Key Takeaways & Executive Findings
- •• Na2SO4 addition during reductive roasting significantly enhances Ni and Co recovery from limonitic laterite, achieving 94.03% Ni and 80.16% Co recoveries. • The formation of dual liquid phases (FeS–FeO–Fe and NaAlSiO4–NaFeSiO4) promotes particle migration and aggregation, yielding high-grade alloy powder. • Pilot-scale rotary kiln trials confirm the industrial scalability and feasibility of the Na2SO4-assisted process. • The study provides a sustainable pathway for extracting critical metals from low-grade laterite ores, addressing the growing demand for battery materials.
Abstract
The growing demand for Ni and Co in the new energy sector necessitates efficient extraction methods for limonitic laterite ores. This study demonstrated the effectiveness of sodium sulfate (Na2SO4) as an additive for enhancing the co-enrichment of Ni and Co during solid-state reduction. Na2SO4 promoted the formation of two distinct liquid phases, low-melting-point FeS–FeO–Fe and NaAlSiO4–NaFeSiO4, facilitating the migration and aggregation of Ni–Co–Fe alloy particles, leading to a high-grade alloy powder with 11.98wt% Ni and 0.88wt% Co and recoveries of 94.03% and 80.16%, respectively. Ni–Co–Fe particle growth was mainly driven by the FeS–FeO–Fe eutectic melt, aligned with a liquid-phase sintering mechanism. Pilot-scale rotary kiln experiments validated the industrial feasibility of this approach, which offers a promising solution for the sustainable extraction of these critical metals.
1. Introduction
The burgeoning new energy industry driven by growing concerns regarding climate change has led to a surge in the demand for power batteries [1–2]. Ni and Co, essential components of Li-ion batteries, are becoming increasingly critical [3]. Laterite ore, comprising approximately 70% and 35% of the global Ni and Co reserves, respectively, has emerged as the primary source of these metals [4–6]. The efficient extraction of Ni and Co from laterite ore is crucial for the sustainable growth of the global new energy industry [7–8].
Laterite ore is stratified from top to bottom into the three zones of limonite, transition, and saprolite beds, based on the degree of weathering in its deposit profile [9–11]. Limonite ores typically contain less than 1.5wt% Ni and 0.1wt%–0.2wt% Co, with low levels of MgO and SiO2. In contrast, saprolite ores hold higher contents of Ni (1.8wt%–3.0wt%) and lower contents of Co (0.02wt%–0.1wt%), alongside high contents of MgO and SiO2. The transition layer exhibits intermediate characteristic contents.
The rotary kiln–electric furnace (RKEF) process, the current predominant method for treating laterite ores, is primarily focused on ferronickel production and best suited for saprolite laterite ores, neglecting Co recovery [12–13]. Limonite ore, which constitutes over 60% of total laterite resources and is crucial for Co storage, has significant potential for expanding industrial development and utilization. Industrial techniques for limonite ore processing include sintering in a blast furnace (BF), selective reduction followed by ammonia leaching (Caron process), and high-pressure acid leaching (HPAL) [14–15]. Owing to stricter environmental regulations, the BF process has been phased out [16]. The Caron process uses recyclable leaching agents, but it only partially recovers Ni and Co (75%–85% and 35%–60%, respectively) and is ineffective for ores with high Mg content [17]. Although HPAL effectively extracts high levels of Ni and Co, it requires substantial investment and generates large quantities of waste [18–19].
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Jing Chen, Yuqi Zhong, Boqi Wang, Jun Luo, Zhiwei Peng, Yanhu Chen, Guanghui Li, Mingjun Rao (2025). Na2SO4-assisted reductive roasting for enhanced Ni and Co recovery from limonitic laterite: Mechanism and pilot-scale rotary kiln validation. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3116-8
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Frequently Asked Questions
What is the role of Na2SO4 in the reductive roasting of limonitic laterite?
Na2SO4 promotes the formation of two distinct liquid phases (FeS–FeO–Fe and NaAlSiO4–NaFeSiO4) that facilitate the migration and aggregation of Ni–Co–Fe alloy particles, thereby enhancing the recovery of Ni and Co.
What are the key results of this study?
The study achieved a high-grade alloy powder with 11.98wt% Ni and 0.88wt% Co, with recoveries of 94.03% for Ni and 80.16% for Co, and validated the process at pilot scale in a rotary kiln.
Why is the recovery of Ni and Co from limonitic laterite important?
Limonitic laterite constitutes over 60% of laterite resources and is a major source of Co. Efficient extraction is crucial for meeting the growing demand for these metals in the new energy sector, particularly for lithium-ion batteries.
What are the advantages of the solid-state reduction followed by magnetic separation (SSRMS) process?
SSRMS offers a simple process flow, low operating temperature, and reduced energy consumption compared to other methods, making it a promising alternative for extracting Ni and Co from laterite ores.
How does this study address the industrial scalability of the process?
The study conducted pilot-scale rotary kiln experiments, which validated the industrial feasibility of the Na2SO4-assisted reductive roasting approach, demonstrating its potential for commercial application.
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