Enhanced perfluorooctane acid mineralization by electrochemical oxidation using Ti3+ self-doping TiO2 nanotube arrays anode

Perfluorooctanoic acid (PFOA) is of increasing concern due to its worldwide application and extremely envi-ronmental persistence. Herein, we demonstrated the electrochemical degradation of PFOA with high efficiency using the Ti3+ self-doping TiO2 nanotube arrays (Ti3+/TiO2-NTA) anode. The fabricated Ti3+/TiO2-NTA anode exhibited vertically aligned uniform nanotubes structure, and was demonstrated good performance on the electrochemical degradation of PFOA in water. The degradation rate, total organic carbon (TOC) removal rate and defluorination rate of PFOA reached 98.1 %, 93.3 % and 74.8 %, respectively, after electrolysis for 90 min at low current density of 2 mA cm(-2). The energy consumption (7.6 Wh L-1) of this electrochemical oxidation system using Ti3+/TiO2-NTA anode for PFOA degradation was about 1 order of magnitude lower than using traditional PbO2 anodes. Cathodic polarization could effectively prolong the electrocatalytic activity of the anode by regenerating Ti3+ sites. PFOA molecular was underwent a rapidly mineralization to CO2 and F-, with only low concentration of short-chain perflfluorocarboxylic acids (PFCAs) intermediates identified. A possible electro-chemical degradation mechanism of PFOA was proposed, in which the initial direct electron transfer (DET) on the anode to yield PFOA free radicals (C7F15COO center dot) and hydroxyl radicals (center dot OH) oxidation were greatly enhanced. This presented study provides a novel approach for the purification of the recalcitrant PFOA from wastewaters.

Automated summary

This study demonstrated the electrochemical degradation of PFOA using Ti3+ self-doping TiO2 nanotube arrays (Ti3+/TiO2-NTA) anode, showing high efficiency and low energy consumption compared to traditional methods. The possible degradation mechanism of PFOA involved enhanced oxidation through direct electron transfer on the anode, leading to rapid mineralization into CO2 and F-.