Abstract
In this study an integrated process is presented as a suitable method to transform Fe3+ oxides present in bauxite residue into magnetic oxides and metallic iron through a microwave roasting reduction, avoiding the formation of hercynite (FeAl2O4). In the first step, all the alumina phases were transformed into sodium aluminates by adding sodium carbonate as a flux to BR and then leached out through alkali-leaching to recover alumina. Subsequently, the leaching residue was mixed with carbon and roasted by using a microwave furnace at the optimum conditions. The iron oxide present in the sinter was converted into metallic iron (98%). In addition, hercynite was not detected. The produced cinder was subjected to a wet high intensity magnetic separation process to separate iron from the other elements.
Highlights
Microwave roasting process has been examined as an emerging technology of mineral processing
Microwave treatment has been employed as an alternative method to recover iron from the bauxite residue (BR) [12,13,14,15,16] which is the solid waste generated during the production of alumina from bauxite ores [6]
Chemical analyses of major and minor elements were executed via XRF glass disk fusion method with lithium tetraborate in AoG. 1 g of BR sample is fused as melt in platinum crucible with 1 g LiNO3 oxidizer, and mixture of flux [40]
Summary
Microwave roasting process has been examined as an emerging technology of mineral processing. Compared to conventional heat treatment methods, this treatment has different advantages such as significantly faster reaction times and potentially lower energy [1] These depend on the interaction between material and electromagnetic field generated during the process. Because iron is the major component in BR (14–45 wt.%), several studies were focused on the recovery of iron based on pyrometallurgical processes [17,18] These works can be classified into two groups: The solid-state reductive roasting followed by magnetic separation [19,20,21,22,23] and the reductive smelting process by using different furnaces (blast furnace, electric arc furnace (EAF), and other types) [24,25,26,27,28,29,30]. A microwave process is an innovative technology utilized in mineral processing
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