Constructing Ti(III)-laden TiO2 nanotube arrays for electrochemical defluorination of levofloxacin

Fluorine-containing fluoroquinolones are cumulative toxins and pose a grave threat to health of animals and human beings, and an effective and feasible strategy to the defluorination by breaking C-F bond to decrease toxicity is in an urgent requirement. Herein, Ti(III)-laden TiO2 nanotube arrays (RTNA) were deliberately fabricated for electrochemical degradation and defluorination of levofloxacin (LVF). Characterizations verified that Ti(III) and oxygen vacancies were generated on RTNA via electrochemical reduction of TiO2 nanotube arrays (TNA). The degradation kinetics of LVF on RTNA (0.85 h-1) was increased by about 15 times as compared with that on TNA (0.06 h-1); the corresponding degradation and defluorination efficiencies by RTNA were also dramatically increased. Moreover, the effect of electrolyte on the defluorination efficiency suggests the signifi-cant role of sulfate; that is, abundant sulfate radical (SO4-center dot) was generated in the media of sodium sulfate during the electrochemical oxidation process, and it served as the dominant radical to break C-F bond for the defluorination of LVF, whereas it is not the case for hydroxyl radical (center dot OH) in sodium carbonate. The pathways and mechanisms of degradation and defluorination in electrolyte of sodium sulfate or carbonate were proposed and further confirmed the difference in the electrolyte-dependent degradation mechanisms.

Automated summary

Fluorine-containing fluoroquinolones, as cumulative toxins, pose a serious threat to the health of animals and humans. This study focuses on the electrochemical degradation and defluorination of levofloxacin (LVF) using Ti(III)-laden TiO2 nanotube arrays (RTNA). The results show that LVF degradation kinetics on RTNA is significantly improved compared to TiO2 nanotube arrays (TNA) due to the presence of Ti(III) and oxygen vacancies. The role of sulfate in electrolyte is found to be crucial for the defluorination efficiency, where sulfate radicals (SO4-center dot) play a dominant role in breaking the C-F bond of LVF.