Amorphous SiO2-stabilized high-valent iron-oxo complexes derived from Fe- and Si-rich solid wastes for efficient tetracycline hydrochloride degradation

High-valent iron-oxo complexes show promise as green oxidants for water remediation, but suffer from critical limitations in stability and pH adaptability. Herein, we report a facile method to synthesize amorphous SiO 2 -stabilized high-valent iron-oxo complexes via Na + diffusion activation of iron/silicon-rich copper smelting slag. In the complex, the synergistic coexistence of two distinct silica‑oxygen tetrahedral configurations-basic Na 2 SiO 3 and acidic SiO 2 oxides establishes a self-regulating pH buffering system that stabilizes solution neutrality. This unique structural design ensures sustained oxidative activity of the complex, representing a significant advancement over conventional silica-supported catalysts due to its intrinsic acid-base regulatory capability. Thus, the deactivations of the oxidants including the proton-induced self-decomposition and the hydrolysis of iron by hydroxyl groups can be efficiently inhibited, thereby expanding the pH applicability (3–11). High-valent iron species can be continuously regenerated during peroxymonosulfate (PMS)-triggered reactions for the selective and efficient oxidation degradation of tetracycline hydrochloride (TC, 98.01% in 15 min) via non-radical pathway. Through methyl phenyl sulfoxide-directed oxidation, electron spin resonance, Mössbauer spectroscopy, and density functional theory calculations, the stabilizing mechanism of silicon was elucidated, confirming that the high valent iron-oxo act as the dominant active species. This work advances both hazardous waste valorization and high valent iron-oxo complex engineering, offering a robust solution for organic pollutant removal in complex aquatic environments.