Adsorption tests in dark conditions were carried out in order to evaluate the equilibrium constants of the dye adsorption on the three materials such as GMAC, hybrid and Anatase-TiO2.
Isotherm models namely Langmuir, Freundlich and Redlich–Peterson were used to analyse the adsorption equilibrium data. The Langmuir model is one of the most widely used isotherm equations for modeling the adsorption equilibrium and is valid for monolayer sorption onto a surface with a finite number of binding sites which are homogeneously distributed over the adsorbent surface (Aksu, 2005) and having the same affinity for the adsorption of a single molecular layer in which there is no interaction between adsorbed molecules. The mathematical description of this model is