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Peroxidase‐mediated degradation of perfluorooctanoic acid
Author(s) -
Colosi Lisa M.,
Pinto Roger A.,
Huang Qingguo,
Weber Walter J. Jr.
Publication year - 2009
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1897/08-282.1
Subject(s) - chemistry , perfluorooctanoic acid , hydrogen peroxide , decarboxylation , horseradish peroxidase , peroxidase , fluoride , reaction rate constant , peroxide , hydroxylation , aqueous solution , degradation (telecommunications) , photochemistry , catalysis , organic chemistry , inorganic chemistry , enzyme , kinetics , telecommunications , physics , quantum mechanics , computer science
Concentrations of aqueous‐phase perfluorooctanoic acid (PFOA), a representative perfluorinated aliphatic (PFA) compound, are shown to be reduced effectively via reaction with horseradish peroxidase (HRP), hydrogen peroxide, and a phenolic cosubstrate (4‐methoxyphenol). Reaction rate profiles are pseudo–first order, yielding an apparent best‐fit removal rate constant of k 1 = 0.003/min ( r 2 = 0.96, n = 14). Approximately 68% depletion of the parent compound and 98% depletion of its related acute aquatic toxicity are achieved in 6 h. Because no PFOA removal is observed in the absence of cosubstrate and/or following consumption thereof, we conclude that radical intermediate species generated during reaction between HRP and 4‐methoxyphenol mediate nonspecific depletion of PFOA and that these intermediates may be sufficiently reactive to sever the extremely stable C–F bonds of PFOA. These results are consistent with measurements of reaction by‐products, including fluoride ion and various aliphatic species of shortened chain length. Based on these findings, we conclude that PFA degradation may occur via one of two mechanisms: Kolbe decarboxylation followed by stepwise conversion of–CF 2 units to CO 2 and fluoride ion, or radical abstraction from a double bond with subsequent fragmentation. Our results indicate that under appropriate conditions, enzymatic degradation may comprise a natural transformation pathway for PFAs. Moreover, we anticipate that appropriately engineered enzymatic processes may hold promise for treatment of PFOA‐contaminated waters. This, to the best of our knowledge, is the first report to substantiate the efficacy of HRP‐catalyzed reactions for contaminant removal via degradative reactions versus polymerization reactions.