Copper extraction from white metal by pressure leaching in H2SO4–FeSO4–O2

In this investigation, pressure leaching experiments were carried out in H2SO4–FeSO4–O2 and H2SO4–O2 media to clarify the role of iron in the leaching of white metal produced in a Teniente Converter reactor. The dissolution rate of copper was studied in the range of 80 to 150 °C, using oxygen partial pressure from 203 to 1013 kPa. The results on the dissolution of white metal in H2SO4–O2 and H2SO4–FeSO4–O2 media indicated that white metal leaches in two stages and iron in the leaching solution affects drastically the rate in the range of 80 to 150 °C. In the presence of iron at temperatures below the melting point of elemental sulfur, the leaching rate, particularly the rate of the second stage increases drastically as compared to the case in the absence of iron. The rate increase is due the indirect leaching mechanism involving Fe3+ ions, which leach the white metal at a faster rate than O2.The kinetics of copper dissolution from white metal was analyzed and activation energies for the two-stage leaching of white metal in H2SO4–FeSO4–O2 medium were calculated as 76 kJ/mol and 32 kJ/mol for the first and second stages, respectively.