Zirconium-chitosan hydrogel beads for removal of boron from aqueous solutions

In this study, zirconium(IV)-chitosan (Zr-CTS) hydrogel beads were synthesized for boron(III) removal. Zr-CTS was characterized by a series of experimental techniques, including SEM, XRD and FTIR. Kinetic, isotherm, and thermodynamic investigations were employed to understand the adsorption behavior. It was found that boron removal is a pH-dependent process, having the highest performance at pH 6-7. It was also shown that the process of boron adsorption follows the pseudo-second-order kinetic model and is dependent on Zr(IV) content in hydrogel beads, achieving the maximum adsorption capacity of 24.5 mg/g. Thermodynamic constants demonstrated a feasible, spontaneous, and endothermic adsorption. Boron removal by Zr-CTS was found to occur through the adsorption of boron species on the surface of amorphous zirconium hydroxide via complexation mechanism. The results indicated that due to its efficiency in removing boron, good regeneration capacity and convenient form, Zr-CTS might be considered as a promising adsorbent for water purification. (C) 2018 Elsevier Ltd. All rights reserved.