The rate of reaction between a solid and fluid can be expressed
in terms of the heterogeneous reaction models. The reaction rate
may be controlled by: (a) film diffusion control model; (b) chemical
reaction control model; (c) product layer diffusion control model
(Abali et al., 2006). The kinetics of film diffusion control model
(M1), chemical reaction control model (M2) and product layer
diffusion control model (M3) are given by the Equations (1)e(3),
respectively. The kinetic mechanism in the leaching process was
investigated by applying the models to the leaching process, and
the curves of M1, M2 and M3 are shown in Fig. 7.