A statistical physics analysis of the adsorption of Fe3+, Al3+ and Cu2+ heavy metals on chitosan films via homogeneous and heterogeneous monolayer models

Abstract A heterogeneous monolayer model with two types of binding site was utilized to analyze and interpret the adsorption mechanism of Fe3+, Al3+ and Cu2+ ions on chitosan films at 25 - 55 °C and pH 6. Theoretical results of statistical physics calculations indicated that the adsorption of Fe3+, Al3+ and Cu2+ ions was multi-ionic where two adsorption sites (i.e., amino and hydroxyl groups) were involved but with a different contribution degree. Adsorption capacities at saturation ranged from 125.99 to 512.27 mg/g for tested operating conditions. The removal mechanism of Al3+ and Cu2+ ions was exothermic, whereas the adsorption of Fe3+ ions was endothermic.