Leaching of nickel laterite ore assisted by microwave technique

The application of microwave technique in the hydrometallurgy of nickel laterite ores was described. The mixture of nickel laterite ores and sulfuric acid was pre-treated by microwave irradiation. The dissolving of nickel was conducted in hot water at the atmospheric pressure. The effects of factors, such as microwave power, microwave irradiation time, and sulfuric acid dosage, were investigated. In microwave field, the migration of ionic species and/or rotation of dipolar species promote the liquid–solid reaction process due to the increased contact area of reactants and leaching reaction rate constant. Thanks to the strengthening action of microwave, the microwave-assisted leaching process has its advantages, such as higher extracting rate than conventional atmospheric leaching, and no need for high-pressure operation as high pressure acid leaching (HPAL). The ferric iron in leaching solution could be effectively removed by sodium jarosite process with a little loss of nickel in the jarosite precipitate.