Method of recovering fluorinated acid surfactants from adsorbent particles loaded therewith
The present invention provides a method of recovering a fluorinated acid surfactant or salt thereof from adsorbent particles to which said fluorinated acid surfactant has been adsorbed. The method comprises mixing adsorbent particles having adsorbed fluorinated acid surfactant or salt thereof with an alcohol and optionally an acid. The mixture is generally heated to cause esterification of the fluorinated acid surfactant or salt thereof with the alcohol so as to form an ester derivative of the fluorinated acid surfactant, distilling the mixture to form a distillate comprising the ester derivative, separating the ester derivative from the distillate and optionally feeding the remainder of the distillate back into the mixture.
1. Method of recovering a fluorinated acid surfactant or salt thereof from adsorbent particles to which said fluorinated acid surfactant has been adsorbed, said method comprising mixing adsorbent particles having adsorbed fluorinated acid surfactant or salt thereof with an alcohol and optionally an acid, causing esterification of said fluorinated acid surfactant or salt thereof with said alcohol so as to form an ester derivative of said fluorinated acid surfactant, distilling the mixture to form a distillate comprising the ester derivative, separating the ester derivative from the distillate and optionally feeding the remainder of the distillate back into said mixture, wherein said method does not include elution with water of the adsorbed fluorinated acid surfactant from the adsorbent particles before distilling the mixture such that the adsorbed particles are included in the mixture being distilled.
2. Method according to claim 1 wherein said adsorbent particles comprise carbon black or an anion exchange resin.
3. Method according to claim 1 wherein said fluorinated acid surfactant comprises a perfluorinated aliphatic acid or salt thereof.
4. Method according to claim 1 wherein said alcohol is an aliphatic alcohol having between 1 and 5 carbon atoms.
5. Method according to claim 1 wherein the amount and nature of said acid is selected such that the mixture has a pH of 2 or less.
6. Method according to claim 5 , wherein said acid is an inorganic acid.
7. Method according to claim 1 wherein said esterification is caused by heating said mixture.
8. Method according to claim 1 wherein said esterification is caused in the presence of water.
9. Method according to claim 1 further comprising converting said ester derivative into the corresponding fluorinated acid surfactant or a salt thereof.