چكيده به لاتين
Pyrometallurgical extraction of zinc from Sphalerite ore, as a critical primary resource of zinc, has been faced with environmental and economic challenges. The current method for hydrometallurgical extraction of zinc from this ore relies on the pressure leaching that requires expensive autoclaves. Thus, researchers are looking for suitable alternative methods based on atmospheric leaching, and for this purpose, different oxidants have been considered. In the present research, atmospheric leaching of sulfidic zinc concentrate of Angouran mine has been examined in the presence of MnO2 powder as the oxidant. The effect of temperature, manganese dioxide to zinc ratio, sulfuric acid concentration and leaching time was investigated by design of experiment approach and central cubic design. Statistical analysis of results showed that temperature was the most influential factor in the leaching experiments. Also, manganese dioxide to zinc ratio was identified as an insignificant parameter under the experimental conditions of the study, likely due to its excessive presence. The highest leaching efficiency of zinc after 180 minutes was 85% under 80 ℃, manganese dioxide to zinc ratio of 1, and sulfuric acid concertation of 1.35 M. By comparing leaching efficiency of zinc and manganese and determination of the stoichiometry of possible reactions, it was found that sulfide ion is oxidized into elemental sulfur and sulfate ion in the system under study. X-Ray diffraction analysis verified the presence of elemental sulfur in the leach residue. The kinetic analysis on the complementary experiments indicated that diffusion through reaction product layer is the controlling step of the reaction with an activation energy of 29 kJ/mol.
