Furthermore, by using an emulsion flow system, such as that shown in Figure 6 of JP 2023-142775 A, as a solvent extraction system (apparatus), it has become possible to significantly reduce or eliminate the environmental impact of solvent extraction. In emulsion flow, a region where the aqueous and organic phases are mixed until they reach an emulsion state (so-called emulsion) and a region where the two phases are separated into a clear phase simultaneously exist. Therefore, unlike mixer-settler systems (typical industrial solvent extraction systems), there is no need to wait for phase separation due to gravity, and no settling section (settler section) is required. Because phase separation occurs from the beginning without waiting for settling, oil is not mixed into the wastewater. While solvent extraction is considered an environmentally unfriendly method that pollutes the aquatic environment due to the introduction of oil into the wastewater, emulsion flow, on the other hand, is extremely effective as a system for effectively and efficiently purifying oil-contaminated wastewater.

[0016] In the present invention, PFAS can be extracted into an organic phase under specific pH conditions, and then the organic phase is brought into contact with an aqueous phase having a pH higher than the pH conditions, thereby recovering the PFAS in the aqueous phase.Furthermore, by controlling the amount or flow rate (flow rate) of the aqueous phase relative to the organic phase, the PFAS can be concentrated and recovered in the aqueous phase.

[0017] More specifically, the method of the present invention makes it possible to effectively and efficiently recover high concentrations of PFAS contained in water, regardless of the type of PFAS. Note that the term "high concentration" used here means a concentration that is difficult to achieve in terms of efficiency and cost using conventional methods such as adsorption, in terms of the capacity for PFAS, the speed of treatment, and the reusability of consumables. Furthermore, the type of PFAS is assumed to be one having a carboxyl group, a sulfonic acid group, or both.

[0018] The present invention will be described in more detail below for the cases where carboxylic acid-based PFAS is to be recovered, sulfonic acid-based PFAS is to be recovered, PFAS having both carboxyl groups and sulfonic acid groups is to be recovered, PFAS having multiple carboxyl groups is to be recovered, PFAS having multiple sulfonic acid groups is to be recovered, and a mixture of carboxylic acid-based PFAS and sulfonic acid-based PFAS is to be recovered.

[0019] When the PFAS to be recovered is a carboxylic acid, the PFAS can be extracted (forward extraction) and back-extracted based on the following chemical reaction formula.

[0020] Here, F-Org － represents the dissociated anion of PFAS, F-Org-H represents the associated molecule of PFAS, the subscript (aq) represents the aqueous phase, and the subscript (org) represents the organic phase.

[0021] Carboxylic acid PFAS exist as dissociated anions when the pH is high (hydrogen ion concentration is low), but as the pH decreases (hydrogen ion concentration increases), they associate with hydrogen ions and change into molecules (associated molecules). Because electrically neutral, bulky associated molecules are more likely to be distributed in the organic phase than in the aqueous phase, lowering the pH promotes extraction of carboxylic acid PFAS into the organic phase (forward extraction). Conversely, as the pH increases (hydrogen ion concentration decreases), the associated molecules change into the form of dissociated anions that have released hydrogen ions. Because negatively charged dissociated anions are more likely to be distributed in the aqueous phase than in the organic phase, increasing the pH promotes back-extraction of carboxylic acid PFAS from the organic phase into the aqueous phase.

[0022] That is, by adding an acid to an aqueous solution containing carboxylic acid-based PFAS (for example, industrial wastewater), the pH is lowered and the PFAS can be extracted into a saturated hydrocarbon phase (organic phase), and the PFAS can then be stripped from the organic phase using water or a dilute alkaline aqueous solution. Note that, because the amount of acid added to molecularize the carboxylic acid-based PFAS is not large, this method is more economical and is thought to generate less carbon dioxide (reduce the environmental load) than the method of recovering carboxylic acid-based PFAS by evaporating (distilling or refluxing) the saturated hydrocarbon solvent.

[0023] When the PFAS to be recovered is a sulfonic acid type, by making protonation (protonated) type cations present in the organic phase, sulfonic acid type PFAS present in the form of dissociated anions can be extracted by ion pair extraction. Also, if the protonation of the protonation type cations is released and they return to molecules, ion pair extraction does not occur and the dissociated anions are back-extracted. The protonation type cations are, so to speak, extractants in a broad sense for sulfonic acid type PFAS.

[0024] Examples of substances that are prone to protonation include, but are not limited to, amines. Essentially, any Bronsted base (a molecule that acts as a hydrogen ion acceptor) can be used. More specifically, the amines can be aliphatic amines, aromatic amines, heterocyclic amines, or mixtures thereof. The skeleton structure of these amines other than the amine is optional.

