equilibrium studies

The ability of chitosan as an adsorbent for Cu (II) and Cr (VI) ions in aqueous solution was studied. The experiments were done as batch processes. Equilibrium studies were done on both cross-linked and non-cross-linked chitosan for both metals. Cr (VI) adsorption behaviour could be described using the Langmuir isotherm over the whole concentration range of 10 to 1000 mg·l-1 Cr. The maximum adsorption capacity for both types of chitosan was found to be 78 mg·g-1 for the non-cross-linked chitosan and 50 mg·g-1 for the cross-linked chitosan for the Cr (VI) removal. For the Cu (II) removal the Freundlich isotherm described the experimental data over the whole concentration range of 10 to 1000 mg·l-1 Cu (II). The maximum adsorption capacity for both types of chitosan can be estimated to be greater than 80 mg·g-1. Cr (VI) removal was the highest at pH 5 but pH did not have a large influence on Cu (II). From these results it is clear that the adsorption of heavy metals is possible with chitosan, but that with this method, end concentrations of below 1 mg·l-1 can hardly be obtained