Enhancing tetracycline degradation in a dual-cathode electro-Fenton system using MoS₂ as an efficient co-catalyst: Mechanistic, DFT analysis, and toxicity assessment

Tetracycline is a commonly used antibiotic that poses potential ecological risks. To improve the degradation efficiency of tetracycline, a novel dual-cathode electro-Fenton system was developed: one cathode consists of Acetylene Black-PTFE (ABP), while the other is a CoFe 2 O 4 /MoS 2 (CFOM) composite. Compared with conventional electro-Fenton processes, the CFOM@ABP dual-electrode system enables in-situ H₂O₂ generation and facilitates rapid redox cycling of Fe(II)/Fe(III) and Co(II)/Co(III). The XRD, SEM, Raman spectra, FTIR spectra and XPS spectra were used to characterize the CFOM. The effects of recombination ratios, pH values, current densities and coexisting ions on degradation efficiency were investigated. Under optimal conditions, the CFOM system achieves 97.6% tetracycline removal within 60 minutes. The CFOM@ABP system was also tested for the removal of other organic pollutants, achieving removal rates of 90.5%, 92.6% and 99.3% for Metronidazole, Ciprofloxacin, and Rhodamine B, separately. After five consecutive cycles, the tetracycline removal rate remains at 89.7%, demonstrating excellent reusability and adaptability to varying conditions. Through the electron spin resonance and free radical quenching experiments, the mechanism of CFOM catalyzing heterogeneous Fenton system was proposed. The liquid chromatography-mass spectrometry was utilized to identify the intermediate products and propose potential degradation pathways. The ecological toxicity of most intermediates is significantly reduced or even eliminated, indicating minimized environmental impact. This dual-electrode electro-Fenton system exhibits broad environmental adaptability, superior stability, reusability, and remarkable reduction in bio-toxicity.