Adsorption and detoxification of poly- and perfluoroalkyl substances (PFAS) with hydrophobic bentonite clays

PFAS is a class of emerging contaminants, and their exposure has been linked to many deleterious health effects which pose major threats to public health. Dietary intake has been recognized as the principal source of PFAS exposure to animals and humans while drinking water is the major route. Given the persistent nature of PFAS in water and the environment, this study was designed to provide effective and potentially scalable strategies to mitigate PFAS toxicity using organoclays. The study has been designed to investigate and characterize the adsorption behavior of four PFAS (PFOA, PFOS, PFBS, and GenX) onto active binding surfaces of four commercially available organoclay products called ENVIRO-TROL™ (ENT), ORGANO-TROL™ (OT2), and AGRI-TROL™ (ATB and ATM). This study evaluates key PFAS binding markers for these organoclays including Gibbs free energy (∆G), adsorption capacity, and binding affinity for PFAS. These parameters served as indicators for predicting the bioavailability of PFAS under the experimental settings. Additionally, the proof-of-concept for the protective role of the organoclay in PFAS-mediated toxicity was evaluated using living organisms (Hydra vulgaris and Lemna minor) as sensitive ecotoxicology models. The results showed varied adsorption behavior from pH 2 to 10. All the organoclays demonstrated the highest PFAS binding at pH 2. OT2 showed the highest adsorption for PFOA (78%), PFOS (47%), GenX (54%), and PFBS (66%), followed by ATM, while ATB and ENT showed slightly lower binding. Isotherm data indicated that all the binding followed a Freundlich model with high adsorption capacity. Moreover, they were all thermodynamically favorable with ∆G values ranging from - /20.00/ to - /30.96/kJ/mol. In vivo data indicated severe toxicity of PFAS exposure to hydra vulgaris and Lemna minor; however, inclusion of the organoclays into the aqueous media of hydra and lemna resulted in over 90 to 100% protection from PFAS toxicity. This finding implies that these organoclays may be used in environmental remediation applications to adsorb PFAS from polluted water and bind and detain it in contaminated soil.