Solid-Phase Reduction and Iron Grain Growth in Red Mud in the Presence of Alkali Metal Salts

The solid-phase carbothermic reduction and the iron grain growth in red mud are studied in the presence of sodium and potassium sulfates and carbonates. The influence of temperature and alkali metal salt additions on the reduction of iron is estimated by Mössbauer spectroscopy during experiments in a laboratory furnace in the temperature range 1000–1200°C. The calculation of the grain size in reduced metallic iron shows that the addition of alkali metal compounds to red mud promotes an increase in the grain size. The experimental data demonstrate that alkali metal sulfates more strongly affect the iron grain growth as compared to alkali metal carbonates. The proposed approach can be used to develop a process of recycling of red mud by solid-phase reduction followed by magnetic separation.