Kinetics of acid-oxygen leaching of low-sulfur Ni-Cu matte at atmospheric pressure

The leaching of low-sulfur Ni-Cu matte in acid-oxygen (CuSO4-H2SO4-O2) solution at atmospheric pressure was researched. This matte was obtained from high grade Ni-Cu matte by magnetic separation, which mainly contained Ni-Cu alloy and a small quantity of sulfides. The effects of temperature, agitation speed, oxygen flow rate, particle size, acid concentration and concentration of copper ion were studied. It is found that the matte particles are leached by shrinking core mechanism and the leaching process is electrochemically controlled. In a temperature range of 30–60 °C, the surface reaction is rate-limiting step, with an apparent activation energy of 41.9 kJ/mol. But at higher temperature (70–85°C), the rate process is controlled by diffusion through the product layer, with an apparent activation energy of 7.3 kJ/mol.