Key Takeaways & Executive Findings
- •• Hematite exhibits the highest magnetic moment among IOT minerals, making it the primary driver of magnetic agglomeration. • The dispersant SDSH hydrolyzes to form HPO4 2− and RSO3 − groups that chemically adsorb onto non-quartz metal ions, increasing electrostatic repulsion. • RSO3 − groups physically adsorb onto quartz surfaces, inducing steric repulsion and enhanced hydrophilicity to inhibit agglomeration. • Under optimal conditions, SiO2 grade increased from 76.32% to 97.42% with a recovery rate of 54.81%, meeting glass-grade quartz sand requirements.
Abstract
The superconducting high gradient magnetic separation (S-HGMS) technology can be used to effectively extract silica from iron ore tailings (IOTs). However, particle agglomeration in strong magnetic fields poses a challenge in achieving optimal performance. In this study, we investigated the agglomeration of IOT particles and the mechanisms for its inhibition through surface analysis, density functional theory (DFT), and extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory. Hematite was found to exhibit the highest magnetic moment among the minerals present in IOTs, making it particularly prone to magnetic agglomeration. The addition of the dispersant SDSH into the slurry was essential in promoting the dispersion of IOT particles during the S-HGMS process. This dispersant hydrolyzed to form HPO4 2− and RSO3 − groups in the solution, which then chemically adsorbed onto the metal ions exposed on the surfaces of non-quartz particles, increasing interparticle electrostatic repulsion. Furthermore, the RSO3 − groups physically adsorbed onto the surface of quartz particles, resulting in strong steric repulsion and enhancing the hydrophilicity of the particle surfaces, thereby inhibiting magnetic agglomeration between the particles. Under optimal conditions, the SiO2 grade of the obtained high-grade silica powder increased from an initial value of 76.32% in IOTs to 97.42%, achieving a SiO2 recovery rate of 54.81%, which meets the requirements for quartz sand used in glass preparation. This study provides valuable insights into the magnetic agglomeration of IOT particles and its inhibition while providing a foundation for regulating S-HGMS processes.
1. Introduction
Iron ore tailings (IOTs) are a typical bulk industrial solid waste generated in large quantities with significant stockpiles and a low utilization rate [1]. In China, the amount of IOTs has exceeded 10 billion tons, and its comprehensive utilization rate remains at only 30% [2]. These tailings are associated with a series of ecological and environmental problems as well as human health-related issues, necessitating their appropriate treatment and utilization. For example, tailing storage facilities or tailing dams are prone to landslide and debris flow [3]. Moreover, some heavy metal ions in the tailings may release into the environment, polluting the atmosphere, water, and soil [4]. Hence, it is necessary to develop a green, added-value, and efficient comprehensive utilization technology for IOTs.
IOTs generated during the beneficiation process of iron ores are of a wide variety and contain complex elements, including Fe, SiO2, CaO, Al2O3, and MgO, as well as small amounts of heavy metal ions [5]. Their mineral compositions are mainly quartz, pyroxene, garnet, hornblende, and feldspar. Currently, IOTs are widely used as construction materials [3], in the preparation of molecular sieves and ferric chloride coagulants [6], in soil remediation, and in the extraction of valuable elements [2], which can help effectively realize the high-value utilization of IOTs. However, current studies have mainly focused on iron recovery from IOTs through magnetization roasting and magnetic separation technology [7] or the suspension reduction technology [8,9]. Notably, quartz is the main mineral in IOTs, and its SiO2 content can reach 70% and above, making IOTs an attractive source for high-grade silica recovery.
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Yongkui Li, Suqin Li, Zekun Zhao (2025). Controlling magnetic agglomeration in superconducting high gradient magnetic separation processing of iron ore tailings for high-grade silica recovery. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.08.006
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Frequently Asked Questions
What is the main challenge in superconducting high gradient magnetic separation of iron ore tailings?
The main challenge is particle agglomeration in strong magnetic fields, which hinders optimal separation performance.
How does the dispersant SDSH inhibit magnetic agglomeration?
SDSH hydrolyzes to form HPO4 2− and RSO3 − groups. The former chemically adsorbs onto metal ions on non-quartz particles, increasing electrostatic repulsion, while the latter physically adsorbs onto quartz surfaces, providing steric repulsion and enhancing hydrophilicity.
What are the optimal results achieved in this study?
Under optimal conditions, the SiO2 grade increased from 76.32% in IOTs to 97.42%, with a recovery rate of 54.81%, meeting the requirements for quartz sand used in glass preparation.
Which mineral in iron ore tailings is most prone to magnetic agglomeration?
Hematite exhibits the highest magnetic moment among the minerals present in IOTs, making it particularly prone to magnetic agglomeration.
What methods were used to investigate the agglomeration mechanisms?
The study employed surface analysis, density functional theory (DFT), and extended Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory to investigate the agglomeration mechanisms.
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