A critical review of the chemical leaching of sphalerite in ferric sulfate and chloride solution

Sphalerite is the main mineral of zinc. The major portion of zinc production is done by a route including roasting followed by hydrometallurgical procedures, which presents some disadvantages from an environmental point of view, when compared to the processes of direct leaching. This contribution presents a critical review of the most important works carried out on dissolution of sphalerite, in medium containing either ferric sulfate or chloride as oxidant agent. The main parameters involved in the sphalerite oxidation are discussed: concentrations of ferric ion [Fe + 3 ] and ferrous ion [Fe + 2 ], formation of an elemental sulfur passive layer, presence of iron in solid solution in the sphalerite and temperature. Several kinetic models developed by different authors will also be presented to describe the process of dissolution of this mineral.