In order to increase the nickel adsorption capacity of raw chitosan beads (CB), they were chemically modified with histidine (HIS-ECH-CB) by using crosslinking agent, epichlorohydrine (ECH). The nature and morphology of the sorbent were characterized using FTIR, TGA and SEM analysis. For optimization of adsorption conditions, sorption experiments were performed by varying contact time, pH, temperature and initial nickel concentration. Based on the adsorption experiment, the HIS-ECH-CB showed the significant adsorption capacity of 55.6 mg/g under the optimal adsorption condition. Nickel adsorption isotherms data were fitted to Freundlich isotherm. Thermodynamic parameters namely Delta G degrees. Delta H degrees and Delta S degrees of the Ni(II) adsorption process were calculated. The negative values of Gibbs free energy of adsorption (Delta G degrees) indicated the spontaneity of the adsorption of Ni(II) ions on the histidine modified chitosan. Desorption of Ni(II) ions from HIS-ECH-CB could be done rapidly by using 0.1 M HCl, HNO3 and EDTA solutions and the beads could be used again to adsorb Ni(II) ions. (C) 2012 Elsevier B.V. All rights reserved.