The influence of the degree of cross-linking on the adsorption properties of chitosan beads
2008
Osifo, Peter O. | Webster, Athena | van der Merwe, Hein | Neomagus, Hein W.J.P. | van der Gun, Marius A. | Grant, David M.
The influence of the degree of cross-linking (DCL) on chitosan beads was studied. Chitosan was prepared from the exoskeleton of Cape rock-lobsters, collected from the surroundings of Cape Town, South Africa. The chitosan beads were characterized; the beads water contents and pK a varied in the range of 90-96% and 4.3-6.0, respectively, and were found to decrease with increasing DCL (0.0-34.0%). A pH-model, which described the reversibility of the metal adsorbed onto the beads, was used to predict the equilibrium properties of copper adsorption onto the cross-linked beads. The model accounts for the effect of pH and the important model parameters, the equilibrium adsorption constant (K ads) and to a lesser extent the adsorbent adsorption capacity (q max) showed to decrease with the DCL. The adsorbent capacity and the adsorption constant were determined as 3.8-5.0mmol/g chitosan and (9-90)x10⁻⁴, respectively. The adsorption kinetics could be described using a shrinking core model and the effective diffusion coefficient (D eff) was determined as (8.0-25.8)x10⁻¹¹ m²/s. It was found that D eff decreases with the DCL mainly due to the decreased in water content of the beads at high DCL.
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