Effects of Coexisting Anions on Adsorption of Perfluorooctane Sulfonates in Road Runoff

Abstract

Adsorptive removal of PFOS in the order of ng/l was investigated using model road runoff water containing NO3^-, PO4^3-, and Cr2O7^2- in different orders of concentration. Since PFOS is an anionic surfactant, effective removal by means of anion exchange can be expected. The removal efficiencies of PFOS with anion exchange materials were, however, lower than that with activated carbon, suggesting the difficulty of application of anion exchange materials. Removal of PFOS with activated carbon was effective not only under pure condition, but also under contaminated condition with coexisting anions in road runoff. Furthermore, PFOS removal was not inhibited by presence of NO3^-, PO4^3-, and Cr₂O7^2- which concentration were, 10 - 10⁴ times as high as PFOS, while adsorption of NO3^- and Cr2O7^2- competed with coexisting anion, resulting in a low removal efficiency. The results that a high removal efficiency of PFOS with activated carbon was obtained and the adsorptive removal performance was not affected by coexisting anions suggest that the hydrophobicity of PFOS become a significant factor when PFOS in the order of ng/l is removed from road runoff by means of adsorption.