Intensification of sulphation and pressure acid leaching of nickel laterite by microwave radiation

The microwave is a clean and environmentally acceptable energy and various microwave-assisted metal extraction processes have been developed. The novel application of microwave irradiation for sulphation of the nickel laterite ore prior to pressure sulphuric acid leaching has been investigated. Under optimum conditions, about 92% of nickel can be extracted from the ore and above 90% of the iron precipitates as hematite with the residual acid content in the leachate lower than 31 g/L. The microwave sulphation proceeds rapidly and a relatively low leaching temperature and low mass ratio of sulphuric acid to ore can be used in the subsequent pressure leaching to achieve a satisfactory nickel extraction. This may potentially reduce the subsequent heavy capital and operation cost of the pressure acid leaching process.