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

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 (0.18min(-1)) at pH 7 was more than 3 times higher than that of homogeneous EF (0.05min(-1)) at pH 3 with 0.1mM Fe(2+) under same current density (9.37mA 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 identical with 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(-), NH4(+) and NO3(-)) 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.