The combination of Ozone and Mn(II) for efficient removal of ozone-resistant N, N-Diethyl-3-toluamide

This study investigates the enhancement of ozonation efficiency through the introduction of manganese ions (O 3 /Mn(II)) that significantly improve the degradation of ozone-persistent organic pollutants. Manganese ions accelerate hydroxyl radical generation by catalyzing ozone decomposition, thereby facilitating more effective oxidative reactions. The application of O 3 /Mn(II) to degrade N, N-Diethyl-3-toluamide (DEET) achieved a decomposition efficiency of 3.6 to 4.1 times higher than ozonation alone. The promotive effect was highly pH-dependent, with the observed rate constant ( k obs ) for O 3 /Mn(II) reaching 97.05 M −1 s −1 at pH 4, approximately 3.3 times greater than ozonation alone, and 686.93 M −1 s −1 at pH 7, around 1.7 times higher. O 3 oxidation contributed approximately 1% to the overall process, while hydroxyl radicals accounted for approximately 80%, and manganese species accounted for approximately 20%. Furthermore, the oxidation state of manganese significantly influenced the cooperative oxidation efficiency, with Mn(VII) achieving the highest k obs (680.87 M −1 s −1 ), while Mn(IV) exhibited the lowest (304.6 M −1 s −1 ). Additionally, intermediate products formed during DEET oxidation were identified using Orbitrap technology, elucidating various degradation pathways (such as decarboxylation, tri-hydration, and aromatic ring opening). These findings provide valuable insights into enhancing ozonation processes for environmental remediation.