[0025] Sulfonic acid-based PFAS is extracted (forward extraction) and back-extracted based on the following chemical reaction formula:

[0026] Here, N-Org is a Bronsted base, typically an amine. N-Org converts into a protonation-type hydrophobic cation (N-Org-H ＋ ), and returns to the molecule (N-Org) where protonation is eliminated due to the decrease in hydrogen ion concentration. Even under conditions of high hydrogen ion concentration, dissociated anions (F-Org － ) is a protonation-type hydrophobic cation (N-Org-H ＋ ) acts as a counter ion, forming an electrically neutral ion pair (F-Org － ・N-Org-H ＋ ) is formed.

[0027] Furthermore, by selecting a substance that is as prone to protonation as possible (a substance that protonates even when the hydrogen ion concentration is low), the amount of acid added for ion-pair extraction of dissociated anions of sulfonic acid-based PFAS can be reduced.

[0028] Furthermore, when it is desired to extract and separate sulfonic acid-based PFAS under low acid concentration conditions, a compound that easily undergoes protonation can be used, and when it is desired to extract and separate sulfonic acid-based PFAS under high acid concentration conditions, a compound that does not easily undergo protonation can be used.

[0029] Since electrically neutral and bulky ion pairs are more likely to be distributed in the organic phase than in the aqueous phase, lowering the pH promotes the extraction of sulfonic acid-based PFAS into the organic phase (forward extraction). Conversely, as the pH increases (the hydrogen ion concentration decreases), the protonation-type hydrophobic cations become molecular, the ion pairs are dissolved, and dissociated anions are liberated. Since negatively charged dissociated anions are more likely to be distributed in the aqueous phase than in the organic phase, increasing the pH promotes the back-extraction of sulfonic acid-based PFAS from the organic phase into the aqueous phase.

[0030] PFAS having both carboxyl and sulfonic acid groups can also be recovered by controlling the extraction (forward extraction) and back-extraction by changing the pH based on a similar method. Taking PFAS having one carboxyl group and one sulfonic acid group as an example, the chemical reaction formula can be shown as follows:

[0031] Here, F-Org ２－ is the dissociated anion when both the carboxyl group and the sulfonic acid group release a hydrogen ion. － ・N-Org-H ＋ shows an ion pair of an anion and a protonation type cation, in which a carboxyl group that has accepted a hydrogen ion and a sulfonic acid group that has maintained a dissociated hydrogen ion coexist.

[0032] Electrically neutral bulky ion pair (F-Org-H － ・N-Org-H ＋ ) is more likely to be distributed in the organic phase than in the aqueous phase, and the free dissociated anion (F-Org ２－ ) tends to be distributed in the aqueous phase rather than the organic phase. Therefore, the extraction (forward extraction) and back extraction of PFAS, which has both carboxyl and sulfonic acid groups, can be controlled by changing the pH.

[0033] PFAS with multiple carboxyl groups can also be recovered using a similar method. Taking PFAS with two carboxyl groups as an example, the chemical reaction formula can be shown as follows:

[0034] Here, F-Org ２－ is the dissociated anion when both carboxyl groups release hydrogen ions. ２ shows a molecule formed when both carboxyl groups have accepted hydrogen ions.

[0035] PFAS having multiple sulfonic acid groups can also be recovered using a similar method. Taking PFAS having two sulfonic acid groups as an example, the chemical reaction formula can be shown as follows:

[0036] Here, F-Org ２－ is the dissociated anion when both sulfonic acid groups release hydrogen ions. ２－ (N-Org-H ＋ ) ２ indicates an electrically neutral ion pair formed by ion association of the dissociated anion with two protonation-type cations.

[0037] The present invention can also be used in a method for separating and selectively recovering multiple PFAS. For example, it is possible to highly selectively recover carboxylic acid PFAS and sulfonic acid PFAS. First, the carboxylic acid PFAS is recovered using an organic phase (which may be a simple solvent or a mixed solvent) that does not contain protonation cations or their unprotonated molecules, and then the sulfonic acid PFAS is recovered using an organic phase that contains protonation cations or their unprotonated molecules.

[0038] Furthermore, when multiple carboxylic acid-based PFAS are contained, it is possible to selectively recover each of them by changing the pH. This is because the acid strength (pKa value) differs depending on factors such as chain length. In addition, differences in the size and shape of the associated molecules and the strength of hydration also affect the ease of distribution into the organic phase. The latter also applies to cases where multiple sulfonic acid-based PFAS are contained.

[0039] Although the embodiments of the present invention have been described above with some examples of types and combinations of PFAS, it is preferable that the system used for these is not a conventional industrial solvent extraction system such as a mixer settler, but an emulsion flow system, which is simple and highly efficient while preventing oil from being mixed into the wastewater. This significantly reduces or eliminates the environmental impact of conventional solvent extraction.

