Hazard, Solidification and Recovery of Soluble Sodium from Red Mud Through Stepwise Separation Via Super-Gravity

Bayer red mud is a kind of solid waste generated during the production of alumina, which is hazardous to environment due to the high alkalinity caused by soluble sodium. Therefore, a green method for solidification and recovery of soluble sodium from red mud through stepwise separation via super-gravity was developed in this research. Firstly, the Na was completely enriched into the Na-rich slag through the separation of FeAl 2 O 4 phase from the red mud via super-gravity. Subsequently, the Na was solidified and recovered further as NaAlSiO 4 from the Na-rich slag via super-gravity separation at its single crystallization temperature of 1423-1323 K. Accordingly, the soluble sodium was recovered stepwise into Na-rich slag and then to the stable phase (NaAlSiO 4 ) from red mud with a high recovery ratio of 78.14%. Moreover, the low leaching ratio of Na + in NaAlSiO 4 confirmed that the soluble sodium in red mud was efficiently solidified and recovered friendly to the environment.