Removal of Perfluorooctanoic Acid from Water Using a Hydrophobic Ionic Liquid Selected Using the Conductor-like Screening Model for Realistic Solvents

The conductor-like screening model for realistic solventswas used to identify ionic liquids (ILs) to efficiently extractperfluorooctanoic acid (PFOA). The infinite dilution chemical potentialsof PFOA in 14 000 ILs were calculated and used as descriptors of thechemical affinities between the ILs and PFOA. Trihexyltetradecylphos-phonium pivalate ([P6,6,6,14][Piv]) was found to be a good IL forextracting PFOA because it gave a well-balanced combination of a strongchemical attraction for PFOA and useful physicochemical properties. Theresults of experiments indicated that [P6,6,6,14][Piv] could remove>99.9% of the PFOA in an aqueous solution. However, problematicemulsification of IL in the aqueous phase occurred at PFOA/IL molarratios <1.9-2.1, and this limited the PFOA removal rate to 80-91%. Theability of the used IL to extract PFOA was found to be partiallyregenerated by washing the IL with 1% NaOH, and the IL could be reused to extract PFOA with a removal rate decreased by similar to 10%in each cycle.