Efficient removal of cadmium(II) with SBA-15 nanoporous silica: studies on equilibrium, isotherm, kinetics and thermodynamics

Abstract

Abstract Nanomesoporous silica SBA-15 was prepared by hydrothermal method. The samples were characterized by powder X-ray diffraction and scanning electron microscopy. The fibrous particles with a diameter of 333 ± 10 nm were obtained. Nanoporous mesoporous SBA-15 was used as an adsorbent to adsorb Cd2+ in water body. The effects of conditions such as acidity were studied, and the optimized adsorption conditions were obtained. The results showed that when the pH value was 5.0, the temperature was 25 ± 1 °C and the adsorption time was 40 min, the nanomesoporous SBA-15 had the best adsorption effect for Cd2+ and the adsorption rate was reached 73.28% and the adsorption capacity was 9.84 mg/g. Study found that the adsorption is the quasi-second-order kinetic model, which belongs to the Freundlich adsorption type. The results of adsorption thermodynamics showed that when the temperature is 25–55 °C, the adsorption is spontaneous exothermic reaction, ∆G 0 < 0, the adsorption enthalpy change ΔH 0 = − 54.732 kJ/mol, the adsorption entropy change ∆S 0 = − 129.343 J/(mol K). The effects of nitric acid and hydrochloric acid on desorption were investigated, respectively. The results showed that the desorption effect of 0.1 mol/L nitric acid as desorbent was better than that of hydrochloric acid. At desorption for 10 h, the desorption rate was the highest, reaching 65.56%.

Keywords

• Cadmium
• Adsorption
• SBA-15
• Desorption
• Kinetics
• Thermodynamics