Investigation of performance of bimodal/functionalized mesoprorous silica nanoparticles on the adsorption of methylene blue from aqueous solution

Abstract

In this study, bimodal mesoporous silica, i.e. UVM-7, was synthesized and functionalized with<br />sulfonic acid and characterized using XRD, nitrogen physisorption, SEM, TEM and acid/base<br />titration. The results displayed that bimodal mesopore structure was firmly formed and acidic<br />functional groups were grafted on the surface of the UVM-7. The concentration of the acidic<br />functional groups was determined via titration by the standard NaOH solution. At the second<br />step, the adsorption of methylene blue from aqueous solutions onto UVM-7 and UVM-7/<br />SO3H was investigated. The effect of PH, temperature, dye concentration, salt concentration<br />and contact time on the adsorption of methylene blue was studied. The adsorption equilibrium<br />isotherms were well fitted to Langmuir rather than Freundlich model. Methylene blue<br />adsorption on UVM-7 increases with increasing the temperature and PH, which indicates<br />that the process is endothermic. Maximum adsorption capacity of methylene blue by UVM-7<br />and UVM-7/SO3H were 107.5 mg/g and 129.9 mg/g, respectively. The adsorption kinetics of<br />methylene blue for both UVM-7 and UVM-SO3H were pseudo-second order and well fitted to<br />Langmuir model.