Degradation of perfluoroalkyl substances using UV/Fe⁰ system with and without the presence of oxygen

ABSTRACT

The wide presence of per- and poly-fluoroalkyl substances (PFAS) in the environment is a global concern, thus their degradation is an imminent task. In this study, oxidative and/or reductive degradation of three representative PFAS – perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonate (PFOS) was achieved using nanoscale zero-valent iron (Fe⁰ NPs) under ultraviolet (UV) light, both with and without the presence of oxygen. Higher degradation and defluorination rates were obtained for a longer chain PFNA compared to PFOA, and a higher removal of PFAS was achieved without the presence of O₂ compared to that with O₂. The degradation followed first-order reaction kinetics, and obtained the highest rates of 97.6, >99.9, and 98.5% without the presence of O₂ for PFOA, PFNA, and PFOS, respectively. The degradation rates increased with an increase in the nanoparticle concentrations in the range of 1–100 mg/L. In addition to fluoride ions, shorter chain perfluorocarboxylic acids (PFCAs) were detected as the main intermediates during PFAS degradation; PFHpS and 6:2 FTS were also detected during PFOS degradation. Hydroxyl radicals (·OH) and superoxide radicals (·O₂⁻) were not involved in the degradation of PFOA, but likely involved in the degradation of PFOS. Emerging contaminants PFAS degradation using the UV/Fe⁰ system is a cost-effective technology owing to the low cost and recyclability of Fe⁰ nanomaterials, low energy consumption in the system, and its capability to degrade PFAS both with and without the presence of oxygen. This technology can be potentially applied to treat PFAS-contaminated waters in the environment.

GRAPHICAL ABSTRACT

KEYWORDS:

• PFAS
• emerging contaminant
• degradation
• UVC light
• nZVI

Acknowledgements

The publication was developed under Assistance Agreement No. 83946001 awarded by the U.S. Environmental Protection Agency to Jia Liu. It has not been formally reviewed by EPA. The views expressed in this document are solely those of C.X. and J.L., and do not necessarily reflect those of the Agency. EPA does not endorse any products or commercial services mentioned in this publication. This research is also sponsored by the Start-up to Jia Liu, Southern Illinois University Carbondale. Thanks are given to Dr. Da Chen, Dr. Boyd M. Goodson, Dr. Yan Wu, and Dr. Max Ehren Gemeinhardt for their kind help.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by the US Environmental Protection Agency [grant number 83946001].