Structure directed reversible adsorption of organic dye on mesoporous silica in aqueous solution

Dynamic adsorption of an organic dye, methylene blue, on mesoporous silica materials with different structures, MCM-41, MCM-48 and MCM-50, were investigated and it was found that dye adsorption presents reversible or irreversible behaviour in dye solution depending on the structure of mesoporous materials. MCM-41 and MCM-48 display a reversible adsorption after reaching equilibrium while MCM-50 exhibits irreversible adsorption. The kinetic studies show that the adsorption of dye on MCM-41, MCM-48 and MCM-50 mesoporous materials follows the second-order kinetics. The desorption of dye from MCM-41 and MCM-48 follows the pseudo-first-order kinetics and the desorption rate constants are much smaller than those of adsorption.