Sulfadiazine removal by peroxymonosulfate activation with sulfide-modified microscale zero-valent iron: Major radicals, the role of sulfur species, and particle size effect

Sulfide-modified zero-valent iron (S-Fe 0 ) is regarded as a promising method to enhance the catalytic activity of Fe 0 for peroxymonosulfate (PMS) activation. However, the roles of sulfidation and the application of the sulfidation treatment method are worth to further investigation. In our study, the effects of the S/Fe ratio, Fe 0 dosage, and initial pH on sulfadiazine (SDZ) removal were investigated. The characterization of S-Fe 0 with SEM, XPS, contact angle and Tafel analysis confirmed that the formation of sulfur species on the Fe 0 surface could enhance the catalytic performance of Fe 0 . S 2− played the major role and SO 3 2- played the minor role in accelerating the conversion of Fe 3+ to Fe 2+ . EPR tests, radical quenching and quantitative determination experiments identified • OH as playing the major role and SO 4 •− also playing an important role in SDZ removal in S-Fe 0 /PMS system. Sulfidation produced no notable change in the role of • OH and SO 4 •− . A possible degradation pathway of SDZ was proposed. Effect of sulfidation on various sizes of Fe 0 was also studied which demonstrated that the smaller sizes of Fe 0 (< 8 µm) were more effective in the sulfidation method treatment. S-Fe 0 /PMS system also showed a good performance in removing antibiotics in natural fresh water.