XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3531
recover iron as ferrous oxalate. UV light induces a ligand to
metal electron transfer in the ferric oxalate ([Fe(C2O4)3]3–)
complex, leading to the formation of [Fe(C2O4)2]2–, CO2
and C2O42– ions in the solution. [Fe(C2O4)2]2– is further
hydrolyzed in the solution and results in the precipitation
of ferrous oxalate dihydrate (FeC2O4.2H2O). The UV
reduction process was carried out for 6 hours employing a
100 W UV lamp (Tanvar and Mishra, 2021). Over 99% of
the dissolved iron was successfully recovered as a precipitate
of ferrous oxalate after reduction. Subsequently, the ferrous
oxalate was thermally treated at 500 °C for 30 min. in a low
oxygen atmosphere to produce magnetite. The magnetite
product exhibited 99% purity, with magnetite identified
as the predominant mineral phase. The chemical constitu-
ents of magnetite products include 99.02% Fe3O4, 0.78%
Al2O3, 0.01% CaO and 0.22% Na2O.
6 6H
2 3H
Fe O C O
O O
kJ/moli
2 3^s 2 4^aq
2-
2 4 2
25°C
"++
+
=-212.75 c
+
_G
^aqh
^aqh
^l h3@3-
h h
h
6Fe^C (1)
2 6H
2 3
Fe O HC O
O4@2+ H O
kJ/moli
2 3^sh 2 4^aq
2
25°C
°
"++
+
=-87.35
-+
_G
^aqh ^l
^aqh h
h 6FeHC2 (2)
5 6H
2 )3H 2
Fe O C O
O O CO
kJ/moli
l
2 3^sh 2 4^aq
2-
2 4 2
2-
2 2^gh
25°C
"++
++
=-152.29 c
+
_G
^aqh
^aqh
^
h
h
6Fe(C @(3)
The residue after iron recovery consists of upgraded
titanium and scandium values and provides a better feed
than the bauxite residue for the recovery of these elements.
Recovery of titanium and scandium from the residue was
attempted through sulfation baking and leaching process.
Sulfation baking was performed by thoroughly mixing 98%
sulfuric acid (H2SO4) with residue in a ratio of 1.3 mL/g
(10% excess to the stoichiometric requirement), followed
by heating at 250 °C for different time durations. Sulfation
experiments were performed in a tubular furnace under
inert atmosphere and the off gas was purged through an
acid scrubber. The sulfated mass was further dissolved after
leaching in 0.5 M H2SO4 for 1 h. Figure 5(a) shows the
dissolution yield of different elements at different heating
durations. The optimal dissolution of titanium (90.2%),
aluminum (93.2%) and scandium (66.9%) were obtained
after 2 h at 250 °C. Figure 5(b) shows the XRD analysis
of the final residue (10.9 wt.% of starting bauxite residue)
dominated by the SiO2 phase.
The leach solution generated after sulfation baking was
composed of 12.3 g/L titanium, 7.3 g/L aluminum, and
7.2 g/L iron. The recovery of titanium was accomplished
through thermal hydrolysis, which was achieved by heating
the solution to boiling for 4 hours (Grzmil et al., 2008).
Iron (III) was first reduced to Fe(II) using iron powder
before undergoing thermal hydrolysis to prevent co-precip-
itation. Following this process, the filtered solution con-
tained 55.1 ppm titanium, 9080.0 ppm iron, 7190.2 ppm
aluminum, and 4.1 ppm scandium. Simultaneously, over
96% of the titanium was successfully recovered as a TiO2
Figure 5. (a) Dissolution of different elements after sulfation baking (250 °C, 1.3 mL/g acid) and water leaching (60 min, 25
°C), (c) XRD spectrum of final leach residue
recover iron as ferrous oxalate. UV light induces a ligand to
metal electron transfer in the ferric oxalate ([Fe(C2O4)3]3–)
complex, leading to the formation of [Fe(C2O4)2]2–, CO2
and C2O42– ions in the solution. [Fe(C2O4)2]2– is further
hydrolyzed in the solution and results in the precipitation
of ferrous oxalate dihydrate (FeC2O4.2H2O). The UV
reduction process was carried out for 6 hours employing a
100 W UV lamp (Tanvar and Mishra, 2021). Over 99% of
the dissolved iron was successfully recovered as a precipitate
of ferrous oxalate after reduction. Subsequently, the ferrous
oxalate was thermally treated at 500 °C for 30 min. in a low
oxygen atmosphere to produce magnetite. The magnetite
product exhibited 99% purity, with magnetite identified
as the predominant mineral phase. The chemical constitu-
ents of magnetite products include 99.02% Fe3O4, 0.78%
Al2O3, 0.01% CaO and 0.22% Na2O.
6 6H
2 3H
Fe O C O
O O
kJ/moli
2 3^s 2 4^aq
2-
2 4 2
25°C
"++
+
=-212.75 c
+
_G
^aqh
^aqh
^l h3@3-
h h
h
6Fe^C (1)
2 6H
2 3
Fe O HC O
O4@2+ H O
kJ/moli
2 3^sh 2 4^aq
2
25°C
°
"++
+
=-87.35
-+
_G
^aqh ^l
^aqh h
h 6FeHC2 (2)
5 6H
2 )3H 2
Fe O C O
O O CO
kJ/moli
l
2 3^sh 2 4^aq
2-
2 4 2
2-
2 2^gh
25°C
"++
++
=-152.29 c
+
_G
^aqh
^aqh
^
h
h
6Fe(C @(3)
The residue after iron recovery consists of upgraded
titanium and scandium values and provides a better feed
than the bauxite residue for the recovery of these elements.
Recovery of titanium and scandium from the residue was
attempted through sulfation baking and leaching process.
Sulfation baking was performed by thoroughly mixing 98%
sulfuric acid (H2SO4) with residue in a ratio of 1.3 mL/g
(10% excess to the stoichiometric requirement), followed
by heating at 250 °C for different time durations. Sulfation
experiments were performed in a tubular furnace under
inert atmosphere and the off gas was purged through an
acid scrubber. The sulfated mass was further dissolved after
leaching in 0.5 M H2SO4 for 1 h. Figure 5(a) shows the
dissolution yield of different elements at different heating
durations. The optimal dissolution of titanium (90.2%),
aluminum (93.2%) and scandium (66.9%) were obtained
after 2 h at 250 °C. Figure 5(b) shows the XRD analysis
of the final residue (10.9 wt.% of starting bauxite residue)
dominated by the SiO2 phase.
The leach solution generated after sulfation baking was
composed of 12.3 g/L titanium, 7.3 g/L aluminum, and
7.2 g/L iron. The recovery of titanium was accomplished
through thermal hydrolysis, which was achieved by heating
the solution to boiling for 4 hours (Grzmil et al., 2008).
Iron (III) was first reduced to Fe(II) using iron powder
before undergoing thermal hydrolysis to prevent co-precip-
itation. Following this process, the filtered solution con-
tained 55.1 ppm titanium, 9080.0 ppm iron, 7190.2 ppm
aluminum, and 4.1 ppm scandium. Simultaneously, over
96% of the titanium was successfully recovered as a TiO2
Figure 5. (a) Dissolution of different elements after sulfation baking (250 °C, 1.3 mL/g acid) and water leaching (60 min, 25
°C), (c) XRD spectrum of final leach residue