Maleic anhydride incorporated onto cellulose and thermodynamics of cation-exchange process at the solid/liquid interface

This investigation explores the chemical modification of cellulose by using a quasi solvent-free procedure, in which the biopolymer was added to molten maleic anhydride, producing a mixture of maleated and fumarated celluloses. Using this pathway mainly surface modifications are observed and more than 2.82 +/- 0.05 mmol of modifier per gram of synthesized polymer were obtained. These chemically modified materials were characterized by elemental analysis, solid-state C-13 NMR CP/MAS, FTIR, XRD, TG and SEM. The chemically modified polysaccharides are able to adsorb cations. The data were adjusted to a modified Langmuir equation to give 1.75 +/- 0.09 and 2.40 +/- 0.12 mmol/g of Co2+ and Ni2+, respectively. The net thermal effects obtained from calorimetric titration measurements were also adjusted to a modified Langmuir equation and the enthalpy of the interaction was calculated to give the endothermic values of 0.29 +/- 0.02 and 0.87 +/- 0.02 kJ/mol for Co2+ and Ni2+, respectively. The thermodynamic data for these systems are favorable for cation adsorption from aqueous solutions at the solid/liquid interface, suggesting the use of this anchored biopolymer for cation removal from the environment. (C) 2009 Elsevier B.V. All rights reserved.