METHOD FOR RECOVERING PERFLUOROSULFONIC ACID FROM WASTE ACID RESIDUE

PROBLEM TO BE SOLVED: To provide a method for recovering perfluorosulfonic acid easily from hydrocarbon residues. SOLUTION: In a method for recovering perfluorosulfonic acid from hydrocarbon residues, (a) the residues are treated with an alkylammonium salt of perfluorosulfonic acid or a mixture of an alkylammonium salt of perfluorosulfonic acid and perfluorosulfonic acid of the needed amount for liquefying the residues at ambient temperatures; (b) the liquefied residue is contacted with water under conditions where an aqueous extract containing perfluorosulfonic acid and/or alkylammonium salt of a perfluoro acid in water is obtained; and (c) water is removed from the aqueous extract to separate perfluorosulfonic acid or a mixture of the acid and ammonium salt.