Degradation of Cationic Red GTL by Catalytic Wet Air Oxidation over Mo–Zn–Al–O Catalyst under Room Temperature and Atmospheric pressure

Abstract

To overcome the drawback of catalytic wet air oxidation (CWAO) with high temperature and high pressure, the catalytic activity of Mo–Zn–Al–O catalyst for degradation of cationic red GTL under room temperature and atmospheric pressure was investigated. Mo–Zn–Al–O catalyst was prepared by coprecipitation and impregnation. XRD, TG-DTG, and XPS were used to characterize the resulting sample. Central composition design using response surface methodology was employed to optimize correlation of factors on the decolorization of cationic red GTL. The results show that the optimal conditions of pH value, initial concentration of dye and catalyst dosage were found to be 4.0, 85 mg/L and 2.72 g/L, respectively, for maximum decolorization of 80.1% and TOC removal of 50.9%. Furthermore, the reaction on the Mo–Zn–Al–O catalyst and degradation mechanism of cationic red GTL was studied by Electron spin resonance (ESR) and GC-MS technique. The possible reaction mechanism was that the Mo–Zn–Al–O catalyst can efficiently react with adsorbed oxygen/H₂O to produce ·OH and ¹O₂ and finally induce the degradation of cationic red GTL. GC-MS analysis of the degradation products indicates that cationic red GTL was initiated by the cleavage of NN and the intermediates were further oxidized by ·OH or ¹O₂