Efficient activation of PMS for norfloxacin detoxification and mineralisation via chlorine-modified iron-based trimetallics: Profound modulation of copper valence states

Currently, enhancing the catalytic activity of Zero-Valent Iron (ZVI) and improving the mineralization rate of pollutants remain significant challenges in ZVI application. In this study, the s-Fe⁰@Cu-Pd catalysts were synthesized using six different copper sources to activate peroxymonosulfate (PMS) for norfloxacin (NOR) degradation. SEM images revealed morphology variations in the s-Fe⁰@Cu-Pd trimetals, with the T-Cl (synthesized using CuCl₂) exhibiting the largest specific surface area and pore volume. XPS characterization and DFT analyses indicated that anions significantly influenced the Cu(I)/Cu(II) ratio in s-Fe⁰@Cu-Pd trimetals. Raman spectroscopy confirmed the generation of CuCl and Cu₂O on the catalyst surface in the presence of chloride ions, with copper valence state was effectively modulated by increasing the amount of chloride ion during synthesis. Among the six s-Fe⁰@Cu-Pd/PMS systems, T-Cl/PMS demonstrated the highest catalytic activity, achieving a 96.25 % NOR removal efficiency under optimized conditions. EPR characterization and radical scavenging experiments elucidated the coexistence of SO₄^•−, ^•OH, O₂^•− and ¹O₂, with SO₄^•− was identified as the predominant active radical. Furthermore, mechanism investigations into NOR degradation by the T-Cl/PMS system facilitated the proposal of potential degradation pathways. The s-Fe⁰@Cu-Pd/PMS system demonstrates considerable potential for the advanced treatment of recalcitrant pollutants in aqueous environments.