Nickel and cobalt losses from laterite ore after the sulfation-roasting-leaching processing

The sulfation-roasting-leaching process has successfully been used to extract nickel and cobalt from laterites due to its flexibility for application to ores with different chemical and mineralogical characteristics. One of the main characteristics of this process is to leave elements such as iron, aluminum, and chromium in the residues as insoluble oxides. In this work, a sample of nickel laterite ore from the northern region of Brazil was processed by the sulfation-roasting-leaching route. The samples after each step of the process were characterized by X-Ray diffraction (XRD), scanning electron microscopy (SEM), and chemical analysis by atomic absorption spectrometry. The phases quantification was carried out by the Rietveld method. Under favorable conditions, nickel and cobalt recoveries were higher than 80 (wt.%) while the iron recovery was only 5.5 (wt.%). Despite the higher nickel and cobalt extraction, it was verified after calculation of the metals distribution throughout the main mineral phases present in the solid leaching residue that hematite was responsible for 29.5 (wt.%) and 60.8 (wt.%) of nickel and cobalt losses in the solid leaching residue, respectively. The sulfation-roasting-leaching process efficiency is influenced by many variables, then, depending on the ore characteristics, furnace choice, and processing conditions. The possibility of reprocessing the hematite in the solid leaching residue to increase the recovery of valuable metals can be a key factor for the route viability.