Remediation of Perfluorooctane Sulfonate in Contaminated Soils by Modified Clay Adsorbent-a Risk-Based Approach

Perfluorooctane sulfonate (PFOS), which has numerous uses besides being an ingredient in the formulation of aqueous film-forming foams, is considered as an emerging pollutant of increasing public health and environmental concern due to recent reports of its worldwide distribution, environmental persistence and bioaccumulation potential. In an attempt to recommend a 'risk-based' remediation strategy, this study investigates the removal of PFOS from impacted waters and fixation of PFOS in impacted soils using a novel modified clay adsorbent (MatCARE (TM), patent number 2009905953). Batch adsorption tests demonstrated a much faster adsorption kinetics (only 60 min to reach equilibrium) and remarkably higher PFOS adsorption capacity (0.09 mmol g(-1)) of the MatCARE (TM) compared to a commercial activated carbon (0.07 mmol g(-1)). Treatability studies, performed by treating the PFOS-contaminated soils with the MatCARE (TM) (10 % w/w) and then incubating at 25 and 37 degrees C temperatures maintaining 60 % of the maximum water holding capacity of the soils for a period of a year, demonstrated a negligible release (water extractable) of the contaminant (only 0.5 to 0.6 %). The fixation of PFOS in soils by the new adsorbent was exothermic in nature. Soils with higher clay and organic matter content, but lower pH values, retained PFOS to a much greater extent. A cost analyses confirmed that the MatCARE (TM) could be an economically viable option for the 'risk-based' remediation of PFOS in contaminated waters and soils.