Swelling and adsorption properties of crosslinked chitosan-based films: kinetic, thermodynamic and optimization studies
Nacer Boudouaia, Ahmed Amine Bendaoudi, Hacène Mahmoudi, Taoufiq Saffaj, Zohra Bengharez
Abstract
ABSTRACT The study was aimed at synthesizing films of crosslinked chitosan-terephthaldehyde (CS-TPA) and investigating their swelling, adsorption, kinetic, isotherm and thermodynamic properties. Films derived from CS-TPA were prepared with different cross-linking rates of 0%, 0.1% and 0.2%. The chemical composition of the films was examined using Fourier-transform infrared spectrometry to confirm formation of Schiff base. The morphology of films was analyzed by scanning electron microscopy. The micrographs showed that the chitosan (CS) films had a homogeneous smooth surface while CS-TPA films had cavities which were related to the cross-linking rate. Thermal properties were characterized by differential scanning calorimetry analysis where results revealed that synthesized films had degradation and glass transition temperatures in agreement with the literature. The swelling behavior of the films was examined by varying the cross-linking rate, reaction time, salinity, pH, and temperature. The swelling process of films was found to be endothermic and spontaneous and obeyed with a pseudo-second-order kinetic model. The adsorption performance of the crosslinked chitosan films was investigated for the removal of hexavalent chromium. The maximum adsorption capacity of 60.53 mg g –1 was obtained using terephthaldehyde 0.1%. The adsorption data fitted well to the Langmuir isotherm and a pseudo-second-order kinetic model. The thermodynamic results indicated that adsorption of chromium onto CS-TPA 0.1% film was favorable, spontaneous, and exothermic with high randomness at the solid/liquid interface.