Highly efficient and stable FeFe 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 FeFe-layered double hydroxide modified carbon felt (FeFe LDH-CF) cathode via in situ solvo-thermal process. Chemical composition and electrochemical characterization of FeFe LDH-CF were tested and analyzed. The apparent rate constant of decay kinetics of ofloxacin (OFC) with FeFe LDH-CF (0.18 min) at pH 7 was more than 3 times higher than that of homogeneous EF (0.05 min) at pH 3 with 0.1 mM Fe under same current density (9.37 mA cm). 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/Fe 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 and NO) 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.