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 SO32- played the minor role in accelerating the conversion of Fe3+ to Fe2+. EPR tests, radical quenching and quantitative determination experiments identified center dot OH as playing the major role and SO4 center dot- also playing an important role in SDZ removal in S-Fe-0/PMS system. Sulfidation produced no notable change in the role of center dot OH and SO4 center dot-. 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 mu m) 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.

Automated summary

The study demonstrated that sulfide-modified zero-valent iron (S-Fe-0) can enhance the catalytic performance for peroxymonosulfate activation. The sulfur species formed on the Fe-0 surface play a crucial role, with S-2(-) and SO32- accelerating the conversion of Fe3+ to Fe2+. Radical quenching experiments identified center dot OH as the major contributor to sulfadiazine removal in S-Fe-0/PMS system. The study also showed that smaller Fe-0 particles (< 8 μm) were more effective in the sulfidation treatment method.