Electrochemical oxidation of perfluoroalkyl and polyfluoroalkyl substances: Mechanisms, implications, and challenges

Abstract

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have recently gained considerable attention due to their potential risks to human health and ecosystems. The response to these concerns has led to regulations and bans on legacy PFASs, such as perfluorooctanoic acid and perfluorooctane sulfonic acid. Thus, fluoride production has shifted toward short-chain PFASs and emerging fluorinated alternatives. Several technologies are available for PFAS degradation, among which electrochemical oxidation (EO) is a promising method to mineralize legacy PFASs and other emerging fluorinated alternatives in water treatment. This review provides an overview of the recent advancements in EO, comprehensively elucidating PFAS degradation mechanisms at the anode and exploring key factors that influence PFAS removal efficiency, such as anode materials as well as reactor designs and configurations. Moreover, the review elucidates the impact of operating conditions and parameters, including current density, electrolytes, pH, initial PFAS concentrations, and other coexisting pollutants, on the EO process. Finally, the constraints in the EO process are discussed when considering practical implementations, including undesired by-product generation, incomplete mineralization resulting in the accumulation of short-chain PFASs, and low PFAS concentrations in the natural environment leading to mass transfer limitations and low defluorination efficiency. Consequently, this review provides a perspective on potential solutions integrating the pre-concentration steps and EO process for effective PFAS remediation.