Insight into the nonradical mechanism of persulfate activation via visible-light for enhanced degradation of sulfonamides without catalyst

Photocatalytic persulfate (PS)-based oxidation processes have showed excellent performance in pollutant removal. However, the focus is usually on the activation of PS induced by the photogenerated carriers or co-catalysis with catalyst itself. The mechanism of PS alone enhanced by visible light (Vis) to remove pollutants that don't absorb Vis is still not clear. Here, the degradation kinetics and differences of sulfonamides via PS enhanced by Vis (Vis/PS) was studied without catalysts. Furthermore, only PS can be enhanced by Vis to degrade sulfamerazine (SMZ) selected as model comparing with peroxymonosulfate and H2O2. Results verified that the interaction between pollutants and PS was critical for enhanced absorption of Vis and generation of active species. Singlet oxygen and electron transfer mediated self-degradation contributed mainly to SMZ removal. The Vis/PS system involved radical and contaminants-dependent nonradical pathways. Therefore, this study will provide new insight into the degradation of pollutants by photoactivated PS, especially Vis.