Recovery of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) from dilute water solution by foam flotation

Abstract

Abstract The separation and recovery of surfactants, namely, Perfluorooctane sulfonate (PFOS) and Perfluorooctanoate (PFOA) was conducted using foam flotation process aided by metallic activators, including Al(III), Fe(III), La(III), Ca(II), Fe(II), and K(I). The PFOS removal efficiency followed the following decreasing order: Fe(III) ⩾ La(III) > Al(III) > Ca(II) > Fe(II) > K(I). Both PFOS and FPOA had a removal efficiency of >99% in the presence of 11.5 mM of Fe(III) in 5 min. High Fe(III) dose and elevated initial PFOS and PFOA concentration enhanced surfactant removal. PFOS and PFOA removal also increased with decreasing pH with maximum removal occurring at the lowest pH of 2.3 studied; whereas no significant removal was observed at pH ⩾ 6. At high pH, hydroxide ion (OH−) competed with PFOS or PFOA for Fe3+ and formed ferric hydroxo species that impeded surfactant removal. However, by adjusting the pH of the concentrate scum to 7.0, approximately 84–91% of PFOS and PFOA could be recovered. Foam flotation using ferric ion as activator, is a simple, fast, and cost-effective method of broad environmental-friendly applications for the separation and recovery of PFOS and PFOA from dilute water solutions.