The sulphation and sulphate decomposition occurring during the oxidation of nickel concentrates were studied by thermal analysis. Samples of industrial nickel concentrates were heated in inert gas to temperatures between 400°C and 850°C and oxidized isothermally in air or in a 4%O2-96%N2 mixture. During isothermal oxidation of the concentrates, SO2 evolved from the roasting reactions led to partial formation of metal sulphates. Following the oxidation and sulphation of the sample, the decomposition of the formed sulphates was studied. This was completed either by heating the sulphated sample to 950°C to thermally decompose the sulphates, or by lowering the partial pressure of oxygen while holding the sample at the isothermal oxidation temperature. The sulphation of the sample was found to follow the parabolic rate law, implying diffusion as the rate controlling-step. The thermal decomposition of the sulphates occurred at a near constant rate, implying zero-order kinetics.

The sulphation and sulphate decomposition occurring during the oxidation of nickel concentrates were studied by thermal analysis. Samples of industrial nickel concentrates were heated in inert gas to temperatures between 400°C and 850°C and oxidized isothermally in air or in a 4%O2-96%N2 mixture. During isothermal oxidation of the concentrates, SO2 evolved from the roasting reactions led to partial formation of metal sulphates. Following the oxidation and sulphation of the sample, the decomposition of the formed sulphates was studied. This was completed either by heating the sulphated sample to 950°C to thermally decompose the sulphates, or by lowering the partial pressure of oxygen while holding the sample at the isothermal oxidation temperature. The sulphation of the sample was found to follow the parabolic rate law, implying diffusion as the rate controlling-step. The thermal decomposition of the sulphates occurred at a near constant rate, implying zero-order kinetics.