Degradation of PFAS in aqueous systems by non-thermal plasma: Critical review of reactor configurations, influential factors and mechanistic pathways

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are persistent organic pollutants (POPs) that resist conventional water treatment due to the exceptional strength of carbon-fluorine bonds. Non-thermal plasma (NTP) has emerged as a promising destructive technology capable of generating a rich mixture of oxidative and reductive species that initiate PFAS defluorination at the gas-liquid interface. This review provides a comprehensive and critical assessment of recent progress in plasma-based PFAS degradation, with particular emphasis on bridging the gap between laboratory demonstrations and practical engineering applications. The discussion focuses on three interconnected dimensions. First, representative plasma reactor configurations are evaluated in terms of their discharge characteristics, plasma-liquid interfacial behavior, and the factors that govern reactive species delivery. Second, operational and environmental conditions, including electrical parameters, gas composition, water matrix constituents, and pollutant structure, are examined to identify their roles in determining degradation efficiency and energy consumption. Third, mechanistic insights into the formation, transport, and reactivity of key species are synthesized to clarify dominant pathways of PFAS decomposition and defluorination. Overall, this review highlights the significant potential of NTP for achieving direct PFAS destruction while identifying the scientific and engineering barriers that currently limit scale-up, such as interfacial mass transfer constraints, matrix-induced scavenging, and long-term reactor stability. By integrating mechanistic understanding with reactor design and process engineering considerations, this work outlines the key directions needed to advance NTP toward reliable, energy-efficient, and industrially deployable PFAS treatment solutions.