Reduction of Red Mud Discharge by Reductive Bayer Digestion: A Comparative Study and Industrial Validation

Abstract

A novel design incorporating both reductive Bayer digestion and iron recovery into diasporic bauxite processing is proposed to remarkably reduce red mud discharge. This paper presents a comparative study on reductive versus typical Bayer digestion, after which an industrial validation test was carried out. During the test, relative alumina recovery of 98% and a reduction of 10.9% in the amount of red mud generated were achieved by substituting 2 wt.% iron powder for 10 wt.% lime of bauxite in the high-temperature digestion. Meanwhile, ~ 60% of the iron minerals were converted to magnetite by iron powder, meaning that processing the resulting red mud by magnetic separation could obtain iron concentrate with total iron concentration of 55.2% and iron recovery of 60.1%. The overall reduction of red mud discharge reached 50% for a ton of alumina. The proposed prototype is conducive to improve the Bayer process, aiming to achieve cleaner production of commercial alumina.