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 (Mn x Cu y O z /γ-Fe 2 O 3 ) was synthesized by the co-precipitation-calcination method. With the initial concentration of 0.2 g/L Mn x Cu y O z /γ-Fe 2 O 3 and 10 mg/L O 3 , 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 O 3 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 Mn x Cu y O z /γ-Fe 2 O 3 , a predictive empirical model was developed for the ozonation with the Mn x Cu y O z /γ-Fe 2 O 3 system. The HCO 3 − /CO 3 2− and phosphates in solution could inhibit the degradation of CAP with the inhibition ratios 8.45% and 13.8%, respectively. The HCO 3 − /CO 3 2− 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, Mn x Cu y O z /γ-Fe 2 O 3 could be easily and efficiently separated from the reaction system with an external magnet, and it possessed excellent reusability and stability.