Extraction of Nickel and Cobalt from Sulawesi Limonite Ore in Nitric Acid Solution at Atmospheric Pressure

Characterization and leaching study of a limonitic laterite ore from Sulawesi has been undertaken in order to find out mineralogical nature and Ni and Co concentration along with dissolution behavior during leaching process in nitric acid. Extraction rates of Ni and Co in different acid concentration and reaction time were also assessed. Mineralogical identification was conducted using optical microscopy and X-ray diffraction (XRD) techniques; whereas Ni and Co content was determined by means of atomic absorption spectrometry (AAS). Results of analyses show that minerals found in lateritic nickel ore studied were dominated by goethite with less quartz, talc, and trace spinel. Goethite was found to be high dissolution rate in nitric acid whereas quartz, talc and spinel were not dissolved during the leaching process. The highest extraction rates of Ni and Co with different acid concentrations at 1 hour leaching time were 13.22% and 24.17% respectively; whereas the maximum Ni and Co extraction rates under 2 molar nitric acid with different leaching times were obtained at 90 minutes with recovery of 24.17% and 56.53% respectively.