• Short-time roasting triggered microcracking in quartz–hematite aggregates. • Microcrack development improved liberation and magnetic separation efficiency. • Thermally induced microcracks enhanced acid leaching. • Roasting, magnetic separation and leaching upgraded iron tailings to 99.819% SiO 2 . • The process reduces time at high temperature compared with conventional calcination. Iron ore tailings (IOT) contain an underutilized quartz-rich fraction that can serve as a secondary source of high-purity silica. Conventional upgrading routes based on magnetic separation followed by acid leaching often rely on fine grinding and multi-hour calcination of the quartz concentrate. Here, we induce liberation by short-time roasting (10 min, 800°C) of the tailings prior to magnetic separation, exploiting the thermoelastic mismatch between quartz and hematite to promote microcracking. A conventional magnetic separator (up to 0.9 T) produced a Si-rich non-magnetic concentrate (up to 98.015% SiO 2 ) with a silica metallurgical recovery of 85.42%. Subsequent mixed-acid leaching (HCl–H 2 SO 4 –HNO 3 , 80°C, 8 h) yielded a final silica grade of 99.819% without additional grinding. Compared with literature benchmarks that typically apply 3 to 4 h calcination at 900°C and extra comminution before leaching, the proposed route achieves comparable product quality with substantially reduced thermal and comminution requirements and greater metallurgical recovery.
Cubi et al. (Mon,) studied this question.