The removal of the indigo carmine dye from aqueous solutions using cross-linked chitosan-Evaluation of adsorption thermodynamics using a full factorial design

The adsorption thermodynamic parameters, namely ΔadsH, ΔadsG, and ΔadsS, were determined for all the factorial design results. Endothermic values were found in relation to the ΔadsH. The positive ΔadsS values indicate that entropy is a driving force for adsorption. The ΔadsG values are also significantly affected by important antagonistic and synergistic effects involving all principal and interactive factors. It is concluded that the thermodynamical spontaneity of the IC adsorption parameters are greatly influenced by the interactive factors and not by the temperature changes alone.