Using Akaike Information Criterion to Select the Optimal Isotherm Equation for Adsorption from Solution

In this study, we measured the adsorption of Basic Blue 41 (BB41) dye on a maize cob adsorbent and on two model adsorbents (cellulose triacetate and cellulose acetate propionate). The experimental adsorption data were evaluated with the isotherm equations of Langmuir, Freundlich, Langmuir-Freundlich and Dubinin-Radushkevich, and constants were obtained exclusively by non-linear regression. In order to select the optimal isotherm equation, Akaike information criterion was used. The celluloses obeyed the Langmuir isotherm in the temperature range tested, whereas the corncob followed the Freundlich equation. This comparative study shows that limited amounts of the cationic dye were adsorbed on the model celluloses than on the cob. BB41 was neither adsorbed horizontally nor vertically onto the cob, whereas it competed with water molecules and despite saturation, did not exhaustively occupy the surface of the celluloses. The Gibbs free energy of adsorption was evaluated using the equilibrium constants obtained by several procedures and the results were found to be inconsistent.