Defect-engineered N/Mn-doped iron-based transition metal silicate from copper smelting slag enable radical/nonradical pathway switching for efficient butyl xanthate degradation

Heterogeneous Fenton-like catalytic oxidation is a promising technology for eliminating refractory organic pollutants, yet precise regulation of its intrinsic pathways (radical or non-radical) remains challenging. In this study, copper smelting slag was employed as a sustainable precursor to synthesize a nitrogen/manganese co-doped iron-based transition metal silicate (N/Mn-Fe-TMSs) catalyst for peroxymonosulfate (PMS) activation. The study demonstrates that Mn doping at Fe sites induces local lattice distortion and charge enrichment in the two-dimensional nanosheet architecture, and increases the d-band electron density of Fe sites, thereby enhancing PMS adsorption. The adsorbed PMS undergoes peroxy bond polarization and cleavage at these electron-enriched sites, with subsequent electron transfer to the metal centers, efficiently promoting singlet oxygen ( 1 O 2 ) generation. Additionally, nitrogen introduction transforms Me–O into unsaturated Me–N coordination, optimizing the d-band center of Fe sites. This modification significantly lowers the activation energy for PMS deprotonation and facilitates the formation of high-valent metal-oxo species. Consequently, the degradation pathway shifts from being predominantly radical-driven (74.5%) to a non-radical-dominated process (64.2%). Owing to these synergistic effects, the N/Mn-Fe-TMSs/PMS system achieves 99.3% removal of butyl xanthate within 15 min, exhibiting a degradation rate 56.4 times faster than that of the undoped system. Furthermore, the system exhibited remarkable resistance to interference from co-existing ions, exceptional structural stability, and excellent reusability. This study presents a sustainable and cost-effective approach for valorizing copper slag while advancing the design of non-radical-driven PMS activation systems for efficient and durable wastewater treatment.