Screening ionic liquids for efficiently extracting perfluoroalkyl chemicals (PFACs) from wastewater

Abstract

Liquid-liquid extraction (LLE) using ionic liquids (ILs)-based methods to remove perfluoroalkyl chemicals (PFACs), such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), from wastewater, is an important strategy. However, the lack of physicochemical and LLE data limits the selection of the most suitable ILs for the extraction of PFACs. In this work, 1763 ILs for PFACs extraction from water were systematically screened using COSMOtherm to estimate the infinite dilution activity coefficient (lnγ^∞)of PFOA and PFOS in water and ILs. To evaluate the accuracy of COSMOtherm, 8 ILs with various lnγ^∞ values were selected, and their extraction efficiency (E) and distribution coefficient (D_exp) were measured experimentally. The results showed that the predicted lnγ^∞ decreased as the increase of experimental extraction efficiency of PFOA or PFOS, while the tendency of predicted distribution coefficient (D_pre) was consistent with the experimental (D_exp) results. This work provides an efficient basis for selecting ILs for the extraction of PFACs from wastewater.

Keywords: Conductor-like screening model for real solvents (COSMO-RS); Ionic liquids; Liquid-liquid extraction; Perfluorooctane sulfonic acid (PFOS); Perfluorooctanoic acid (PFOA).