Extraction of Aluminum and Iron from Bauxite: A Unique Closed-Loop Ore
Refining Process Utilizing Oxalate Chemistry
Abstract
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·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·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.