Sodium-Salt-Assisted Reductive Roasting for Separation and Enrichment of Valuable Components from Lateritic Iron Ore

The dual effect of sodium-salt-assisted reductive roasting for iron recovery and chromium enrichment from lateritic iron ore was investigated. Iron oxides were reduced to metallic iron through reductive roasting, while Al- and Si-bearing components were transformed to sodium aluminosilicate and/or diaoyudaoite. Thus, direct reduced iron (DRI) was recovered by magnetic separation, while Cr(III) element was enriched as nontoxic picotite in a Cr-bearing concentrate through sulfuric acid leaching. Na2CO3 was preferred due to its positive effect in activating Al- and Si-bearing components and contribution to good chromium enrichment. In contrast, Na2SO4 exhibited a stronger ability to improve the growth of metallic iron, resulting in better magnetic separation. Addition of Na2SO4 generally led to inferior aluminum leaching performance due to the formation of insoluble diaoyudaoite (NaAl11O17). When using combined addition of sodium salts in the optimized proportion in reductive roasting, DRI with 89.21% Fe and chromium concentrate with 40.42% Cr2O3 were obtained.