Method for separating low-molecular-weight organic fluorine compound, method for decomposing low-molecular-weight organic fluorine compound, and apparatus

Abstract

The present disclosure provides: a method which is for separating a low-molecular-weight organic fluorine compound and by which a low-molecular-weight organic fluorine compound can be efficiently separated; a method which is for decomposing a low-molecular-weight organic fluorine compound and which uses said separation method; and an apparatus capable of separating a low-molecular-weight organic fluorine compound with a simple configuration. The present disclosure pertains to a method for separating a low-molecular-weight organic fluorine compound, the method comprising a step for bringing a fluorinated extraction solvent into contact with a composition containing a low-molecular-weight organic fluorine compound, and extracting the low-molecular-weight organic fluorine compound into the fluorinated extraction solvent.

Description

Method for separating low molecular weight organofluorine compounds, method for decomposing low molecular weight organofluorine compounds, and apparatus.

[0001] This disclosure relates to a method for separating low molecular weight organofluorine compounds, a method for decomposing low molecular weight organofluorine compounds, and an apparatus for such decomposition.

[0002] A method for liquid-liquid extraction of metal ions and the like in aqueous solutions using an extraction solvent such as isooctane is known (see, for example, Patent Document 1).

[0003] Japanese Patent Publication No. 2008-289975

[0004] In the extraction of low molecular weight organofluorine compounds, there is a problem in that petroleum-based solvents such as isooctane do not provide sufficient extraction efficiency.

[0005] This disclosure aims to provide a method for separating low molecular weight organofluorine compounds that can efficiently separate the low molecular weight organofluorine compounds, a method for decomposing low molecular weight organofluorine compounds using the separation method, and an apparatus capable of separating low molecular weight organofluorine compounds with a simple configuration.

[0006] (1) This disclosure is a method for separating low molecular weight organofluorine compounds, comprising the step of contacting a composition containing a low molecular weight organofluorine compound with a fluorinated extraction solvent to extract the low molecular weight organofluorine compound into the fluorinated extraction solvent.

[0007] Disclosure (2) is a method for separating a low molecular weight organofluorine compound according to Disclosure (1), wherein the low molecular weight organofluorine compound is a perfluoroalkyl compound and / or a polyfluoroalkyl compound.

[0008] Disclosure (3) is a method for separating a low molecular weight organofluorine compound according to Disclosure (1) or (2), wherein the low molecular weight organofluorine compound is a fluorine-containing carboxylic acid and / or a fluorine-containing sulfonic acid.

[0009] Disclosure (4) is a method for separating low molecular weight organofluorine compounds in any combination of any of Disclosures (1) to (3), wherein the molecular weight of the low molecular weight organofluorine compound is 100 to 1000.

[0010] The present disclosure (5) provides a method for separating a low-molecular-weight organic fluorine compound in any combination with any one of the above (1) to (4), wherein the fluorinated extraction solvent is at least one selected from the group consisting of hydrofluoroethers and fluorocarbons.

[0011] The present disclosure (6) provides the method for separating a low-molecular-weight organic fluorine compound according to the present disclosure (5), wherein the hydrofluoroether is a compound represented by the following formula (1): (R １ -O) ｎ -R ２ (1) (In the formula, n is an integer of 1 to 3; R １ and R ２ are the same or different, each being an alkyl group or an aryl group; R １ and R ２ has at least one fluorine atom; R １ and R ２ has at least one hydrogen atom; R １ and R ２ may contain at least one selected from the group consisting of a heteroatom, an unsaturated bond and a substituent.)

[0012] The present disclosure (7) provides the method for separating a low-molecular-weight organic fluorine compound according to the present disclosure (5) or (6), wherein the fluorocarbon is hexafluoropropene trimer.

[0013] The present disclosure (8) provides a method for separating a low-molecular-weight organic fluorine compound in any combination with any one of the above (1) to (7), wherein the fluorinated extraction solvent is (CF ３ ) ２ CHOCH ３ , CF ３ CFHCF ２ OCH ３ and / or hexafluoropropene trimer.

[0014] The present disclosure (9) provides a method for separating a low-molecular-weight organic fluorine compound in any combination with any one of the above (1) to (8), wherein the composition is an aqueous solution having a pH of 7 or lower.

[0015] This disclosure (10) is a method for separating low molecular weight organofluorine compounds in any combination of the composition with any of the disclosures (1) to (8), wherein the composition is at least one solid adsorbent selected from the group consisting of organic porous materials and inorganic porous materials.

[0016] Disclosure (11) is a method for decomposing a low molecular weight organofluorine compound, which includes a step of decomposing the low molecular weight organofluorine compound separated by a method for separating a low molecular weight organofluorine compound in any combination of any of Disclosures (1) to (10).

[0017] The present disclosure (12) is an apparatus comprising a composition containing a low molecular weight organofluorine compound and a tank into which a fluorinating extraction solvent is introduced; a first introduction section for introducing the fluorinating extraction solvent into the tank; and a first discharge section for discharging the fluorinating extraction solvent introduced into the tank, wherein the low molecular weight organofluorine compound is extracted into the fluorinating extraction solvent by contact between the composition and the fluorinating extraction solvent within the tank.

[0018] The present disclosure (13) is the apparatus according to the present disclosure (12) wherein the introduction of the fluorinated extraction solvent into the tank and the discharge of the fluorinated extraction solvent from the tank are performed continuously.

