Recycling iron tailings is significant for environmental security and resource recovery, as they contain iron-rich minerals. Given the complex composition of iron minerals and the low grade of iron present in the tailings, innovative suspension roasting-magnetic separation (SRMS) technology was proposed to treat iron tailings that would separate out the iron minerals for recovery. In this study, the reduction kinetics, phase transformation, and structure evolution of the iron tailings were investigated to explain the mechanism behind magnetite production from iron tailings. These studies were conducted using chemical analyses, X-ray diffraction, Brunauer-Emmett-Teller specific surface area, and scanning electron microscopy. The results showed that high temperatures during the suspension reduction process were conducive to improving the reduction rate of the iron tailings. The best kinetics model for this reduction reaction of iron tailings is the P1 model, which demonstrated a linear increase in the conversion degree with the extension of the reaction time. The corresponding mechanism function was f(α) = 1, the apparent activation energy (Eα) was 51.56 kJ/mol, and the kinetics equation was k = 3.14exp(- 51.56/RT). Using the SRMS technology, magnetite gradually formed from hematite, starting at the outer particle layers and moving inward toward the core. The microcracks and pores in the surface of the particles increased, which promoted CO penetration into the particles where it reacted with the hematite. Our results provide important insight into the efficient and clean recycling of iron tailings.
Keywords: Iron phase transformation; Iron tailings; Microstructural evolution; Reduction mechanism model; SRMS technology.
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