Modeling of adsorption isotherms of reactive red RR-120 on spirulina platensis by statistical physics formalism involving interaction effect between adsorbate molecules.

In this study, the formalism of statistical physics is used to describe and interpret the adsorption mechanism by applying the law of real gas which takes into account the interaction between the reactive red 120 dye (RR-120) molecules due to its very large size (approximately 2.11 nm). Modeling of the RR-120 dye adsorption isotherms on Spirulina platensis sp. is performed. Five models based on statistical physics formalism are developed: Hill model with one adsorbed site energy, Hill model with two energies, Hill model with three energies, double layer model with one energy and double layer model with two energies. These five models are treated alternatively with the ideal gas law (IG) and with the law of Ven Der Waals (VDW) real gas (RG). Fitting of six adsorption isotherms at different temperatures (298K, 303K,308K, 313K, 318K and 328K) is performed with, the pH fixed to 2. According to values of correlation coefficient, the Hill model with one energy and a VDW real gas interaction has been chosen as the adequate model to best fit the experimental data.