Equilibrium modeling of single and binary adsorption of Food Yellow 4 and Food Blue 2 on modified chitosan using a statistical physics theory: new microscopic interpretations

Abstract

For a good understanding of the single and binary adsorption systems, the use of statistical physics models is paramount. In this research, the monolayer model with two energies and the extended monolayer model with two energies were applied to interpret the single and binary adsorption isotherms of Food Yellow 4 (FY4) and Food Blue 2 (FB2) on modified chitosan at different temperatures. The equilibrium isotherms were constructed experimentally in batch systems at 298, 308, 318 and 328K. The statistical physics models were developed using the grand canonical ensemble containing different steric and energetic physicochemical parameters, which allow the microscopic interpretation of the adsorption process. The adsorption isotherms were interpreted according to these parameters, which were obtained by numerical simulation. The main contribution of this work is to attribute new microscopic interpretations for the adsorption of FY4 and FB2 on modified chitosan, in single and binary systems at different temperatures. A multimolecular and multianchorage process in single and binary system respectively was described by the study of the number of molecules per site. The investigation of the adsorption energy indicated that the electrostatic interaction and hydrogen bond interactions are the dominant contribution describing the adsorption of these dyes for the single and binary adsorption.