WO2003066533A1

WO2003066533A1 - Method of recovering fluorochemical emulsifying agent

Info

Publication number: WO2003066533A1
Application number: PCT/JP2003/000659
Authority: WO
Inventors: Koichi Yanase; Masataka Eda; Hiroki Kamiya; Kota Omori; Takeshi Kamiya
Original assignee: Jemco Inc.; Asahi Glass Company, Limited
Priority date: 2002-01-25
Filing date: 2003-01-24
Publication date: 2003-08-14
Also published as: JP2003285076A; AU2003203383A1

Abstract

A method of recovering a fluorochemical emulsifying agent with a lamellar composite hydroxide from a wastewater resulting from polymerization for fluoropolymer production and containing the fluorochemical emulsifying agent, which comprises yielding a lamellar composite hydroxide containing the fluorochemical emulsifying agent trapped between sheets thereof, separating the lamellar composite hydroxide from the coagulation wastewater, dissolving the hydroxide in a mineral acid, and extracting the fluorochemical emulsifying agent from the solution with a fluorinated hydrocarbon. The fluorochemical emulsifying agent can be economically recovered through a simple procedure.

Description

Description Recovery method of fluorine-containing emulsifier

The present invention relates to a method for recovering a fluorinated emulsifier using a layered double hydroxide. Background art

Conventionally, as a method for recovering a fluorinated emulsifier used for emulsion polymerization of a fluorinated polymer, a technique using an anion exchange resin (hereinafter referred to as IER) is known. No. 51233) describes a method of coagulating and washing an emulsion polymerization latex, collecting an emulsifier as an aqueous solution, concentrating the solution, and recovering the fluorinated emulsifier with an organic solvent. A method for recovering the fluorinated emulsifier using ER is also described.

Patent Document 2 (US 3882153) describes a method in which a dilute emulsifier aqueous solution is brought into contact with a weakly basic IER within a pH range of 0 to 7 to adsorb the emulsifier and desorb it with aqueous ammonia. .

Patent Document 3 (WO 99/62830) discloses that a nonionic or cationic surfactant is added to coagulated waste water of a fluorine-containing polymer, and fine particles of polytetrafluoroethylene (hereinafter referred to as PTFE) in the coagulated waste water. Methods are described to stabilize and prevent clogging of the packed tower of the IER.

Patent Document 4 (Japanese Patent Application Laid-Open No. 55-120630), Patent Document 5 (US Pat. No. 4,369,266) and Patent Document 6 (DE 2908001) condense the coagulated PTFE wastewater by ultrafiltration and use it for PTFE production. It describes a method of recovering a part of the used fluorinated emulsifier and then adsorbing and recovering the fluorinated emulsifier by ER. Patent Document 2, Patent Document 7 (Japanese Patent Application Laid-Open No. 55-104651), and Patent Document 8 (DE 2903981) describe that a fluorine-containing emulsifier is adsorbed on an IER, and then a mixture of an acid and an organic solvent is used. Thus, a method for desorbing and recovering perfluorooctanoic acid has been disclosed.

Patent Document 9 (WO 99/62858) discloses a coagulated drainage of a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer (hereinafter referred to as PFA). Then, lime water is added in advance to adjust the pH to 6 to 7.5, and a metal salt such as aluminum chloride or iron chloride is added to coagulate unagglomerated PFA. A method is described in which after separation and removal, the pH of the obtained wastewater is adjusted to 7 or less with sulfuric acid, and the fluorinated emulsifier is adsorbed and recovered using a strongly basic IER.

Patent Document 10 (Japanese Patent Application Laid-Open No. 2000-61231) discloses a method of desorbing a fluorine-containing emulsifier adsorbed on an ion-exchange resin using a mixed solution of water, an alkali and an organic solvent. Is described.

In addition, Non-Patent Document 1 (Chemical Proceedings of the 76th Annual Meeting of the Chemical Society of Japan, Published on March 15, 2001, p. 600) and Non-Patent Document 2 (Chemical Society of Japan No. 80 Proceedings of the Annual Meeting of the Autumn Meeting, published on September 7, 2001, p. 41), using perfluorooctanoic acid and its ammonium salt using layered double hydroxides of aluminum and zinc. Insertion and fixation techniques have been reported.

However, in the method using the IER, it is necessary to remove suspended solid components (hereinafter, referred to as SS components) including unagglomerated fluorine-containing polymer before contacting with the IER. In addition to having a great effect on the recovery efficiency of the fluorine emulsifier, there are still many problems in actual operation, such as no simple and efficient method for removing SS has been found.

In addition, the insertion fixing method using a layered double hydroxide reported in Non-patent Documents 1 and 2 only shows insertion fixing with an aqueous solution in which only perfluorooctanoic acid and its ammonium salt are dissolved. However, there is no known report that shows insertion and fixation using actual flocculated wastewater of a fluoropolymer containing other contaminants. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for easily recovering a fluorine-containing emulsifier from a coagulated drainage of a fluorine-containing polymer containing a fluorine-containing emulsifier using a layered double hydroxide. I have. Disclosure of the invention

In order to achieve the above object, the present invention provides a mixed aqueous solution containing a divalent metal ion and a trivalent metal ion, a fluorinated emulsifier, and a content of a suspended solid and a substance that can be a suspended solid. The wastewater after polymerization of the fluorine-containing polymer of 1% by mass or less is maintained at a pH at which a layered double hydroxide of the divalent metal and the trivalent metal is formed. Mixing to form a layered double hydroxide containing a fluorinated emulsifier between layers, subsequently dissolving the layered double hydroxide separated from the wastewater in a mineral acid, and using a fluorinated hydrocarbon from the dissolved solution. A method for recovering a fluorinated emulsifier, comprising extracting the fluorinated emulsifier is provided.

Further, the present invention provides a method of adding a mixed aqueous solution containing a divalent metal ion and a trivalent metal ion to an aqueous solution maintained at pH at which a layered double hydroxide of the divalent metal and the trivalent metal is formed. A layered double hydroxide is generated in advance and added to wastewater after polymerization of a fluorine-containing polymer containing a fluorine-containing emulsifier and containing 1% by mass or less of a suspended solid and a substance that can become a suspended solid. To form a layered double hydroxide containing a fluorinated emulsifier between layers, then dissolve the layered double hydroxide separated from the wastewater in a mineral acid, and use the fluorinated hydrocarbon from the dissolved solution. There is provided a method for recovering a fluorine-containing emulsifier, comprising extracting the fluorine-containing emulsifier.

