The biopolymer chitosan was chemically modified in a two step reaction with glycidylmethacrylate and diethylenetriamine. The first step leads to the opening of the three-member epoxide ring of glycidylmethacrylate, leaving a double a bond for further reaction. This product reacted with diethylenetriamine through the free glycidylmethacrylate double bond in a second step. The chemically modified biopolymer was characterized by elemental analysis, IR, C-13 NMR, TG, SEM and employed for copper, lead and cadmium biosorption. Elemental analysis data based on nitrogen atom content gave an incorporation of 4.89 mmol of organic pendant groups for each gram of the biopolymer. Nuclear magnetic resonance of the carbon nucleus in the solid state and infrared spectroscopies are in agreement with the success of the proposed chemical modification, while the TG curve demonstrated that the final product is less stable than the precursor biopolymer. The increment of basic centers attached to the pendant chains showed that the metal sorption capability of the final chelating material was higher than chitosan, presenting cation sorptions from aqueous solution in the order Cu2+ > Pb2+ > Cd2+. The experimental data were adjusted to the Langmuir, the Freundlich and the Temkin sorption isotherm models. The behavior suggested that this new modified biopolymer could be employed as a promising sorbent for cation removal from polluted systems. (C) 2011 Elsevier B.V. All rights reserved.