Comparative atmospheric leaching characteristics of scandium in two different types of laterite nickel ore from Indonesia

Highlights

• Study atmospheric leaching characteristics of Scandium in laterite from Indonesia.

• Study the kinetics and mechanism of Scandium dissolution.

• Analyze the relationship and interaction of Scandium and other metals.

• This research assists in the development of a more efficient process for exacting Scandium.

Abstract

Atmospheric acid leaching behaviour of scandium (Sc) in two different types of laterite nickel ore from Indonesia was investigated. Ore and leaching residue characterization was performed by XRD, FTIR, XPS, and SEM-EDX. Ore characterisation showed that the major minerals in limonitic laterite were goethite, magnetite, hematite, and saprolitic laterite mainly consisted of goethite, magnetite, lizardite, clinochlore. Sc in two different types of laterite nickel ore are distributed widely among minerals, but it mainly hosts in Al-bearing goethite and silicate minerals. Sc host minerals in limonitic and saprolitic laterite nickel ore are different. 84.27% and 59.86% of Sc in limonitic and saprolitic laterite could be leached under the experimental conditions of 3 mol/L H₂SO₄, 80℃ reaction temperature, leaching duration 3 h and liquid to solid ratio 6:1, respectively. The results show that Sc and Mn, Mg in limonitic laterite have similar dissolution characteristics because the extractions of Sc and Mn, Mg are linearly correlated. Sc in limonitic laterite is susceptible to acid attack and easier to be extracted than other metals except for Mn. Sc and Ni in saprolitic laterite have similar dissolution characteristics because Sc is not strongly related to metals other than Ni. Sc in saprolitic laterite is more difficult to extract than Mg and Ni, but it is easier to be leached than other metals. The dissolution kinetics was found to fit well to the shrinking core model with the diffusion through the product layer as the rate controlling step. Results of this research may assist in the development of a more efficient process for exacting Sc from laterite nickel ores.

Introduction

Scandium (Sc), a member of rare earth elements (RE), is not scarce but highly dispersed in the earth’s crust. Its average crustal abundance of 22 g/t, ranked the 34th most abundant element in the earth (Le et al., 2018, Qing et al., 2018, Ramasamy et al., 2018, Wang and Cheng, 2011, Wang et al., 2011). It has the characteristics of high activity, lightweight, softness, and high melting point (Chakhmouradian et al., 2015, Hu et al., 2020, Liu et al., 2019), and has been widely used in the fields of national defense and military industry, metallurgy and chemical industry, light high-temperature resistant alloy, and new electric light source material, etc. (Davris et al., 2016, Kerkove et al., 2014, Wang et al., 2011, Yin et al., 2011). At present, the main application of Sc is Al-Sc alloy and Zr-based solid oxide fuel cells (A et al., 2019, Kaya et al., 2017, Wang et al., 2011). The global supply of Sc is about 15 tons per year (Kim and Azimi, 2020;). The ores with a Sc content range of 0.002–0.005% can be used as Sc resources, which is worthy of deserving exploitation and utilization (Shaoquan and Suqing, 1996, Zhou et al., 2018). The Sc minerals containing appreciable quantities of Sc such as euxenite, thortveitite, and gadolinite are scarce and hard to meet the requirements of industrial exploitation in scale (Qing et al., 2018). However, a trace amount of Sc frequently coexists in the ores of aluminum, titanium, tungsten, nickel. Generally, it is obtained as a by-product in the production of other metals or recovered from the residues or waste liquid, such as wolframite residue, bauxite residue, waste liquor of titanium pigment, and so on (Borra et al., 2016, Fujinaga et al., 2013, Li et al., 2018, Liu and Li, 2015, Ochsenkühn-Petropulu et al., 1995, Onal and Topkaya, 2014, Shaoquan and Suqing, 1996, Wang et al., 2011). The absence of reliable and long-term production coupled with the high price of Sc has limited the commercial applications of Sc. In short, industrial applications are waiting for a sufficient, reliable, and reasonably priced Sc supply.

The laterite nickel ores containing from 50 g/t up to 600 g/t of Sc are proposed as the most promising Sc resources for its production shortly (Chasse et al., 2017, Guo et al., 2021, Kim and Azimi, 2020, Luo et al., 2015, Makuza et al., 2021, Meshram et al., 2019, Van der Ent et al., 2013, Yan et al., 2021). Laterites can be classified into limonites or saprolites, depending on the iron and magnesium content (Garces-Granda et al., 2018). High pressure acid leaching (HPAL) and atmospheric acid leaching (AL) are the two prevailing technologies for hydrometallurgical processing of laterite nickel ores (Luo et al., 2021). In recent years, AL for processing laterite nickel ores has become a research hotspot in hydrometallurgy because of the method’s use of small equipment, mild reaction conditions, and low technical risk (Guo et al., 2015). Usually, extractions of valuable metals such as nickel and cobalt through AL rely on the complete dissolution of nickeliferous minerals. Hence, a proper understanding of mineral dissolution behavior in acidic solutions is helpful for leaching valuable metals from laterite nickel ores. Previous studies have provided some information on the dissolution behavior of laterite minerals at atmospheric pressure. Overall, these studies suggest that leaching behavior strongly depends on ore mineralogy and chemical composition, and process conditions. The sulphuric acid leachability of metal values associated with different minerals follows the order: lizardite > goethite > maghemite > magnetite ≈ hematite > chromite ≈ ringwoodite (Luo et al., 2015, Senanayake et al., 2011). It has been thought from extensive studies that metal cations exist in nickeliferous laterites in two modes, (a) weakly adsorbed to the mineral surface and (b) as a substitute in the mineral structure (Liu et al., 2009). The extent of substitution has a significant impact on the dissolution behavior of laterite minerals. In laterite nickel ores where nickel and cobalt are disseminated in different associated/interlocked minerals, the ore mineralogy type can dramatically impact H₂SO₄ leachability and consumption rate (Luo et al., 2015). Until recently, Sc, a potential by-product not considered by previous for its dissolution behavior during AL. Sc in laterite nickel ores is distributed widely among minerals but it may be especially associated with goethite, clay minerals, or manganese oxides, in which it substitutes for Fe³⁺ and Al³⁺ because of the similarities in ionic radius (Ferizoglu et al., 2018, Kaya et al., 2017). Kaya (Kaya et al., 2017) also speculated that Sc and nickel should have similar dissolution characteristics because Sc occurs together with nickel in the same minerals of laterite nickel ores.

The laterite nickel ores from Indonesia are a typical tropical laterite deposit, about 12% of world nickel resources (Luo et al., 2021). The aims of the present work were to investigate the leaching characteristics of Sc in two different types of laterite nickel ore from Indonesia during atmospheric acid leaching. Based on the leaching results, the kinetics and mechanism of Sc dissolution from limonitic and saprolitic laterite material, especially the relationship and interaction of Sc and other metals were studied. Results of this research may assist in the development of a more efficient process for exacting Sc from laterite nickel ores.