Mn doped nitrogen containing carbon activating peroxymonosulfate for enhancing sulfadiazine degradation via single oxygen pathway: Performance and mechanism

Abstract

In this work, manganese (Mn) with different contents doped CNs (CNs-Mn) was prepared via the thermal polymerization of the mixture of melamine, β-lactose and manganese sulfate and used as peroxymonosulfate (PMS) activator for sulfadiazine (SD) degradation. The optimum CNs-Mn(ii) delivered admirable PMS activation efficiency toward SD degradation and the contents of oxidized N and Mn2+ in catalysts displayed strongly positive correlation with SD degradation constant. Electron paramagnetic resonance (EPR) and quenching experiments revealed that the content of generated 1O2 species was higher than other radicals and 1O2 dominated SD degradation in the CNs-Mn(ii)/PMS system. The density functional theory (DFT) calculation analysis revealed a novel direct evolutionary pathway of 1O2 formation, that is the cleavage of S-O and O–H of PMS lead to two O atoms to form 1O2. Furthermore, CNs-Mn(ii) displayed good stability, anti-interference ability and performed well in the wide pH range of 4.5 ∼ 9.5. This study would give new insights into 1O2 generation mechanism and essential atomic-scale understanding of the roles of oxidized N and Mn species in 1O2 generation during Mn doped N containing carbon activating PMS process, as well as develop one new strategy to promote 1O2 generation efficiency.