Efficient degradation of tetracycline by heterogeneous electro-Fenton process using Cu-doped Fe@Fe2O3: Mechanism and degradation pathway

The degradation of tetracycline (TC) in aqueous environment has been studied by a novel heterogeneous electro-Fenton (HEEF) process using Cu-doped Fe@Fe2O3 core-shell nanoparticles (CFF) as catalyst loaded on the nickel foam as cathode. CFF was synthesized by a facile two-step reduction method and aging process, and characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy mapping (STEM-mapping), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The effects of operating parameters, such as the initial pH of solution, the mass ratio of Cu/Fe and aeration mode, were investigated. The prepared CFF exhibited rapid degradation (98.1% within 2 h) and high mineralization efficiency of TC (89.8% after 6 h). Furthermore, the degradation of TC in solution remained over 90% till the seventh cycle, indicating the high stability of CFF. The mechanism of the HEEF process catalyzed by CFF was also proposed. Additionally, based on the identification of main representative by-products, plausible pathways for the mineralization of TC in aqueous solution by center dot OH was speculated.