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

Abstract

The present invention 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. [Solution] 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 fluorinating extraction solvent and extracting the low molecular weight organofluorine compound into the fluorinating extraction solvent.

Description

[Technical Field]

[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. [Background technology]

[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). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-289975 [Overview of the project] [Problems that the invention aims to solve]

[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. [Means for solving the problem]

[0006] (1) This disclosure provides 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] The present disclosure (2) is the method for separating a low-molecular-weight organic fluorine compound according to the present disclosure (1), wherein the low-molecular-weight organic fluorine compound is a perfluoroalkyl compound and / or a polyfluoroalkyl compound.

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

[0009] The present disclosure (4) is the method for separating a low-molecular-weight organic fluorine compound in any combination with any one of the present disclosures (1) to (3), wherein the molecular weight of the low-molecular-weight organic fluorine compound is 100 to 1000.

[0010] The present disclosure (5) is the method for separating a low-molecular-weight organic fluorine compound in any combination with any one of the present disclosures (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) is 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 and each represents an alkyl group or an aryl group, at least one of R 1 and R 2 contains a fluorine atom, and at least one of R 1 and R 2 contains a hydrogen atom. R 1 and R 2 may contain at least one selected from the group consisting of heteroatoms, unsaturated bonds and substituents.)

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

[0013] Disclosure (8) is a method for separating low molecular weight organofluorine compounds in any combination of any of Disclosures (1) to (7), wherein the fluorinating extraction solvent is at least one selected from the group consisting of (CF3)2CHOCH3, CF3CFHCF2OCH3, and hexafluoropropene trimers.

[0014] Disclosure (9) is a method for separating low molecular weight organofluorine compounds in any combination of any of Disclosures (1) to (8), wherein the composition is an aqueous solution and has a pH of 7 or less.

[0015] Disclosure (10) is a method for separating low molecular weight organofluorine compounds in any combination of the composition with any of 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] This disclosure (12) relates to a composition comprising a low molecular weight organofluorine compound, and a tank into which a fluorinated extraction solvent is introduced, The tank includes a first introduction section for introducing the fluorinated extraction solvent, The tank comprises a first discharge section for discharging the fluorinated extraction solvent introduced into the tank, This apparatus is used in which the composition and the fluorinating extraction solvent come into contact within the tank, thereby extracting the low molecular weight organofluorine compound into the fluorinating extraction solvent.

[0018] The present disclosure (13) is the apparatus according to the present disclosure (12) in which 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] This disclosure (14) is that the composition is an aqueous solution, The apparatus according to disclosure (12) or (13), wherein a layer of the fluorinated extraction solvent is formed below a layer of the aqueous solution in the tank. [Effects of the Invention]

[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. [Brief explanation of the drawing]

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

[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 above low-molecular-weight organofluorine compounds can be determined by calculation from their chemical formulas.

[0026] The carbon number of the above low molecular weight organofluorine compound is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, also 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 number of carbon atoms.

[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 (-SO3H) and their salt forms. Among these, at least one selected from the group consisting of carboxyl groups (-COOH) and their salt forms, and sulfo groups (-SO3H) and their salt forms is preferred, and at least one selected from the group consisting of carboxyl groups (-COOH) and their salt forms 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. In particular, 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, they may all contain an ether bond (-O-).

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

[0031] If 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. When the pH is within the above range, low-molecular-weight organofluorine compounds become more easily soluble in the fluorinated extraction solvent, allowing for more efficient separation of these 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-mentioned solid adsorbents include activated carbon, ion exchange resin, silica gel, zeolite, etc., and one or more types 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] For HFE, see formula (1): (R 1 -O) n -R 2 (1) (In the formula, n is an integer between 1 and 3. 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 (This may include at least one selected from the group consisting of heteroatoms, unsaturated bonds, and substituents.) Compounds represented by are preferred.

