The natural biopolymer cellulose was first modified with thionyl chloride, followed by reaction with 1,4-diaminebutane to yield 6-(4'-aminobutylamino)-6-deoxycellulose. From 1.85% of nitrogen incorporated in the polysaccharide backbone, the amount of 0.66 +/- 0.11 mmol of this molecule was anchored per gram of the chemically modified cellulose. The resulting chemically immobilized surface was characterized by elemental analysis, infrared spectroscopy, and nuclear magnetic resonance of the carbon nucleus in the solid state and thermogravimetry. The newly synthesized biopolymer gave maximum sorption capacities of 0.32 +/- 0.03, 0.29 +/- 0.01, 0.26 +/- 0.03 and 0.25 +/- 0.02 mmol g(-1) for divalent copper, cobalt, nickel, and zinc cations, using the batch method, whose data were fitted to different sorption models. The thermal effects obtained from a calorimetric titration procedure gave favorable thermodynamic data for cation sorption from aqueous solutions at the solid/liquid interface, suggesting the use of this anchored biopolymer for cation removal from the environment.