Facile synthesis of Co₃O₄ nanoparticle-functionalized mesoporous SiO₂ for catalytic degradation of methylene blue from aqueous solutions

In this study, a series of Co₃O₄ nanoparticle-functionalized mesoporous SiO₂ (Co-SiO₂) were successfully synthesized via a spontaneous infiltration route. Co species were firstly infiltrated into the confined spaces between the surfactant and silica walls, with the assistance of grinding CoCl₃·6H₂O and the as-prepared mesoporous SiO₂. Then, Co₃O₄ nanoparticles (NPs) were formed and grown in the limited space of the mesopores, after calcination. Structures, morphologies, and compositions of the materials were characterized by X-ray diffraction, transmission electron microscopy, energy dispersion spectrum, N₂ adsorption, and Fourier transform infrared spectra. Results showed that the high content of Co (rCo:Si = 0.17) can be efficiently dispersed into the mesoporous SiO₂ as forms of Co₃O₄ NPs, and the structural ordering of the mesoporous SiO₂ was well-preserved at the same time. The Co₃O₄ NP functionalized mesoporous SiO₂ materials were used as Fenton-like catalysts for removing methylene blue (MB) from aqueous solutions. The catalyst prepared at rCo:Si = 0.17 could completely remove the high-concentration of MB (120 mg·L^-1), and also showed an excellent performance with a removal capacity of 138 mg·g^-1 to 180 mg·L^-1 of MB. Catalytic mechanisms were further revealed, based on the degradation results.