Per-and polyfluoroalkyl substances (PFAS) in wastewater has become widespread and has attracted increasing attention due to its broad use in manufacturing and in industrial applications as flame retardants, and stain, grease and water repellants. However, if present in drinking water, PFAS are acutely toxic causing tumors, and kidney and liver diseases in humans as well as immunological effects in aquatic animals. Successful degradation of PFAS remains a key environmental challenge due to the extreme strength and stability of characteristic carbon-fluorine PFAS bonds. Therefore, developing an environmentally-friendly, mild and convenient approach for PFAS degradation is highly desirable. Herein, a facile and green method is developed, which shows extremely efficient defluorination of PFAS in the presence of vanadium carbide (V2C) nanosheets and H2O2 under physiological conditions. The as-prepared V2C layered nanostructures were exfoliated into nanosheets resulting in a significant enlargement of V2C surface area and reactive sites which facilitates the fast degradation rate of PFAS. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were selected as representative PFAS at initial concentrations of 50 µg/L. Defluorination reactions were conducted at pH 7 under aerobic conditions. PFOA and PFOS were first adsorbed to the carbon nanosheets, then defluorination occurred via singlet oxygen generation and the cooperative catalysis of the nearby vanadium nanosheets and hydroxyl radicals to effectively degrade PFAS. The V2C-H2O2 defluorination mechanism is so effective, that over 80% PFOS and over 45% PFOA defluorination was observed with less than 0.15 mg/mL V2C within 4 h of reaction at circumneutral pH and in the presence of dissolved oxygen. The findings from this work of high reactivity and efficiency of PFAS degradation employing V2C nanosheets coupled with the addition of a mild oxidant under environmentally relevant conditions can translate to other applications in contaminant removal, such as degradation of halogenated disinfection byproducts.

Simple and efficient defluorination of PFAS in wastewater by V2C nanosheets and H2O2

ACS Fall 2020 Virtual Meeting

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