Study on SBA-15 as an effective sorbent for dye butyl rhodamine B

Abstract

Nano mesoporous silica molecular sieve material SBA (Santa Barbara Amorphous)-15 was prepared by hydrothermal method and characterized by means of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption-desorption studies. Butyl rhodamine B (BRB) was adsorbed by the SBA-15. The impacts of solution acidity, adsorbent dosage, the initial concentration of butyl rhodamine B, contact time, and temperature on the effects of adsorption were studied and the optimum adsorptive conditions were obtained. The experimental results of adsorption showed that the optimal adsorptive conditions were: pH = 5.0, (SBA-15): BRB = 750: 1, room temperature 30 ± 1 °C and the contact time 20 min. At this time, the adsorption capacity is 1.30 mg/g and the adsorption ratio is 97.52%. Dynamic and thermodynamic properties of the adsorption for butyl rhodamine B by SBA-15 were studied, and the results showed that the adsorption of butyl rhodamine B by SBA-15 is a pseudo-second-order kinetic adsorption. The adsorption thermodynamic data showed that in the 4–30 °C interval ∆G0 0 showed that the adsorption of butyl rhodamine B by SBA-15 is an endothermic process. ΔS0 = 204.9 J / (mol · K) > 0 illustrated that the adsorption process is a reaction of entropy increase. In the 30–60 °C interval, ∆G0 < 0, the reaction can occur spontaneously. ΔH0 = −32.371 kJ/mol < 0 showed that the adsorption of butyl rhodamine B by SBA-15 is an exothermic process. ΔS0 = −30.2 J / (mol · K) < 0 illustrated that the adsorption process is a reaction of entropy decrease. ΔG0 is between −20 and −80 kJ/mol, showing that this adsorption is a coexisting of chemical and physical adsorption. The adsorption of butyl rhodamine B by SBA-15 satisfies the Freundlich adsorption isotherm and belongs to a heterogeneous adsorption.