Synthesized cellulose/succinic anhydride as an ion exchanger. Calorimetry of divalent cations in aqueous suspension

A synthetic route to a biopolymer/anhydride ion exchanger adds cellulose directly to molten succinic anhydride in a quasi solvent-free procedure. An amount of 3.07 +/- 0.05 mmol of pendant groups incorporated onto the polymeric structure, which was characterized by elemental analysis, solid state carbon NMR, infrared, X-ray and thermogravimetry. The new polysaccharide is able to exchange cations from aqueous solution through a batchwise methodology, to obtain 2.46 +/- 0.09 mmol g(-1) for divalent cobalt and nickel cations. The net thermal effects obtained from calorimetric titrations gave endothermic values of 3.81 +/- 0.02 and 2.35 +/- 0.01 kJ mol(-1). The spontaneity of this ion-exchange process reflected in negative Gibbs energies and also a positive entropic contribution. These thermodynamic data at the solid/liquid interface suggests a favorable ion exchange process for this anchored biopolymer, for cation removal from the environment. (C) 2011 Elsevier B.V. All rights reserved.