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

Spherical chitosan-tripolyphosphate (TPP) chelating resins are successfully synthesized by an in-liquid ionotropic crosslinking method, and are then e mployed to examine their uptaking ability for copper(II) ion. The crosslink ing characteristics of the beads were improved by the modification of the i n-liquid curing mechanism in different pH of TPP solution. Sorption capacit ies and kinetics of the gel beads are greatly influenced by the polymeric p hysical or physicochemical characteristics of the chitosan-TPP networks, su ch as ionic crosslinking and swelling properties. Ionic crosslinking not on ly reduced the crystallinity of the beads but also decreased the amino bind ing site on chitosan for metal ions uptakes, thus resulting in a decrease o f Cu2+ adsorption. The copper(II) ions adsorbed by the chitosan beads at lo wer 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 Cu2+ solution (pH similar to 5) is conditioned by the intraparticular diffusion of metal ions into th e glassy gel phase, which has been examined by EDS analysis. The excellent saturation adsorption capacity of chitosan-TPP beads for Cu2+ ion at the be st working condition (pH similar to 5) was about 200 mg Cu2+ ion per gram a t an initial concentration of 1000 ppm of Cu2+ ions. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.