Sulfur-containing iron nanocomposites confined in S/N co-doped carbon for catalytic peroxymonosulfate oxidation of organic pollutants: Low iron leaching, degradation mechanism and intermediates

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 404; p. 126499
• Main Authors: Long, Yangke, Li, Shun, Su, Yiping, Wang, Shuyang, Zhao, Shiyin, Wang, Shubin, Zhang, Zhen, Huang, Wei, Liu, Yong, Zhang, Zuotai
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.01.2021
• Subjects: Electron-transfer mechanism; Metal ions leaching; Peroxymonosulfate; Sulfur and nitrogen co-doping; Sulfur-containing iron compounds; Sulfur-containing iron compounds; Metal ions leaching; Peroxymonosulfate; Electron-transfer mechanism; Sulfur and nitrogen co-doping
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2020.126499

Sulfur-containing iron nano-composites confined in S/N co-doped carbon (Fe-S@SNC) have been synthesized, showing excellent PMS activation efficiency for the degradation of organic pollutants with low iron leaching during catalysis. [Display omitted] •Fe-S@SNC catalysts with different morphology and particle size were obtained through a simple pyrolysis technique.•Fe-S@SNC exhibited excellent PMS activation performance with low iron leaching during catalysis.•Dominant radial species (O2−) was verified and catalytic pathways were elucidated.•The degradation products were significantly dependent on solution pH and background species. The poor performance and severe metal leaching of iron-based Fenton-like catalysts during reaction are the main bottlenecks that suppress their practical applications. Herein, a well-defined structure was achieved by confining catalytically active but unstable sulfur-containing iron species within S/N co-doped porous carbon (Fe-S@SNC) through a simple pyrolysis route. The hierarchically porous and highly conductive carbon host not only provided abundant exposed active sites and fast mass/electron-transfer, but also prohibited the aggregation of iron composites during catalysis. The synergistic effects of confined iron nano-composites and heteroatoms (S/N) significantly elevated the activation of peroxymonosulfate (PMS). As a result, the Fe-S@SNC/PMS system exhibited excellent catalytic degradation performance for various contaminants including dyes, phenolic compounds, and antibiotics. Importantly, a low iron leaching was detected during usage due to the nano-confinement effect of carbon layers, and therefore solves the long-term issue of secondary pollution caused by metal leaching. Furthermore, the underlying degradation mechanism of Fe-S@SNC/PMS system was systematically investigated by radical quenching tests, EPR analysis, and chronoamperometry experiments. It was found that the superoxide anion radical (O2−) was the predominant free radicals that contributed to the radical oxidation of organic pollutants, while the electron transfer mediation on Fe-S@SNC resulted in the non-radical oxidation. Additionally, the LC-MS results coupled with time-dependent HPLC spectra validated that the degradation efficiency and intermediate products were significantly dependent on solution pH and background species. This work provides new insight into the design and activation mechanism of iron-based PMS activators.