[0019] The present disclosure (14) is an apparatus according to the present disclosure (12) or (13), wherein the composition is an aqueous solution, and a layer of the fluorinated extraction solvent is formed below the layer of the aqueous solution in the tank.

[0020] This disclosure provides a method for separating low molecular weight organofluorine compounds that can efficiently separate the low molecular weight organofluorine compounds, a method for decomposing low molecular weight organofluorine compounds using the separation method, and an apparatus capable of separating low molecular weight organofluorine compounds with a simple configuration.

[0021] A schematic diagram showing an example of a method and apparatus for separating low-molecular-weight organofluorine compounds according to Embodiment (1). A schematic diagram showing an example of a method and apparatus for separating low-molecular-weight organofluorine compounds according to Embodiment (2).

[0022] The following provides a detailed explanation of this disclosure.

[0023] This disclosure provides a method for separating low molecular weight organofluorine compounds (hereinafter also referred to as the separation method of this disclosure), which includes the step of contacting a composition containing a low molecular weight organofluorine compound with a fluorinated extraction solvent and extracting the low molecular weight organofluorine compound into the fluorinated extraction solvent.

[0024] The separation method of this disclosure uses a fluorinated extraction solvent for the extraction of low molecular weight organofluorine compounds, thus enabling efficient separation of low molecular weight organofluorine compounds from a composition. Furthermore, the fluorinated extraction solvent has low reactivity, making it easy to handle. Moreover, the separation method of this disclosure can be carried out with simple equipment.

[0025] The low molecular weight organofluorine compound in the separation method of this disclosure may be any low molecular weight organic compound having a fluorine atom, but it is preferably 1000 or less in molecular weight, more preferably 800 or less, even more preferably 500 or less, and preferably 100 or more. The molecular weight of the low molecular weight organofluorine compound can be determined by calculation from its chemical formula.

[0026] The carbon number of the low molecular weight organofluorine compound is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, preferably 21 or less, more preferably 15 or less, even more preferably 14 or less, even more preferably 13 or less, even more preferably 10 or less, even more preferably 8 or less, even more preferably 7 or less, and particularly preferably 6 or less. According to the separation method of this disclosure, low molecular weight organofluorine compounds can be efficiently separated regardless of the carbon number.

[0027] The above low molecular weight organofluorine compounds may have hydrophilic groups. Examples of hydrophilic groups include carboxyl groups (-COOH) and their salt forms, and sulfo groups (-SO). ３ Examples include H) and its salt forms. In particular, carboxyl groups (-COOH) and their salt forms, and sulfo groups (-SO). ３ At least one selected from the group consisting of H) and its salt form group is preferred, and at least one selected from the group consisting of a carboxyl group (-COOH) and its salt form group is more preferred.

[0028] The above low molecular weight organofluorine compound is preferably a perfluoroalkyl compound and / or a polyfluoroalkyl compound.

[0029] Examples of the low molecular weight organofluorine compounds mentioned above include fluorine-containing carboxylic acids and their salts, fluorine-containing sulfonic acids and their salts, and one or more of these can be used. Among these, at least one selected from the group consisting of fluorine-containing carboxylic acids and their salts, and fluorine-containing sulfonic acids and their salts is preferred, and at least one selected from the group consisting of perfluorocarboxylic acids and their salts, and perfluorosulfonic acids and their salts is more preferred. The number of carbon atoms in these compounds is preferably within the range described above. Furthermore, all of these may have an ether linkage (-O-).

[0030] The composition in the separation method of this disclosure is not limited and may be liquid, solid, or a combination thereof. Among these, the composition is preferably liquid and / or solid, and more preferably aqueous solution and / or solid adsorbent.

[0031] When the above composition is an aqueous solution, the pH is preferably 7 or less, more preferably less than 7, even more preferably 6 or less, even more preferably 5 or less, particularly preferably 4 or less, and also preferably greater than 0, and more preferably 1 or more. Having the pH within this range makes it easier for low molecular weight organofluorine compounds to dissolve in the fluorination extraction solvent, allowing for more efficient separation of the low molecular weight organofluorine compounds. The pH of the above composition can be measured using a pH meter. The pH of the above composition can be adjusted, for example, by adding an acidic substance.

[0032] When the above composition is a solid adsorbent, it is preferable that it be at least one selected from the group consisting of organic porous materials and inorganic porous materials. Examples of the above solid adsorbent include activated carbon, ion exchange resin, silica gel, zeolite, etc., and one or more of these can be used.

[0033] The content of the low molecular weight organofluorine compound in the above composition is not particularly limited, but for example, it is preferably 4 ppt by mass or more, more preferably 100 ppt by mass or more, preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.01% by mass or less.

[0034] The above-mentioned fluorinated extraction solvent is preferably a fluorinated liquid capable of dissolving low molecular weight organofluorine compounds. The above-mentioned fluorinated extraction solvent is preferably a liquid at 25°C and 1 atm, and preferably insoluble in water.

[0035] Examples of the fluorinated extraction solvents mentioned above include fluoroethers and fluorocarbons, and one or more of these can be used.

[0036] The above-mentioned fluoroether may be a hydrofluoroether (HFE) or a perfluoroether, but it is preferably an HFE.

[0037] HFE is given by the following formula (1): (R １ -O) ｎ -R ２ (1) (wherein n is an integer from 1 to 3. R １ and R ２ R is the same or different alkyl group or aryl group, １ and R ２ At least one of them contains a fluorine atom, R １ and R ２ At least one of them contains a hydrogen atom. １ and R ２ Compounds represented by (which may include at least one selected from the group consisting of heteroatoms, unsaturated bonds, and substituents) are preferred.

