Kinetic modeling of the adsorption process of Pd(II) complex ions onto activated carbon

In this work, the results of kinetic studies of Pd(II) chloride complex ion adsorption process on activated carbon are presented. The experiments were conducted for different temperatures, initial concentrations of Pd(II) complex ions as well as for different amount of activated carbon. These results confirmed that the mechanism of the adsorption process is complex and can be described by two step reaction model. A new form of the adsorption isotherm based on kinetic mechanism is suggested and can describe the observed process. Moreover, it was shown that for specific conditions, the proposed isotherm can be transformed into the Freundlich’s isotherm. The activation energies of the subsequent stages of the studied process were determined and are equal to E1 = − 9 ± 9, E2 = − 6 ± 1.4 and E3 = − 85 ± 8.9 J mol−1, respectively. It is also suggested that the observed positive Gibbs energy change during adsorption can be related only to the first step of this process which does not lead to the final product.