Solid-state preparation of mesoporous Ce–Mn–Co ternary mixed oxide nanoparticles for catalytic degradation of methylene blue

Abstract

Mesoporous Ce–Mn–Co ternary metal oxide was fabricated via an efficient oxalate-precursor-based soft reactive grinding route and used to activate H2O2 for advanced oxidation of methylene blue in water. In addition, Mn–Co binary oxide and pure Co3O4 and Mn3O4 were also synthesized as reference catalysts. These catalysts were characterized by X-ray diffraction, N2 adsorption–desorption, H2-temperature programmed reduction, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The results demonstrate that part of the Ce and Mn can be incorporated into the lattice of Co3O4 and cause severe lattice distortion of the unit cell. Compared with the single or binary system, Ce–Mn–Co ternary metal oxide exhibits the best activity in methylene blue removal and nearly 100% decomposition rate and 84% COD removal rate can be achieved in 12 h, and with degradation rate of 93.5% after three rounds. These results are primarily attributed to the synergistic effect of Ce, Mn and Co, which can promote the formation of more lattice defects, higher specific surface area and smaller particle size. Quenching tests show that hydroxyl radicals (·OH) play more dominant role than superoxide radicals (·O2-). Kinetic studies were studied and the activation energies of all the catalysts were calculated.