Mn–Fe ₃ O ₄ heterogeneous Fenton catalytic oxidation: mechanism and performance in sauce-flavored liquor wastewater degradation

This study aims to investigate the mechanism of synthesized Mn-Fe₃O₄ catalysts in the deep degradation of COD in sauce-flavored liquor wastewater by heterogeneous Fenton oxidation. Additionally, the study evaluates the impact of operational factors, including pH, catalyst composition, and dosage on the COD removal rate. The physicochemical characteristics of Mn-Fe₃O₄ catalysts were comprehensively analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The oxidation mechanism of the Mn-Fe₃O₄ heterogeneous Fenton system was elucidated through gas chromatography-mass spectrometry (GC-MS) analysis, kinetic modeling, and radical quenching experiments involving <i>tert</i>-butanol (TBA) and benzoquinone (BQ). The results demonstrated that the Mn-Fe₃O₄-based system enhanced COD removal by 26% compared to the conventional Fenton process, exhibiting remarkable stability and magnetic recoverability. The catalyst system followed second-order kinetics, with the dual Mn-Fe active centers on the catalyst surface facilitating electron transfer <i>via</i> charge redistribution, promoting redox cycling of Fe²⁺/Fe³⁺ and Mn²⁺/Mn³⁺, and significantly increasing hydroxyl radical (·OH) production, thereby enabling the efficient degradation of refractory organic pollutants. This study provides valuable insights for the development of innovative catalytic materials for the effective treatment of industrial wastewater containing phenolic quinones, which are challenging to degrade, and sets the stage for further industrial applications.