Furthermore, the present invention provides a method in which a mixed aqueous solution containing a divalent metal ion and a trivalent metal ion is added to the aqueous solution maintained at ρΗ at which the layered double hydroxide of the divalent metal and the trivalent metal is formed. By firing the layered double hydroxide produced in this way, a layered double hydroxide in which the anion contained therein has been desorbed is generated, and this is a material containing a fluorine emulsifier, which can be a suspended solid and a substance that can be a suspended solid. A layered double hydroxide containing a fluorine-containing emulsifier between layers by adding to a wastewater after polymerization of a fluorine-containing polymer having a content of 1% by mass or less, and then separating the layered double hydroxide from the wastewater A method for recovering a fluorinated emulsifier, comprising: dissolving fluorinated emulsifier in a mineral acid; and extracting the fluorinated emulsifier from the solution using a fluorinated hydrocarbon.

In the present invention, the divalent metal ion is preferably one or two selected from a magnesium ion and a zinc ion, and the trivalent metal ion is preferably an aluminum ion.

In the method for recovering a fluorinated emulsifier of the present invention, the mineral acid is preferably at least one selected from the group consisting of hydrochloric acid, nitric acid and sulfuric acid.

In addition, the fluoropolymer includes polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene / propylene copolymer, tetrafluoroethylene-propylene / vinylidene fluoride copolymer, and tetrafluoroethylene. Chemical styrene Ζ hexafluoride Kapuguchipi alkylene copolymer, tetrafluoroethylene modified styrene _{_{/ CF 2 = CFO (CF ¾}} ) 2 CF 3 copolymer,及 And one or more selected from polyvinylidene fluoride. Further, it is preferable that the fluorine-containing emulsifier is ammonium perfluorooctanoate.

In addition, it is preferable to recover the fluorinated emulsifier from waste water after polymerization of the fluorinated polymer having a concentration of the fluorinated emulsifier of 1 mass% or more and 10 mass% or less. MODES FOR CARRYING OUT THE INVENTION ''

In the present invention, as the fluorinated emulsifier, salts such as perfluoroalkanoic acid, ω-hydroperfluoroalkanoic acid, ω-chloroperfluoroalkanoic acid, and perfluoroalkanesulfonic acid having 5 to 13 carbon atoms are used. It is preferable that they have a linear structure or a branched structure, or a mixture thereof. Further, the molecule may contain an etheric oxygen atom. When the number of carbon atoms is in this range, the effect as an emulsifier is excellent. As the salt of the acid, an alkali metal salt such as a lithium salt, a sodium salt, and a potassium salt or an ammonium salt is preferable, an ammonium salt or a sodium salt is more preferable, and an ammonium salt is most preferable.

Specific examples of the acid include perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, and perfluoropentanoic acid. Fluorododecanoic acid, ω-hydroperfluoroheptanoic acid, ω-hydroperfluorooctanoic acid, ω-hydroperfluorononanoic acid, ω-cloperperfluoroheptanoic acid, ω— Black mouth perfluorooctanoic acid, ω Black mouth perfluorononanoic acid, etc.

CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CO〇H, CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COOH, CF ₃ CF ₂ CF ₂ 〇 (CF (CF ₃ ) CF ₂ 0] ₂ CF (CF ₃ ) COOH, CF ₃ CF ₂ CF ₂ 0 [CF (CF ₃ ) CF ₂ 〇] ₃ CF (CFJ COOH, CF, CF CF ₉ CF _? CF ₂ OCF (C FJ COOH etc.

And sulfonic acid.

Specific examples of ammonium salts include 'acid ammonium, Ammonium perfluorohexanoate, ammonium perfluoroheptanoate, ammonium perfluorooctanoate (hereinafter referred to as APFO), ammonium perfluorononanoate, ammonium perfluorodecanoate, ammonium perfluorodecanoate, ω-hydroperfluoroheptanoate ammonium, ω-hydroperfluorooctanoate ammonium, ω-hydroperfluorononanoate ammonium, ω-cloperperfluoroheptanoate ammonium, ω-clo Oral perfluorooctanoic acid ammonium, ω-chloroperfluorononanoic acid ammonium, etc.

CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COONH ₄ , CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ , CF ₃ CF ₂ CF ₂ 0 [CF (CF ₃ ) CF ₂ 0] ₂ CF (CF ₃ ) COONH ₄ , CF ₃ CF ₂ CF ₂ 0 [CF (CF ₃ ) CF ₂ Ol ₃ CF (CF ₃ ) COONH ₄ , CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF (CF ₃ ) COONH ₄ etc.

And ammonium perfluorohexane sulfonate, ammonium perfluoroheptane sulfonate, ammonium perfluorooctane sulfonate, ammonium perfluorononane sulfonate, ammonium perfluorodecane sulfonate, and the like.

Specific examples of the lithium salt include lithium perfluoropentanoate, lithium perfluorohexanoate, lithium perfluoroheptanoate, lithium perfluorooctanoate, lithium perfluorononanoate, and lithium perfluoronate. Lithium orthodecanoate, lithium perfluorododecanoate, lithium ω-hydroperfluoroheptanoate, ω-lithium lithium hydroperfluorooctanoate, ω-lithium lithium hydroperfluorononate, ω -Lithium perfluoroheptanoate, ω-Lithium perfluorooctanoate, ω-Lithium perfluorononanoate, etc.

CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COOL i, CF ₃ CF ₂ CF ₂ 〇CF (CF ₃ ) CF ₂ OCF (CF ₃ ) COOL i, CF ₃ CF ₂ CF ₂₀ (CF (CF ₃ ) CF ₂ 0] ₂ CF (CF ₃ ) COOL i, CF ₃ CF ₂ CF ₂ 0 [CF (CF ₃ ) CF ₂₀ ] ₃ CF (CF ₃ ) COOL i, CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF ( CF ₃ ) COOL i, etc.

Lithium perfluorohexane sulfonate, Lithium, lithium perfluorooctanesulfonate,

And lithium perfluorodecane sulfonate. Specific examples of the sodium salt include sodium perfluoropentanoate, sodium perfluorohexanoate, sodium perfluorohepnoate, sodium perfluorooctanoate, sodium perfluorononanoate, sodium perfluorononate, sodium perfluorodenoate, Sodium perfluorododecanoate, Sodium hydroperfluoroheptanoate, Sodium hydroperfluorooctanoate, Sodium hydroperfluorononanoate, Sodium hydroperfluorononanoate, Sodium heptanoate, sodium ω-cloper perfluorooctanoate, sodium ω-cloper perfluorononanoate, etc.

CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COON a, CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COON a, CF ₃ CF ₂ CF ₂ 0 [CF (CF ₃ ) CF ₂ 0] ₂ CF (CF ₃ ) COON a, CF ₃ CF ₂ CF ₂ 0 [CF (CF ₃ ) CF ₂₀ ] ₃ CF (CF ₃ ) COON a, CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF (CF ₃ ) COONa and the like, sodium acid, sodium perfluorooctanesulfonate, sodium perfluorononanesulfonate, sodium perfluorodecanesulfonate and the like.

Specific examples of the potassium salt include potassium perfluoropentanoate, potassium perfluorohexanoate, potassium perfluoroheptanoate, potassium perfluorooctanoate, potassium perfluorononanoate, and perfluolonate. Potassium orolodecanoate, potassium perfluorododecanoate, potassium ω-hydroperfluoroheptanoate, potassium ω_hydroperfluorooctanoate, potassium ω-hydroperfluorononanoate, ω-potassium perfluoroheptanoate, ω-potassium perfluoride potassium tannate, ω-chloroperfluoronanoic acid potassium, etc.

CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) COOK, CF ₃ CF ₂ CF ₂ OCF (CF ₃ ) CF ₂ 〇CF (CF ₃ ) COOK, CF ₃ CF ₂ CF ₂ 0 [CF (CF ₃ ) CF ₂ 0 ] ₂ CF (CF ₃ ) COOK, CF ₃ CF ₂ CF ₂₀ [CF (CF ₃ ) CF ₂₀ ] ₃ C F (CF ₃ ) COOK, CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ OCF (CF ₃ ) COOK, etc.

Potassium, perfluorooctanesulfonic acid

And potassium perfluoronate and potassium perfluorodecane sulfonate. As the fluorinated emulsifier in the present invention, in particular, an ammonium salt of a perfluoroalkanoic acid having 6 to 12 carbon atoms is preferable, and ammonium perfluoroheptanoate, APFO, ammonium perfluorononanoate or perfluonium Ammonium orolodecanoate is more preferred, and APFO is most preferred.

In the present invention, the effluent after polymerization of the fluorinated polymer is the effluent after separating the fluorinated polymer obtained by polymerizing at least one fluorinated monomer in an aqueous medium containing a fluorinated emulsifier. Usually, coagulation wastewater of the fluoropolymer after emulsion polymerization is preferable, and coagulation wastewater from the process of producing a polymer of the fluoromonomer or a copolymer of the fluoromonomer and a monomer other than the fluoromonomer is particularly preferable. . Specifically, the coagulated waste water from the production step is obtained by emulsion polymerization or aqueous dispersion polymerization of a fluorinated monomer or a fluorinated monomer and a monomer other than the fluorinated monomer in an aqueous medium containing a fluorinated emulsifier. This refers to waste water obtained by coagulating a fluoropolymer from the obtained aqueous dispersion of a fluoropolymer by salting out or the like and separating the fluoropolymer. The wastewater contains not only the fluorinated emulsifier used in the polymerization of the fluorinated monomer but also an SS component such as a non-aggregated fluorinated polymer. Hereinafter, the coagulated wastewater will be described as a typical example.

Examples of the fluorine-containing monomers include tetrafluoroethylene (tetrafluoroethylene, hereinafter referred to as TFE), CF ₂ = CFC 1, CFH = CF ₂ , CFH = CH ₂ ,

CF ₂ = CH ₂ (vinylidene fluoride, hereafter referred to as VdF), such as fluoroethylene, propylene hexafluoride (hexafluoropropylene, hereafter referred to as HEP)

Full O b propylene such as _{_{_{CF 2 = CHCF 3, CF 2}}} = CFOCF 3, CF 2 = C

FO (CF ₂ ) ₂ CF ₃ (hereinafter referred to as PPVE), CF ₂ = CFO (CF ₂ ) ₄

Pel full O b vinyl carbon atoms 3-10 of CF ₃ and the like, CH ₂ == CH (C Examples thereof include (perfluoroalkyl) ethylene having 4 to 10 carbon atoms, such as F ₂ ) ₃ CF ₃ . These fluorine-containing monomers may be used alone or in combination of two or more. In the present invention, at least one of the fluorine-containing monomers is preferably TFE.

Monomers other than the fluorinated monomer include vinyl esters such as vinyl acetate, pinyl ethers such as ethyl vinyl ether, cyclohexyl vinyl ether, and hydroxybutyl vinyl ether; monomers having a cyclic structure such as norpolenene and norbonagen; Examples thereof include aryl ethers such as a lyl ether, ethylene (hereinafter, referred to as E), propylene (hereinafter, referred to as P), and olefins such as isobutylene. Monomers other than the fluorinated monomer may be used alone or in combination of two or more.

In the present invention, examples of the fluoropolymer include PTFE, TFE / P copolymer, TFEZPZVd F copolymer, TFE / HFP copolymer, PFA / PPVE copolymer, EZTFE copolymer, polyvinylidene fluoride and the like. Can be More preferably, it is PTFE, TFEZP copolymer, TFE / PZVdF copolymer or PFA / PPVE copolymer, most preferably PTFE.

To form a layered double hydroxide containing a fluorine-containing emulsifier between layers, a method of adding divalent and trivalent metal ions to the coagulated waste water of a fluorine-containing polymer (hereinafter referred to as a coprecipitation method), A method of adding a layered double hydroxide formed in a solution containing no emulsifier to the coagulated wastewater of a fluorine-containing polymer (hereinafter referred to as an ion exchange method); and a method of forming a layered double hydroxide formed in a solution containing no fluorine-containing emulsifier. It is possible to use a method in which the hydroxide is calcined and then added to the coagulated wastewater of the fluorine-containing polymer (hereinafter referred to as a reconstitution method).

In the present invention, to the flocculant wastewater of the fluoropolymer, and the solution containing no fluorinated emulsifier in the ion exchange method and the reconstitution method, potassium hydroxide and / or sodium hydroxide are added in advance to adjust the PH of the wastewater. Adjust to 6 or more and 9 or less when using aluminum ion and zinc ion, and 9 or more and 11 or less when using aluminum ion and magnesium ion. If the pH is out of the above range, In the method of adding a salt of aluminum and zinc or a salt of aluminum and magnesium to water, these metals form hydroxides individually and form aluminum hydroxide, zinc hydroxide, and magnesium hydroxide. It becomes difficult to form double hydroxide, and as a result, the recovery efficiency of the fluorinated emulsifier is significantly reduced. In addition, in the method of adding a layered double hydroxide to the wastewater, these metals are eluted from the layered double hydroxide, and as a result, the recovery efficiency of the fluorinated emulsifier is significantly reduced.

