Adsorption of Rhodamine B from water by activated char obtained from end-of-life tyre pyrolysis

Three activated chars obtained from end-of-life tyre pyrolysis differing in activation time (AC110 - 110 min, AC130 - 130 min, and AC150 - 150 min) were successfully used as adsorbents for the removal of model dye - Rhodamine B (RhB) from aqueous solutions. The effects of solution pH, adsorption kinetics, and equilibrium adsorption were investigated. The results showed that the adsorption was strongly pH-dependent; the highest percentage of RhB dye adsorbed was obtained at pH 2.0 and the removal efficiency decreased with an increase in solution pH. Adsorption kinetics was analyzed using pseudo-first-order, pseudo-second-order, Weber-Morris, and Boyd kinetic models. It was found that the pseudo-second-order kinetic equation was the most appropriate for describing the adsorption kinetics and that the RhB adsorption process was controlled by a film diffusion mechanism. Adsorption equilibrium data were fitted to the Langmuir, Freundlich, Temkin, and Elovich isotherm models. The equilibrium data were best represented by the Langmuir model with the monolayer adsorption capacities of 69.96, 94.34, and 133.3 mu mol/g for AC110, AC130, and AC150, respectively. It was concluded that the adsorption of RhB was closely correlated with the specific surface area (and activation time) of the activated chars.