Leaching of a complex sulfidic, silicate-containing zinc ore in sulfuric acid solution under oxygen pressure

This paper reports an acid leaching process study on the selective extraction of base metals from complex sulfidic, silicate-containing zinc ore containing sphalerite, hemimorphite, smithsonite, quartz, galena, pyrite, troilite, muscovite, calcium aluminate, calcite, gypsum and cerussite with traces of other minerals under oxygen pressure. The effects of influential factors (leaching temperature, sulfuric acid concentration, leaching time, ore particle size distribution, liquid/solid ratio and pressure) on the dissolution efficiencies of zinc, iron and silica from said ore were investigated. The optimum conditions, which were sought for reducing downstream purification requirements by limiting iron and silica dissolution, were found to be a leaching temperature of 160 °C, a liquid/solid ratio of 6 mL/g, a sulfuric acid concentration of 0.42 mol/L, a leaching time of 150 min, a particle size of −98 + 74 μm and 1.6 MPa partial pressure. Under these conditions, the zinc extraction was above 97%, with an iron and silica dissolution of less than 25% and 0.3%, respectively. The reduction of silica dissolution during leaching also promotes easier solid–liquid separation.

► Silica content is on a very low level under oxygen pressure sulfuric acid leaching.
► Its technical feasibility is demonstrated as a new alternative for the leaching of complex sulfidic, silicate-containing zinc ore.
► Having excellent solid–liquid separation characteristics of the slurry will be achieved.
► Impurities (such as iron and silica) dissolution minimization for purification is achieved.
► Molten sulfur viscosity at high temperatures is likely to promote the silica precipitation.