Environmentally friendly separation of heavy-metal ions onto porous chitosan beads

Chitin and chitosan, which are found in crustacea, mollusca, and fungus, are natural polymers. The average molecular weight and the degree of deacetylation of the chitosan used were found to be 8.2 X 10(5) and 85%, respectively. The chitosan solution was prepared by dissolving chitosan powder into a 2 wt% aqueous acetic acid solution. Sodium hydroxide solution was used as a gelation agent. Spherical chitosan beads for of fixed-bed experiments were made by the sol-gel method. Single-component isotherms Cu2+ and Cd2+ fit well with the Sips isotherm. The adsorption behavior in a fixed-bed was observed in terms of the flow rates for single-and binary-component systems. The adsorption affinity Of Cu2+ onto chitosan beads is larger than that of Cd2+ In the binary system, the breakthrough data of the lower-selectivity ion showed an excess concentration; the exit concentration is higher than the initial concentration at the inlet. Intraparticle diffusion is explained by the pore diffusion mechanism. Adsorption dynamics of Cu2+ and Cd2+ in a fixed- bed can be simulated by LDFA (linear driving force approximation).