In this study, the catalytic activation of persulfate (PS) via metal oxides was investigated, and the AMn(2)O(3) nanocatalyst was found to have the highest efficiency among other PS activators for the degradation of organic contaminants. Additionally, A-Mn2O3 exhibited a remarkable efficiency in activating PS for the degradation of phenol compared to both B-Mn2O3 and C-Mn2O3. This was attributed to the longer bonds between edge-sharing MnO6 octahedra, the unique structure, the high content surface -OH groups, and the average oxidation states. This indicated that all these properties played an important role in an efficient PS activation. Electron paramagnetic resonance (EPR) spectroscopy, scavenger tests, and chemical probes were conducted to investigate the reactive oxygen species (ROS). Singlet oxygen (O-1(2)) was determined to be the main ROS generated from PS activation. A plausible mechanism study was proposed, which involved inner-sphere interactions. An electron transfer of the Mn species facilitated the decomposition of PS to generate HO2 center dot/O-2(center dot) radicals, which were utilized as a precursor for O-1(2) generation via direct oxidation or the recombination of HO2 center dot/O-2(center dot) (-). Finally, the phenol and Sulfachloropyridazine (SCP) degradation pathways were proposed by O-1(2) over the A-Mn2O3/PS system according to HPLC and LC-MS results. (C) 2020 Published by Elsevier Inc.