Unlocking iron from oolitic hematite: Clean mineral phase transformation for primary iron concentrate production

• Published in: Process safety and environmental protection Vol. 200; p. 107377
• Main Authors: Zhang, Xiaolong, Cheng, Shaokai, Gao, Peng, Han, Yuexin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2025
• Subjects: Efficient recovery of iron; H2 reducing gas; Magnetic separation; Oolitic hematite; Primary iron concentrate; H2 reducing gas; Primary iron concentrate; Magnetic separation; Oolitic hematite; Efficient recovery of iron
• ISSN: 0957-5820
• DOI: 10.1016/j.psep.2025.107377

Oolitic hematite is recognized as an extremely refractory iron ore due to the fine-grained intergrowth of iron and gangue minerals. Mineralogical characterization in this study revealed that the oolitic hematite sample contained 48.80 % hematite and 15.57 % limonite, but was intimately associated with gangue minerals. The monomeric liberation of the particles was not above 5 %, posing a significant challenge for efficient beneficiation. In this study, an exploratory experiment on hydrogen mineral phase transformation (HMPT) was conducted. Under optimal conditions with HMPT temperature at 520 °C, HMPT time lasting 20 min, H2 concentration set to 30 %, total gas flow rate of 600 mL/min, weakly magnetic iron minerals were converted into strongly magnetic phases. Subsequent grinding (90 % passing 45 μm) and low-intensity magnetic separation (LIMS, 120 kA/m for 5 min) produced a primary iron concentrate with a TFe grade of 58.14 % and an iron recovery of 95.75 %. Relevant analytical tests indicated that the transformation of iron phases was complete, with Fe in the HMPT product predominantly existing as magnetite, and both the specific saturation magnetization and maximum magnetic susceptibility significantly increased. The HMPT product was observed to have a porous fissure structure, which facilitated mineral liberation during grinding. These findings provide insights into the efficient and clean utilization of oolitic hematite, but further processing is required to remove residual silicon and phosphorus from the primary iron concentrate.