Potential routes to obtain value-added iron-containing compounds from red mud

Red mud, an aluminum industry large-scale waste, was used as a precursor to prepare sodium ferrate(VI) and sodium ferrite following different reaction pathways. Ferrous oxalate extracted from red mud has been used as an intermediate for the preparation of these compounds. The conversion rate to sodium ferrate(VI) from ferrous oxalate was as high as 64% in sodium hydroxide solution with sodium hypochlorite. Furthermore, sodium ferrite was formed after performing the solid–solid reaction at 600 °C using a 1:1 weight ratio of iron oxide (prepared via the ferrous oxalate extraction route from red mud) and sodium peroxide. In contrast, sodium iron silicon oxides were formed when red mud was reacted directly, following similar experimental procedures. These results present an interesting alternative to convert an environmentally unfriendly waste to new value-added products. It is envisaged that sodium ferrate(VI) might be of great interest in terms of wastewater treatment, whereas sodium ferrite and NawFexSiyOz might be of interest in the development of new materials for energy storage.