Thermochemistry of interaction between cellulose modified with 2-aminomethylpyridine and divalent cations

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, 13 C 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 Cu 2+ > Co 2+ > Ni 2+ > Zn 2+ . The quantitative cation/base center interactions were calorimetrically determined and showed exothermic enthalpies of −(13.25 ± 0.12), −(15.11 ± 0.22), −(17.23 ± 0.15), and −(14.66 ± 0.27) kJ mol −1 ; negative Gibbs energies of −(16.3 ± 0.7), −(14.7 ± 0.7), −(14.4 ± 0.7), and −(13.3 ± 0.7) kJ mol −1 ; and entropies of 10 ± 2, −1 ± 1, −10 ± 1, and −5 ± 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.