[0038] In formula (1), n ​​is an integer between 1 and 3, but is preferably 1 or 2, and more preferably 1.

[0039] R １ and R ２The alkyl group as is preferably has 10 or fewer carbon atoms, more preferably 8 or fewer, even more preferably 5 or fewer, even more preferably 4 or fewer, particularly preferably 3 or fewer, and may also have 1 or more carbon atoms. １ and R ２ The aryl group has 20 or fewer carbon atoms, more preferably 15 or fewer, even more preferably 10 or fewer, even more preferably 8 or fewer, and may have 6 or more carbon atoms.

[0040] R １ and R ２ It may or may not contain a fluorine atom. It may also contain a hydrogen atom. However, R １ and R ２ At least one of them contains a fluorine atom, R １ and R ２ At least one of them must contain a hydrogen atom. １ and R ２ Preferably, one of the elements contains a fluorine atom, and the other does not contain a fluorine atom but contains a hydrogen atom.

[0041] R １ and R ２ In this case, it is preferable that the total number of hydrogen atoms is less than or equal to the total number of fluorine atoms.

[0042] R １ and R ２ It may contain at least one selected from the group consisting of heteroatoms, unsaturated bonds, and substituents. Examples of heteroatoms include at least one selected from the group consisting of oxygen atoms, nitrogen atoms, and sulfur atoms, with at least one selected from the group consisting of oxygen atoms and nitrogen atoms being preferred. These may be catenary heteroatoms or non-catenary heteroatoms. An unsaturated carbon-carbon bond is preferred as the unsaturated bond. Examples of substituents include carbonyl groups, carboxyl groups, thio groups, amino groups, amide groups, ester groups, ether bonds, hydroxyl groups, mercapto groups, etc. R １ and R ２The group represented by may not contain heteroatoms other than fluorine atoms, unsaturated bonds, or substituents.

[0043] R １ and R ２ It may contain chlorine atoms, but if chlorine atoms are present, the R on which those chlorine atoms are located １ or R ２ It is preferable that at least two hydrogen atoms are present on top.

[0044] R １ and R ２ The chain may be linear, branched, or ring-shaped.

[0045] R １ and R ２ It is preferably an alkyl group, R １ and R ２ Preferably, one of the alkyl groups is an alkyl group containing a fluorine atom, and the other is an alkyl group that does not contain a fluorine atom but contains a hydrogen atom. Examples of alkyl groups that do not contain a fluorine atom but contain a hydrogen atom include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, s-butyl group, t-butyl group, pentyl group, n-hexyl group, cyclohexyl group, heptyl group, octyl group, nonyl group, decyl group, CH ２ Cl-, CH ３ Examples include CHCl-, etc. Among these, methyl and ethyl groups are preferred, and methyl groups are more preferred. Examples of alkyl groups containing the fluorine atom include CF ３ -, CF ２ H-, CH ２ F-, C ２ F ５ -, C ２ F ４ H-, C ３ F ７ - HC ３ F ６ -, (CF ３ ) ２ CH-, CF ３ CFHCF ２ -, C ４ F ９ - (For example, n-C) ４ F ９ -, CF３ CF(CF ３ )CF ２ -, (CF ３ ) ３ C-), C ５ F １１ -, C ４ F ７ CF ２ -, C ６ F １３ -, C ６ F １２ -, C ７ F １５ -, C ６ F １１ CF ２ -, CF ３ C ６ F １０ -, C ２ F ５ C ６ F １０ -, C １０ F ２１ - and the like. Among these, (CF ３ ) ２ CH-, CF ３ CFHCF ２ - is preferable.

[0046] As HFE, the compound represented by the following formula (2): Rf １ -(O-R ３ ) ｎ (2) (wherein, n is an integer of 1 to 3. Rf １ is an alkyl group or an aryl group and contains a fluorine atom. R ３ is an alkyl group or an aryl group and does not contain a fluorine atom.) is preferable.

[0047] In formula (2), n is the same as n in formula (1). Rf １ is the same as R in formula (1) １ and R ２ among alkyl groups and aryl groups serving as the foregoing, is the same as those containing a fluorine atom. Rf １ may contain a chlorine atom, but preferably does not contain a chlorine atom. R ３ is the same as R in formula (1) １ and R ２This is similar to alkyl and aryl groups that do not contain a fluorine atom but contain a hydrogen atom. Rf １ It is preferable that R is an alkyl group containing a fluorine atom, ３ It is preferable that the alkyl group does not contain fluorine atoms but contains hydrogen atoms.

[0048] Rf １ and R ３ In this case, it is preferable that the total number of hydrogen atoms is less than or equal to the total number of fluorine atoms.

[0049] As for HFE, also, the following formula (3): X - (Rf ２ -O) ｙ -R ４ H (3) (wherein X is F, H, or a perfluoroalkyl group having 1 to 3 carbon atoms. Rf ２ -CF ２ -, -C ２ F ４ - and -C ３ F ６ - is at least one group selected from the group consisting of . ４ is a divalent organic group having 1 to 3 carbon atoms, preferably perfluorinated. y is an integer from 1 to 3. However, if X is F, then R ４ Compounds represented by (which contains at least one fluorine atom) are also preferred.