In the present invention, the concentration of the fluorinated emulsifier to be recovered is preferably 1 ppm (based on mass, the same applies hereinafter) or more and 10 mass% or less, more preferably 10 ppm or more and 1 mass% or less, particularly preferably 50 ppm or less. The content is preferably at least 0.5% by mass. When the concentration of the fluorinated emulsifier is 1 ppm or more, there is no problem that the efficiency of capturing the fluorinated emulsifier by the layered double hydroxide in the recovered liquid is reduced. When the concentration of the fluorine-containing emulsifier is higher than 10% by mass, a simpler and more efficient method such as precipitation of the fluorine-containing emulsifier by changing pH can be used.

Substances that can become suspended solids and suspended solids, such as unagglomerated fluoropolymer fine particles, contained in the flocculated wastewater (hereinafter collectively referred to as SS components) are used to recover the fluorine-containing emulsifier and Although it does not adversely affect the recovery rate, it may hinder the regeneration of the fluorinated emulsifier from the generated layered double hydroxide, so remove it to 1% by mass or less before forming the layered double hydroxide. It is important to keep. The SS component in the coagulated wastewater is more preferably removed to 0.3% by mass or less, particularly preferably to 0.05% by mass or less. Examples of the substance that can become a suspended solid include a metal salt used for salting out and coagulation of a fluoropolymer and / or a substance that precipitates due to a change in pH of the coagulated wastewater.

As a method for removing the non-aggregated S S component such as a fluoropolymer, salting out by adding a metal salt containing a polyvalent metal cation to coagulate the S S component is effective. Specific examples of the metal salt include metal chlorides such as aluminum chloride, polyaluminum chloride, ferrous chloride, and ferric chloride.

Agglomerates generated by salting out should precipitate in the state containing APFO. Therefore, it is preferable to re-dissolve APFO from aggregates in water by adjusting the pH to 7 or more by adding sodium hydroxide and / or Z or a hydroxylating steam.

A common solid-liquid separation method can be used as a method for removing the SS component aggregates obtained by adding the above-mentioned metal chloride to the aggregated wastewater, particularly from filtration, decantation, centrifugation and thickener. It is more preferable to use one or more methods selected from the group consisting of: The filtration is also preferably performed under pressure. Further, it is preferable that the wastewater containing the aggregate is allowed to stand still, the aggregate is settled, and the supernatant is filtered to remove the aggregate. Thickeners or screw decanters are most preferable in terms of facility maintenance.

In the present invention, a trivalent metal (a metal that becomes a trivalent ion when ionized) and a divalent metal (a metal that becomes divalent ion when ionized) used to form the layered double hydroxide are used. Metal) has a range in which the pH of the ion of the trivalent metal forms a hydroxide overlaps with the range of the pH in which the ion of the divalent metal forms a hydroxide, or If the range of H is close, a layered double hydroxide can be formed. Examples of the divalent metal include beryllium, cadmium, cobalt, chromium (II), copper (II), iron (II), magnesium, manganese (II), nickel, lead, platinum, palladium, zinc, tin, and calcium. And the like. Examples of the trivalent metal include aluminum, bismuth, cerium, chromium (II), iron (III), gallium, indium, manganese (III), titanium, and thallium. In consideration of the effect on the environment and the availability, in the present invention, it is preferable to use one or two selected from magnesium and zinc as the divalent metal and to use aluminum as the trivalent metal. . Hereinafter, the case where the preferable divalent metal and trivalent metal are used will be described. In the present invention, as described above, the pH of the wastewater is 9 or more when the layered double hydroxide of aluminum and magnesium is used. Adjust to the following. Then, an aqueous solution in which the molar ratio of aluminum ion: magnesium ion is 1: 2 and the concentration of aluminum ion and magnesium ion is 0.0 lmo 1 ZL or more and 2 mo 1 ZL or less is added while stirring. I do. Aluminum: There is no problem with using any kind of raw material, but aluminum ion is preferably aluminum chloride, aluminum chloride hexahydrate, aluminum sulfate, or aluminum nitrate because of its availability. Aluminum chloride, aluminum chloride hexahydrate Japanese is more preferred. It is preferable to use magnesium chloride, magnesium chloride hexahydrate, magnesium nitrate hexahydrate, magnesium nitrate, magnesium oxide, magnesium sulfate, magnesium sulfate heptahydrate, and magnesium carbonate as a raw material for magnesium ions, and in particular, chloride Magnesium and magnesium chloride hexahydrate are preferred.

In the present invention, the pH of the wastewater is adjusted to 6 or more and 9 or less when the layered double hydroxide of aluminum and zinc is used as described above. Then, an aqueous solution in which the molar ratio of aluminum ion: zinc ion is 1: 2 and the concentration of aluminum ion and zinc ion is 0.0 lmo 1 / L or more and 2 mo 1 ZL or less is added with stirring. I do. Aluminum ion and zinc ion can be made of any raw material, but aluminum ion is preferably aluminum chloride, aluminum chloride hexahydrate, aluminum sulfate, or aluminum nitrate because of availability. More preferably, aluminum chloride and aluminum chloride hexahydrate are used. As a raw material for zinc ions, it is preferable to use zinc chloride, zinc nitrate hexahydrate, zinc oxide, zinc sulfate, and zinc sulfate heptahydrate, and zinc chloride is more preferable.

A mixed aqueous solution containing divalent and trivalent metal ions (hereinafter, referred to as a metal ion aqueous solution) is preferably used in an aqueous solution having a concentration of not less than 0.01 mO 17 and not more than 211101 ZL. If the metal ion concentration is lower than this, the amount of water increases when the required metal is added, and the total amount of the layered double hydroxide dissolved in the aqueous solution increases, which is not preferable. If the metal ion concentration is higher than this, since the metal ion aqueous solution is acidic, when forming the layered double hydroxide, a part of the aqueous solution is locally layered double hydroxide by adding the metal ion aqueous solution. When the pH is out of the optimum range for forming a product, the metal ion is not effectively used for forming a layered double hydroxide. However, even if an aqueous metal ion solution outside the above concentration range is once added, a layered double hydroxide can be synthesized by adding a metal ion aqueous solution having an appropriate concentration range again.

