Catalytic wet peroxide degradation of acrylonitrile wastewater by ordered mesoporous Ag/CeO2: synthesis, performance and kinetics

Abstract

Ordered mesoporous Ag/CeO₂ catalysts have been successfully synthesized by a microwave assisted soft template method. The morphology, structure and chemical composition of the catalyst were characterized by XRD, N₂ adsorption–desorption, SEM, EDS, TEM and XPS. The study of catalytic performance and reaction kinetics of organic matter degradation in acrylonitrile wastewater was performed in a catalytic wet peroxide (CWPO) system. The degradation pathways of organic matter in acrylonitrile wastewater were elucidated by temporal evolution of intermediates and final products detected by GC/MS analysis along with a continuous flow experiment study. The results show that the Ag/CeO₂ has an ordered mesoporous structure, the specific surface area is 91.4–118.2 m² g⁻¹ and the average pore size is 12.63–16.86 nm. 0.4-Ag/CeO₂ showed the best catalytic performance, the COD removal rate reached 94.6%, which was 30% higher than that of CeO₂. The degradation is in accordance with the second-order reaction kinetics of the Arrhenius empirical model and Langmuir–Hinshelwood kinetic model. However the latter fits better, and the linear correlation coefficient R² is more than 0.98, which describes the adsorption catalytic mechanism of Ag/CeO₂. According to the analysis by GC/MS, the organic compounds in acrylonitrile wastewater oxidized into intermediate compounds and other small compounds, then are further oxidized into carbon dioxide and water. The catalytic activity of Ag/CeO₂ was the result of the combination of Lewis acid–base position of CeO₂ and redox cycle of Ce³⁺/Ce⁴⁺.