Insight into the activation mechanism of sulfite over amorphous Fe1-xCoxS: Key role of Fe3+/Fe2+ self-cycling and oxysulfur radicals generation

• Published in: Inorganic chemistry communications 2024-05, Vol.163, p.112305, Article 112305
• Main Authors: Zhang, Jinyuan, Xing, Ziqin, Liu, Jianxin, Wang, Yawen, Zhang, Xiaochao, Li, Rui, Wang, Yunfang, Fan, Caimei
• Format: Article
• Language: English
• Subjects: Fe1-xCoxS; Fe3+/Fe2+ self-cycling; Oxysulfur radicals; Sulfite activation
• ISSN: 1387-7003; 1879-0259
• DOI: 10.1016/j.inoche.2024.112305

In this study, a amorphous Fe1-xCoxS were successfully prepared by ultrasonic-assisted method and exhibited high performance in activating sulfite for RhB degradation in acidic and neutral conditions. For the heterogeneous Fe1-xCoxS/sulfite system, on the one hand, doping Co into the crystal textures of FeS would lead to the increase of electron density, the slowing down of corrosion and the reduction of impedance, which is beneficial to accelerate the electron transfer efficiency. In addition, a non-radical activation pathway has been proposed. On the other hand, the electron-rich S(-Ⅱ) is key to promote the self-cycling of Fe3+/Fe2+, and S(-Ⅱ) reduces the accumulated ≡Fe(Ⅲ) to ≡Fe(Ⅱ). As a result, the synergistic effect of these processes is conducive to RhB removal. [Display omitted] •A novel amorphous Fe1-xCoxS were prepared by ultrasonic-assisted method.•The Fe1-xCoxS was first reported as heterogeneous catalyst for sulfite activation.•The doping Co into FeS accelerated electron transfer of Fe1-xCoxS/sulfite system.•The electron-rich S(-Ⅱ) is key to promote the self-cycling of Fe3+/Fe2+.•The mechanism of sulfite activation by Fe1-xCoxS was proposed. Sulfite activation has been considered as a promising advanced oxidation technique for treating organic pollutants in water. In this work, a series of cobalt-doped FeS (Fe1-xCoxS) samples were synthesized via ultrasonic-assisted precipitation route and applied them in sulfite activation and Rhodamine B (RhB) removal in water at the same time, and their physical properties were characterized by XRD, SEM, TEM, XPS and electrochemical analysis. Benefiting from its high electron density, low corrosion voltage and impedance that beneficial to accelerate the electron transfer rate in the Fe1-xCoxS/sulfite system and the reducing sulfur species rich in electrons which beneficial to promote the self-cycling of Fe3+/Fe2+, the activity of Fe1-xCoxS for sulfite activation on the RhB removal was better than that of FeS in both acidic and neutral conditions. The redox cycle of metal ions on the surface of Fe1-xCoxS efficiently triggered sulfite activation. The hydroxyl radical (·OH), resulting from the conversion of oxysulfur radicals, plays a crucial role in the degradation of RhB. Additionally, a non-radical activation pathway of sulfite has been proposed. The present study provided a new idea and effective strategy for sulfite activation to environmental removal of organic matter in water.