The amount of the layered double hydroxide to be added to the coagulated waste water of the fluoropolymer is as follows: 03 00659

12 The trivalent ions in the double hydroxide are at least 1 mol times and at most 30 mol times with respect to the fluorinated emulsifier, and the divalent ions are at least 1 mol time and at most 60 mol times with respect to the fluorinated emulsifier. preferable. The molar ratio of trivalent ions to divalent ions in the layered double hydroxide is 3

: 1: 1: 3 is preferable, and 1: 1 to 1: 3 is more preferable. By making the amount of the calcined layered double hydroxide 1 mole or more, the recovery rate of the fluorinated emulsifier is improved, and the amount of the layered double hydroxide to be added is within the above range. Since the ratio of the fluorinated emulsifier to the layered double hydroxide becomes too small, it is possible to eliminate the problem that the final regeneration efficiency of the fluorinated emulsifier is reduced. In addition, excessive use of the layered double hydroxide is not preferable from the viewpoint of increasing the load in the final wastewater treatment process due to the contained metal component.

In the present invention, it is preferable to stir the fluorinated emulsifier-containing wastewater or water when adding the metal ion aqueous solution to the fluorinated emulsifier-containing wastewater or water. The stirring method is not particularly limited, but is preferably a method that does not mechanically destroy the aggregate particles generated by the stirring. As a stirring blade of such a stirring device, a stirring blade capable of uniformly mixing the entire wastewater at a low rotation speed is preferable, and one type selected from the group consisting of a full zone blade, a max blend blade, and an anchor blade is preferable. G value during stirring at the stirring blade is preferably from 1 to 3 0 0 ^s-1, more preferably from 5 to 2 5 0 s ^1,

10-20 s- ¹ is most preferred. Here, the G value is a value derived by the following equation.

P

G =

V 'η

[Where 式 represents the stirring power (W), V represents the liquid volume (m ³ ), and 7? Represents the liquid viscosity coefficient (P a 's). ]

In the coprecipitation method and the ion exchange method, during the dropping of the metal ion aqueous solution, elimination of carbonate ions and Z or carbon dioxide gas present in the system is performed by publishing with an inert gas such as nitrogen gas or argon gas, or inert gas. After expelling the carbonate ion and Z or carbon dioxide gas with the above, the reaction vessel is preferably sealed. This is because the layered double hydroxide reacts with the carbonate ion and hinders the recovery of the fluorinated emulsifier. Publishing The flow rate of the inert gas is 0. I Nm ³ /! ~ 10 Nm ³ / h is preferred, 0. L Nm ³ Z l! ~ Δ Νπι ³ / !! is more preferable. The gas flow rate ^{^{0. 1 Nm 3 Z m 3}} · h or more and the carbonate ions in the system by removing becomes to be sufficiently performed, it is set to lower than or equal to ^{^{1 0 Nm 3 Zm 3 · h}} , vaporized The problem that the temperature of the aqueous solution decreases due to heat can be prevented.

In the reconstruction method, the firing of the layered double hydroxide is preferably performed at a temperature of at least 300 ° C. and less than 600 ° C., more preferably at least 400 and less than 500 ° C. At temperatures lower than this, the contained carbonate ions are not sufficiently desorbed, or it takes a long time for sufficient desorption. If the temperature is higher than this, the crystal structure of the layered double hydroxide collapses, which causes a reduction in the recovery efficiency of the fluorinated emulsifier.

The reaction is preferably carried out at a water temperature of 10 ° C. or more and 50 ° C. or less. If the water temperature is lower or higher than this, the recovery of the fluorinated emulsifier by the layered double hydroxide decreases. In particular, it is preferable to equip the reactor with a heating device because the recovery rate at a lower water temperature is significantly reduced.

In this way, a layered double hydroxide containing a fluorinated emulsifier between layers is generated in the coagulated wastewater. By separating the generated layered double hydroxide from the coagulated wastewater, the fluorinated emulsifier is separated from the coagulated wastewater. Can be recovered.

As a method for separating the layered double hydroxide from the coagulated wastewater, a well-known solid-liquid separation method can be used as appropriate, and in particular, at least one selected from the group consisting of filtration, decantation, centrifugation, and thickener It is more preferable to use the method described above. The filtration is also preferably performed under pressure.

Furthermore, the fluorinated emulsifier recovered in the form of being encapsulated in the layered double hydroxide is, for example, redissolved the layered double hydroxide with hydrochloric acid and / or sulfuric acid and a strong acid such as Z or nitric acid. It can be regenerated by a method such as extraction from a liquid with a water-insoluble organic solvent.

Mineral acids used in the present invention include hydrochloric acid, sulfuric acid, and nitric acid. In particular, hydrochloric acid is preferred. Hydrochloric acid is an acid having a boiling point of 85 ° C, and hydrochloric acid mixed into the extract can be easily removed from the extract by a subsequent concentration operation. As the fluorinated hydrocarbon in the present invention, those having 2 or 3 carbon atoms and containing one or more hydrogen atoms and one or more fluorine atoms are preferable. The boiling point of the fluorinated hydrocarbon is preferably 5 to 120 ° C, more preferably 10 to 80 ° C. When it is in this range, the fluorinated hydrocarbon can be easily distilled and recovered, which is preferable. As specific examples, and more preferably C ₃ HC 1 ₂ F ₅ and C _₃ H ₃ F 1 or more _{to 5} selected from the group consisting of.

C ₃ The _{_{_{HC 1 2 F 5, CF 3}}} CF 2 CHC 1 2, CC 1 F 2 CF 2 CHC 1 F, CC 1 F 2 CHFCC 1 F 2, CF 3 CHFCC 1 2 F, CF 3 CHC 1 CC 1 F ₂ is mentioned, and CF ₃ CF ₂ CHC 1 ₂ and CC 1 F ₂ CF ₂ CHC 1 F are most preferred.

Examples of C ₃ H ₃ F ₅ include CF ₃ CH ₂ CHF ₂ , CF ₃ CHFCH ₂ F, and CHF ₂ CH FCH F ₂ , with CF ₃ CH ₂ CHF ₂ being most preferred.

That is, the fluorine-containing hydrocarbon, and most preferably _{_{CF 3 CF 2 CHC 1 2,}} CC 1 F 2 CF 2 CHC 1 F and CF ₃ CH ₂ 1 or more selected from the group consisting of CHF _2.

