Kinetic models of zinc dissolution from artificial sphalerite with different iron contents in oxygen pressure leaching

The oxygen pressure leaching of sphalerite in sulphuric acid solutions is a slow process in the absence of iron because of the limitations of the oxygen delivery carrier (redox couple: Fe3+/Fe2+). Herein, the artificial sphalerite with 25.70%, 15.20%, 5.75% iron contents and non-iron was prepared via the sintering of ZnS and FeS and used in the kinetic oxygen pressure leaching experiment. The results indicated that the zinc leaching rate of non-iron sphalerite was significantly lower than those of sphalerite with 25.70%, 15.20%, and 5.75% iron contents. This ratio decreased from 90 to 98% to approximately 65% at a temperature of 403 K, sulphuric acid concentration of 110 g L−1, oxygen partial pressure of 0.8 MPa, and leaching time of 70 min. Furthermore, when compared to the artificial sphalerite with 25.70%, 15.20%, 5.75% iron contents, the activation energy decreased from 32.31 kJ mol−1 for non-iron sphalerite to 29.02, 26.30, and 21.60 kJ mol−1, respectively. The leaching reaction process followed a shrinking unreacted core model that gradually shifted from surface reaction control to diffusion control. The orders of reaction for the sulphuric acid concentration and oxygen partial pressure were also obtained. Finally, artificial sphalerite leaching kinetics model equations with different iron contents were established.