Efficient catalytic ozonation of 4-chloro-3-methylphenol by Mn-Cu/Al2O3: Performance, mechanism, and degradation pathways

In this study, Mn-Cu/Al₂O₃ was successfully synthesized by using the ultrasonic impregnation–calcination method for the catalytic ozonation of preservative 4-chloro-3-methylphenol (PCMC). The optimal preparation conditions of Mn-Cu/Al₂O₃ were investigated, and the catalyst was characterized by using various characterization methods. The generation of oxygen vacancies on the catalyst surface was accompanied with the transition of the valence state of metal oxides (Mn³⁺/Mn⁴⁺ and Cu⁺/Cu²⁺), which remarkably promoted ozone decomposition and reactive oxygen species (ROS) generation. The influence of different experimental conditions on PCMC degradation was investigated. The ideal PCMC removal rate of 100 % was achieved in 30 min under optimized conditions with ozone dosage of 4.0 mg/min, Mn-Cu/Al₂O₃ dosage of 15 g/L and initial pH of 7. The reusability experiments and metal leaching analysis confirmed the catalyst excellent potential for practical engineering applications. The mechanism of Mn-Cu/Al₂O₃ catalytic ozonation was surmised. Additionally, the potential degradation pathways of PCMC were speculated based on the identified intermediate products.