Sulfamethazine removal by peracetic acid activation with sulfide-modified zero-valent iron: Efficiency, the role of sulfur species, and mechanisms

Sulfide-modified zero-valent iron (S-Fe-0) has been regarded as a promising method to enhance the catalytic activity of Fe-0. Therefore, peracetic acid (PAA) firstly activated by S-Fe-0 was conducted to remove sulfamethazine (SMT) in this study. Only 13.1% SMT could be removed within 60 min in Fe-0/PAA system while 86.5% SMT could be removed within 60 min in S-Fe-0/PAA system at condition of [PAA] = 100 mu M [S-Fe-0] = 20 mg/L, [SMT] = 5 mg/L, pH = 4.0. The effect of S/Fe ratio, S-Fe-0 dosage, PAA concentration and initial pH on SMT removal were investigated. The characterization of S-Fe-0 such as SEM, XPS, contact angle and Tafel confirmed that the formation of sulfur species on Fe-0 surface could enhance the catalytic performance of Fe-0. S2- played the major role and SO32- played the minor role in accelerating the conversion of Fe3+ to Fe2+. (OH)-O-center dot and R-O-center dot exhibited 67.1% and 32.5% contribution for SMT removal in S-Fe-0/PAA system, respectively. The possible degradation pathway of SMT was also proposed. Cr and HCO3- had a negligible adverse effect on SMT removal in S-Fe-0/PAA system indicating the good adaptability of inorganic ions. In addition, S-Fe-0/PAA system had the good recycle ability of S-Fe-0 and showed a better performance in removing SMT in the natural fresh water. Therefore, this study notably showed the potential applicability of S-Fe-0/PAA system in degrading SMT in natural fresh water.