Confined CuFe₂O₄ spinel coated on hierarchical SiO₂ for enhanced continuous-flow Fenton-like wastewater treatment

Heterogeneous Fenton-like catalysis offers a promising route for oxidative water treatment, yet its practical implementation remains constrained by the difficulty of integrating highly active powder catalysts into continuous-flow operation. Herein, we report a pore-confined CuFe₂O₄ spinel catalyst coated on hierarchical SiO₂ particles and demonstrate its use in an up-flow fixed-bed reactor for continuous tetracycline degradation. A multi-cycle impregnation-precipitation strategy enables the progressive in-pore growth of CuFe₂O₄, achieving a high active-phase loading of 5.16 wt% while preserving accessible mesoporosity. Under continuous-flow operation at a hydraulic retention time of 5 min, the optimized Fe/Cu@SiO₂-3 catalyst maintained >93% tetracycline removal over 60 min. Quenching experiments and ESR analysis identify •OH and ¹O₂ as the dominant oxidative species, indicating a dual radical/non-radical oxidation pathway. XPS and DFT calculations provide complementary evidence for an electronic-structure-level mechanism for the enhanced H₂O₂ activation. Favorable adsorption (-0.80 eV) induces interfacial charge redistribution and raises the work function from 5.543 to 5.626 eV. PDOS reveals near-Fermi Cu 3d states and Fe 3d-O 2p coupling, supporting Cu-mediated electron transfer, Fe-O activation, and sustained Fe³⁺/Fe²⁺ cycling through the Cu-O-Fe pathway during efficient interfacial peroxide conversion. This work links pore-confined spinel construction with continuous-flow Fenton-like catalysis, providing a structurally stable catalyst design with a mechanistically grounded understanding of the Fenton-like process.