Metal activators enhanced the foam separation of perfluorooctanonic surfactants.
The foam separation efficiency follow the order: Fe(III) ⩾ La(III) > Al(III) > Ca(II) > Fe(II) > K(I).
Perfluorooctanonic surfactants had >99% removal efficiency using 11.5 mM of Fe(III) in 5 min.
Acidic pH, e.g., 2.3 favored the foam separation of perfluorooctanonic surfactants.
Adjusting the pH of the foamate to 7.0, ca. 84–91% of perfluorooctanonic surfactants were recovered.