γ-ray radiation-induced synthesis and Fe(III) ion adsorption of carboxymethylated chitosan hydrogels

The carboxymethylated chitosan (CMCts) hydrogels were synthesized by γ-ray radiation-induced crosslinking at paste-like state with the concentration of CMCts from 12% to 22%. The gel fraction firstly increased with adsorbed dose and leveled off at ca. 20 kGy. The diffusion behavior of water in CMCts gels was Fickian diffusion, and the swelling of CMCts gels was affected by pH and ionic strength. Preliminary crosslinking mechanism of CMCts with γ-ray irradiation was discussed based on the FTIR and sol-gel analysis. The adsorption kinetics study showed that the adsorption of Fe(III) ions onto CMCts gels was very fast (ca. 20 min) due to the coordination of Fe(III) ions with amino, hydroxyl and carboxyl groups of CMCts molecules. pH 4.7 was the optimum for the adsorption of Fe(III) ions onto CMCts gels. The maximum uptake of Fe(III) ions, based on Langmuir equation, was determined to be 18.5 mg/g gel.