Photocatalytic decolorization of methyl orange using MnCeOx–TiO2 composite catalyst: experimental evaluation and statistical analysis

Abstract

MnCeOx/TiO2 composite catalysts were synthesized and characterized to investigate their photocatalytic efficiency in methyl orange decolorization. Structural and textural analyses revealed mesoporous architectures with specific surface areas ranging from 31.38 to 68.46 m2 g−1, pore volumes of 0.252–0.505 cm3 g−1, and average pore diameters of 14.75–29.50 nm. FT-IR, XRD, and UV–Vis/DRS confirmed successful MnCeOx incorporation and band gap tuning (2.87–3.46 eV), indicating enhanced charge transfer capabilities. Photocatalytic experiments demonstrated that MO decolorization is highly sensitive to solution pH, temperature, MnCeOx/TiO2 weight ratio, and reaction time. Optimal conditions—pH = 3, temperature ≈ 39.6 °C, MnCeOx/TiO2 = 0.31, and reaction time = 35 min—achieved a maximum photo decolorization efficiency of 41.93%. Kinetic studies revealed pseudo-first-order behavior (k = 0.04927 min−1 for MCT-0.1), with performance strongly influenced by surface charge interactions and active site accessibility. A Response Surface Methodology-Central Composite Design model was developed, demonstrating excellent predictability (R2 = 0.99, Pred R2 = 0.96) and a desirability score of 0.97. ANOVA confirmed the significance of main effects and binary interactions, particularly between pH, MnCeOx/TiO2 ratio, and reaction time, on MO PDE.