David A. Reckhow
Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals that are extremely persistent in the environment. They classified as emerging contaminants and have been linked to impacts on the developmental, liver, immune, and thyroid systems, and are possible carcinogens. PFAS’ resistance to biodegradation and conventional oxidation processes make them one of the hardest chemicals to remove from water. With the discovery of PFAS in public water supplies, existing technologies are not capable of removing these recalcitrant contaminants to levels expected for the health of the public. Even in cases when conventional technologies can remove PFAS compounds, removal is often the separation of the contaminants from water to another phase for further treatment. Electrochemical treatment has been shown to not just transfer PFAS to other phases, but to destroy these compounds. These electrochemical systems have emerged as a novel water treatment technology which has been performed at both bench-scale and pilot-scale. This study explored the degradation of six of the most commonly regulated PFAS compounds on a scale that could be used in industrial applications. Two designs of Magnéli phase Ti4O7 anodes, solid and microporous which differ in flow pattern, were tested. These reactors were evaluated for the ability to destroy individual PFAS compounds at two voltages, two amperages, and with the addition of sodium sulfate to the base conductivity of sodium chloride. Previous Aclarity research designated the settings that were tested. The reactors were not capable of removing shorter-chain compounds, such as PFOA, PFHpA, and PFHxS, likely due to the hydrophilic functional groups. While PFOS, PFNA, and PFDA were easily removed due to their hydrophobic functional groups. The reactors removed the most contaminants at higher voltages and amperages. Further investigation is required to remove short-chain compounds with this large-scale reactor and to make the system more energy efficient.