FIG. 9.

Plot of 1 − 3(1 − X)^2/3 + 2(1 − X) versus time showing that the shrinking-core model with diffusion through the product layer as the rate-controlling step describes the leaching of sphalerite at high concentrations of ferrous ions in the absence of bacteria after about 10 h of reaction time. X is calculated from the data presented in Fig. 2B.