A comparative study of activation of peroxymonosulfate and peroxydisulfate by greigite (Fe3S4) for the degradation of sulfamethazine in water

In this study, greigite (Fe 3 S 4 ) was used to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) for sulfamethoazine (SMT) degradation in water. The possible influencing factors such as oxidant concentration, sulfur sources, iron sources and initial pH were investigated.   Experimental results showed that SMT could be completely removed at 0.1 mM PMS in 15 min in Fe 3 S 4 /PMS system. 96.7% of SMT was removed at 1.0 mM PDS in 60 min in Fe 3 S 4 /PDS system.   Both systems had good performance over a wide pH range of 3–9. In addition, different sulfur sources could affect the crystal structure, morphology and composition of the synthesized catalysts, while different iron sources had little influence. Quenching experiments and electron paramagnetic resonance (EPR) test evidenced that the activation of PMS and PDS by Fe 3 S 4 was a multi-reactive oxygen species process with the coexistence of •OH, SO 4 •− , O 2 •− and 1 O 2 . SO 4 •− was the main active species in the Fe 3 S 4 /PMS system, while SO 4 •− and •OH were the main free radicals in the Fe 3 S 4 /PDS system. X-ray photoelectron spectroscopy (XPS) experiments showed that Fe(II) on Fe 3 S 4 surface effectively activated PMS and PDS, and S 2− species were key factors controlling Fe(II) regeneration and subsequent activation of PMS and PDS.   However, the consumption of Fe(II) and S 2− in Fe 3 S 4 /PDS system was higher than that in Fe 3 S 4 /PMS system. In addition, in the two systems, the degradation intermediates of SMT and their practical application were also evaluated.   This study provided a systematic evaluation of the performance of Fe 3 S 4 /PMS and Fe 3 S 4 /PDS systems for treatment of antibiotic contaminated water.