Pelletizing and alkaline leaching of powdery low grade zinc oxide ores

Low grade powdery zinc oxide ores (5.2% Zn, < 2 mm) are mixed with cement 5 wt.%, pelletized and solidified. The diameters of the pellets obtained are between 5 mm to 8 mm. When the pellet solidification periods are 3 days, 10 days and 45 days respectively, the alkaline leaching rates of zinc in the pellets are up to 92.2%, 87.3% and 72.9% respectively. Decreasing the solidification time can reduce reaction time, increase dissolution of zinc in pellets and lower the effect of initial zinc concentration on leaching rate. The experiment results show that the minimum solidification time is three days, and the kinetic study indicates that alkaline leaching of the low grade zinc oxide pellets is controlled by the diffusion of the leach liquor through the gangue layer in the whole leach process, and the apparent rate constants are 3.51 × 10− 2 day− 1, 8.09 × 10− 3 day− 1, 4.74 × 10− 3 day− 1 respectively.