Novel α-MnO2/AC catalysts for heterogeneous catalytic ozonation process to remove BAA in dye wastewater

Designing catalysts that are both efficient and resistant to interference poses a significant challenge in the field of catalytic ozone oxidation. In this study, four composite nanomaterials with different crystalline phase structures of MnO2 and its loading onto activated carbon were synthesized by hydrothermal synthesis-calcination method and successfully used to catalyze the degradation of BAA by ozonation. The synthesized α-MnO2/AC showed excellent performance and stability, and the degradation rate of 100 mg/L BAA could reach 96.27 % within 40 min under optimal conditions. Compared with MnO2 alone, α-MnO2/AC possessed lower polarization resistance, faster charge transfer rate, and higher Mn3+ and oxygen vacancy contents. Through the mechanistic study of Heterogeneous catalytic ozonation (HCO), it was confirmed that Mn(III) and oxygen vacancies together acted as active sites to enable O3 adsorption and activation to generate ROS, and OH and 1O2 reacted with BAA as the main ROS in this system. In addition, a potential pathway for the degradation of BAA by HCO was proposed and evaluated for its toxicity. This study provides a new strategy and understanding for designing manganese dioxide composite catalysts with different crystalline phases and the mechanistic exploration of the HCO pathway.