Sulfonate-functionalized nanoporous silica spheres as adsorbent for methylene blue

Sulfonate-functionalized nanoporous silica spheres (NSS-SO3) were prepared by conversion of epoxide to sulfonate with sulfonic acid salts. NSS-SO3 was used as an adsorbent for removal of methylene blue (MB) cationic dye. The adsorbent was characterized by means of scanning electron microscopy (SEM), N-2 adsorption-desorption isotherms, Fourier-transform infrared (FTIR) and Raman spectroscopy, and thermogravimetric analysis. SEM images showed the spherical morphology of the material. The synthesized material was successfully applied for MB removal from synthetic solution in batch systems. The equilibrium sorption isotherm and kinetics were investigated. The adsorption of dye onto the adsorbent could reach equilibrium after 60 min. The equilibrium adsorption data were best described by the Langmuir isotherm. A maximum monolayer sorption capacity of 208 mg g(-1) was found. The kinetic studies indicated that the adsorption process could be well fited by a pseudo-second-order kinetic model.