C ₃ HC 1 ₂ F ₅ and C ₃ H ₃ F solubility of the fluorinated emulsifier for ₅ Jikurorome Tan, larger than black opening Holm, Ru can extract the fluorinated emulsifier in the smaller amount of medium. In addition, all are nonflammable and have low toxicity compared to conventional chlorinated hydrocarbons, and their boiling points and latent heats of vaporization are suitable for concentration and recovery operations. It is also chemically more stable than conventional chlorinated hydrocarbons and can be used repeatedly for concentration and recovery. Furthermore, when chlorinated hydrocarbons are used for the extraction of fluorinated emulsifiers, it is necessary to treat chlorinated hydrocarbons that dissolve in the aqueous phase, whereas the solubility of fluorinated hydrocarbons in water is chlorinated hydrocarbons. Such a process is not necessary because it is lower. In addition, there is an advantage that a clear liquid-liquid interface is formed between the aqueous phase and the fluorinated hydrocarbon phase more quickly than in the case of the chlorinated hydrocarbon after the extraction operation.

In the present invention, conventionally used devices and equipment can be used for the above-mentioned extraction operation of the fluorinated emulsifier. Examples of the extraction device include a batch extraction device, a cocurrent multiple extraction device, a countercurrent multistage extraction device, and a continuous countercurrent extraction device. The extraction conditions were as follows: at a temperature lower than the boiling point of the solvent, a layered double hydroxide containing a fluorinated emulsifier was added between the layers. The acid solution and the extraction solvent are mixed. Usually, 20 to 100% by mass, preferably 30 to 50% by mass of the extraction solvent is added to the acid solution. By using a larger amount of extraction solvent, the extraction rate of the fluorinated emulsifier is improved, but the throughput of the solvent in steps such as concentration is increased. Upon mixing, the extraction medium is dispersed in the acid solution by stirring, flowing, shaking, or the like. When the dispersion is performed so that the diameter of the droplets of the extraction medium is 0.1 mm or less, the extraction is completed in less than 10 minutes. After the extraction is completed, allow to stand to separate the aqueous and medium phases. Separation is required until the interface between the two phases is clear, but this is usually achieved in less than 10 minutes.

Next, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto. The concentration of APFO, perfluorooctanoic acid (hereinafter referred to as PFOA) or sodium perfluorooctanoate is determined by a high-performance liquid chromatography using a mixed solution of methanol and water as a solvent. It was measured using the Kuttle method. Species to be detected by this method is per full O Roo Kuta Noe Ichito (C ₇ F ₁₅ COO I).

[Example 1]

The concentration of APF〇 in the waste water after coagulation after emulsion polymerization of PTFE was 148 ppm when measured. The pH was adjusted to 10.0 by adding a 0.2 N aqueous solution of sodium hydroxide to this aqueous solution. The liquid temperature was 26 ° C. Then this solution 10 L (80 content 1. 48 g, 3. 43mmo 1) aluminum and mixed aqueous solution of chloride mug Neshiumu chloride [A 1 ³⁺ ion concentration 0. 075mo 1 ZL, Mg ²⁺ ions 0. Approximately 229 mL [A 1 total ion amount 17.2 mmo 1, Mg ²⁺ total ion amount 34.3 mmo 1] was dropped over 2 hours. During the dropping, stirring was continued using an anchor blade so that the G value became 100 s "" ¹ . Further, under the aqueous solution of metal ions, nitrogen gas was bubbled at a constant flow rate of 1 Nm ³ Zm ³ · h through the coagulated waste water to remove dissolved carbonate ions and carbon dioxide in the aqueous solution. During the dropwise addition, a 0.2 N aqueous sodium hydroxide solution was appropriately added dropwise to adjust the pH to 9.8 or more and 10.2 or less. Immediately after the dropwise addition of the mixed aqueous solution of aluminum chloride and magnesium chloride, the extremely pale milky liquid began to aggregate and began to form a white precipitate. Two hours after the start of the dropwise addition of the mixed aqueous solution, the formation of the precipitate was completed. When the stirring was stopped, the generated precipitate immediately settled, and completely settled in about 10 minutes. The supernatant was colorless and transparent. Average mouth of sediment The solution was collected by a 3 m-diameter membrane filter. The precipitate was dried together with the filter paper at 0 ° C. for 15 hours. The dry weight of the precipitate was 25.0 g. The dried precipitate was analyzed by differential thermogravimetric analysis (DTA), infrared absorption spectrum (IR), and XRD. was detected. From this, it was confirmed that this precipitate was PTFE and PFOA precipitated together with the layered double hydroxide. When the supernatant was analyzed, the concentration of APFO was 2 ppm, and thus the fixation rate of PFOA contained in the layered double hydroxide was 98.6%. Then added a 10 mass% hydrochloric acid 10 0 g to precipitate, After stirring at room temperature for 3 hours _{_{CF 2 C 1 CF 2 CHC 1}} F / CF 3 CF 2 CHC 1 2 mixed medium (molar ratio 55/45, 30 g of Asahi Glass 225 (hereinafter, referred to as AK 225) was added and shaken vigorously for 10 minutes. After allowing this solution to stand and separate into two phases, the upper aqueous phase contained 0.14% by weight of PFOA and the lower AK225 phase contained 4.03% by weight of PFOA. The recovery rate from the original coagulated wastewater was 85.1%.

[Example 2]

The same effluent after coagulation after PTFE emulsion polymerization as in Example 1 was added to this aqueous solution.

The pH was adjusted to 7.0 by addition of a 2N aqueous sodium hydroxide solution. The liquid temperature was 26 ° C. Then 10 L of this solution (8? 0 content 1.48 g, 3.43 mmo

1) Aqueous mixed solution of aluminum chloride and zinc chloride [A13 ⁺ ion concentration 0.075mo1 / L, Zn2 ⁺ ion 0.15mo1ZL] Approx.45.8mL [Total amount of A13 ⁺ ion 3. 43 mmol, Zn ²⁺ ion total amount 6.86 mmol 1] was dropped over 2 hours. During the dropping, stirring was continued using an anchor blade so that the G value became 100 s ^_1 . During the addition of the metal ion aqueous solution, the coagulated waste water was bubbled with nitrogen gas at a constant flow rate of 1 Nm ³ Zm ³ · h to remove dissolved carbonate ions and carbon dioxide in the aqueous solution. During the dropping, add 0.2 N sodium hydroxide aqueous solution appropriately to adjust the pH to 6.5 or more.

