Abstract
Chitosan, a natural polymer obtained from the de-acetylation of chitin, has been extensively studied in adsorption applications because its amino and hydroxyl groups can act as chelation sites. However, this material is rarely used as an adsorbent, mainly because of mechanical strength limitations. A possible means of making its use viable is the immobilization of chitosan onto solid matrices using particle-coating techniques. Studies have shown that the use of immobilized chitosan not only improves the mechanical strength of the adsorbent, but also enhances its mass-transfer properties. In this context, the present study has investigated the adsorption application of chitosan coated onto glass beads in batch and dynamic systems for the removal of copper ions from aqueous solution. The adsorption equilibrium properties were measured at different temperatures (25, 40, 50 and 60 oC) and the Langmuir, Freundlich and Langmuir–Freundlich models were used to fit the equilibrium data. Kinetic studies showed that adsorption equilibrium was attained after 10 h. The pseudo-first-order and pseudo-second-order kinetic models in both linear and non-linear forms together with the intra-particle diffusion model were used to fit the adsorption kinetics data. The best fit was obtained with the pseudo-second-order kinetic model, thereby suggesting that the limiting factor to mass transfer was chemical adsorption. The results indicate that chitosan immobilized onto glass beads demonstrate a good adsorption performance, with similar or even better results relative to other chitosan-based materials. Dynamic adsorption studies using the coated beads in a fixed bed system demonstrated the viability of their use for wastewater treatment.