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

[0041] Example 1 (Batch Distribution Test of Carboxylic Acid-Based PFAS) Perfluorooctanoic acid (PFOA) was selected as the carboxylic acid-based PFAS, and a batch test was conducted in a test tube to examine the distribution of PFOA between two liquid phases. A sulfuric acid aqueous solution containing PFOA at a concentration of 169 mg / L and having a pH of 1.01 was prepared, and this was placed in a centrifuge tube (made of polypropylene, 50 mL) together with the same volume of dodecane, and then shaken for 10 minutes using a vertical shaker. The solution was then centrifuged at 3,000 rpm for 5 minutes using a centrifuge. After centrifugation, the aqueous phase (sulfuric acid aqueous solution) was collected, and the concentration of PFOA was measured, resulting in a value of 14 mg / L. The pH did not change.

[0042] From this result, it was found that 155 mg / L of the 169 mg / L of PFOA was distributed to the organic phase, and therefore the extraction rate of PFOA into dodecane in the batch test was calculated to be 91.7%.

[0043] Example 2 (Partition test of carboxylic acid-based PFAS in emulsion flow) A continuous flow test was conducted to examine the partitioning of PFOA between two liquid phases using a benchtop (1 L container) single-stage mechanically stirred emulsion flow device. The same aqueous phase (sulfuric acid aqueous solution containing 169 mg / L of PFOA, pH 1.01) and organic phase (dodecane) as in the batch test were used, and the flow rates of the aqueous and organic phases were the same, with the reaction time set to 10 minutes. As a result, the concentration of PFOA in the discharged aqueous phase was 15 mg / L.

[0044] That is, of the 169 mg / L of PFOA, 154 mg / L was distributed to the organic phase, and the extraction rate of PFOA into dodecane in the emulsion flow test was calculated to be 91.1%.

[0045] In the emulsion flow test, stripping using a dilute alkaline solution was also investigated. In this experiment, a dilute aqueous sodium hydroxide solution was used as the aqueous phase for stripping, in contrast to the organic phase (containing 154 mg / L of PFOA) used in the direct extraction experiment. The flow rates of the aqueous and organic phases were the same, and the reaction time was set to 10 minutes. As a result, the concentration of PFOA in the discharged aqueous phase was 148 mg / L.

[0046] From these results, it was found that of the 154 mg / L of PFOA in the organic phase, 148 mg / L was back-extracted into the dilute alkaline aqueous solution, and therefore the back-extraction rate of PFOA into the dilute alkaline aqueous solution in the emulsion flow test was calculated to be 96.1%.

[0047] The results of the batch test and emulsion flow test described above were obtained using a single operation or a single-stage (single-stage) device. It is easy to imagine that the desired extraction and stripping rates can be obtained by using multiple operations or a multi-stage device.

[0048] Example 3 (Batch Distribution Test of Sulfonic Acid-Based PFAS) Perfluorooctanesulfonic acid (PFOS) was selected as the sulfonic acid-based PFAS, and an alkyldiamidoamine with five ethylhexyl groups was selected as an amine, a representative substance prone to protonation. A test tube batch test was conducted to examine the distribution of PFOS between two liquid phases. A hydrochloric acid solution containing PFOS at a concentration of 3000 mg / L and a pH of 1.00 was prepared. This solution was then placed in a centrifuge tube (polypropylene, 50 mL) along with an equal volume of a dodecane solution containing the alkyldiamidoamine at a concentration of 0.05 mol / L. The tube was then shaken for 10 minutes using a vertical shaker. The tube was then centrifuged at 3000 rpm for 5 minutes. After centrifugation, the aqueous phase (hydrochloric acid solution) was sampled and the PFOS concentration was measured, resulting in a value of 240 mg / L. The pH remained unchanged.

[0049] From this result, it was found that 2760 mg / L of the 3000 mg / L of PFOS was distributed to the organic phase, and therefore the extraction rate of PFOS into the dodecane solution in the batch test was calculated to be 92.0%.

[0050] A batch test was also conducted to investigate the stripping of PFOS using a dilute alkaline solution. A dilute aqueous sodium hydroxide solution was used as the aqueous phase for stripping, in contrast to the organic phase used in the forward extraction experiment (containing 2760 mg / L of PFOS). In the batch test, as in the forward extraction, equal volumes of the aqueous and organic phases were placed in a centrifuge tube, shaken for 10 minutes using a vertical shaker, and then centrifuged for 5 minutes at 3000 rpm using a centrifuge. After centrifugation, the aqueous phase (dilute sodium hydroxide solution) was collected and the PFOS concentration was measured, resulting in a concentration of 2620 mg / L.

[0051] From these results, it was found that of the 2760 mg / L of PFOS in the organic phase, 2620 mg / L was back-extracted into the dilute alkaline aqueous solution, and therefore the back-extraction rate of PFOS into the dilute alkaline aqueous solution in the batch test was calculated to be 94.9%.

