Energy-Positive Removal of Norfloxacin in the Bioelectro Fenton System with Nanoferrite-Based Composite Electrodes

The present work investigated the degradation of norfloxacin (NOR) antibiotics as a model pollutant in the bioelectro-Fenton (BEF) system. The BEF was catalyzed by three types of composite electrodes incorporated with nanoferrites, that is, Fe3O4, Fe3O4@MoS2, and CuFe2O4 as heterogeneous Fenton catalysts at three pH levels (3, 7, and 9). The synthesized materials were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The anode chambers were inoculated with anaerobic digestion (AD) sludge and marine sludge. The highest current and power output were evident in a reactor (BEF 2) inoculated with marine sludge, and this phenomenon influenced the NOR removal as well. Among the composite catalysts, Fe3O4 exhibited the best performance in terms of NOR degradation (ca. 90%), followed by CuFe2O4 and Fe3O4@MoS2 (82–87 and 80–86%, respectively) at pH 3 using AD sludge and marine sludge. The BEF system with all composite electrodes produced negligible concentration of residual iron, which was far below the permissible limit of China and European Union. The microbial community analyses showed Proteobacteria, Firmicutes, and Actinobacteria as the dominant phyla in both inocula. The results indicated that using the BEF system with composite electrodes is a promising approach to not only remove biorecalcitrant pollutants but also generate more bioelectricity.

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