Use of SBA-15 ordered nano mesoporous silica for removal of copper(II) from aqueous media: Studies on equilibrium, isotherm, kinetics and thermodynamics

Abstract

Copper is a heavy metal. When its content is low, it is good to the health of biological body. However, when its content is high, it has the toxic effect on biological body. At this time, removal of the toxicity of copper is very important. SBA-15 molecular sieve was prepared by hydrothermal synthesis method. The sample was characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, 77 K adsorption-desorption isotherm of nitrogen. The fibrous particles with a diameter of 333 ± 10 nm were obtained. Nano mesoporous SBA-15 with Brunner-Emmett-Teller specific surface area 503 m2 g−1 was used as an adsorbent to adsorb Cu(II) from solution. The effects of acidity, temperature, contact time, amount of adsorbent and initial concentration of Cu(II) on the adsorption were studied. Under the optimized adsorption conditions, the maximum adsorption rate of Cu(II) by nano-mesoporous SBA-15 was 89.0% and the maximum adsorption capacity was 11.39 mg/g. By studying kinetics, it was found that the adsorption belongs to the quasi-second-order kinetic model, simultaneously belonging to the Freundlich adsorption isotherm. The results of adsorption thermodynamics showed that when temperature is 25–55 °C, △G° < 0, the adsorption enthalpy change ΔH° = −50.185 kJ/mol, the adsorption entropy change △S° = −127.703 J /(mol K), the adsorption is spontaneous exothermic entropy reduction process. Desorption studies were carried out by using nitric acid and hydrochloric acid, respectively. The results showed that the desorption effect using 0.1 mol/L nitric acid as desorbent is better than that of hydrochloric acid. The desorption rate is the highest at desorption for 10 h, reaching 73.0%. This method has a potential to remove other heavy metals.