Theoretical
and Experimental Insights into the Electrochemical
Mineralization Mechanism of Perfluorooctanoic Acid
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Abstract
The
electrochemical mineralization mechanism of environmentally
persistent perfluorooctanoic acid (PFOA) at a Ce-doped modified porous
nanocrystalline PbO<sub>2</sub> film anode was investigated using
density functional theory (DFT) simulation and further validated experimentally.
The potential energy surface was mapped out for all possible reactions
during electrochemical mineralization reaction of PFOA. The hydroxyl
radical (·OH), O<sub>2</sub> and H<sub>2</sub>O took part in
the mineralization process and played different roles. The ·OH-initiated
process was found to be the main degradation pathway, and the existence
of O<sub>2</sub> obviously accelerated the degradation process of
PFOA in aqueous solution. On the basis of the DFT calculations, an
optimal electrochemical mineralization mechanism of PFOA was proposed,
which involved the electronic migration, decarboxylation, radical
reaction, hydrogen abstraction reaction, and radical fragmentation
reaction. The proposed mechanism was verified by the dynamics and
intermediate determination experiments. Furthermore, the observed
·OH concentration showed that the electrolysis system could produce
enough ·OH for PFOA mineralization process, indicating that the
proposed ·OH-initiated process derived from DFT calculations
was feasible. These insightful findings are instrumental for a comprehensive
understanding of the mineralization of PFOA in the electrolysis system