Synergistic effects of persistent free radicals and visible radiation on peroxymonosulfate activation by ferric citrate for the decomposition of organic contaminants

- ACFs (PFRs) was coupled with Fe(III)-photocatalysts to construct an efficient catalytic oxidation system.
- The synergistic enhancement effect of PFRs and visible light endowed the constructed catalyst with strong catalytic activity.
- The enhanced activity was attributed to more OH and SO4− generation.

In this work, persistent free radicals (PFRs) of activated carbon fibers (ACFs) were innovatively coupled with Fe(III)-photocatalysts to construct a distinctive catalytic oxidation system, FeCit@ACFs/PMS/visible light. Herein, PFRs acted as an electron sink by donating electrons to ferric citrate (Cit-Fe), thereby accelerating the ligand-to-metal charge transfer (LMCT) processes that govern the rate-determining step of the reaction transforming Cit-FeIII to Cit-FeII. Moreover, visible radiation can serve as another powerful assistor to further enhance the LMCT processes because Cit-Fe exhibits highly intrinsic photosensitivity. The synergistic enhancement effect of PFRs and visible light endowed the constructed FeCit@ACFs catalyst with strong catalytic activity, which could effectively activate peroxymonosulfate (PMS) to generate reactive oxygen species (ROS) for contaminants decomposition. To investigate the ROS generated in this experiment, we adopted a hybrid method that combines electron paramagnetic resonance technology with different radical scavengers, and the results indicated that OH and SO4− were generated and played a major role in the catalytic oxidation process. This work provided a new insight into the positive role of PFRs and presented an up-to-date research domain of PFRs-enhanced catalysis. It also paved an avenue for developing high-efficiency processes for the generation of ROS, which can be subsequently used in environmental catalysis.

133