Preparation of Na2FeO4 from Red Mud Sodium Roasting and Alkali Leaching Residue with the Aid of Ultrasound

Red mud is rich in Fe, Al, Si and Ti elements and is the main solid waste of the alumina industry, which has great recycling value. The red mud after sodium roasting is studied in this paper, considering the influences of leaching temperature, leaching time and solid-liquid ratio on the leaching rates of Al and Si elements in red mud. The result shows that the leaching rates of Al and Si elements are 96.28% and 54.04% under the optimum condition. The dissolubility of Al and Si elements in alkali leaching solution is analyzed from the phase changes of red mud after sodium roasting. The influences of ultrasound on the synthesis conditions of Na₂FeO₄ are researched, and the results show that the application of ultrasound can shorten the reaction time of Na₂FeO₄ and increase the concentration of Na₂FeO₄. The mechanism of promoting Na₂FeO₄ formation by ultrasonic was elucidated from the effects of physics and chemistry. Moreover, the response surface method is used to optimize the preparation process of Na₂FeO₄ by ultrasound.