Characterization and adsorption behaviors of a novel synthesized mesoporous silica coated carbon composite

A novel mesoporous silica coated carbon composite (denoted SEG) with hierarchical pore structure has been successfully prepared in an aqueous solution that contains triblock copolymer template, aluminum chloride, siliceous source and expanded graphite. Textural property and morphology of the SEG composite were characterized by the combination of X-ray diffraction, N2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared measurements. Results show that mesoporous silica is steadily and uniformly grown on the surface of the graphite slices and the thickness of the silica layer can be finely tuned according to the silica/C molar ratio in the initial reaction solution. This newly synthesized SEG composite shows greatly increased adsorption capacity to methylene blue than the pristine expanded graphite in the batch tests. Both Langmuir and Frendlich models were further used to evaluate the adsorption isotherms of methylene blue over expanded graphite and SEG samples with different silica contents. Finally, pseudo-second-order model was used to describe the kinetics of methylene blue over expanded graphite and the silica-carbon composites.