High valent manganese-oxo species activation of peroxymonosulfate by different phases manganese oxides nanoplates for catalytic water decontamination

Advanced oxidation processes involving high-valent metal-oxo species have garnered increasing attention for their effective pollutant degradation in water. However, less is known about the mechanism of the species in the manganese oxides (MnO x ) system. Therefore, it is crucial to design MnO x catalysts to systematically clarify the high-valent metal-oxo species reaction mechanism. In this study, MnO x nanoplates including Mn 3 O 4 , Mn 5 O 8 , and Mn 2 O 3 were synthesized via a facile thermal treatment of a Mn(OH) 2 precursor to activate peroxymonosulfate (PMS) for mechanism studies. The Mn 3 O 4 catalyst exhibited superior catalytic performance and reusability owing to its unique spinel structure and rapid electron transfer properties. The first-order rate constant for Mn 3 O 4 is 0.64 min −1 , which is 3.7 and 1.5 times higher than those of Mn 5 O 8 and Mn 2 O 3 , respectively. Scavenging experiments, electron paramagnetic resonance, and electrochemical analysis revealed that free radicals played a negligible role, while the formation of high-valent Mn-oxo species was promoted, facilitated by the Mn 3 O 4 -PMS* complex. These high-valent Mn-oxo species were highly reactive towards various pollutants. Moreover, the degradation intermediates of bisphenol A (BPA) in the Mn 3 O 4 /PMS system were identified, further elucidating the interactions between high-valent Mn-oxo species and BPA. Additionally, the Mn 3 O 4 catalyst exhibited excellent catalytic performance under practical conditions and maintained superior stability over six cycles. This work provides crucial insights into the role of transition metal oxides in activating PMS for the catalytic degradation of emerging pollutants.