Bio-FeMnOx integrated carbonaceous gas-diffusion cathode for the efficient degradation of ofloxacin by heterogeneous electro-Fenton process

[Display omitted] •A novel cathode composed of biogenic Fe-Mn oxides (BioFeMnOx) and carbon black.•The microbial cultivation time and the ratio of BioFeMnOx to carbon black essentially regulating the cathode performance.•The degradation of ofloxacin with BioFeMnOx was 2 times faster than with the chemogenic peer.•Main Possible reactive species including OH, O−2, and high-valent Fe/Mn.•Highly stable in 10 cycles of usage and effective to remove organic contaminants and toxicity of real wastewater. The efficiency of heterogeneous electro-Fenton is strongly influenced by the cathode composition. In this study, a novel cathode was fabricated with biogenic Fe-Mn oxides (Bio-FeMnOx) and carbon black for the first time. It was found that the cultivation time of the applied microbes can effectively regulate the crystalline and the metal valence of Bio-FeMnOx and consequently impact the efficiency of degrading ofloxacin. The degradation kinetic constant with Bio-FeMnOx was 2 times that of the chemogenic peer under the same conditions. The novel cathode worked very well in the broad pH range (pH 3–8). The presence of chloride in water can largely enhance the degradation kinetics of OFL possibly due to the formation of active chlorine species: up to 18 folds higher with 70 mM NaCl. Electron paramagnetic resonance and scavenger tests indicated the participation of OH, O−2, and active Fe/Mn species. The cathode presented a high stability with 95% of its degradation kinetic constant remained after 10 cycles of usage. Finally the applicability was validated with real livestock wastewater. The efficient removal of OFL, UV254, COD and TOC in real wastewater and its toxicity were achieved. Thus, the study provides a novel protocol to fabricate an efficient and stable cathode for heterogeneous electro-Fenton process.