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

[0039] R 1 and R 2 The alkyl group 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. R 1 and R 2 The aryl group preferably 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 or may not 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. R 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 the above 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. As the above unsaturated bond, an unsaturated carbon-carbon bond is preferred. Examples of the substituents mentioned above include carbonyl groups, carboxyl groups, thio groups, amino groups, amide groups, ester groups, ether bonds, hydroxyl groups, and mercapto groups. R 1 and R 2 The 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 elements 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 fluorine atoms but contain hydrogen atoms 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, CH2Cl-, CH3CHCl-, etc. Among these, methyl group and ethyl group are preferred, and methyl group is more preferred. Examples of alkyl groups containing the above fluorine atom include CF3-, CF2H-, CH2F-, C2F5-, C2F4H-, C3F7-, HC3F6-, (CF3)2CH-, CF3CFHCF2-, C4F9- (e.g., n-C4F9-, CF3CF(CF3)CF2-, (CF3)3C-), C5F 11 -, C4F7CF2-, C6F 13 -, C6F 12 -, C7F 15 -, C6F 11 CF2-, CF3C6F 10 -, C2F5C6F 10 -, C 10 F 21 - are some examples. Among them, (CF3)2CH- and CF3CFHCF2- are preferred.

[0046] For HFE, see formula (2): Rf 1 -(OR 3 ) n (2) (In the formula, n is an integer between 1 and 3. Rf 1 R is an alkyl or aryl group and contains a fluorine atom. 3 (It is an alkyl or aryl group and does not contain a fluorine atom.) Compounds represented by are preferred.

[0047] In equation (2), n is the same as n in equation (1). Rf 1 R in equation (1) 1 and R 2 This is similar to alkyl and aryl groups containing a fluorine atom. Rf 1 It may contain chlorine atoms, but it is preferable that it does not contain chlorine atoms. R 3 R in equation (1) 1 and R 2 This is similar to alkyl and aryl groups that do not contain a fluorine atom but do contain a hydrogen atom. Rf 1 It is preferable that R is an alkyl group containing a fluorine atom, 3It 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, see formula (3): X-(Rf 2 -O) y -R 4 H (3) (In the formula, X is F, H, or a perfluoroalkyl group having 1 to 3 carbon atoms. n is an integer from 1 to 3. Rf 2 is at least one group selected from the group consisting of -CF2-, -C2F4-, and -C3F6-. 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 It contains at least one fluorine atom. Compounds represented by are also preferred.

[0050] As for HFE, also, see formula (4): Rf 3 -(OR 5 ) x (4) (In the formula, x is an integer between 1 and 3. Rf 3 R is a linear, branched, or cyclic perfluorocarbon group with x valency. 4 (These are independently linear or branched alkyl groups having 1 to 3 carbon atoms.) Compounds represented by 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 3 The 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 may optionally comprise an acyclic moiety and / or a cyclic moiety, and may optionally contain a catenary heteroatom. Rf 3 as C m F 2m+1 m-, wherein m is an integer of 3 to 10, is preferable, and may be any isomer of n-, i-, s-, and t-. R 4 the alkyl group as R may optionally contain a chlorine atom, and may optionally contain a catenary heteroatom. R 4 a methyl group, an ethyl group, an n-propyl group, and an i-propyl group are preferable.

[0052] Examples of HFEs (including those represented by formulae (1) to (4)) include the following compounds.

[0053] (CF3)2CHOCH3 CF3CFHCF2OCH3 C3F7OCH3 C3F7OC2H5 C7F 15 OC2H5 C4F9OCF2H C4F9OC2F4H HC3F6OC3F6H HC3F6OCH3 C5F 11 OC2F4H C6F 13 OCF2H C3F7OCH2F HCF2OCF2OCF2H HCF2OCF2OC2F4OCF2H C3F7O[CF(CF3)CF2O] p CF(CF3)H(p=0~1) HCF2OC2F4OCF2H HCF2OCF2OCF2OCF2H HCF2OC2F4OC2F4OCF2H HCF2OCF2OCF2H HCF2OCF2OC2F4OCF2H n-C4F9OCH3 n-C4F9OC2H5 CF3CF(CF3)CF2OCH3 C3F7OCF(CF3)CF2OCH3 CF3CF(CF3)CF2OC2H5 C5F 11 OC2H5 CF3OC2F4OC2H5 (CF3)3C-OCH3 (CF3)3C-OC2H5 C4F9OCH2Cl C4F9OCHClCH3 C 10 F 21 OCH3 C 10 F 21 OC2H5 (C2F5)2NCF2CF2OCH3 (CF3)2N(CF2)3OCH3 (CF3)2N(CF2)2OC2H5 (C2F5)2NCF2CF2OCH3 CF3CF(OCH3)CF(CF3)2 CF3CF(OC2H5)CF(CF3)2 C2F5CF(OCH3)CF(CF3)2 C2F5CF(OC2H5)CF(CF3)2 C3F7CF(OCH3)CF(CF3)2 C3F7CF(OC2H5)CF(CF3)2

