Sulfide-modified zero-valent iron activated periodate for sulfadiazine removal: Performance and dominant routine of reactive species production.

In this work, sulfide-modified zero-valent iron (S-Fe) was used to activate periodate (IO, PI) for sulfadiazine (SDZ) removal. 60 μM SDZ could be completely removed within only 1 min by S-Fe/PI process. Compared with other oxidants including HO, peroxymonosulfate (PMS), peroxydisulfate (PDS), S-Fe activated PI exhibited better performance for SDZ removal but with lower Fe leaching. Compared with Fe/PI process, S-Fe/PI process could reduce more than 80% Fe and PI dosage. Inorganic ions and nature organic matters had negligible effect on SDZ removal in S-Fe/PI system inducing its good SDZ removal efficiency in natural fresh water. 80.2% SDZ still could be removed within 2 min after 7th run. S-Fe/PI process also exhibited 2.5 - 20.1 folds enhancement for various pollutants removal compared with Fe/PI process. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical tests, and density functional theory (DFT) calculation were conducted to confirm the presence of sulfurs could enhance the reactivity of S-Fe thus increased the efficiency of PI activation for antibiotics removal. Electron paramagnetic resonance spectroscopy (EPR) tests, radical quenching experiments, quantitative detection and DFT calculation were performed to illustrate the role of multiple reactive species in SDZ removal and the dominant pathway of multiple reactive species production. IO, OH, O, O, Fe, and SO all participated in SDZ removal. OH played the major role in SDZ removal and the dominant routine of OH production was IO → O → HO → OH. Meanwhile, S-Fe/PI process could efficiently mineralize SDZ and reduce the toxicity. Comparison with other PI activation approaches and SDZ treatment techniques further demonstrated S-Fe was an efficient catalyst for PI activation and present study process was a promising approach for antibiotics removal.