Preparation, characterization and catalytic performance of mesoporous silicates derived from natural diatomite: Comparative studies

This paper aims at preparation of disordered mesoporous silicates from the diatomite ore as a natural resource of silica. Studying the morphological, chemical and textural properties of the prepared silicate samples was evaluated by field-emission scanning electron microscope (FE-SEM) combined with energy dispersive spectroscopy (EDS), high-resolution transmission electron microscope (HR-TEM), X-ray diffraction (XRD) and nitrogen adsorption isotherms at −196 °C. Catalytic oxidation studies were performed for methylene blue dye (MB) in presence of H2O2. Effects of different parameters like catalyst dose, pH, temperature, and initial concentrations of MB dye solution were investigated. Nanospherical and mesoporous silicates were formed without and with addition of cetyltrimethylammonium bromide (CTAB) surfactant, respectively. The obtained results in catalytic oxidation of MB dye are mainly related to the changes in surface area and mesopore size distributions as well as the significant effect of Fe (III) ions. The most effective catalytic oxidation studies were attained with catalyst dose (2 g/L), pH (4), temperature (50 °C) and initial dye concentration of MB dye (25 mg/L). A sharp decomposition proceeded during the first hour of the reaction. The obtained mesoporous silicate containing well-dispersed iron species as catalyst with the highest surface area and the lowest mesopore diameter showed excellent catalytic activity toward the removal of MB dye.