[0054] [ka]

[0055] [ka]

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

[0057] As HFE, at least one selected from the group consisting of (CF3)2CHOCH3 (1,1,1,3,3,3-hexafluoroisopropyl methyl ether, HFE-356mmz) and CF3CFHCF2OCH3 (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, the HFP trimer is preferred.

[0059] As an HFP trimer, C9F 18 A wide range of known compounds represented by the following formulas can be adopted, for example, at least one selected from the group consisting of compounds represented by the following formulas (I) to (III).

[0060] [ka]

[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 of the compounds represented by formulas (I) to (III), or it may contain two or three of them. In addition, it may contain C9F compounds other than those represented by formulas (I) to (III). 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 trimer. 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 trimer.

[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 trimer.

[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 trimer.

[0066] Among the above fluorinated extraction solvents, at least one selected from the group consisting of hydrofluoroethers and fluorocarbons is preferred, at least one selected from the group consisting of hydrofluoroethers and HFP trimers is more preferred, and at least one selected from the group consisting of (CF3)2CHOCH3, CF3CFHCF2OCH3, and hexafluoropropene trimers is even more preferred.

[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. Since the decomposition 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 above-mentioned fluorinated extraction solvent may be pre-filled into the reaction vessel in the required amount, or the filled state may be maintained by continuously introducing and discharging it from the reaction vessel. Continuous introduction and discharge is preferable in that it facilitates 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 that it facilitates large-scale processing. Furthermore, in order to improve 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 multiple micropores. The diameter of the above-mentioned micropores is preferably 100 μm or less, more preferably 50 μm or less, 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 compounds have been removed from the reaction vessel.

[0079] In the embodiment in which the above 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 in that it facilitates large-scale processing. Furthermore, from a similar perspective, it is preferable that the fluorinated extraction solvent after processing (a fluorinated extraction solvent containing a low molecular weight organofluorine compound 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 introduction section for introducing the fluorinated extraction solvent into the tank, and a first discharge section 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. The apparatus described herein allows for the separation of low-molecular-weight organofluorine compounds 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 the need for mechanical stirring components, thus simplifying the apparatus configuration.

[0085] The first introductory section introduces the fluorinated extraction solvent used in the process into the tank. The first discharge section discharges the treated fluorinated extraction solvent (a fluorinated extraction solvent containing a low-molecular-weight organofluorine compound extracted from the above composition) from the tank.

[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 tank in the region where the fluorinated extraction solvent layer is formed, and more preferably in the region where the fluorinated extraction solvent layer is formed, they are located closer to the bottom of the tank (the part that becomes the bottom when in use).

