Adsorption of tannic acid from aqueous solution by aminopropyl functionalized SBA-15

Abstract

Tannic acid (TA) is generally considered as one of the refractory organic pollutants in water. In this study, aminopropyl functionalized SBA-15 (SBA-15-NH2) was prepared by post-grafting method and the adsorption behavior of TA on the synthetic adsorbent was investigated using batch experiments and adsorption kinetic tests. The adsorbent was characterized by a variety of experimental and spectroscopic techniques with respect to structural, porosity, and surface characteristics. Characterization results showed that SBA-15-NH2 has ordered mesoporous structure, BET surface area of 245.49 m2/g, and the pore volume of 0.43 cm3/g. Batch adsorption tests showed that SBA-15-NH2 adsorbent exhibited high adsorption affinity to TA with a maximum adsorption capacity of 272.4 mg/g. TA adsorption over the adsorbents could be well described by Freundlich adsorption model, suggesting that the adsorption process is heterogeneous. The hydrogen bonding ability and electrostatic interaction between the TA and aminopropyl groups further conformed by pH and ionic strength experiments. In addition, the adsorption process obeyed the pseudo-second-order kinetics and the rate constant decreased with initial TA concentration.