Kinetic characteristic in a sorbent depends not only on the presence of the active metal site but also depends on the accessibility of the metal site without sterical hindrance which is greatly
determined by the matrices of the sorbent. This means that, the mechanism of sorption depends on the physical and chemical characteristics of the sorbent as well as on the mass transfer process. Therefore, the rate kinetics of Cd, Cu and Pb ions sorption onto modified orange peel were analyzed using pseudo first-order, pseudo-second order and Elovich kinetic model, which are the most commonly used models [27]. The conformity between experimental data and the model-predicted values was expressed by the correlation coefficients (R2, values close to 1). The relatively higher value is the more applicable model to the kinetics of Cd, Cu and Pb ions sorption.