Theoretical and experimental insights into the electrochemical mineralization mechanism of perfluorooctanoic acid.

The electrochemical mineralization mechanism of environmentally persistent perfluorooctanoic acid (PFOA) at a Ce-doped modified porous nanocrystalline PbO2 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), O2 and H2O 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 O2 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.