Enhanced superoxide radical production for ofloxacin removal via persulfate activation with Cu-Fe oxide

Cu-Fe composite oxides with different Cu:Fe ratios were synthesized by a hydrothermal method and investigated as a heterogeneous catalyst for persulfate activation. The obtained samples exhibited much higher activity than CuFe2O4 for the degradation and mineralization of ofloxacin with persulfate, and the optimized Cu:Fe ratio was 1:1 (CuFe1). The results of catalyst characterization and electron paramagnetic resonance analysis indicate that the activities of the catalysts for ofloxacin degradation and superoxide radical (O2−) production are highly positively correlated with their redox ability. The removal efficiencies of ofloxacin in the presence of different scavengers further demonstrate that O2− is the dominant reactive species in this process, which is quite different from previous studies. It is suggested that CuFe1 with higher oxidation ability could weaken the SO bond of adsorbed persulfate, thus promoting the decomposition persulfate into O2−. Finally, the possible degradation pathway of ofloxacin was proposed according to the liquid chromatography−mass spectrometry result.