Generalized fractal-like adsorption kinetic models: Application to adsorption of copper on Argan nut shell

In this study three fractal-like adsorption kinetic equations were generalized, taking into consideration the changes of solute concentration in time. The equations are the pseudo-(n, alpha) (p-(n, alpha)), the fractal-like mixed-1,2 order (f-MO) and the fractal-like multi-exponential (f-mexp). The new equations were used for the analysis of kinetic adsorption of copper on Argan nut shell (ArNS). The modeling results show a better agreement between theoretical and experimental data in the whole time range for the three fractal-like equations. In addition, the variation of temperature, or initial concentration of adsorbate, affects the fractal exponent and the kinetic constants for the fractal-like models. Temperature dependence was analyzed using model-independent adsorption half-times. The proposed equations were applied to fit the experimental data from literature. The results indicate that the new equations can describe very well kinetic of adsorption, in both homogeneous and heterogeneous solid surfaces. (C) 2018 Elsevier B.V. All rights reserved.