[0050] As for HFE, also, the following formula (4): Rf ３ - (O-R ５ ) ｘ (4) (wherein x is an integer between 1 and 3. Rf ３ R is a linear, branched, or cyclic perfluorocarbon group with x valency. ５ Compounds represented by (where is independently a linear or branched alkyl group having 1 to 3 carbon atoms) are also preferred.

[0051] In equation (4), x is an integer between 1 and 3, but is preferably 1 or 2, and more preferably 1. Rf ３The number of carbon atoms in the perfluorohydrocarbon group is preferably 3 or more, more preferably 4 or more, preferably 12 or less, and more preferably 10 or less. Rf ３ It may include an acyclic portion and / or a cyclic portion, and may also include a catenary heteroatom. Rf ３ C ｍ F ２ｍ＋１ A group represented by - (where m is an integer from 3 to 10) is preferred, and any of the isomers n-, i-, s-, or t- may be used. ５ The alkyl group may contain a chlorine atom or a catenary heteroatom. ５ Preferably, the group is a methyl group, an ethyl group, an n-propyl group, or an i-propyl group.

[0052] Examples of HFE (including those represented by formulas (1) to (4)) include the following compounds:

[0053] (CF ３ ) ２ CHOCH ３ CF ３ CFHCF ２ OCH ３ C ３ F ７ OCH ３ C ３ F ７ OC ２ H ５ C ７ F １５ OC ２ H ５ C ４ F ９ OCF ２ H C ４ F ９ OC ２ F ４ H HC ３ F ６ OC ３ F ６ H HC ３ F ６ OCH ３ C ５ F １１ OC ２ F ４ H C ６ F１３ OCF ２ H C ３ F ７ OCH ２ F HCF ２ OCF ２ OCF ２ H HCF ２ OCF ２ OC ２ F ４ OCF ２ H C ３ F ７ O[CF(CF ３ )CF ２ O] ｐ CF(CF ３ )H (p is an integer of 0 to 1) HCF ２ OC ２ F ４ OCF ２ H HCF ２ OCF ２ OCF ２ OCF ２ H HCF ２ OC ２ F ４ OC ２ F ４ OCF ２ H HCF ２ OCF ２ OCF ２ H HCF ２ OCF ２ OC ２ F ４ OCF ２ H n-C ４ F ９ OCH ３ n-C ４ F ９ OC ２ H ５ CF ３ CF(CF ３ )CF ２ OCH ３ C ３ F ７ OCF(CF ３ )CF ２ OCH ３ CF ３ CF(CF ３ )CF ２ OC ２ H ５ C５ F １１ OC ２ H ５ CF ３ OC ２ F ４ OC ２ H ５ (CF ３ ) ３ C-OCH ３ (CF ３ ) ３ C-OC ２ H ５ C ４ F ９ OCH ２ C-C ４ F ９ OCHC-CH ３ C １０ F ２１ OCH ３ C １０ F ２１ OC ２ H ５ (C ２ F ５ ) ２ NCF ２ CF ２ OCH ３ (CF ３ ) ２ N (CF ２ ) ３ OCH ３ (CF ３ ) ２ N (CF ２ ) ２ OC ２ H ５ (C ２ F ５ ) ２ NCF ２ CF ２ OCH ３ CF ３ CF(OCH ３ )CF(CF ３ ) ２ CF ３ CF(OC ２ H ５ )CF(CF ３ ) ２ C ２ F ５ CF(OCH ３ )CF(CF３ ) ２ C ２ F ５ CF (OC ２ H ５ ) CF (CF ３ ) ２ C ３ F ７ CF(OCH) ３ ) CF (CF ３ ) ２ C ３ F ７ CF (OC ２ H ５ ) CF (CF ３ ) ２

[0054]

[0055]

[0056] In the above formula, the "F" written inside the cyclic structure indicates that the cyclic structure is perfluorinated.

[0057] Among HFEs, (CF ３ ) ２ CHOCH ３ (1,1,1,3,3,3-Hexafluoroisopropyl methyl ether, HFE-356 MHz), CF ３ CFHCF ２ OCH ３ At least one selected from the group consisting of (1,1,2,3,3,3-hexafluoropropyl methyl ether, HFE-356mec) is preferred.

[0058] Examples of the fluorocarbons mentioned above include hexafluoropropene (HFP) trimers, and one or more types can be used. Among these, HFP trimers are preferred.

[0059] As an HFP trimer, C ９ F １８ A wide range of known compounds represented by the formulas (I) to (III) below can be adopted, for example, at least one selected from the group consisting of compounds represented by the following formulas (I) to (III).

[0060]

[0061] In this specification, unless otherwise specified, the compound represented by formula (I) includes both the E and Z isomers of the diastereomer.

[0062] The HFP trimer may contain only one compound from formulas (I) to (III), or it may contain two or three compounds. In addition, C may be present in addition to the compounds represented by formulas (I) to (III). ９ F １８ It may contain an HFP trimer represented by .

[0063] The content of the compound represented by formula (I) is preferably 1% by mass or more, more preferably 10% by mass or more, even more preferably 30% by mass or more, even more preferably 40% by mass or more, even more preferably 45% by mass or more, particularly preferably 50% by mass or more, and may also be 85% by mass or more, based on the total amount of HFP trimers. Furthermore, the content of the compound represented by formula (I) is preferably 99% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less (or less), even more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less, based on the total amount of HFP trimers.

[0064] The content of the compound represented by formula (II) is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, preferably 70% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less, based on the total amount of HFP trimers.

[0065] The content of the compound represented by formula (III) is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, preferably 70% by mass or less, more preferably 50% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less, based on the total amount of HFP trimers.

