Three-dimensional electro-Fenton oxidation of levofloxacin with a cerium doped-acidified red mud and biochar particle electrode

In this study, a cerium doped-acidified red mud and powder biochar particle electrode (ARM-PBC/Ce electrode) was fabricated with impregnation-coprecipitation-calcination method, and was employed in a three-dimensional electro-Fenton (3D/EF) system for levofloxacin (LEV) degradation. The preparation conditions of ARM-PBC/Ce electrode were optimized, and the electrode was characterized by various techniques. In contrast with RM, the ARM-PBC/Ce electrode had higher specific surface area, lower charge transfer resistance and excellent electrochemical performance, and the valence state conversions of Fe and Ce facilitated the generation of ⋅OH. Under the optimum degradation conditions (0.03 M Na₂SO₄ solution, initial pH 5, ARM-PBC/Ce dosage 0.4 g, applied voltage 6 V, and aeration rate 300 mL⋅min⁻¹), the removal efficiency of 10 mg·L⁻¹ LEV reached 95.82% in 60 min electro-Fenton oxidation, and the bacterial toxicity decreased significantly. The 3D/EF system demonstrated superior oxidation capability and energy efficiency compared to the 2D/EF system, and ⋅OH and ⋅O₂⁻ were the dominant active species in the electro-Fenton oxidation of LEV. The potential degradation pathways, mainly including decarboxylation, demethylation, piperazine ring opening and hydroxylation, were proposed based on the identification of intermediate products and active species. Moreover, the particle electrode remained remarkable stability and reusability after five cycles, suggesting its promising potential for the efficient treatment of LEV in wastewater.