Efficient antibiotic tetracycline degradation and toxicity abatement via the perovskite-type CaFexNi1-xO3 assisted heterogeneous electro-Fenton system

As one of the emerging contaminants, antibiotics are posing a great threat to the human health and environment, which requires effective treatment methods. Heterogeneous electro-Fenton is a promising technique for organic contaminant elimination, but preparation of an appropriate heterogeneous electro-Fenton catalyst still remains challenging. In this work, the feasibility of perovskite-type CaFe_xNi_1-xO₃ as heterogeneous electro-Fenton catalyst for tetracycline (TC) removal and toxicity abatement has been explored. It was found that, among the examined CaFe_xNi_1-xO₃ catalysts with different Ni doping amount, CaFe_3/4Ni_1/4O₃ exhibited the best performance, achieving 92.1 % TC removal within 30 min without pH adjustment in the presence of 0.05 M Na₂SO₄ electrolyte. Choosing Cl⁻-containing electrolyte enabled further improvement towards TC elimination. In addition, the CaFe_3/4Ni_1/4O₃ based heterogeneous electro-Fenton system presented other advantages including good recyclability and universal applicability, and significant toxicity reduction (verified via both ECOSAR simulation and soybean germination test). The TC degradation pathways were elucidated through identification of intermediate products and DFT calculations. Mechanism investigations revealed that there existed a strong synergy between Fe and Ni, and ·OH and ·O₂⁻ played the primary roles in the system while ¹O₂ played an auxiliary role. This study presented a promising heterogeneous electro-Fenton catalyst for degradation of antibiotics such as tetracycline.