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, 13C 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 ± 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.