Process for the recovery of perfluorinated sulphonic acids from spent acid residue

Process for the recovery of perfluorinated sulphonic acid from a hydrocarbon residue, comprising the steps of (a) treating the residue with an alkyl ammonium salt of the perfluorinated sulphonic acid or a mixture of an alkyl ammonium salt of the perfluorinated sulphonic acid and the perfluorinated sulphonic acid in an amount being effective to liquefy the residue at ambient temperature; (b) contacting the liquefied residue with water at conditions to obtaining an aqueous extract containing the perfluorinated sulphonic acid and/or the alkyl ammonium salt of the perfluorinated acid into water; and (c) separating water from the aqueous extract to recover the perfluorinated sulphonic acid or the mixture of the acid and the ammonium salt.