Efficient Methylene Blue Degradation via Fenton-like Oxidation over a Hydroxyl-Rich Fe₂O₃/Fe₃O₄ Catalyst: Mechanistic and Kinetic Insights

Abstract interest in low-cost heterogeneous catalysts for dye degradation. In this study, an iron-based catalyst was synthesized and characterized to evaluate its performance in methylene blue (MB) removal through a Fenton-like oxidation process. The catalyst exhibited a dark brown, homogeneous powder texture with a surface area of 45.3 m² g⁻¹, indicating moderate porosity suitable for mass transfer. FTIR analysis confirmed the presence of Fe–O and O–H functional groups, suggesting successful formation of Fe 2 O 3 /Fe 3 O 4 phases and active surface hydroxylation. Adsorption tests showed rapid dye uptake within 10 minutes, while catalytic experiments demonstrated 90% degradation of MB after 60 minutes under optimal conditions (pH 5, 0.05 g catalyst dosage, and 1.0 mM H_2 O_2 ). Kinetic evaluation followed a pseudo-first-order model with a rate constant of 0.034 min⁻¹ (R² = 0.982), confirming that the degradation was governed by surface-mediated hydroxyl radical reactions. The proposed mechanism involves Fe²⁺/Fe³⁺ cycling for continuous •OH generation and efficient oxidation of MB into CO 2 and H 2 O. Overall, the synthesized Fe-based catalyst exhibits high activity, stability, and cost-effectiveness under mild conditions, underscoring its potential for scalable and sustainable wastewater treatment applications.