Leaching behaviour of limonite ores from Lapaopao, Southeast Sulawesi, Indonesia: Effect of mineralogy and acid types

Abstract

An atmospheric leaching study of limonite ores from Lapaopao, Southeast Sulawesi, using hydrochloric acid (HCl), nitric acid (HNO₃), and sulfuric acid (H₂SO₄) has been performed. The objectives of this study were to analyze the effect of ore mineralogy and acid types on the dissolution behavior of minerals and the leaching rate of Ni and Co at atmospheric pressure conditions. Mineralogical analysis was carried out using optical microscopy, scanning electron microscopy (SEM), and X-ray diffractometry (XRD), while the ore's chemical composition was determined by using X-ray fluorescence spectrometry (XRF) and atomic absorption spectrophotometry (AAS). Mineralogically, the limonite ores are dominated by goethite, followed by gibbsite, talc, and lizardite, with less amounts of hematite and quartz. Analysis results of solid residues revealed that mineral dissolution order was determined as follows: goethite > lizardite > gibbsite> hematite > talc> quartz. The results of the leaching experiment exhibited that the order of leaching rates of Ni in the three ores samples using three different acids were found as follows: Ore-1 > Ore-2 > Ore-3. Comparison of HCl, HNO₃, and H₂SO₄ as the lixiviants for the leaching of limonite ores demonstrated that HCl was the most reactive acid, followed by HNO₃ and then H₂SO₄. This might be due to the differences in mineralogical nature and reactivities of acids during the leaching process.