Crucial Role of Mössbauer Characterization in Studying the Catalytic Mechanism of Novel Iron-Based Fenton Systems

Recent advancements in persulfate-based advanced oxidation processes have garnered significant interest due to their capability to generate sulfate radicals, which possess superior oxidation power and longevity compared to hydroxyl radicals. Iron-based catalysts are particularly promising due to their affordability and eco-friendliness, but there remains a critical need to develop highly efficient iron-based catalysts and to elucidate their structure-activity relationships. This presentation delves into three innovative iron-based catalysts, each with distinct activation mechanisms.

Firstly, the PB(Prussian blue)@MoS₂ composite catalyst, synthesized through a simple hydrothermal method, has been identified as an exceptional peroxymonosulfate (PMS) activator under visible light. It markedly outperforms pure PB and MoS₂ due to enhanced interfacial interactions, which accelerate charge carrier transfer and Fe^II/Fe^III cycling, thereby improving PMS activation and pollutant degradation efficiency. Secondly, Zn-Fe double oxides, prepared by calcining Zn_1-xFe_x-Fe Prussian blue analogues (PBAs), exhibit outstanding catalytic performance under visible light and PMS. These catalysts retain high stability and effectiveness even with elevated organic matter concentrations due to their ability to transition from a radical-based pathway to a singlet oxygen (¹O₂)-dominated nonradical mechanism. This adaptability makes them suitable for various water matrices, overcoming the limitations of traditional radical-based systems. Thirdly, a Fe, N-codoped carbon single-atom catalyst, produced by calcining PB with melamine, demonstrates remarkable catalytic activity for bisphenol A degradation across diverse conditions. Advanced characterization techniques, including Mössbauer spectroscopy, confirm that ¹O₂ is the primary reactive species, with FeN_x sites playing a crucial role in its generation. This catalyst not only offers an effective strategy for advanced water remediation but also provides valuable insights into the direct ¹O₂-modulated mechanisms in the FeN_x/PMS Fenton-like process. Overall, these study not only provided effective Fe-based catalyst synthetic strategy with high selectivity, adaptability and efficiency for advanced water remediation, but also proposed novel and crucial insights into reaction mechanism in PMS-based Fenton-like process.