Key Takeaways & Executive Findings
- •• Optimal leaching conditions for magnesium from copper–nickel tailings are 2 M HCl, 50 g/L solid-to-liquid ratio, and 90°C, achieving a maximum leaching rate of 83.88%. • A modified shrinking core model accurately describes the leaching kinetics, indicating a mixed control by chemical reaction and product layer diffusion. • The apparent activation energy for magnesium dissolution is 77.51 kJ·mol−1, providing insight into the rate-limiting steps. • The study demonstrates the feasibility of using copper–nickel tailings as a medium for CO2 mineral sequestration, offering a dual benefit of waste management and carbon capture.
Abstract
Copper–nickel tailings (CNTs), consisting of more than 80wt% magnesium-bearing silicate minerals, show great potential for CO2 mineral sequestration. The dissolution kinetics of CNTs in HCl solution was investigated through a leaching experiment and kinetic modeling, and the effects of reaction time, HCl concentration, solid-to-liquid ratio, and reaction temperature on the leaching rate of magnesium were comprehensively studied. Results show that the suitable leaching conditions for magnesium in CNTs are 2 M HCl, a solid-to-liquid ratio of 50 g·L−1, and 90°C, at which the maximum leaching rate of magnesium is as high as 83.88%. A modified shrinking core model can well describe the leaching kinetics of magnesium. The dissolution of magnesium was dominated by a combination of chemical reaction and product layer diffusion, with a calculated apparent activation energy of 77.51 kJ·mol−1. This study demonstrates the feasibility of using CNTs as a media for CO2 mineral sequestration.
1. Introduction
Rapid developments in human society have led to large-scale fossil fuel consumption, which has boosted atmospheric greenhouse gases and global climate anomalies. CO2 emissions from human activities reached the highest level in 2021 at 36.3 Gt [1–2]. Hence, CO2 capture and storage becomes increasingly necessary [3]. CO2 capture and storage in geological structures is achieved by injecting high-density CO2 into rock strata below the Earth’s surface (such as oil and gas reservoirs, deep saline formations, and unmineable coal beds). This approach can sequester approximately 20% of global CO2 emissions per year, but can be mainly applied to emitters with annual CO2 emissions exceeding 106 t [4–5].
CO2 capture and storage by mineral (CCSM) can fixate CO2 as stable carbonates by reacting with industrial solid waste rich in magnesium or calcium [6]. The carbon capture potential of this method is two orders of magnitude higher than geological storage [7], and the method does not have the risk of CO2 leakage at later stages and is thus safer than geological storage [8].
The considerable amount of copper–nickel tailings (CNTs), which are the final nonselectable copper–nickel ore processing tailings and have huge quantities, should be addressed. For example, Jinchuan, which is located in the northwestern Gansu Province of China, produces almost 4 × 106 t CNTs annually. Discarded CNTs occupy a large amount of land resources and pose a serious threat to the ecological safety of areas around tailings ponds [9–10]. Interestingly, CNTs are rich in magnesium and calcium and are thus feasible media for CO2 sequestration [11]. Therefore, CCSM with CNTs not only reduces anthropogenic CO2 emissions but also mitigates resource waste and environmental pollution caused by tailings stockpiling.
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Zhenghong Yang, Haiyun Gu, Sijia Liu, Kai Wu, Linglin Xu, Lijie Guo (2025). Insights into the dissolution kinetics of copper–nickel tailings for CO2 mineral sequestration. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-3081-7
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Frequently Asked Questions
What are the optimal conditions for magnesium leaching from copper-nickel tailings?
The optimal conditions are 2 M HCl, a solid-to-liquid ratio of 50 g/L, and a temperature of 90°C, achieving a maximum magnesium leaching rate of 83.88%.
How does the shrinking core model describe the leaching kinetics?
A modified shrinking core model accurately describes the leaching kinetics, indicating that the dissolution is controlled by a combination of chemical reaction and product layer diffusion.
What is the apparent activation energy for magnesium dissolution?
The calculated apparent activation energy is 77.51 kJ·mol−1, which provides insight into the energy barrier for the leaching process.
Why are copper-nickel tailings considered for CO2 mineral sequestration?
Copper-nickel tailings contain over 80 wt% magnesium-bearing silicate minerals, which can react with CO2 to form stable carbonates, offering a dual benefit of carbon capture and waste management.
What are the environmental benefits of using copper-nickel tailings for CO2 sequestration?
This approach reduces CO2 emissions, mitigates land occupation and ecological risks from tailings ponds, and promotes resource utilization of industrial waste.
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