Oxygen-Pressure Leaching Kinetics of Sphalerite in the H2SO4-Fe2(SO4)3 System

The kinetics of oxygen-pressure sulfuric acid (H2SO4) leaching of sphalerite containing 0.56% Fe was investigated using a ferric sulfate (Fe-2(SO4)(3)) medium. The effects of stirring speed, temperature, particle size, H2SO4 concentration, oxygen partial pressure, and Fe3+ concentration were examined. The results indicated that zinc (Zn) extraction was almost independent of agitation rate above 600 rpm. An increase in temperature facilitated the leaching reaction, while variations in Fe3+ concentration and oxygen partial pressure above 10 g/L and 0.8 MPa, respectively, exhibited no significant effect on the leaching process. Subsequently, Zn extraction decreased with increasing H2SO4 concentration and increased significantly with decreasing particle size. SEM-EDS and XRD analyses of the leaching residue produced through leaching at 10 g/L Fe3+, 60 g/L H2SO4, 30 g/L liquid-to-solid ratio, 600 rpm, oxygen partial pressure of 0.8 MPa, and 130 degrees C for 120 min showed that the apparent activation energy, oxygen partial pressure, and H2SO4 concentration reaction order were 21.81 kJ/mol, 0.28, and similar to 0.12, respectively. A kinetic equation of the leaching process was established.