Development of roasting-acid leaching-magnetic separation technology for recovery of iron from "dead ores"

Utilization of plentiful fine-disseminated iron oxide ores resources attracted increasing attention in these years due to the depletion of easy-dressing iron ore reserves. In this paper, an improved Fe recovery method from the refractory fine-grained iron ores was proposed, and iron can be stepwise recovered by microwave-assisted reduction roasting with the addition of Na2SO4, followed by acid leaching of roasted ore and then magnetic separation of leached ore. Experimental and mechanism analysis results indicated that during the roasting process, 70.38% of Na2SO4 would react with fine-disseminated kaolinite in raw ore to form acid-soluble NaAlSiO4, achieving the crude extraction of ore samples by acid leaching. Moreover, the images of SEM showed that the addition of Na2SO4 during the roasting process can also promote the aggregation and growth of iron-rich particles, promoting the iron-rich particles' liberation in milling and resulting in a further dramatic improvement in Fe grade and Fe recovery ratio of iron concentrate by magnetic separation. The iron concentrate contained 56.91% Fe, 9.48% Mn, 3.11% Al, and 1.64% Si with a recovery of 83.52%, indeed up to the iron ores quality requirement of the steel and iron industry. This technology can also provide an inspiring idea for utilizing and processing other similar raw materials.