Method for recovering anionic fluorinated emulsifier
To provide a method for recovering an acid of an anionic fluorinated emulsifier with a high yield from a basic ion exchange resin having a nonionic surfactant physically adsorbed thereon and having the anionic fluorinated emulsifier adsorbed thereon. A method for eluting and recovering an acid of an anionic fluorinated emulsifier from a basic ion exchange resin having a nonionic surfactant physically adsorbed thereon and having the anionic fluorinated emulsifier adsorbed thereon, which comprises a step (1) of bringing the basic ion exchange resin into contact with a water-soluble organic solvent and a step (2) of recovering the acid of the anionic fluorinated emulsifier from the basic ion exchange resin from which the ionic surfactant is eluted in the step (1).
1. A method for recovering an anionic fluorinated emulsifier, which comprises eluting an anionic fluorinated emulsifier from a basic ion exchange resin having a nonionic surfactant physically adsorbed thereon and having the anionic fluorinated emulsifier adsorbed thereon and recovering it as an acid of the anionic fluorinated emulsifier, and which is characterized by comprising a step (1) of bringing the basic ion exchange resin into contact with a water-soluble organic solvent, and then a step (2) of recovering the acid of the anionic fluorinated emulsifier from the basic ion exchange resin from which the ionic surfactant is eluted in the step (1)
wherein the step (2) comprises a step (2-1) of bringing the basic ion exchange resin into contact with an aqueous inorganic acid solution and a water-soluble organic solvent.
2. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the step (2) comprises the above step (2-1), and a step (2-2) of separating the mixture into the basic ion exchange resin and a liquid phase and recovering the liquid phase, and a step (2-3) of recovering the acid of the anionic fluorinated emulsifier from the liquid phase, in this order.
3. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the step (2-1) comprises a step (2-1-1) of bringing the basic ion exchange resin into contact with the aqueous inorganic acid solution and then a step (2-1-2) of bringing the basic ion exchange resin into contact with the water-soluble organic solution.
4. The method for recovering an anionic fluorinated emulsifier according to claim 3 , which comprises the above step (2-1-1), then a step (2-1-1-2) of separating and recovering the basic ion exchange resin, and then the step (2-1-2).
5. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the water-soluble organic solvent is at least one member selected from the group consisting of an organic solvent having a nitrile group, an alcohol, a ketone and an ester.
6. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the aqueous inorganic acid solution is at least one member selected from the group consisting of an aqueous hydrochloric acid solution, an aqueous sulfuric acid solution, an aqueous nitric acid solution and an aqueous phosphoric acid solution.
7. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the water-soluble organic solvent is an organic solvent having a nitrile group, and the organic solvent having a nitrile group is at least one member selected from the group consisting of acetonitrile, propionitrile, butyronitrile and isobutyronitrile.
8. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the acid of the anionic fluorinated emulsifier is a fluorinated carboxylic acid.
9. The method for recovering an anionic fluorinated emulsifier according to claim 8 , wherein the acid of the anionic fluorinated emulsifier is a C 5-7 fluorinated carboxylic acid which may have from 1 to 3 etheric oxygen atoms.
10. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the basic ion exchange resin is a strongly basic ion exchange resin.
11. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the concentration of the aqueous inorganic acid solution is at least 5.0 mass %.
12. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the amount of the inorganic acid in the aqueous inorganic acid solution is within such a range that the acid of the anionic fluorinated emulsifier to be eluted/the inorganic acid is from 1/20 to 1.5/1 by the molar ratio.
13. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the ratio of the basic ion exchange resin to the aqueous inorganic acid solution is from 90/10 to 10/90 by the mass ratio.
14. The method for recovering an anionic fluorinated emulsifier according to claim 1 , wherein the ratio of the basic ion exchange resin to the water-soluble organic solvent is from 10/90 to 70/30 by the mass ratio.