Adjusted to 7.5 or less. Immediately after the dropwise addition of the mixed aqueous solution of aluminum chloride and zinc chloride, the extremely pale milky liquid began to aggregate and began to form a white precipitate. Two hours after the start of the dropwise addition of the mixed aqueous solution, the formation of the precipitate was completed. When the stirring was stopped, the precipitate formed quickly settled out, and completely settled in about 10 minutes. The supernatant was colorless and transparent . The precipitate was collected by filtration through a membrane filter having an average diameter of 3 xm. When the supernatant was analyzed, the concentration of APFO was 2 ppm, and thus the fixation rate of PFOA contained in the layered double hydroxide was 98.9%. Then, 100 g of 10% by mass hydrochloric acid was added to the precipitate, and the mixture was stirred at room temperature for 3 hours. Then, 30 g of AK 225 was added, followed by vigorous shaking for 10 minutes. After allowing this solution to stand and separate into two phases, the upper aqueous phase contained 0.14% by weight PFOA and the lower AK225 phase contained 4.06% by weight PFOA. The recovery from the original flocculated wastewater was 85.8%.

[Example 3]

The same operation as in Example 1 was performed on the waste water after coagulation after the emulsion polymerization of PTFE as in Example 1 except that the pH was adjusted to 10.0 using potassium hydroxide instead of sodium hydroxide. . The fixed rate of PFOA contained in the layered double hydroxide was 97.5%, and when AK 225 was extracted in the same manner as in Example 1, the recovery from the original wastewater was 84.1%. .

[Example 4]

The same operation as in Example 2 was performed on the waste water after coagulation after the emulsion polymerization of PTFE as in Example 2, except that the pH was adjusted to 7.0 using potassium hydroxide instead of sodium hydroxide. . The fixed rate of PFO A contained in the layered double hydroxide was 98.6%, and when AK 225 was extracted in the same manner as in Example 1, the recovery from the original wastewater was 84.9%. there were.

[Comparative Example 1]

The same operation as in Example 1 was performed on the waste water after coagulation after the emulsion polymerization of PTFE as in Example 1 except that 30 g of trichloromethane was used as an extraction medium.Layered PFOA contained in double hydroxide The fixed rate was 98.1%, and the recovery rate from the original wastewater was 76.7% after trichloromethane extraction.

[Comparative Example 2]

The same operation as in Example 1 was performed on the waste water after coagulation after the emulsion polymerization of PTFE, except that 30 g of dichloromethane was used as the extraction medium. Fixation of PF OA contained in the layered double hydroxide The recovery was 97.8%, and the recovery from the original wastewater was 70.2% after dichloromethane extraction. [Example 5]

The same fixing operation as in Example 1 was performed on the waste water after coagulation after the emulsion polymerization of PTFE as in Example 1. The fixing rate of PFO A contained in the layered double hydroxide was 97.8%. AK 225 extraction was performed in the same manner as in Example 1 except that 100 g of 3% by mass sulfuric acid was used instead of 100% of 10% by mass hydrochloric acid as a mineral acid used for dissolving the layered double hydroxide. However, the recovery rate from the original wastewater was 83.7%

[Example 6]

The same fixing operation as in Example 1 was performed on the waste water after coagulation after the emulsion polymerization of PTF E as in Example 1. The fixed rate of PFOA contained in the layered double hydroxide was 98.1%. Extraction of AK225 was performed in the same manner as in Example 1 except that 100 g of 10% by mass of nitric acid was used instead of 100% of 10% by mass of hydrochloric acid as the mineral acid used for dissolving the layered double hydroxide. The recovery rate from wastewater was 84.5%.

[Example 7]

The pH was adjusted to 10.0 by adding a 0.2 N aqueous sodium hydroxide solution to distilled water. The liquid temperature was 26 ° C. Then the solution 1 L aluminum mixed aqueous solution of chloride magnetic Shiumu chloride [A 1 ³⁺ ion concentration 0. 075mo 1 ZL, Mg ²⁺ ions 0. 15mo 1 ZL] about 229 mL [A 1 ³⁺ ions total 1 I .2 mmo1, Mg ^{2 +} ion total amount of 34.3 mmo 13 was added dropwise over 2 hours. During the dropwise addition the G value using an anchor blade was continued stirring such that the 100 s ^1. During the addition of the metal ion aqueous solution, the coagulated wastewater was bubbled with nitrogen gas at a constant flow rate of 1 Nm ³ / m ³ · h to remove dissolved carbonate ions and carbon dioxide gas in the aqueous solution. During the dropwise addition, a 0.2 N aqueous sodium hydroxide solution was appropriately added dropwise to adjust the pH to 9.8 or more and 10.2 or less. Immediately after the dropwise addition of the mixed aqueous solution of aluminum chloride and magnesium chloride, the extremely pale milky liquid began to aggregate and began to form a white precipitate. Two hours after the start of the dropwise addition of the mixed aqueous solution, the formation of the precipitate was completed. When the stirring was stopped, the precipitate formed slowly settled. The precipitate was collected by filtration through a membrane filter having an average diameter of 3 m.

Next, PTFE water obtained by polymerizing TFE using APFO as an emulsifier PTFE is flocculated from the aqueous dispersion. Coagulated wastewater after separation (SS component: 400 ppm, APF〇 concentration: 148 ppm, pH 4.5). The precipitate was added and stirred at room temperature for 1 hour. When the stirring was stopped, the precipitate settled out slowly. The precipitate was collected by filtration through a membrane filter having an average diameter of 3 m. When the supernatant was analyzed, the concentration of APFO was 63 ppm, and therefore, the fixing ratio of PFOA contained in the layered double hydroxide was 57.4%. Then, 100 g of 10% by mass hydrochloric acid was added to the precipitate, and the mixture was stirred at room temperature for 3 hours. Then, 30 g of AK 225 was added, and the mixture was vigorously shaken for 10 minutes. After allowing this solution to stand and separate into two phases, the upper aqueous phase contained 0.05% by weight of PFOA, and the lower AK 225 phase contained 2.58% by weight of PFOA. The recovery from the original coagulated wastewater was 53.7%.

