Abstract
Silica mesoporous materials of MCM-48 type were successfully synthesized using different types of silica-bearing solid wastes including silica fume, silica gel from rice husk ash and glass wastes as adsorbents for safranin dye. This represents an effective recycling technique for the production of such advanced materials from low-cost solid wastes instead of chemicals. The materials were synthesized by hydrothermal treatment process for 48 h in the presence of an organic template at 110 °C followed by calcination at 550 °C. The products were identified utilizing XRD and SEM analyses to investigate the structural and the morphological features. The used silica precursors exhibit a significant effect on the morphologies of synthetic MCM-48 materials and their adsorption behaviors. The adsorption properties were addressed based on a series of traditional and advanced equilibrium models. The adsorption results reflected the higher capacity for the dye molecules using glass-based MCM-48 than fume-based MCM-48 and rice silica gel-MCM-48. However, the uptake results of glass-based MCM-48 is of monolayer type and can be explained by Langmuir model and the uptake by the other synthetic products (fume-based MCM-48 and rice gel-based MCM-48) is of multilayer type and fitted with Freundlich model. The mathematical parameters of advanced isotherm model (monolayer model of two energies) reflected the theoretical values of adsorption capacity, number of adsorbed safranin molecules per active site, the average number of sites occupied by dye and the density of the present receptor sites.