Application of nanosilica-based adsorbent for the removal of rhodamine B and methylene blue from aqueous solutions

In this study, an adsorbent based on nanosilica molecules was synthesized by chemical activation and changing the structure of a sodium silicate )Na 2 SiO 3 (. The adsorbent was characterized by scanning electron microscope/energy-dispersive X-ray spectroscope, X-ray diffraction analysis, transmission electron microscope, and Brunauer–Emmett–Teller analysis for morphologic properties and determination of specific surface area. Sorption experiments were carried out to evaluate the effects of variables, such as initial dye concentration, contact time, and pH on the dye removal. Different isotherm and kinetic models were used to evaluate the sorption equilibrium and describe the sorption process. More than 75% removal efficiency was obtained within 15 min at adsorbent dose of 10 g/L for initial dye concentration of 150 mg/L. The maximum sorption capacity was found to be 92.9 mg/g at pH 10 and 70.9 mg/g at pH 9 for RB and MB, respectively. The best fit was achieved by the Langmuir isotherm equation (R 2 values = 0.99 and 0.98) for RB and MB, respectively. The kinetic studies showed that the RB and MB dye sorption onto the nanoadsorbent was best described by the pseudo-second-order kinetic model. This study showed that the sodium silicate nanoadsorbent can be an ideal adsorbent for dye removal and may also be used in environmental research in other fields.