Equilibrium and kinetic studies of copper(II) ion uptake by chitosan-tripolyphosphate chelating resin

Abstract

Spherical chitosan-tripolyphosphate (TPP) chelating resins are successfully synthesized by an in-liquid ionotropic crosslinking method, and are then employed to examine their uptaking ability for copper(II) ion. The crosslinking characteristics of the beads were improved by the modification of the in-liquid curing mechanism in different pH of TPP solution. Sorption capacities and kinetics of the gel beads are greatly influenced by the polymeric physical or physicochemical characteristics of the chitosan-TPP networks, such as ionic crosslinking and swelling properties. Ionic crosslinking not only reduced the crystallinity of the beads but also decreased the amino binding site on chitosan for metal ions uptakes, thus resulting in a decrease of Cu 2+ adsorption. The copper(II) ions adsorbed by the chitosan beads at lower pH (pH 2 and 3) are limited by the poor complex reaction between metal ions and macromolecules at swelling state. The rate of uptake of metal ions to the chitosan beads at the original pH of the Cu 2+ solution (pH ∼ 5) is conditioned by the intraparticular diffusion of metal ions into the glassy gel phase, which has been examined by EDS analysis. The excellent saturation adsorption capacity of chitosan-TPP beads for Cu 2+ ion at the best working condition (pH ∼ 5) was about 200 mg Cu 2+ ion per gram at an initial concentration of 1000 ppm of Cu 2+ ions.