Cellulose, a biopolymer seemingly inert, was chlorinated initially by reaction with thionyl chloride and then after it becomes more reactive, reacted with 2-aminomethylpyridine molecule for increasing its capacity of removal of divalent cations from an aqueous medium. These materials were characterized by means of elemental analysis, C-13 NMR, and FTIR techniques, which have proved that a successful modification has occurred. The final material (Celamp), after being characterized was submitted to adsorption assays to evaluate its interaction with cations, whose affinity was found to be Cu2+ > Co2+ > Ni2+ > Zn2+. The quantitative cation/base center interactions were calorimetrically determined and showed exothermic enthalpies of -(13.25 +/- A 0.12), -(15.11 +/- A 0.22), -(17.23 +/- A 0.15), and -(14.66 +/- A 0.27) kJ mol(-1); negative Gibbs energies of -(16.3 +/- A 0.7), -(14.7 +/- A 0.7), -(14.4 +/- A 0.7), and -(13.3 +/- A 0.7) kJ mol(-1); and entropies of 10 +/- A 2, -1 +/- A 1, -10 +/- A 1, and -5 +/- A 1 J mol(-1) K-1 for the same sequence of cations. These favorable thermodynamic data suggest that the synthesis involving cellulose produces a new useful material for cation removal from the environment.1141423429