Nickel carriers in laterite ores and their influence on the mechanism of nickel extraction by sulfation-roasting-leaching process

The influence of nickel carriers minerals, contained in three different laterite ore samples, on their extraction by a sulfation-roasting-leaching process, is investigated in this paper. X-ray diffraction, scanning electron microscopy coupled to energy dispersive spectroscopy and chemical analyses by atomic absorption spectrometry were the techniques employed to characterize ore samples and leaching solid residues. Phase quantification was carried out by the Rietveld method. Nickel recovery showed to be strongly dependent on the minerals to which it was associated. Unlike expected, almost all the nickel contained in silicate minerals was extracted; however, some silicates, especially serpentine, interfere in nickel extraction when it is predominantly associated with the octahedral sites of goethite. The highest nickel recovery (93.0%) was achieved with the sample in which goethite was the main nickel carrier and its serpentine content was the lowest. The worst nickel recovery (76.1%) was obtained with the sample in which its association was predominantly with silicate minerals and the amorphous phase. Cobalt recoveries were higher than 81.0% for the three processed samples.