MWCNT/Ag/β-MnO2 Hybrid Nanostructures for Optimized Photocatalytic Wastewater Treatment via Unified Kinetic Modeling

• A novel Ag/MWCNT/MnO 2 hybrid photocatalyst achieves 89.2 % degradation of mixed dyes under visible light irradiation. • The surface plasmons generated by the Ag nanoparticles facilitate charge separation and transfer, leading to improved photocatalytic performance. • A unified l -H model across catalysts provides mechanistic insight into dye degradation beyond empirical kinetics. MWCNT/Ag/β-MnO 2 hybrid photocatalyst was synthesized using a hydrothermal method, and the Ag NPs loading was carefully optimized to achieve the best efficiency. The hybrid structure was clearly validated by multiple analyses, including XRD, HR-TEM, FTIR, and elemental mapping, all of which consistently confirmed its successful formation. Electrochemical impedance spectroscopy (EIS) analysis showed that incorporating Ag NPs into the MWCNT/β-MnO 2 matrix significantly enhanced charge-carrier transfer and effectively reduced recombination. Among the different concentrations of Ag NPs loading, the MAM-4 was able to degrade 87 % of a mixed dye solution (methylene blue and rhodamine B) within 75 min under visible light (λ > 420 nm, 250 W Xe lamp). The photocatalytic reaction kinetics followed a pseudo-first-order model, with an apparent rate constant (k app ) of 0.027 min −1 . Also, the as-prepared MAM-4 catalyst exhibited good durability, retaining about 80 % of its initial photocatalytic efficiency after five consecutive cycles, highlighting its robust cyclic stability. Radical-trapping experiments showed that superoxide radicals (•O 2 ⁻) play the primary role in the pollutant degradation process, contributing approximately 48 % of the total degradation. The L-H kinetics confirmed that the enhanced degradation performance resulted from the combined contributions of adsorption and surface reaction processes. Furthermore, the synergistic heterojunction in the MAM hybrid promoted efficient charge separation, resulting in a marked improvement in photocatalytic performance under visible-light irradiation. This study presents an optimized MWCNT/Ag/β-MnO 2 hybrid with unified kinetic modeling, providing deeper mechanistic insight and demonstrating superior visible-light dye degradation.