Catalytic ozonation of sulfamethoxazole over Fe₃O₄/Co₃O₄ composites

In this study, Fe₃O₄/Co₃O₄ composites were prepared and applied in the catalytic ozonation of sulfamethoxazole (SMX). Various parameters including initial solution pH, Fe₃O₄/Co₃O₄ composites dose, O₃ dose and SMX concentration were investigated. Results showed that Fe₃O₄/Co₃O₄ composites could significantly improve the mineralization of SMX by catalytic ozonation system and a synergic effect between Fe₃O₄ and Co₃O₄ was observed. Only about 16% total organic carbon (TOC) could be removed in 60 min by single ozonation under the condition of 20 mg/L SMX, 6.0 mg/min O₃, pH 5.1 and room temperature, While in the presence of 0.10 g/L Fe₃O₄/Co₃O₄ composites at the same conditions, 60% TOC removal were obtained by catalytic ozonation process. SMX could be degradation by O₃ rapidly and the removal was not significantly affected by the changing parameters. However, those operating parameters exerted different effects on SMX mineralization. Furthermore, the generation of hydroxyl radicals (OH) and the utilization efficiency of O₃ would increase with the addition of Fe₃O₄/Co₃O₄ composites. The quenching experiments indicated that OH might account for the enhancement of SMX mineralization and the mechanism of catalytic ozonation was proposed. Additionally, the intermediates were detected by using a high-performance liquid chromatography-mass spectrometry (LC-MS), from which some plausible transformation pathways were proposed.