Ofloxacin degradation by Fe3O4-CeO2/AC Fenton-like system: Optimization, kinetics, and degradation pathways

In this work, ofloxacin degradation was investigated by using Fe3O4-CeO2/activated carbon (AC) as heterogeneous Fenton catalyst. Response surface methodology based on central composite design (CCD) was used to investigate individual and interactive effects of three parameters on the ofloxacin degradation, i.e., solution pH, H2O2 dosage and initial ofloxacin concentration. Optimal conditions were determined to be pH 3.3, H2O2 20.0 mM, ofloxacin 12.0 mg L-1 and catalyst 0.5 g.L-1. The ofloxacin degradation efficiency and the total organic carbon (TOC) removal was 95% and 54% within 60 min, respectively. The obtained results agreed well with the modeling prediction (R-2 = 0.9826, and Adj-R-2 = 0.9783). The kinetic analysis implied that the reaction followed first-order kinetic with R-2 = 0.9965. According to mass spectrometry qualitative analysis, eight intermediates of ofloxacin were detected and two possible degradation pathways were proposed. The catalyst still showed degradation efficiency of 82.4% toward ofloxacin after five runs.