Green Synthesis for MCM-41 and SBA-15 Silica Using the Waste Mother Liquor

Abstract The synthesis of mesoporous materials such as MCM-41 and SBA-15 requires large amounts of water to neutralize the resulting products. The filtrate (mother liquor) therefore contains unreacted components that can be recycled and reused. The addition of the mother liquor in consecutive syntheses was carried out in order to evaluate the different effects on the physical and chemical properties of the mesoporous materials. For this purpose, the mother liquor from the initial synthesis (1st Generation) was saved and used for the second synthesis (2nd Generation) and successively for the third synthesis (3rd Generation). The three generations of each material were then characterized using different techniques such as X-ray diffraction, X-ray dispersive energy fluorescence, electron microscopy, infrared spectroscopy, Thermal behavior by thermogravimetric analysis and N2 adsorption. The materials obtained showed similar diffractograms for the three generations and also showed similar percentages of silica through XRF. The SEM and IR results for molecular sieves showed the effectiveness of the processes of MCM-41 and SBA-15 synthesis using mother liquor. The results made it possible to observe that the structures of the materials had no significant differences in their physical and chemical properties, favoring the use of mother liquor for up to three generations.