Process Optimization\nfor Gangue Removal from Low-Grade\nIron Ore by a Flow-Type Reactor with a NaOH Solution

This research aims to develop technology\nthat can improve low-grade\niron ore containing a large amount of α-FeOOH and gangue to\nthe same level as the high-grade iron ores that are conventionally\nused. The main goal is to optimize the alkaline hydrothermal treatment\nconditions for iron ore when using a flow-type reactor for constructing\na development framework for an upgrading process for low-grade iron\nore. Gangue removal extents during 5 M NaOH hydrothermal treatment\nincreased with increasing treatment temperature, with around 80% of\nSi, Al, and P removed by treatment at 250 °C. The removal extents\nalso increased with increasing NaOH concentration, decreasing particle\nsize, and decreasing solid-liquid ratio. The ore species was found\nto have virtually no effect on gangue removal by alkaline hydrothermal\ntreatment. Based on the results obtained, the optimal parameters for\ngangue removal were a particle size of <1000 μm, a solvent\nconcentration of >0.1 M, and a heating temperature of 250 °C.\nThe FeOOH present in the iron ore changed to Fe<sub>2</sub>O<sub>3</sub> after alkaline hydrothermal treatment. Furthermore, this method\nwas also effective for gangue removal from sorted particles with a\nlarge gangue content.