Products, reactive species and mechanisms of PFOA degradation in a self-pulsing discharge (SPD) plasma reactor

Non-thermal plasma is a promising tool for novel technologies to treat water contaminated by recalcitrant pollutants. We report here on products, reactive species and mechanisms of the efficient degradation of perfluorooctanoic acid (PFOA) achieved with a self-pulsing discharge developed previously in our lab. Air or argon were used as plasma feed gas, ultrapure or tap water as aqueous medium. Identified organic intermediate products arise from chain-shortening and defluorination reactions, the latter achieving not only C–F to C–H exchange (hydro-de-fluorination), as reported in the literature, but also C–F to C–OH exchange (hydroxy-de-fluorination). In contrast with chain-shortening, yielding lower homologues of PFOA via selective cleavage of the C–C bond at the carboxylate group, defluorination occurs at various sites of the alkyl chain giving mixtures of different isomeric products. Plasma generated reactive species were investigated under all experimental conditions tested, using s...