Extract of nickel from Indian lateritic ores by gas-phase sulphation with SO2-air mixtures

Lateritic ore with high iron (36-46%) and low nickel (0.8-1.1%) contents from the Sukinda region of Orissa, India, was sulphated with sulphur dioxide-air mixtures to give selective extraction of the nickel. Various roasting parameters were studied, such as the partial pressures Of SO2 and O-2, temperature and roasting time. Selective extraction of nickel could be achieved at a SO2 partial pressure of 0.25-0.12 atm, temperature of 700 degreesC and roasting time of 1 h. Under the optimum roasting conditions about 85% of the nickel was extracted with 4% of the iron. The reaction was observed to follow a Ginstling-Brounstein diffusion-controlled mechanism with an activation energy of about 23 kJ/mole. The nickel extraction can be improved by a further 10% through the addition of 5 wt% alkali sulphates during roasting.