[Example 8]

The pH was adjusted to 10.0 by adding a 0.2 N aqueous sodium hydroxide solution to distilled water. The liquid temperature was 26 ° C. There, 1.82 g (17.2 mmo 1) of sodium carbonate was dissolved. Then a mixed aqueous solution of magnesium chloride and chloride Aruminiu arm to the dilute sodium carbonate solution 1 L [A l ³⁺ ion concentration 0. 075mo l ZL, Mg ²⁺ ions 0. 15mo 1 ZL] about 229 mL [A 1 ³⁺ ions The total amount was 17.2 mmo, and Mg ²⁺ ion total amount 34.3 mmo 1] was added dropwise over 2 hours. During the addition of the metal ion aqueous solution, the coagulated wastewater was bubbled with nitrogen gas at a constant flow rate of 1 Nm ³ Zm ³ · h to remove dissolved carbonate ions and carbon dioxide gas in the aqueous solution. During the dropwise addition the G value by using the anchor part is stirring was continued so that the 100 s ^1. During the dropwise addition, a 0.2 N aqueous sodium hydroxide solution was appropriately added dropwise to adjust the pH to 9.8 or more and 10.2 or less. Immediately after the dropwise addition of the mixed aqueous solution of aluminum chloride and magnesium chloride, the extremely pale milky liquid began to aggregate and began to form a white precipitate. Two hours after the start of the dropwise addition of the mixed aqueous solution, the formation of the precipitate was completed. When the stirring was stopped, the precipitate formed slowly settled. The precipitate was collected by filtration through a membrane filter having an average diameter of 3 m. The precipitate was calcined together with the filter paper at 400 ° C for 3 hours using an electric furnace. The weight of the precipitate after firing was 1.4.

On the other hand, PTFE is coagulated from an aqueous dispersion of PTFE obtained by polymerizing TFE using APFO as an emulsifier. Coagulated wastewater after separation (SS component is 400 ppm, To 10 L of an APFO concentration of 148 ppm, pH 4.5) was added the layered double hydroxide precipitate calcined above, and the mixture was stirred for 1 hour at room temperature. did. The precipitate was collected by filtration through a membrane filter having an average diameter of 3 / im. When the supernatant was analyzed, the concentration of APFO was 121 ppm, and therefore, the fixing rate of PFOA contained in the layered double hydroxide was 18.2%. Then, 100 g of 10% by mass hydrochloric acid was added to the precipitate, and the mixture was stirred at room temperature for 3 hours. Then, 30 g of AK 225 was added, followed by vigorous shaking for 10 minutes. After the solution was allowed to stand and separated into two phases, the upper aqueous phase contained 0.01% by weight of PFOA and the lower AK225 phase contained 0.85% by weight of PFOA. The recovery from the original flocculated wastewater was 17.4%.

[Example 9]

APFO was fixed to the layered double hydroxide in the same manner as in Example 1 with respect to the coagulated waste water after emulsion polymerization of PTFE as in Example 1. Fixed rate of P FO A contained in the layered double hydroxide is 8% 97., followed by the same method as in Example 1 except for using 30 g of C HF _₂ CH ₂ CF ₃ in place of AK 225 When the extraction operation was performed, the recovery rate from the original wastewater was 79.4%. Industrial applicability

According to the recovery method of the present invention, a fluorine-containing emulsifier can be economically recovered by a simple operation.

Claims

The scope of the claims

1. A mixed aqueous solution containing divalent metal ions and trivalent metal ions, and a fluorine-containing polymer containing a fluorine-containing emulsifier and containing 1% by mass or less of suspended solids and substances that can become suspended solids Is mixed with the waste water after the polymerization while maintaining the pH at which a layered double hydroxide of the divalent metal and the trivalent metal is formed, to form a layered double hydroxide containing a fluorinated emulsifier between the layers. Then, the layered double hydroxide separated from the wastewater is dissolved in a mineral acid, and the fluorinated emulsifier is extracted from the solution using a fluorinated hydrocarbon.

2. A mixed aqueous solution containing a divalent metal ion and a trivalent metal ion is added to an aqueous solution maintained at a pH at which a layered double hydroxide of the divalent metal and the trivalent metal is formed, and the layered double hydroxide is added. A product containing a fluorine-containing emulsifier, containing 1% by mass or less of suspended solids and substances that can become suspended solids, is added to wastewater after polymerization of a fluorine-containing polymer to produce a fluorine-containing product. A layered double hydroxide containing an emulsifier between layers is generated. Subsequently, the layered double hydroxide separated from the wastewater is dissolved in a mineral acid, and the fluorine-containing emulsifier is dissolved from the solution using a fluorine-containing hydrocarbon. A method for recovering a fluorinated emulsifier, characterized by extracting.

3. A layered complex formed by adding a mixed aqueous solution containing a divalent metal ion and a trivalent metal ion to an aqueous solution maintained at pH at which a layered double hydroxide of the divalent metal and the trivalent metal is formed. By firing the hydroxide, a layered double hydroxide in which anions contained therein are eliminated is generated, and the content of the solid containing a fluorine emulsifier and a substance capable of forming a suspended solid is 1 mass%. % Of the fluorinated polymer added to the wastewater after polymerization to form a layered double hydroxide containing a fluorinated emulsifier between layers, and then the layered double hydroxide separated from the wastewater is converted into a mineral acid. A method for recovering a fluorinated emulsifier, comprising dissolving and extracting the fluorinated emulsifier from the solution using a fluorinated hydrocarbon.

4. The fluorine-containing emulsifier according to any one of claims 1 to 3, wherein the divalent metal ion is one or two selected from a magnesium ion and a zinc ion, and the trivalent metal ion is an aluminum ion. Recovery method.

5. The mineral acid is at least one selected from the group consisting of hydrochloric acid, nitric acid and sulfuric acid. The method for recovering a fluorinated emulsifier according to any one of claims 1 to 4.

6. The fluorine-containing polymer is polytetrafluoroethylene, tetrafluoroethylene / ethylene copolymer, tetrafluoroethylene / propylene copolymer, tetrafluoroethylene Zpropylene, vinylidene fluoride copolymer, tetrafluoride modified styrene / hexafluoropropylene copolymer is tetrafluoroethylene modified styrene _{_{/ CF 2 = CFO (CF 2}} ) 2 CF 3 copolymer, and one or more selected from Po Rifu' fluoride according The method for recovering a fluorinated emulsifier according to any one of ranges 1 to 5.

7. The method for recovering a fluorinated emulsifier according to any one of claims 1 to 6, wherein the fluorinated emulsifier is ammonium perfluorooctanoate.

8. The method according to any one of claims 1 to 7, wherein the fluorinated emulsifier is recovered from waste water after polymerization of the fluorinated polymer having a concentration of the fluorinated emulsifier of 1 to 10% by mass. The method for recovering a fluorinated emulsifier according to the above.