[0066] Among the above fluorinated extraction solvents, at least one selected from the group consisting of hydrofluoroethers and fluorocarbons is preferred, and at least one selected from the group consisting of hydrofluoroethers and HFP trimers is more preferred, (CF ３ ) ２ CHOCH ３ CF ３ CFHCF ２ OCH ３ A further preference is at least one selected from the group consisting of and hexafluoropropene trimers.

[0067] The purity of the above-mentioned fluorinated extraction solvent is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 99% by mass or more, and may be 100% by mass or less.

[0068] If the above-mentioned fluorinated extraction solvent contains at least one selected from the group consisting of hydrofluoroethers and HFP trimers, the total content of these substances is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 99% by mass or more, and may be 100% by mass or less, relative to the above-mentioned fluorinated extraction solvent.

[0069] The purity and component content of the above-mentioned fluorinated extraction solvent are measured by gas chromatography.

[0070] By contacting the above composition with the above fluorinated extraction solvent, the low molecular weight organofluorine compounds in the composition are extracted into the fluorinated extraction solvent. Contact between the above composition and the above fluorinated extraction solvent can be carried out in a batch or continuous manner. Continuous processing is preferred because it facilitates large-scale processing. Multiple batch processing can also be performed.

[0071] The above contact does not require mechanical stirring by a stirring blade or the like. Because the separation method of this disclosure has high extraction efficiency, low molecular weight organofluorine compounds can be efficiently separated even without mechanical stirring.

[0072] The temperature of the above contact is not particularly limited, but for example, from the viewpoint of increasing reactivity, it is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 30°C or higher. Furthermore, from the viewpoint of suppressing the vaporization of the above fluorinated extraction solvent, it is preferably below the boiling point of the above fluorinated extraction solvent, and more preferably 50°C or lower.

[0073] The method for contacting the above composition with the above fluorinated extraction solvent is not particularly limited. Both may be introduced into a reaction vessel and mixed, or one may be introduced into a reaction vessel filled with the other. The introduction may be done all at once, intermittently, or continuously.

[0074] In embodiments where the above composition is an aqueous solution (hereinafter also referred to as Embodiment (1)), it is preferable to introduce the aqueous solution to be treated into the fluorinated extraction solvent, and more preferably to introduce the aqueous solution to be treated into the fluorinated extraction solvent filled in the reaction vessel. The fluorinated extraction solvent may be pre-filled in the reaction vessel in the required amount, or the filled state may be maintained by continuously introducing it into and discharging it from the reaction vessel. Continuous introduction and discharge is preferable in terms of facilitating large-scale processing.

[0075] In Embodiment (1), the method for introducing the aqueous solution to be treated into the fluorinated extraction solvent is not particularly limited, but continuous introduction is preferable in terms of facilitating large-scale processing. Furthermore, in terms of improving extraction efficiency, it is preferable to atomize the aqueous solution and introduce it into the fluorinated extraction solvent. The atomization method is not limited, but one example is to spray the aqueous solution from an introduction section having a plurality of micropores. The diameter of the micropores is preferably 100 μm or less, more preferably 50 μm or less, and preferably 1 μm or more, and more preferably 5 μm or more.

[0076] Since the aqueous solution to be treated usually has a lower specific gravity than the fluorination extraction solvent, the aqueous solution introduced into the fluorination extraction solvent rises through the solvent. As it rises, the low molecular weight organofluorine compounds in the aqueous solution are extracted into the fluorination extraction solvent, and a layer of aqueous solution from which the low molecular weight organofluorine compounds have been removed (aqueous layer) is formed on top of the layer of fluorination extraction solvent (solvent layer).

[0077] To increase the contact time with the fluorinated extraction solvent and improve extraction efficiency, it is preferable to introduce the aqueous solution to be treated from the bottom of the reaction vessel (the part closest to the bottom of the reaction vessel during use).

[0078] Furthermore, in terms of facilitating large-scale processing, it is preferable to continuously discharge the aqueous solution from which the low-molecular-weight organofluorine compound has been removed from the reaction vessel.

[0079] In embodiments where the composition is a solid adsorbent (hereinafter also referred to as Embodiment (2)), it is preferable to introduce the fluorinated extraction solvent into the solid adsorbent to be treated, and more preferable to introduce the fluorinated extraction solvent into the solid adsorbent to be treated that is filled into the reaction vessel. It is preferable to fill the reaction vessel with the required amount of the solid adsorbent in advance. The solid adsorbent may be fixed in the reaction vessel, or it may be arranged so that it can flow when in contact with the fluorinated extraction solvent.

[0080] The method for introducing the fluorinated extraction solvent into the solid adsorbent is not particularly limited, but continuous introduction is preferable for ease of large-scale processing. Similarly, it is preferable that the fluorinated extraction solvent after processing (fluorinated extraction solvent containing low molecular weight organofluorine compounds extracted from the solid adsorbent) be continuously discharged from the reaction vessel.

[0081] In embodiment (2), it is preferable to pre-dry the solid adsorbent to be treated in order to suppress the repulsion of the fluorinating extraction solvent by moisture. The drying method is not particularly limited, and commonly used methods such as natural drying, hot air drying, and vacuum drying can be used.

