Tailings mitigation and valorization through green mineral phase transformation: A pilot-scale strategy for separating superior iron concentrate

• Published in: Separation and purification technology Vol. 377; p. 134198
• Main Authors: Tang, Zhidong, Cheng, Shaokai, Wang, Mingxing, Yue, Yuanxing, Gao, Peng, Han, Yuexin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 19.12.2025
• Subjects: Clean reducing gas; Hydrogen-based mineral phase transformation; Phase transitions; Tailings mitigation; Phase transitions; Tailings mitigation; Clean reducing gas; Hydrogen-based mineral phase transformation
• ISSN: 1383-5866
• DOI: 10.1016/j.seppur.2025.134198

•Realizing the mitigation and valorization of Bayan Obo tailings.•Enhancing magnetic contrast through mineral phase transformation.•Employing hydrogen-based reducing gas in this pilot-scale test.•Hematite was reduced to magnetite, bastnaesite decomposed to rare earth oxides. Bayan Obo tailings contain valuable resources such as rare earths, iron, niobium, and fluorite, making tailings mitigation and valuable components recovery highly beneficial. This study proposed a hydrogen-based mineral phase transformation (HMPT) to enhance magnetic contrast and efficiently separate iron minerals. Magnetic pre-enrichment was initially applied to upgrade the iron grade and reject the gangue minerals, thereby improving the HMPT efficiency. Subsequently, a 48-hour continuous pilot-scale test was conducted under optimal HMPT parameters, which was evaluated to yield an excellent and stable roasted product. A high-quality iron concentrate with 64.84 % TFe grade and 75.62 % operational recovery was produced by grinding and 3-stage low-intensity magnetic separation (LIMS). Relevant analytical tests were employed to study phase transitions, magnetic changes, surface properties and micro-morphology during HMPT. The results indicated that hematite was reduced to magnetite, bastnaesite decomposed into rare earth oxides, while fluorite remained unchanged. Additionally, the specific saturation magnetization increased from 2.92 A m2/kg to 8.42 A m2/kg, while the BET surface area decreased from 3.57 m2/g to 2.36 m2/g, and the average pore diameter increased from 12.6 nm to 23.3 nm. After HMPT, the dense and smooth ore particles developed extensive cracks. The pilot-scale test explored in this study provides a promising approach for Bayan Obo tailings reduction and holds potential for industrial application.