Perfluorooctanesulfonate (PFOS) is a compound that has wide applications with an extremely long half-life in the environment, the potential to bioaccumulate and induce adverse effects to ecosystems. Little is known about the degradation of PFOS in the environment. We investigated the degradation of PFOS by laccase-induced enzyme catalyzed oxidative humification reactions (ECOHRs) using 1-hydroxybenzotriazole (HBT) as a mediator under environmentally relevant conditions. Approximately 59% of PFOS was transformed over 162 days of incubation. The reaction followed the pseudo-first order with reaction rate constant of 0.0043/d (r2 = 0.86). Using differential absorption spectra and theoretical simulation, we confirmed the interaction between Cu2+/Mg2+ and PFOS, and proposed that Cu2+ and Mg2+could serve as a bridge to bring the negatively charged PFOS and laccase to proximity, thus increasing the chance of radicals that are released from laccase to reach and react with PFOS. In addition, DFT modeling showed that PFOS complexation to the metal ions could unlock its helical configuration, and decrease the C-C bond energy of PFOS. These changes allow the attack of PFOS C-C backbone by radicals become easier. Based on products identification, it is proposed that direct attack of perfluoroalkyl acids by HBT radical initiated the free radical chain reaction processes and led to the formation of fluoride and partially fluorinated compounds. These results suggest that ECOHRs is a potential pathway by which PFOS could be degraded in the environment, and it may make a viable approach to remediate PFOS contamination via amendment of appropriate enzymes and mediators.

Degradation of perfluorooctanesulfonate in a laccase-mediator system

256th National Meeting (2018)

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