[0082] The contact between the above composition and the fluorinated extraction solvent may be carried out using any apparatus that allows the above-described embodiments to be applied, but it is preferable to carry out the contact using an apparatus that includes, for example, a composition containing a low molecular weight organofluorine compound and a tank into which the fluorinated extraction solvent is introduced, a first inlet for introducing the fluorinated extraction solvent into the tank, and a first outlet for discharging the fluorinated extraction solvent introduced into the tank, wherein the low molecular weight organofluorine compound is extracted into the fluorinated extraction solvent by contact between the above composition and the fluorinated extraction solvent in the tank. This disclosure also relates to such an apparatus. According to the apparatus of this disclosure, low molecular weight organofluorine compounds can be separated with a simple configuration.

[0083] The tank in the apparatus of this disclosure functions as a reaction vessel. The tank may be made of a material that does not corrode when in contact with the composition and the fluorinated extraction solvent.

[0084] The apparatus of this disclosure may have mechanical stirring members such as stirring blades, but it is preferable that it does not have mechanical stirring members. By using a fluorinated extraction solvent for extraction, low molecular weight organofluorine compounds can be efficiently separated without using mechanical stirring members, thus simplifying the apparatus configuration.

[0085] The first inlet section introduces the fluorinated extraction solvent used for processing into the tank. The first discharge section discharges the fluorinated extraction solvent (a fluorinated extraction solvent containing a low-molecular-weight organofluorine compound extracted from the composition) from the tank after processing.

[0086] In the apparatus of this disclosure, it is preferable that the introduction of the fluorinated extraction solvent into the tank and the discharge of the fluorinated extraction solvent from the tank are performed continuously, as this facilitates large-scale processing.

[0087] In the embodiment (1) described above, that is, in the embodiment in which the composition is an aqueous solution, a layer of the fluorinated extraction solvent is usually formed below the layer of the aqueous solution in the tank. The layer of aqueous solution may be a layer of aqueous solution from which low molecular weight organofluorine compounds have been removed.

[0088] The first inlet and first discharge sections described above are preferably provided in the region of the tank where the layer of fluorinated extraction solvent is formed, and more preferably are provided in a position close to the bottom of the tank (the part that becomes the bottom when in use) within the region where the layer of fluorinated extraction solvent is formed.

[0089] In embodiment (1), the apparatus preferably includes a second introduction unit for introducing an aqueous solution containing a low molecular weight organofluorine compound into the tank, and a second discharge unit for discharging the aqueous solution from which the low molecular weight organofluorine compound has been removed from the tank.

[0090] The second inlet is preferably provided in the region of the tank where the layer of the fluorinated extraction solvent is formed, and is more preferably provided in a location close to the bottom of the tank within the region where the layer of the fluorinated extraction solvent is formed, in order to increase the contact time between the aqueous solution and the fluorinated extraction solvent and improve extraction efficiency. Furthermore, in order to improve extraction efficiency, the second inlet is preferably provided with a plurality of micropores that atomize and eject the aqueous solution. The preferred diameter of the micropores is as described in the separation method of this disclosure.

[0091] The second discharge section is preferably provided in the tank in the region where the layer of aqueous solution is formed.

[0092] In terms of facilitating large-scale processing, it is preferable that the introduction of the aqueous solution into the tank and the discharge of the aqueous solution from the tank be carried out continuously.

[0093] Figure 1 shows an example of a method and apparatus for separating low molecular weight organofluorine compounds according to Embodiment (1). In Figure 1, the apparatus 1 comprises a tank 10, an introduction unit 11 for introducing a fluorination extraction solvent into the tank 10, an discharge unit 12 for discharging the fluorination extraction solvent introduced into the tank 10, an introduction unit 13 for introducing an aqueous solution containing the low molecular weight organofluorine compound to be treated into the tank 10, and an discharge unit 15 for discharging the aqueous solution from which the low molecular weight organofluorine compound has been removed from the tank 10. Inside the tank 10, a solvent layer 16, which is a layer of the fluorination extraction solvent, is formed below an aqueous layer 18, which is a layer of the aqueous solution. The introduction unit 11 is located in the tank 10 in a position close to the bottom of the tank 10 in the region where the solvent layer 16 is formed, and continuously introduces the fluorination extraction solvent used for treatment. The discharge section 12 is located in the tank 10, near the bottom of the tank 10, in the region where the solvent layer 16 is formed, and continuously discharges the fluorinated extraction solvent (fluorinated extraction solvent containing extracted low-molecular-weight organofluorine compounds) after treatment. The introduction section 13 is connected to the piping 14, and the aqueous solution containing the low-molecular-weight organofluorine compounds to be treated is continuously introduced into the solvent layer 16 at the bottom of the tank 10 via the piping 14 and the top of the tank 10. In Figure 1, the aqueous solution is introduced via the top of the tank 10, but this is not the only configuration; for example, the aqueous solution may be introduced directly from the bottom of the tank 10 without going through the top of the tank 10. The introduction section 13 has a plurality of micropores (not shown) that atomize the aqueous solution to be treated and eject it into the solvent layer 16. As the ejected droplets 17 of the aqueous solution rise in the solvent layer 16, the low-molecular-weight organofluorine compounds are extracted from the droplets 17 into the solvent layer 16. The droplets 17 from which the low molecular weight organofluorine compound has been removed reach the solvent layer 16 and form an aqueous layer 18. The discharge section 15 is provided in the tank 10 in the region where the aqueous layer 18 is formed, and continuously discharges the aqueous solution from which the low molecular weight organofluorine compound has been removed.

