Production and characterization of a novel hierarchical porous silica adsorbent for removal of methylene blue dye from wastewaters

ABSTRACTAdsorption of methylene blue (MB) dye by hierarchical porous silica (HPS) is reported as a means of removing the dye from wastewater. HPS was produced through a sol–gel process by templating on rubber particles in skimmed natural rubber latex. The silica precursor was tetraethyl orthosilicate and the costructure directing agent was 3-aminopropyltriethoxysilane. Based on nitrogen-sorption, the HPS had a total pore volume of 1.0 cm3/g, a specific surface area of 237 m2/g, and a peak pore size of 4 nm. Larger pores (sizes >100 nm to 1 µm) were observed by scanning electron microscopy. The pores had an ink-bottle morphology of narrow necks connected to large cavities. The adsorption obeyed the Langmuir isotherm and was endothermic. Pseudo-second-order adsorption kinetics were observed. The specific adsorption of MB on HPS was 0.225 mmol/g at equilibrium. HPS was superior to many adsorbents reported for removing MB from aqueous media.