Sulfide enhances the Fe(II)/Fe(III) cycle in Fe(III)-peroxymonosulfate system for rapid removal of organic contaminants: Treatment efficiency, kinetics and mechanism

The activation of peroxymonosulfate (PMS) by Fe(II) or Fe(III) for environmental decontamination is severely limited by the low conversion rate from Fe(III) to Fe(II). Here, we found that this puzzling problem could virtually be solved by introducing trace amounts of S2-. With the addition of 0.2 mM S2-, the bisphenol A (BPA) degradation efficiency and total organic carbon (TOC) removal in PMS/Fe(III) system were improved by 3.8 and 6.0 times, respectively. Meanwhile, the kobs and PMS utilization efficiency also markedly increased by 650% and 160%, respectively. The constructed PMS/Fe(III)/S2- system exhibited a good applicability to a wide pH range (3.2 ~ 9.5) and high resistance to humic acid, Cl- and NO3- . The main reactive oxidant species in PMS/Fe(III)/S2system were identified by scavenging experiments, electron paramagnetic resonance measurement, chemical probe approach, and 18O isotope-labeling technique. The identification results revealed that FeIVO2+ was the primary reactive oxidant species, while center dot OH, SO4 center dot-, O2 center dot- and 1O2 were also involved in the degradation of BPA. Finally, the generalizability of PMS/Fe(III)/S2- system was evaluated by varying the target pollutants, oxidants,

Automated summary

The efficiency of Fe(III) activation of peroxymonosulfate (PMS) can be improved by introducing trace amounts of S2-, leading to enhanced degradation of bisphenol A (BPA) and increased utilization efficiency of PMS. The primary reactive oxidant species in this system is identified as FeIVO2+, and other reactive species such as center dot OH, SO4 center dot-, O2 center dot-, and 1O2 are also involved in the degradation of BPA. The PMS/Fe(III)/S2- system shows good applicability under a wide pH range and high resistance to various interfering substances.