[0052] The present invention relates to a method for effectively and efficiently separating, recovering, extracting and separating organofluorine compounds having carboxyl groups, sulfonic acid groups or both from industrial wastewater or the like containing such compounds at high concentrations. The term "high concentration" used here refers to a concentration that is difficult to achieve in terms of efficiency and cost using conventional methods such as adsorption, ion exchange and membrane separation in terms of the capacity for the organofluorine compounds, the speed of treatment and the reusability of consumables.

[0053] These organic fluorine compounds are widely used in various industries, but their significant impact on health and ecosystems has raised concerns. Organic fluorine compounds are persistent, and some are toxic. However, they remain stable in the environment for long periods and tend to disperse over long distances. Therefore, in recent years, there has been a rapid, global trend to gradually restrict or phase out their use unless they are proven to be socially essential. Meanwhile, in many cases, alternatives are difficult to find for industrial or consumer use. For so-called essential uses, even if their use is not abolished, strict restrictions are imposed on factory emissions. Therefore, technology capable of handling aqueous solutions containing high concentrations of organic fluorine compounds, such as industrial wastewater, is essential. Furthermore, not only from the perspective of health and ecosystem impacts, but also from the perspectives of resource circulation and carbon dioxide reduction, consideration must be given to recycling organic fluorine compounds for essential uses in a completely closed system without discharge. The present invention addresses these urgent industrial needs.

Claims

1. A method for recovering organic fluorine compounds, comprising: in a two-liquid-phase system consisting of an aqueous phase, which is an aqueous solution containing organic fluorine compounds, and an organic phase, lowering the pH of the aqueous phase to convert the organic fluorine compounds to electrically neutral chemical species, solvent-extracting the organic fluorine compounds from the aqueous phase into the organic phase; then contacting the organic phase from which the organic fluorine compounds have been extracted with an aqueous phase whose pH is higher than that used when the organic fluorine compounds were solvent-extracted from the aqueous phase into the organic phase, converting the organic fluorine compounds solvent-extracted into the organic phase to electrically negative chemical species, and back-extracting the organic fluorine compounds into the aqueous phase.

2. A method for recovering an organic fluorine compound according to claim 1, characterized in that the amount or flow rate of the aqueous phase relative to the organic phase is controlled to concentrate the organic fluorine compound in the aqueous phase and recover it.

3. A method for recovering organic fluorine compounds according to claim 1 or 2, characterized in that an organic phase containing no protonation-type hydrophobic cations is used to selectively extract and separate organic fluorine compounds whose charge is easily changed by pH, and then an organic phase containing said protonation-type hydrophobic cations is used to selectively recover organic fluorine compounds whose charge is not easily changed by pH.

4. A method for recovering an organic fluorine compound according to any one of claims 1 to 3, characterized in that the organic fluorine compound is recovered using an emulsion flow system.

5. A method for recovering an organic fluorine compound according to any one of claims 1 to 3, wherein the organic fluorine compound has a carboxyl group, a sulfonic acid group, or both.

6. A method for recovering an organic fluorine compound, comprising: in a two-liquid-phase system consisting of an aqueous phase, which is an aqueous solution containing an organic fluorine compound, and an organic phase, lowering the pH of the aqueous phase to convert the organic fluorine compound into an electrically neutral chemical species based on either acid molecularization of the organic fluorine compound or ion pair formation with a protonation-type hydrophobic cation, or both, thereby promoting partitioning of the organic fluorine compound into the organic phase, thereby directly extracting the organic fluorine compound into the organic phase; thereafter, contacting the organic phase with an aqueous phase whose pH is higher than that used to promote partitioning into the organic phase, thereby converting the organic fluorine compound into a negatively charged chemical species based on either ionization due to acid dissociation of the organic fluorine compound or molecularization of the protonation-type hydrophobic cation, or both, thereby promoting partitioning of the organic fluorine compound into the aqueous phase, thereby stripping and recovering the organic fluorine compound from the organic phase into the aqueous phase.

7. A method for recovering an organic fluorine compound according to claim 6, characterized in that the amount or flow rate of the aqueous phase relative to the organic phase is controlled to concentrate the organic fluorine compound in the aqueous phase and recover it.

8. A method for recovering organic fluorine compounds according to claim 6 or 7, characterized in that an organic phase containing no protonation-type hydrophobic cations is used to selectively extract and separate organic fluorine compounds whose charge is easily changed by pH, and then an organic phase containing said protonation-type hydrophobic cations is used to selectively recover organic fluorine compounds whose charge is not easily changed by pH.

9. A method for recovering an organic fluorine compound according to any one of claims 6 to 8, wherein the organic fluorine compound is recovered using an emulsion flow system.

10. A method for recovering an organic fluorine compound according to any one of claims 6 to 8, wherein the organic fluorine compound has a carboxyl group, a sulfonic acid group, or both.