3530 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
mol following a non-reductive dissolution mechanism (Lee
et al., 2006, Salmimies et al., 2012, Tanvar and Mishra,
2021). Therefore, leaching experiments were performed
at 95 °C temperature to enhance the dissolution kinetics.
Figure 4 (a) shows the dissolution of different elements
using 2 M oxalic acid, 95 °C temperature and 100 g/L
pulp density. The dissolution of iron is kinetically limited,
resulting in a parabolic dissolution curve with the maxi-
mum dissolution of approx. 81% after 2.5 h. The leaching
process also results in the dissolution of 44.7% aluminum,
29.5% silicon and 5.5% titanium. The XRD analysis of the
leach residue shown in Figure 4(b) confirms the dominance
of anatase, rutile and boehmite as the key mineral phases
present in the residue. The leach residue corresponding to
about 27 wt.% of bauxite residue feed consists of approx.
10.3% silicon, 15.1% titanium, 10.1% iron, 13.8% alumi-
num and 0.0086% scandium. The titanium and scandium
species behaved inertly during HCl and oxalic acid leach-
ing, resulting in an upgrade of up to 4-fold in the residue.
The leach liquor collected after oxalic acid leaching con-
tains a dissolved ferric oxalate complex that possesses photo-
chemical activity and can be reduced using photochemical
energy. Consequently, the ferric oxalate leach liquor was
subjected to photochemical reduction under UV light to
Figure 3. (a) Chemical analysis of residue obtained after HCl leaching (25 °C, 15 min., 100 g/L pulp density), (b) XRD
spectrum of raw and neutralized bauxite residue
Figure 4. (a) Dissolution of different elements after leaching with oxalic acid (2 M acid, 95 °C, 100 g/L pulp density), (b) XRD
spectrum of residue obtained after oxalic acid leaching
mol following a non-reductive dissolution mechanism (Lee
et al., 2006, Salmimies et al., 2012, Tanvar and Mishra,
2021). Therefore, leaching experiments were performed
at 95 °C temperature to enhance the dissolution kinetics.
Figure 4 (a) shows the dissolution of different elements
using 2 M oxalic acid, 95 °C temperature and 100 g/L
pulp density. The dissolution of iron is kinetically limited,
resulting in a parabolic dissolution curve with the maxi-
mum dissolution of approx. 81% after 2.5 h. The leaching
process also results in the dissolution of 44.7% aluminum,
29.5% silicon and 5.5% titanium. The XRD analysis of the
leach residue shown in Figure 4(b) confirms the dominance
of anatase, rutile and boehmite as the key mineral phases
present in the residue. The leach residue corresponding to
about 27 wt.% of bauxite residue feed consists of approx.
10.3% silicon, 15.1% titanium, 10.1% iron, 13.8% alumi-
num and 0.0086% scandium. The titanium and scandium
species behaved inertly during HCl and oxalic acid leach-
ing, resulting in an upgrade of up to 4-fold in the residue.
The leach liquor collected after oxalic acid leaching con-
tains a dissolved ferric oxalate complex that possesses photo-
chemical activity and can be reduced using photochemical
energy. Consequently, the ferric oxalate leach liquor was
subjected to photochemical reduction under UV light to
Figure 3. (a) Chemical analysis of residue obtained after HCl leaching (25 °C, 15 min., 100 g/L pulp density), (b) XRD
spectrum of raw and neutralized bauxite residue
Figure 4. (a) Dissolution of different elements after leaching with oxalic acid (2 M acid, 95 °C, 100 g/L pulp density), (b) XRD
spectrum of residue obtained after oxalic acid leaching