Insights into the singlet oxygen mechanism of Fe-doped activated carbon for Rhodamine B advanced oxidation

Carbon-based catalyst-activated persulfate-driven advanced oxidation processes (AOPs) have received great attention for wastewater treatment. Herein, a magnetic Fe-doped activated carbon (FeC2O4/AC) was successfully prepared via a conventional method using FeC2O4 as an iron source and Zoysia sinica as biomass. FeC2O4/AC was characterized and used to activate peroxymonosulfate (PMS) for Rhodamine B (RhB) degradation. The influence of various factors on RhB removal was evaluated, including initial pH, temperature, coexisting ions, RhB concentration, PMS concentration and catalyst dosage. Under the optimized condition, the removal efficiency of FeC2O4/AC for RhB (300 mg/L) reached up to 97% within 150 min. Radical scavenging results and EPR experiments confirm that singlet-oxygen (1O2) was confirmed as the main active species in the degradation of RhB in the FeC2O4/AC/PMS system. More importantly, the possible route of 1O2 generation was revealed: the synergistic effect of Fe species and the activated carbon acts as a crucial part in promoting the PMS activation and contributing to the generation of 1O2. The reaction rate constant (kobs) of FeC2O4/AC is about 7.4 times that of pure AC, and the excellent leaching rate of Fe2+ (<0.09%) proves that this material is an excellent catalyst. This research on the development of Fe-doped activated carbon with high activity and high stability has profound implications for the effective treatment of organic wastewater.