Activation of persulfate by photoexcited dye for antibiotic degradation: Radical and nonradical reactions

Abstract Despite numerous studies on peroxydisulfate (PS) activation with catalysts, the PS activation by organic contaminants themselves has been rarely reported. Here, we found that PS can be activated by dyes such as rhodamine B (RhB), eosin Y (EY) and methylene blue (MB) under visible light (Vis) irradiation, achieving simultaneous degradation of dye and antibiotics (e.g., tetracycline hydrochloride) via both radical and nonradical pathways. Experimental results demonstrated that the radical reaction was the major route, which was caused by the reduction of PS by photogenerated electrons of the dye. Dye-mediated electron transfer from pollutants to the oxidized dye (dye*+) was responsible for the nonradical reaction. Compared with EY and MB, the most negative LUMO (lowest unoccupied molecular orbital) level of RhB facilitated rapid electron transfer from RhB to PS, resulting in the highest activation efficiency. Interestingly, post-processing with base can further increase the mineralization efficiency due to the PS activation by generated phenolic intermediates of RhB degradation. This work elucidated a new pathway of PS activation and provide a new “using waste to treat waste” strategy for the disposal of dye wastewater and complex wastewater containing dye.