Highly efficient and stable FeIIFeIII LDH carbon felt cathode for removal of pharmaceutical ofloxacin at neutral pH

Schematic diagram for degradation of the antibiotic ofloxacine in heterogeneous EF with Fe II Fe III LDH-CF cathode. • Degradation rate of OFC with Fe II Fe III LDH-CF was 3 times higher than CF in EF. • Surface catalysis via ≡ Fe II /Fe III on LDH extended applied range of pH in EF. • OFC was completely removed in heterogeneous EF with Fe II Fe III LDH-CF at pH 7. • A plausible degradation pathway of OFC by • OH in heterogeneous EF was proposed. The traditional electro-Fenton (EF) has been facing major challenges including narrow suitable range of pH and non-reusability of catalyst. To overcome these drawbacks we synthesized Fe II Fe III -layered double hydroxide modified carbon felt (Fe II Fe III LDH-CF) cathode via in situ solvo-thermal process. Chemical composition and electrochemical characterization of Fe II Fe III LDH-CF were tested and analyzed. The apparent rate constant of decay kinetics of ofloxacin (OFC) with Fe II Fe III LDH-CF (0.18 min −1 ) at pH 7 was more than 3 times higher than that of homogeneous EF (0.05 min −1 ) at pH 3 with 0.1 mM Fe 2+ under same current density (9.37 mA cm -2 ). Also, a series of experiments including evolution of solution pH, iron leaching, OFC removal with trapping agent and quantitative detection of hydroxyl radicals ( OH) were conducted, demonstrating the dominant role of OH generated by surface catalyst via ≡ Fe II /Fe III on LDH cathode for degradation of organics as well contributing to high efficiency and good stability at neutral pH. Besides, formation and evolution of aromatic intermediates, carboxylic acids and inorganic ions (F – , NH 4 + and NO 3 – ) were identified by High-Performance Liquid chromatography, Gas Chromatography–Mass Spectrometry and ionic chromatography analyses. These findings allowed proposing a plausible degradation pathway of OFC by OH generated in the heterogeneous EF process.