Adsorption of silver ions onto chitosan hydrogel: Structural studies

Abstract

Chitosan indicate a significant potential in the field of water treatment due to polymer high porosity, large specific surface area and its ability to bind strongly heavy metal ions form aqueous solutions. Therefore, chitosan based hydrogels have been fabricated by physical crosslinking of the polymer chains via sol–gel method using sodium β-glycerophosphate (β-GP) for silver ions (Ag) removal from water solutions. The aim of this study was to provide experimental studies under batch conditions to perform adsorption isotherm and evaluate the effect of silver adsorption onto chitosan hydrogel morphological and structural changes using SEM, XRD, FTIR and EDX analyses. Obtained results provides the data on the structural changes in the chitosan hydrogels under Ag adsorption process. The FTIR spectra confirmed that the C-NH2 and OH groups contribute to the formation of chitosan - silver ion complexes. The presence of adsorbed Ag in the samples < 0.8 gAgL−1 were evidenced by the characteristic peak at 2θ = 46.35°. Regarding to EDX analysis the adsorption efficiency toward Ag ions, rises with an increase in Ag initial concentration, resulting in L-type isotherm. The percentage removal of silver ions efficiency obtained 34 % for the highest Ag initial concentration (10 gAg L−1). SEM micrographs after Ag adsorption performed morphology as homogeneous porous network and reveals Ag present in the structure resulting from effective Ag adsorption. This study verified structural changes resulted from silver ions adsorption and confirmed the potential for thermosensitive chitosan hydrogels to applied as an adsorbent for water treatment applications.