Catalytic ozonation of chloramphenicol with manganese-copper oxides/maghemite in solution: Empirical kinetics model, degradation pathway, catalytic mechanism, and antibacterial activity.

The composite material of manganese-copper oxide/maghemite (MnxCuyOz/γ-Fe2O3) was synthesized by the co-precipitation-calcination method. With the initial concentration of 0.2 g/L MnxCuyOz/γ-Fe2O3 and 10 mg/L O3, the chloramphenicol (CAP, 10 mg/L) could be completely degraded, which was about 2.22 times of that treated with ozonation alone. The contribution of O3 and hydroxyl radical (•OH) for CAP degradation in the catalytic process was 6.9% and 93.1%, respectively. According to the effects of catalyst dosage, ozone dosage, and pH on the catalytic performance of MnxCuyOz/γ-Fe2O3, a predictive empirical model was developed for the ozonation with the MnxCuyOz/γ-Fe2O3 system. The HCO3-/CO32- and phosphates in solution could inhibit the degradation of CAP with the inhibition ratios 8.45% and 13.8%, respectively. The HCO3-/CO32- could compete with CAP and react with •OH, and the phosphates were considered as poisons for catalysts by blocking the surface active sites to inhibit ozone decomposition. The intermediates and possible degradation pathways were detected and proposed. The catalytic ozonation could effectively control the toxicity of the treated solution, but the toxicity was still not negligible. Furthermore, MnxCuyOz/γ-Fe2O3 could be easily and efficiently separated from the reaction system with an external magnet, and it possessed excellent reusability and stability.