XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3527
the potential of recovering different metallic values from
bauxite residue. The metallic values present within baux-
ite residue include 20–60% iron, 1–15% titanium. 5–30%
aluminum, and rare earth elements such as 0.001–0.012%
scandium, which have high commercial value (Hammond
et al., 2013). Recovery of these elements from waste reduces
the waste volume, provides an alternative source for these
critical elements, and reduces the environmental impacts
associated with disposal.
Hematite is the most abundant mineral in bauxite
residue and can be utilized as an alternative feed in iron-
making furnaces. However, low iron grade and the presence
of a high amount of sodium (5–15%) and silicon (5–50%),
along with very fine particle size, restricts the utilization
of bauxite residue as a feed for iron making. The reduc-
tion roasting of bauxite residue is reported in the context of
converting hematite to magnetite and recovering magnetic
concentrate after magnetic separation (Mishra et al., 2002,
Agrawal et al., 2019). Reduction roasting and magnetic
separation provide low separation efficiency (40–50% Fe
grade, 70–80% recovery) due to very fine particle size and
the formation of mixed phases such as fayalite and herc-
ynite. Heat treatment with sodium-based fluxes (NaOH,
Na2CO3) forms sodium aluminate, which is easily sepa-
rated after leaching with water and subsequently enhances
the grade and recovery during reduction roasting and mag-
netic separation. However, even after additional processing,
the product purity is limited to a grade of 90% magnetite
with a low recovery of 15–20%.
Reductive smelting of bauxite residue in an induction
furnace is another method explored in the past. The bauxite
residue is mixed with fluxing agents (lime, calcite and dolo-
mite) along with reductant (C, CO) and heated to a tem-
perature of 1500–1600 °C in an induction or electric arc
furnace (Mishra et al., 2002, Borra et al., 2015, Cardenia et
al., 2018). The process results in iron recovery in the form
of pig iron (Fe grade 90%, 90–95% recovery) and subse-
quently generates a slag consisting of titanium, aluminum,
and rare earth elements (Borra et al., 2015, Ekstroem et al.,
2021).
Hydrometallurgical methods have recently gained sig-
nificant interest in recycling bauxite residue (Borra et al.,
2015 .The key advantage of hydrometallurgical methods
is the potential for recovering rare earth elements, includ-
ing scandium. The demand for rare earths has significantly
increased over the last decade, driven by the growth of the
high-tech industry however, there are limited raw mate-
rials for these elements, resulting in high prices and sup-
ply risk. Considering the presence of scandium in bauxite
residue, it can be used as an alternative source. However, a
very low concentration of scandium (~50 ppm) provides a
low-volume product, consumes large quantities of chemi-
cal reagents, and does not provide high-volume utilization.
Furthermore, the dissolution of multiple elements presents
technical difficulties in the downstream separation process.
Since iron is the major constituent of bauxite residue, it
is expected that extraction of iron can result in high vol-
ume utilization of bauxite residue and will concentrate the
Figure 1. Global mine production of bauxite, refinery production of alumina and corresponding bauxite
residue (red mud) generated over the last decade
the potential of recovering different metallic values from
bauxite residue. The metallic values present within baux-
ite residue include 20–60% iron, 1–15% titanium. 5–30%
aluminum, and rare earth elements such as 0.001–0.012%
scandium, which have high commercial value (Hammond
et al., 2013). Recovery of these elements from waste reduces
the waste volume, provides an alternative source for these
critical elements, and reduces the environmental impacts
associated with disposal.
Hematite is the most abundant mineral in bauxite
residue and can be utilized as an alternative feed in iron-
making furnaces. However, low iron grade and the presence
of a high amount of sodium (5–15%) and silicon (5–50%),
along with very fine particle size, restricts the utilization
of bauxite residue as a feed for iron making. The reduc-
tion roasting of bauxite residue is reported in the context of
converting hematite to magnetite and recovering magnetic
concentrate after magnetic separation (Mishra et al., 2002,
Agrawal et al., 2019). Reduction roasting and magnetic
separation provide low separation efficiency (40–50% Fe
grade, 70–80% recovery) due to very fine particle size and
the formation of mixed phases such as fayalite and herc-
ynite. Heat treatment with sodium-based fluxes (NaOH,
Na2CO3) forms sodium aluminate, which is easily sepa-
rated after leaching with water and subsequently enhances
the grade and recovery during reduction roasting and mag-
netic separation. However, even after additional processing,
the product purity is limited to a grade of 90% magnetite
with a low recovery of 15–20%.
Reductive smelting of bauxite residue in an induction
furnace is another method explored in the past. The bauxite
residue is mixed with fluxing agents (lime, calcite and dolo-
mite) along with reductant (C, CO) and heated to a tem-
perature of 1500–1600 °C in an induction or electric arc
furnace (Mishra et al., 2002, Borra et al., 2015, Cardenia et
al., 2018). The process results in iron recovery in the form
of pig iron (Fe grade 90%, 90–95% recovery) and subse-
quently generates a slag consisting of titanium, aluminum,
and rare earth elements (Borra et al., 2015, Ekstroem et al.,
2021).
Hydrometallurgical methods have recently gained sig-
nificant interest in recycling bauxite residue (Borra et al.,
2015 .The key advantage of hydrometallurgical methods
is the potential for recovering rare earth elements, includ-
ing scandium. The demand for rare earths has significantly
increased over the last decade, driven by the growth of the
high-tech industry however, there are limited raw mate-
rials for these elements, resulting in high prices and sup-
ply risk. Considering the presence of scandium in bauxite
residue, it can be used as an alternative source. However, a
very low concentration of scandium (~50 ppm) provides a
low-volume product, consumes large quantities of chemi-
cal reagents, and does not provide high-volume utilization.
Furthermore, the dissolution of multiple elements presents
technical difficulties in the downstream separation process.
Since iron is the major constituent of bauxite residue, it
is expected that extraction of iron can result in high vol-
ume utilization of bauxite residue and will concentrate the
Figure 1. Global mine production of bauxite, refinery production of alumina and corresponding bauxite
residue (red mud) generated over the last decade
