Ternary adsorption of cobalt, nickel and methylene blue on a modified chitin: Phenomenological modeling and physical interpretation of the adsorption mechanism

The simultaneous adsorption of three pollutants cobalt (Co), methylene blue (MB) and nickel (Ni) on a modified chitin surface from ternary systems was investigated. Multicomponent experimental adsorption data were determined at 298–328 K and pH 6. These experimental studies indicated that Ni adsorption was higher than those obtained for Co and MB. The multicomponent adsorption mechanism of this ternary system was analyzed with statistical physics theory where a set of new models with different hypotheses was developed and tested. Results showed that an adsorption model assuming that the pollutants Co, MB and Ni were adsorbed on three different types of modified chitin receptor sites was the most appropriate. This model was also utilized to calculate the corresponding adsorption energies to describe the possible interactions between these adsorbates and the surface of modified chitin. A general analysis of trends and magnitude of the model parameters provided a deeper understanding of the ternary adsorption mechanism at molecular level. Macroscopically, the ternary adsorption mechanism was interpreted via a calculation of three thermodynamic functions.