Steric and energetic investigations of adsorption isotherms of methylene blue on new polymeric multi-layered material-based k-carrageenan and alginate

In this research study, we examined the adsorption behavior of methylene blue (MB) on a novel biosorbent made of polyelectrolyte multilayers (PEM) biopolymeric material at three different temperatures. Various models derived from statistical physics formalism were employed to analyze the adsorption isotherms. An alternative approach based on the application of multilayer models from statistical physics theory was used to better investigate the adsorption mechanisms of MB on the PEM grafting material. We adjusted various parameters within this model across temperatures of 295K, 313 K, and333K, and these parameters played a crucial role in comprehending the adsorption mechanism. In addition, this approach revealed that the MB dye is linked through a multilayer process on the PEM grafting material with 'non-parallel' configurations and multimolecular process. The PEM grafting material showed maximum adsorption capacities ranging from 632.23 mg⁄g to 463.76 mg⁄g for the removal of MB over a pH of 6. The calculated adsorption energies ranged from 11.6 to 18.65kJ/mol, indicating that the MB adsorption process was primarily of a physisorption nature influenced by both hydrogen bonding and van der Waals interactions. Thus, the theoretical analysis indicated that this low-cost adsorbent material (PEM grafting) is a promising material for the removal of MB dye from the solution. Additionally, we examined the adsorption behavior by calculating the entropy, the free energy and the internal energy which govern the adsorption process of MB onto the PEM grafting material.