Chemical modification of chitosan and equilibrium study for mercury ion removal

To increase the uptake capacity of mercury ions, several chemical modifications of chitosan beads which are cross-linked with glutaraldehyde were performed. Among them, aminated chitosan bead prepared through chemical reaction with ethylenediamine had a high uptake capacity of about 2.3 mmol g^-1 dry mass at pH 7. The increased number of amine groups was confirmed by IR analysis and measuring the saturation capacities for adsorption of HCl. The surface condition and existence of mercury ions on the beads was confirmed by the environmental scanning electron microscope and energy dispersive X-ray spectroscopy instrumental analyses. The beads showed the characteristic of competitive sorption between mercury and hydrogen ions and it was successfully modelled by an equilibrium model.