Analysis of the adsorption of Hg2+, Ni2+ and Cu2+ on chitosan hydrogels

Abstract

Chitosan-based adsorbents have high efficiency in removing heavy metals from water. In this study, the adsorption of Hg2+, Ni2+ and Cu2+ onto chitosan/glutaraldehyde hydrogels were analyzed using the semi-empirical method PM3. Based on thermodynamic analysis of these systems, the adsorption processes were spontaneous, exothermic and highly stable, because all the values of the Gibbs free energy, the enthalpy of formation and the binding energy were negative, on the other hand, each of the systems were analyzed using electrostatic potential maps, where it was observed that the functional groups amino (NH2) and hydroxyl (OH) are the main active sites of the adsorbent. Through an FTIR analysis, the correct cross-linking between chitosan and glutaraldehyde was confirmed, as well as the union of the different cations on the surface of the adsorbent.