Light-driven periodate activation via Fe-N doped semi-coke for enhanced norfloxacin degradation

Semi-coke (SC), a solid waste generated from the dry distillation of oil shale, is rich in organic matter, classifying it as a functional carbon-based material. Combining the progressive advantages of functionalized carbon-based materials in advanced oxidation technology, this study prepared Fe-N co-doped semi-coke (Fe-N-SC) through a facile one-step pyrolysis of SC pre-impregnated with potassium ferricyanide. Under visible light (VIS) irradiation, Fe-N-SC was able to activate periodate (PI) to establish an Fe-N-SC/PI/VIS system for degrading norfloxacin (NOR). The results showed that this system achieved 99.5%-NOR removal, with a mineralization degree of up to 68.6%- within 30 min. Furthermore, Fe-N-SC exhibited stable performance over a wide pH range (3−9) and maintained high NOR removal efficiency in real water matrices, indicating its robustness and practical applicability. Electron paramagnetic resonance and free radical quenching experiments revealed that h + and ·OH were the primary species responsible for NOR degradation in Fe-N-SC/PI/VIS system. The proposed mechanism involved reactive oxygen species-driven oxidative cleavage of piperazine ring in NOR, leading to its stepwise breakdown and mineralization into harmless end-products. During the degradation process, no toxic intermediates were detected, highlighting the environmental safety of Fe-N-SC/PI/VIS system for sustainable and highly effective removal of antibiotics from aquatic environment.