Oxygen pressure acid leaching of artificial sphalerite catalyzed by Fe³⁺/Fe²⁺ self-precipitation

Abstract

The mechanism of oxygen pressure acid leaching of sphalerite catalyzed by Fe³⁺/Fe²⁺ self-precipitation was investigated in this study. Artificial sphalerite was fabricated with varying amounts of iron content via the sintering of ZnS and FeS and used for the pressure acid leaching experiment. The variations in the potential of the pressure leaching system were investigated by using a self-designed potential autoclave. The results showed that compared to the non-iron sphalerite, there was a violent redox reaction between the 25.70% Fe-artificial sphalerite and dissolved oxygen during the process of pressure leaching; and the catalytic mechanism was attributed to the redox couple Fe³⁺/Fe²⁺, where Fe³⁺oxidizes the H2S gas film and the reduced Fe²⁺ state is subsequently oxidized by the dissolved oxygen. Furthermore, the effect of temperature, H₂SO₄ concentration, and oxygen partial pressure on the artificial sphalerite with different iron contents was studied. The sphalerite samples with iron content were observed to dissolve more easily in sulfuric acid compared to the non-iron samples. Moreover, the activation energy of artificial sphalerite was observed to be lower in the sample with 25.70% iron content (22.26 kJ/mol) compared to that with no iron (32.31 kJ/mol); and the apparent reaction orders were obtained with respect to H₂SO₄ concentration (1.10 and 1.36) and oxygen partial pressure (1.29 and 1.41), respectively. A comprehensive kinetic model was developed on the basis of the experimental data and the fitted leaching ratio plot; and the kinetic equations for the leaching of sphalerite catalyzed by Fe³⁺/Fe²⁺ self-precipitation were determined.

Keywords

leaching mechanism catalyzed by Fe³⁺/Fe²⁺ self-precipitation / potential curves / artificial sphalerite / leaching kinetics / activation energy / reaction orders

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