Adsorption of Pb2+, Cu2+ and Cd2+ by sulfhydryl modified chitosan beads

A chitosan-based bead was synthesized by crosslinking as well as sulfhydryl modification reaction and its removal ability of Pb2+, Cu2+ and Cd2+ was investigated. The test results showed that the crystal structure of chitosan was destroyed completely and the specific surface area was greatly increased after modification. The adsorption of Pb2+, Cu2+ and Cd2+ by the beads was carried out at different pH, ionic strength, contact time and initial concentration and the maximum adsorption capacities were 273.7 mg/g, 163.3 mg/g and 183.1 mg/g, respectively. Furthermore, due to the large ion radius of Pb2+, its adsorption was seriously disturbed by other ions in the competitive adsorption process. Finally, the adsorption processes of Pb2+, Cu2+ and Cd2+ were well fitted by the Langmuir isotherm model and the pseudo second-order kinetics model, respectively. Combined with the results of X-ray photoelectron spectroscopy, chemical coordination is the main adsorption mechanism.