Miraculous dye-photosensitization-assisted peroxymonosulfate activation at the carbon nitride interface: Enhanced activity and synergistic mechanism

Heterogeneous activation of peroxymonosulfate (PMS) with the assistance of visible light is an emerging technology for organic wastewater decontamination. However, such a combined system is often affected by the inherent characteristics of the target pollutants and photocatalyst or may suffer from undesirable photoactivity, metal precipitation, catalyst deactivation, and increased toxicity. In this study, typical carbon nitride (g-C3N4) nanosheets were selected as a catalytic reaction interface, and photosensitive rhodamine B (RhB) served as the model pollutant to achieve pollutant-driven oxidant activation using PMS, and nearly 7.7 times compared to the single g-C3N4/vis system was thus achieved. Capture experiments and electron spin resonance (ESR) analyses verified the major contribution of superoxide radical (center dot O2-) and its subspecies singlet oxygen (1O2) to the enhanced catalytic performance. Theoretical calculations showed that the RhB molecule could be excited to form RhB* under visible light, transferring e- to the conduction band of g-C3N4, and thereby PMS was rapidly activated by accumulated electrons. This work highlights the role of photosensitization in the treatment of complex organic wastewater.

Automated summary

Heterogeneous activation of peroxymonosulfate (PMS) with the assistance of visible light is a promising technology for organic wastewater decontamination. However, there are challenges such as target pollutant characteristics and catalyst deactivation that can affect the efficiency of this combined system. In this study, carbon nitride (g-C3N4) nanosheets and photosensitive rhodamine B (RhB) were used as the catalyst and model pollutant respectively, achieving nearly 7.7 times enhancement compared to the single g-C3N4/vis system. Superoxide radical (·O2-) and singlet oxygen (1O2) were identified as the major contributors to the enhanced catalytic performance. Theoretical calculations explained the mechanism behind the enhanced activation of PMS through electron transfer from the excited RhB molecule to g-C3N4 under visible light. This work emphasizes the importance of photosensitization in treating complex organic wastewater.