[0094] In the embodiment (2) described above, that is, in the embodiment in which the composition is a solid adsorbent, it is preferable that the first introduction section and the first discharge section are provided in the tank on opposite sides of the area in which the solid adsorbent is filled. In the tank, the solid adsorbent may be fixed or may be arranged to flow when in contact with the fluorinated extraction solvent. In embodiment (2), it is preferable that the fluorinated extraction solvent is introduced so as to come into contact with all of the solid adsorbent filled in the tank.

[0095] Figure 2 shows an example of a method and apparatus for separating low molecular weight organofluorine compounds according to Embodiment (2). In Figure 2, the apparatus 2 comprises a tank 20, an introduction unit 21 for introducing a fluorination extraction solvent into the tank 20, and an discharge unit 22 for discharging the fluorination extraction solvent introduced into the tank 20. The tank 20 is pre-filled with a solid adsorbent 23 containing the low molecular weight organofluorine compound to be treated. The introduction unit 21 is located below the area in the tank 20 where the solid adsorbent 23 is filled, and continuously introduces the fluorination extraction solvent used for treatment. The discharge unit 22 is located above the area in the tank 20 where the solid adsorbent 23 is filled, and continuously discharges the fluorination extraction solvent (fluorination extraction solvent containing the extracted low molecular weight organofluorine compound) after treatment. Because the introduction section 21 is located at the bottom and the discharge section 22 is located at the top, the fluorinated extraction solvent 24 introduced into the tank 20 comes into contact with all of the solid adsorbent 23 filling the tank 20, and the low molecular weight organofluorine compounds contained in the solid adsorbent 23 are extracted into the fluorinated extraction solvent 24.

[0096] By using the separation method and / or apparatus of the present disclosure, a composition from which low molecular weight organofluorine compounds have been removed can be obtained. The low molecular weight organofluorine compounds may be partially or completely removed. The removal rate of the low molecular weight organofluorine compounds is preferably 50% or more, more preferably 70% or more, and may be 100% or less, or 95% or less. The removal rate is determined by the following formula: Removal rate (%) = {(Mass of low molecular weight organofluorine compounds in the composition before treatment) - (Mass of low molecular weight organofluorine compounds in the composition after treatment)} / (Mass of low molecular weight organofluorine compounds in the composition before treatment) × 100 The content of low molecular weight organofluorine compounds in the composition before and after treatment is measured by liquid chromatography.

[0097] The composition obtained using the separation method and / or apparatus of the present disclosure, from which some of the low molecular weight organofluorine compounds have been removed, may be brought into contact with a fluorinating extraction solvent again to further separate the low molecular weight organofluorine compounds. The composition from which the low molecular weight organofluorine compounds have been sufficiently removed can also be reused.

[0098] Furthermore, by using the separation method and / or apparatus of this disclosure, a fluorinated extraction solvent containing a low molecular weight organofluorine compound extracted from the above composition can be obtained. This fluorinated extraction solvent containing the low molecular weight organofluorine compound can be suitably used in the decomposition method described later. In addition, the fluorinated extraction solvent can be reused by separating the low molecular weight organofluorine compound from it.

[0099] This disclosure also relates to a method for decomposing low molecular weight organofluorine compounds (hereinafter also referred to as the decomposition method of this disclosure), which includes a step of decomposing the low molecular weight organofluorine compounds separated by the separation method of low molecular weight organofluorine compounds of this disclosure described above. By separating the low molecular weight organofluorine compounds from a composition containing them in advance and then decomposing them, even when the amount of low molecular weight organofluorine compounds in the original composition is small, a certain amount of low molecular weight organofluorine compounds can be efficiently decomposed all at once.

[0100] In the decomposition method of this disclosure, the fluorinated extraction solvent containing the low molecular weight organofluorine compound obtained by the separation method of this disclosure may be subjected to the decomposition treatment as is, or the concentration of the low molecular weight organofluorine compound may be increased by a concentration operation or the like before being subjected to the decomposition treatment, or the low molecular weight organofluorine compound in the fluorinated extraction solvent may be separated by methods such as adsorption, distillation, or back extraction before being subjected to the decomposition treatment.

[0101] Methods for decomposing the above-mentioned low-molecular-weight organofluorine compounds are not particularly limited, but include biological treatment, ultraviolet irradiation, photocatalytic treatment, accelerated oxidation treatment, hydrated electron treatment, plasma treatment, electron beam irradiation, treatment with zero-valent iron, acoustic chemical treatment, incineration, supercritical water oxidation, and thermal decomposition, and these can be used individually or in combination. Among these, ultraviolet irradiation, electron beam irradiation, and thermal decomposition are preferred.

[0102] The separation method and apparatus of this disclosure can be suitably used to separate and remove low molecular weight organofluorine compounds from any composition containing such compounds, particularly from aqueous solutions and solid adsorbents. They can also be used to concentrate the low molecular weight organofluorine compounds as a pretreatment for efficient decomposition. The decomposition method of this disclosure can be suitably used for the decomposition of low molecular weight organofluorine compounds contained in any composition, and is particularly suitable for the decomposition of low molecular weight organofluorine compounds contained in a composition at low concentrations.

[0103] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0104] The present disclosure will now be further described with reference to examples, but the present disclosure is not limited to these examples.

[0105] The following substances were used in each example.

[0106] <Composition containing low molecular weight organofluorine compounds> An aqueous solution containing 20 ppb by mass of PFHxA (perfluorohexanoic acid) and 1 ppb by mass of PFOA (perfluorooctanoic acid) (hydrochloric acid was added to a 1N solution to adjust the pH to 1 or less).

