Sacrificial template-directed fabrication of mesoporous manganese oxide based catalysts: Relationship between the ordering degree of pore structure and Fenton-like catalytic activity

Abstract

In this study, novel mesoporous MnOx-based catalysts were prepared via the hard template method by using the mesoporous silica as a template. The performances of these catalysts were evaluated in catalytic wet H2O2 oxidation for Rhodamine B (RhB) in high-salinity wastewater (10% Na2SO4 solution containing RhB). The microstructure characterization indicated that the order of pore structures and the MnOx crystallinity in mesoporous materials improved as the number of repetitions of the immersion and calcination–molding process increased. Given good selective adsorption performance for RhB and rich Mn3+/Mn4+ couples, MnOx mesoporous materials with ordered regular pores exhibited excellent Fenton-like catalytic performance and the highest removal rate of RhB in high-salinity wastewater reached approximately 90% after 150 min of degradation. Moreover, because of the accelerated generation of the free radicals catalyzed by the Fe3+/Fe2+ couples, the loading of Fe species increased the performance of the MnOx ordered catalysts for RhB degradation. Furthermore, the Fe-loading MnOx catalyst exhibited only slight activity loss within the five cycles of catalytic degradation (the removal rate for RhB within the five cycles all exceeded 95%), due to the morphological stability of the MnOx ordered catalyst and the presence of stable Fe3+/Fe2+ couples during the RhB degradation process.