• Citric acid modification enhances dispersion of Mn-Ce oxides on Al2O3, increasing surface area and hydroxyl groups for improved catalytic ozonation.
• Mn-Ce/CA-Al2O3 achieves near-complete decolorization of Reactive Black 5 within 60 min and 60% COD removal, outperforming sole ozonation (30%).
• The catalyst operates effectively across a wide pH range (3-11) and shows excellent stability for real dye wastewater treatment.
• The redox cycles of Mn3+/Mn4+ and Ce3+/Ce4+ accelerate electron transfer, promoting ROS generation and enhancing pollutant degradation.