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

[0090] The second introduction section 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 position 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 the extraction efficiency. Furthermore, in terms of improving extraction efficiency, the second introduction section preferably has 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 section 11 for introducing a fluorinating extraction solvent into the tank 10, an discharge section 12 for discharging the fluorinating extraction solvent introduced into the tank 10, an introduction section 13 for introducing an aqueous solution containing the low molecular weight organofluorine compound to be treated into the tank 10, and an discharge section 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 the fluorinated extraction solvent layer, is formed below the aqueous layer 18, which is the aqueous solution layer. The introduction section 11 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 introduces the fluorinated extraction solvent used for the 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 treated fluorinated extraction solvent (fluorinated extraction solvent containing extracted low-molecular-weight organofluorine compounds). The introduction section 13 is connected to the piping 14, and the aqueous solution containing the low molecular weight organofluorine compound to be processed is continuously introduced through the piping 14, through the top of the tank 10, and into the solvent layer 16 at the bottom of the tank 10. In Figure 1, the aqueous solution is introduced through 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 multiple micropores (not shown) that atomize the aqueous solution to be treated and eject it into the solvent layer 16. As the ejected aqueous solution droplets 17 rise through the solvent layer 16, 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 compounds have been removed reach the top of the solvent layer 16 and form an aqueous layer 18. The discharge section 15 is located in the region of the tank 10 where the water 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 inlet and the first discharge section are provided in the tank on opposite sides of the area in which the solid adsorbent is filled. Within the tank, the solid adsorbent may be fixed in place, or it may be arranged so as to be able 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 adsorbents packed 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 section 21 for introducing a fluorinated extraction solvent into the tank 20, and an discharge section 22 for discharging the fluorinated 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 section 21 is located below the area in the tank 20 where the solid adsorbent 23 is filled, and continuously introduces the fluorinated extraction solvent used for the treatment. The discharge section 22 is located above the area in the tank 20 where the solid adsorbent 23 is filled, and continuously discharges the treated fluorinated extraction solvent (fluorinated extraction solvent containing extracted low molecular weight organofluorine compounds). Because the inlet 21 is located at the bottom and the discharge 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 above low molecular weight organofluorine compound is preferably 50% or more, more preferably 70% or more, and may be 100% or less, or 95% or less. The above removal rate is calculated using 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 beforehand and then decomposing them, it is possible to efficiently decompose a certain amount of low-molecular-weight organofluorine compounds together, even when the original composition contains only trace amounts of them.

[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 aqueous solutions and solid adsorbents. They can also be used to concentrate the low molecular weight organofluorine compounds as a pretreatment for efficient decomposition of the compounds. The decomposition method of this disclosure can be suitably used for the decomposition of low molecular weight organofluorine compounds contained in any composition, and in particular, it can be suitably used 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. [Examples]

[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) (pH adjusted to 1 or less by adding hydrochloric acid to a 1N solution).

[0107] <Fluorinated extraction solvent> HFP trimer HFE-356mec

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

[0109] <Removal rate of low molecular weight organofluorine compounds> It was calculated using 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 was measured by liquid chromatography. The calculation was based on concentration, assuming that the mass of the aqueous solution does 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 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 concentration. The removal rates were determined from the PFHxA and PFOA content in the aqueous solution before treatment and the aqueous solution separated from the solvent after treatment. The results were 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 PFHxA and PFOA content in the aqueous solution before treatment and the aqueous solution separated from the solvent after treatment. The results were 54.9% for PFHxA and 70.3% for PFOA. [Explanation of symbols]

[0112] 1, 2: Equipment 10, 20: Tank 11, 21: Inlet section (for fluorinated extraction solvent) 12, 22: Discharge section (for fluorinated extraction solvent) 13:Introduction part (for aqueous solution) 14: Piping 15: Discharge part (for aqueous solution) 16: Solvent layer 17:Droplet 18: Water layer 23: Solid adsorbents 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 fluorinating extraction solvent to extract the low molecular weight organofluorine compound into the fluorinating 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. The method for separating a low molecular weight organofluorine compound according to claim 1 or 2, wherein the molecular weight of the low molecular weight organofluorine compound is 100 to 1000.

5. The method for separating low molecular weight organofluorine compounds according to claim 1 or 2, 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 organofluorine compound according to claim 5, wherein the hydrofluoroether is a compound represented by the following formula (1). (R １ -O) ｎ -R ２ (1) (wherein 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 containing a fluorine atom, and R １ and R ２ has at least one containing a hydrogen atom. R １ and R ２ may contain at least one selected from the group consisting of a hetero atom, an unsaturated bond and a substituent.)

7. The method for separating low molecular weight organofluorine compounds according to claim 5, 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 claim 1 or 2, wherein the selected compound is at least one selected from the group consisting of and hexafluoropropene trimers.

9. The method for separating low molecular weight organofluorine compounds according to claim 1 or 2, 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 claim 1 or 2, 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 claim 1 or 2.

12. A composition containing a low molecular weight organofluorine compound, and a tank into which a fluorinated extraction solvent is introduced, The tank includes a first introduction section for introducing the fluorinated extraction solvent, The tank comprises a first discharge section for discharging the fluorinated extraction solvent introduced into the tank, An apparatus in which the composition and the fluorinating extraction solvent come into contact within the tank, thereby extracting the low molecular weight organofluorine compound into the fluorinating extraction solvent.

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

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