Metal uptake by chitosan derivatives and structure studies of the polymer metal complexes

Abstract

Two modified chitosan polymers were obtained by reaction of chitosan with cinnamoyl chloride and cinnamoyl isothiocyanate to produce two new derivatives. The new modified polymers were characterized by elemental and spectral analysis to confirm their structures. Their metal up take capacity was investigated both under competitive and noncompetitive conditions. At pH 5.6, the (ChitoCin and ChitoThioCin) polymers exhibit higher capacity for Cu(II) (0.461–0.572 mmol/g) than the other metal ions used. Where the capacities of the other metal ions are: Fe(III) (0.235–0.341 mmol/g), Cr(III) (0.078–0.099 mmol/g), Co(II) (0.046–0.057 mmol/g) and Ni(II) (0.041–0.053 mmol/g). These results show that the capacity of ChitoThioCin polymer is higher than that of ChitoCin for each metal ion. However, at lower pH the capacities (for Cr(III) pH < 1.8 and Fe(III) pH < 3.1) are higher than other metal ions under investigation. It has been found that the absorption follows the Langmuir isotherm better than that of the Freundlich isotherm. The metal complexes with several metal cations were isolated and their structures with the new chitosan polymers were found to be octahedral and schematic representations of the complexes were given.