Poly - and perfluoroalkyl substances (PFASs) have attracted increasing concern because of their widespread occurrence and possible toxicity, with perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) being two model compounds commonly present and of great interest. Our recent study demonstrated effective electrochemical oxidation of PFOA and PFOS on Magnéli phase Ti4O7 electrode leading to their mineralization. While Ti4O7-based anodic oxidation may be a promising technology to treat PFASs in water, the process may also generate undesirable chlorinated byproducts in the presence of chloride, including chlorate, perchlorate and organic chlorines, which has to be taken into consideration when the process is applied for PFAS removal. Our on - going study focuses on a systematic investigation into the dynamics and mechanisms of chlorinated byproducts formation during electrochemical degradation of PFASs on Ti4O7 anode under a variety of different water and operation conditions, including chloride concentrations, current density, and the presence and absence of common natural water constituents and co-existing contaminants. The reaction behaviors on different anodes will also be examined for comparison. The rates of both organic and inorganic chlorinated byproducts formation and disappearance will be examined at different time scales relative to PFASs degradation. The mechanisms of byproducts formation will be investigated by intermediate identification and characterization of reaction systems perturbed by different probe chemicals. Means to mitigate byproducts formation will be explored and tested. The results will help with design of a Ti4O7-based anodic oxidation process for PFAS treatment to achieve optimum efficiency and minimum byproduct formation, as well as development of new electrode materials to avoid byproducts formation during anodic oxidation.

Formation of chlorinated byproducts during electrochemical oxidation of perfluoroalkyl acids in the presence of chloride

256th National Meeting (2018)

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