Catalytic ozonation of ciprofloxacin using MnO2/biochar nanohybrid integrated with peroxymonosulfate in a circulating fluidized bed reactor

Abstract

The objective of this study is to prepare a biochar catalyst loaded with manganese (IV) oxide to enhance the degradation of ciprofloxacin (CIP) antibiotic in the catalytic ozonation process (COP) and COP/peroxymonosulfate (PMS) process. XPS, FE-SEM, EDS, TEM, XRD, FTIR, and N₂ adsorption-desorption isotherms were used to characterize the β-MnO₂/biochar catalyst. According to N₂ adsorption-desorption isotherms, activation at 800 °C in 120 min with a weight ratio of 1:1 (KOH/BC) fabricates biochar with a high specific surface area (1149 m².gr⁻¹). The results of the characterization techniques confirmed the successful loading of β-MnO₂ nanorods on the porous biochar substrate. D-optimal method to save time and cost of experiments. Based on the results, the optimal conditions in the COP were obtained with the catalyst amount of 0.15 g L⁻¹, initial CIP concentration of 20 ppm, input ozone flow rate of 1.25 mg min⁻¹, and pH = 7. The degradation efficiencies of CIP in 30 min for COP and sole ozonation process (SOP) were 98.7 and 48.8 %, respectively. PMS was used, to improve the degradation rate and mineralization efficiency of the processes. The results showed that the degradation rate increased from 0.120 min⁻¹ to 0.219 min⁻¹ in the presence of PMS. Measuring the COD showed the high performance of the COP/PMS process compared to COP and SOP with a mineralization efficiency of 78, 56.4, and 17.1 % within 30 min, respectively. The reactive oxygen species involved in the mentioned processes were identified by inorganic and organic scavengers. According to the results, the ^•OH had the largest contribution to these processes. The circulating fluidized bed reactor showed better performance compared to the semi-continuous reactor due to better mixing conditions. The β-MnO₂/BC_1–800-120 catalyst could maintain its catalytic activity after three cycles of use in the COP, which shows its high stability.