An environmental-friendly method for recovery of soluble sodium and harmless utilization of red mud: Solidification, separation, and mechanism

Red mud is a hazardous waste produced from Bayer process, and its high alkalinity caused by soluble sodium (Na) poses a major threat to environment. In this study, an environmental-friendly method was proposed for recovery of soluble sodium (Na) and harmless utilization of red mud. First, soluble sodium was selectively so-lidified into Na-rich phases (anorthite and melilite). Subsequently, high-purity Na-rich phases were efficiently recovered from red mud under super gravity. Finally, solidification mechanism of sodium in anorthite and melilite was confirmed by characterizing high-purity Na-rich crystals. The leaching rates of Na+ were only 0.01% and 0.04% in anorthite and melilite, respectively, and high alkalinity was minimized. In addition, the anorthite was found to possess a stronger solidification capacity of Na as compared with melilite based on the reaction mechanism of Na+ + Si4+= Ca2+ + Al3+. This provides a theoretical basis for alkalinity minimization and harmless utilization of red mud.

Automated summary

In this study, an environmental-friendly method was proposed for the recovery and harmless utilization of soluble sodium in red mud. The soluble sodium was selectively solidified and efficiently recovered from red mud, minimizing its high alkalinity. The solidification mechanism of sodium in anorthite and melilite was confirmed, providing a theoretical basis for minimizing alkalinity and making red mud harmless.