The Evaluation of Sphalerite Surface Formed During Oxidative Leaching in Acidic Ferric Sulfate Media

摘要

The main problem associated with the oxidative leaching process of sphalerite is the slow dissolution rate in acidic ferric solution due to the formation of a passive layer on the sphalerite surface. This research examined the surface structure of the sphalerite concentrate, non-oxidized and oxidized in ferric sulfate solution using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HRSEM). The oxidative leaching of sphalerite with D80 of 21 mu m was conducted in an acidic ferric sulfate solution with ferric concentration of 1.2 M, temperature of 80 degrees C, sulfuric acid concentration of 0.5 M, and leaching time of 6 h. XRD analysis showed that elemental sulfur was the main by-product of the oxidation process. The results of the HRSEM and EDS map confirmed the formation of elemental sulfur layers on the oxidized sphalerite surface. Both Raman spectroscopy and XPS analysis detected sulfur and polysulfide layers on the leached sphalerite surface. The XPS study, together with Raman spectroscopy showed that the iron-free layer formed on the oxidized sphalerite surface could be another reason for the slow kinetics of the sphalerite leaching in the oxidative leaching condition.