Atmospheric leaching behavior and kinetics study of roasted laterite ore

Laterite ores, rich in essential metals like nickel, iron and cobalt, are a crucial resource for modern technology. However, the extraction of nickel from laterite ores is a complex process due to their intricate mineral compositions and low nickel concentrations. This paper presents the results of a study to understand the leaching behavior of preroasted laterite ore and the impact of roasting on leaching kinetics. The ore was subjected to roasting at 280 and 610 °C for a duration of three hours, followed by leaching in sulfuric acid (H2SO4) under atmospheric conditions. The results show that preroasting the ore at 610 °C significantly improved the recovery of nickel during leaching, with recovery rate of up to 93 percent, and the leaching process of the preroasted ore was primarily controlled by diffusion through the ash layer. The activation energy values were found to be 20.97 kJ/mol for the ore roasted at 280 °C, and 18.97 kJ/mol for the ore roasted at 610°C. These findings suggest that preroasting can enhance the leaching performance of laterite ore, potentially paving the way for more efficient and sustainable nickel extraction processes. Introduction Laterite ores are a valuable type of ore that contain a mineral component that carries metals essential for modern technology, mainly electronic technology. The significant metals found in laterite ores include nickel (Ni), iron (Fe) and cobalt (Co), which are crucial for technological advancements. The need for Ni metal is growing as lithium battery technology advances, as stated by several sources. Currently, most Ni is obtained from sulfide ores (around 60 percent), but this is gradually changing to oxide ores like laterite ores as sulfide reserves are depleted. Laterite ores possess complicated mineral compositions, and unlike sulfide ores, the metals found in laterite ores are challenging to enhance. Numerous studies have discovered that pretreatment of laterite ores enhances recovery rates in hydrometallurgical operations. It has been observed that preheating eliminates water that is chemically bonded to laterite ores, which increases the surface area and improves the extraction process. The present study aims to investigate the leaching behavior of preroasted laterite ore and the effect of roasting on the leaching kinetics. Method In this study, limonite-type laterite ore containing 39.5 percent Fe2O3 (13.8 percent Fe), 1.9 percent Ni and 2.5 percent Mn was obtained from mining activities in the Morowali region of Indonesia. The laterite ore (smaller than 180 μm in size) was roasted for three hours using a muffle furnace at temperatures of 280 and 610 °C. The roasted laterite ore was then leached using H2SO4 to determine the metal recoveries of Ni, Fe and Mn. The shrinking core model was used to analyze the kinetics of the leaching process. Results and discussion Roasting characterization. Heat treatment of laterite ore can result in the formation of hematite from goethite. In this study, it was found that the intensity of the hematite phase increased while that of goethite decreased, and the formation of quartz and forsterite phases due to the decomposition of lizardite was confirmed. This decomposition process facilitates the leaching process. Leaching behavior of roasted ore. The results show a significant improvement in the recoveries of Ni and Fe at a leaching temperature of 90 °C for both the ores roasted at 280 and 610 °C. The highest recovery efficiencies for Fe and Ni were 95 and 93 percent, respectively, for the ore roasted at 610 °C at an H2SO4 concentration of 2 M, leaching time of 120 minutes, solid-to-liquid ratio of 1/10 g/mL and stirring rate of 200 rpm. The results of our current investigation demonstrate a noteworthy increase of 10 percent in overall recoveries and a 23 percent increase in Fe recovery, as compared to our previous study on nonroasted ore leached under atmospheric conditions [1]. The improved recoveries for roasted ore are attributed to the newly synthesized OH-hematite from goethite dehydroxylation above 280 °C. The observed trend is explained by the fact that hematite has a higher dissolubility than goethite [2]. Figure 1 depicts the recovery profiles of Ni, Fe and Mn from this study. Kinetic analysis. The kinetics of leaching was observed based on the recovery data of average metal (Fe, Ni and Mn). The results show that only the diffusion through ash layer kinetic model yields a linear relationship for the roasted ore (280 and 610 °C) and nonroasted ore, whereas the diffusion through film layer and reaction kinetic models fail to produce a similar outcome. The fit of the kinetics model of diffusion through the ash layer was also confirmed by the highest R2 value (close to 1) in Table 1. The activation energy was obtained using the Arrhenius equation, with the diffusion through ash layer kinetic model providing the value of k (Table 1). The slope of the Arrhenius equation was used to calculate the activation energy values for the leaching process of the samples roasted at 280 and 610 °C, which were 20.97 and 18.97 kJ/mol, respectively. Figure 2 shows the Arrhenius graph. This decreased activation energy value for roasted ore demonstrates that the roasting treatment reduces the energy required for the leaching process. The characteristic of the process being controlled by diffusion through the ash layer is also shown by the range of activation energy values [3]. Diffusion-controlled processes through the ash layer usually have an activation energy value range of 1 to 40 kJ/mol [4]. Conclusion The roasting method was observed to improve Fe, Ni and Mn leaching recoveries. The highest average metal recovery, reaching 76.5 percent, was obtained from ore roasted at 610 °C, followed by leaching at 90 °C using an H2SO4 concentration of 2 M, leaching time of 120 minutes, solid-to-liquid ratio of 1/10 g/mL and stirring rate of 200 rpm. The preroasted laterite ore leaching process is controlled by diffusion through the ash layer with activation energy values of 20.97 and 18.97 kJ/mol for laterite ore roasted at 280 and 610 °C, respectively.These findings emphasize the important influence of roasting temperature and leaching conditions on roasted laterite ore leaching behavior and metal recovery, providing essential information for further understanding and optimizing the metallurgical processes. ■ Selected references Prameswara G, Tyassena FYP, Pasaribu M, Trisnawati I, Petrus HTBM (2023) Transactions of the Indian Institute of Metals 76:1341 Landers M, Gilkes RJ, Wells M (2009) Appl Clay Sci 42:615 Prameswara G, Trisnawati I, Mulyono P, Prasetya A, Petrus HTBM (2021) JOM 73:988 Stopic S, Friedrich B (2016) Vojnotehnicki Glasnik 64:1033

Atmospheric leaching behavior and kinetics study of roasted laterite ore

Authored by: Gyan Prameswara, Idi Amin, Andi Nurfaadhilah Ulfah, Iga Trisnawati, Himawan Tri Bayu Murti Petrus, and Fitria Puspita

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