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.