[0107] <Fluorinated Extraction Solvent> HFP trimer HFE-356mec

[0108] Each value was determined using the following method.

[0109] <Removal Rate of Low-Molecular-Weight Organic Fluorine Compounds> The removal rate was calculated using the following formula: Removal rate (%) = {(Mass of low-molecular-weight organic fluorine compounds in the composition before treatment) - (Mass of low-molecular-weight organic fluorine compounds in the composition after treatment)} / (Mass of low-molecular-weight organic fluorine compounds in the composition before treatment) × 100 The content of low-molecular-weight organic fluorine compounds in the composition before and after treatment was measured by liquid chromatography. It was calculated based on the concentration, assuming that the mass of the aqueous solution did not change.

[0110] Example 1 The above aqueous solution was treated using an HFP trimer as the fluorinating extraction solvent. Specifically, the aqueous solution and the fluorinating extraction solvent were added to a container using a graduated cylinder in a volume ratio of 1:1. The container was held in the hand and shaken for 3 minutes. After shaking, the liquid was separated using a separatory funnel. The aqueous solution samples before and after extraction were analyzed by liquid chromatography to quantify the concentrations. The removal rates were determined from the content of PFHxA and PFOA in the aqueous solution before treatment and the aqueous solution separated from the solvent after treatment, and were found to be 64.6% for PFHxA and 86.0% for PFOA.

[0111] Example 2 The aqueous solution was treated in the same manner as in Example 1, using HFE-356mec instead of the HFP trimer as the fluorinating extraction solvent. The removal rates were determined from the content of PFHxA and PFOA in the aqueous solution before treatment and in the aqueous solution separated from the solvent after treatment. The results were 54.9% for PFHxA and 70.3% for PFOA.

[0112] 1, 2: Apparatus 10, 20: Tanks 11, 21: Inlet (for fluorinated extraction solvent) 12, 22: Outlet (for fluorinated extraction solvent) 13: Inlet (for aqueous solution) 14: Piping 15: Outlet (for aqueous solution) 16: Solvent layer 17: Droplets 18: Aqueous layer 23: Solid adsorbent 24: Fluorinated extraction solvent

Claims

1. A method for separating low molecular weight organofluorine compounds, comprising the step of contacting a composition containing a low molecular weight organofluorine compound with a fluorinated extraction solvent and extracting the low molecular weight organofluorine compound into the fluorinated extraction solvent.

2. The method for separating a low molecular weight organofluorine compound according to claim 1, wherein the low molecular weight organofluorine compound is a perfluoroalkyl compound and / or a polyfluoroalkyl compound.

3. The method for separating a low molecular weight organofluorine compound according to claim 1 or 2, wherein the low molecular weight organofluorine compound is a fluorine-containing carboxylic acid and / or a fluorine-containing sulfonic acid.

4. A method for separating a low molecular weight organofluorine compound according to any one of claims 1 to 3, wherein the molecular weight of the low molecular weight organofluorine compound is 100 to 1000.

5. A method for separating low molecular weight organofluorine compounds according to any one of claims 1 to 4, wherein the fluorinating extraction solvent is at least one selected from the group consisting of hydrofluoroethers and fluorocarbons.

6. The method for separating a low-molecular-weight organic fluorine compound according to claim 5, wherein the hydrofluoroether is a compound represented by the following formula (1): (R １ -O) ｎ -R ２ (1) (In the formula, n is an integer of 1 to 3. R １ and R ２ are the same or different and each is an alkyl group or an aryl group; R １ and R ２ comprises at least one fluorine atom; and at least one of R １ and R ２ comprises at least one hydrogen atom. R １ and R ２ may optionally comprise at least one selected from the group consisting of hetero atoms, unsaturated bonds and substituents.) 7. The method for separating low molecular weight organofluorine compounds according to claim 5 or 6, wherein the fluorocarbon is a hexafluoropropene trimer.

8. The fluorinated extraction solvent is (CF ３ ) ２ CHOCH ３ CF ３ CFHCF ２ OCH ３ A method for separating low molecular weight organofluorine compounds according to any one of claims 1 to 7, wherein the selected compound is at least one selected from the group consisting of and hexafluoropropene trimers.

9. A method for separating low molecular weight organofluorine compounds according to any one of claims 1 to 8, wherein the composition is an aqueous solution and its pH is 7 or less.

10. The method for separating low molecular weight organofluorine compounds according to any one of claims 1 to 8, wherein the composition is at least one solid adsorbent selected from the group consisting of organic porous materials and inorganic porous materials.

11. A method for decomposing a low molecular weight organofluorine compound, comprising the step of decomposing a low molecular weight organofluorine compound separated by the method for separating a low molecular weight organofluorine compound according to any one of claims 1 to 10.

12. An apparatus comprising: a tank into which a composition containing a low molecular weight organofluorine compound and a fluorinating extraction solvent are introduced; a first introduction section for introducing the fluorinating extraction solvent into the tank; and a first discharge section for discharging the fluorinating extraction solvent introduced into the tank, wherein the low molecular weight organofluorine compound is extracted into the fluorinating extraction solvent by contact between the composition and the fluorinating extraction solvent within the tank.

13. The apparatus according to claim 12, wherein the introduction of the fluorinated extraction solvent into the tank and the discharge of the fluorinated extraction solvent from the tank are performed continuously.

14. The apparatus according to claim 12 or 13, wherein the composition is an aqueous solution, and a layer of the fluorinated extraction solvent is formed below the layer of the aqueous solution in the tank.

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