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A composite catalyst nZVI/Co/N-CNT was prepared by loading nano-zero-valent iron-cobalt bimetals on porous materials (N-CNT) by a liquid-phase reduction method. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and the X-ray electron spectroscopy (XPS) characterization method were used to characterize and analyze the structure of the prepared samples. The effects of different factors on the removal of levofloxacin(LOF) by the nZVI/Co/N-CNT activated persulfate (PMS) system were compared. The results show that the removal rate of LOF can reach 98.14% when the LOF concentration is 20 mg/L, the iron-cobalt molar ratio is 5:1, the dosage of nZVI/Co/N-CNT is 0.3 g·L−1, and the dosage of PMS is 0.2 g·L−1 and pH = 7. Free radical quenching experiments showed that SO4−· and ·OH coexisted during the reaction, and ·OH was the main active species, and the possible removal mechanism of LOF was speculated.

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BACKGROUND: Elements of transition metals have a distinct non-nuclear electronic structure, and modifying electrodes with transition metals can increase electrocatalytic activity. Due to its low cost and high electrical conductivity, graphite felt (GF) is frequently used as the carbon base material for modified electrodes. GF was treated with KOH and subsequently loaded with the bimetal Fe and Co to create a cathode (Fe@Co/GF) with enhanced catalytic activity in this study.RESULTS: Under optimal experimental conditions (initial levofloxacin (LEV) concentration of 30 mg L −1 , electric voltage of 8 V, GF thickness of 3 mm, an aeration rate of 3 × 4.5 L min −1 , Na 2 SO 4 concentration of 0.05 mol L −1 , initial Fe 2+ concentration of 0.1 mmol L −1 , initial pH of 3, KOH activation temperature of 900 °C and Fe@Co ratio of 1:3), the LEV elimination rate was 90.38% and the mineralization rate was 88.53% within 160 min. Compared to the GF cathode, both the total LEV degradation rate and the total mineralization rate increased by approximately 20%. When Fe@Co/GF was used as the cathode in an electro-Fenton (EF) system without an applied iron source, the Fenton reaction could still occur. In addition, Fe@Co/GF also promoted the degradation of ciprofloxacin in the EF system. CONCLUSION: According to morphological and other statistical data, the modified cathode has a larger specific surface area, larger pores and a greater number of active sites. Electrochemical performance measurements indicate that the modified cathode is more responsive to current. Fe@Co/GF cathode was simple to prepare and contributed significantly to the LEV removal process when used as the cathode in an EF system, thereby decreasing the LEV degradation time.

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