Extraction of aluminum and iron from bauxite: A unique closed-loop ore refining process utilizing oxalate chemistry

The Bayer process holds an exclusive status for alumina extraction, but a massive amount of caustic "red mud" waste is generated. In this work, three oxalate reagents: potassium hydrogen oxalate (KHC2O4), potassium tetraoxalate (KHC2O4 center dot H2C2O4), and oxalic acid (H2C2O4) were investigated for the Al and Fe extraction process from NIST SRM 600 Australian-Darling range bauxite ore. More than 90% of Al and Fe was extracted into the aqueous phase in less than 2 h with 0.50 M C2O42- for all three reagents. The Fe and Al can be selectively precipitated by hydrolyzing the aqueous phase. By acidifying the Al and Fe free filtrate, 80% of the C2O42- can be precipitated as KHC2O4 center dot H2C2O4. Greater than 90% of the aqueous acid can also be recycled using a cation-exchange resin. The proposed closed-loop process is an energy-efficient, cost-effective, environmentally-friendly route for extracting Al and Fe from bauxite ore.