Behaviors and mechanisms of tannic acid adsorption on an amino-functionalized magnetic nanoadsorbent

Tannic acid is known as one of the refractory organic pollutants in water. Amino-functionalized magnetic nanoadsorbent (Fe(3)O(4)@SiO(2)-NH(2)) exhibited high adsorption capacity for aqueous TA with maximum adsorption amount of 136.23 mg/g at 25 degrees C. TA adsorption on the adsorbent could be well described by Langmuir adsorption model and the adsorption process was endothermic. Furthermore, pseudo-second adsorption kinetics can fit TA adsorption data very well, and the adsorption rate decreased with increasing initial TA concentration. The presence of Na(+), K(+), and Ca(2+) may result in enhanced TA adsorption. In addition, TA adsorption over the adsorbent was highly dependent on solution pH and the maximum adsorption amount was found to be at pH 6.0. The XPS analysis revealed that TA adsorption over the adsorbent may be attributed to the surface complexation between the amino groups of the adsorbent and TA in solution. The TA loaded adsorbent can be effectively desorbed in a 0.5 M HCl solution, and the regenerated adsorbent can be recycled. (C) 2011 Elsevier B.V. All rights reserved.