XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1657
significant difference in Sc recoveries between two hours
and six hours of baking, suggesting that the particle size
does not affect the Sc recovery from RM using TABWL. It
can be concluded that the RM agglomerates as large as 500
microns can be used without additional grinding energy.
Effect of Baking Parameters
Effect of Acid to RM Ratio
The TABWL tests were performed using 0.9 to 2 times the
stoichiometrically required amounts of H2SO4 (acid was
split in half for each baking stage). The range was selected
to evaluate the effect of the acid dosing on the Sc recov-
ery below and above the required stoichiometric ratio. The
samples were baked for two hours at 200°C and leached in
water at 75°C for two hours with an S/L of 1/20. Figure 7
shows that the sub-stoichiometric amount of acid was
insufficient to completely sulfate the major phases, limit-
ing Sc recovery to 70%. Increasing the acid dosage to 1.2
times the stoichiometric amount (1 ml/g) increased the
Sc recovery using TABWL to 78%. Beyond 1.2 times the
stoichiometric amount of acid, Sc recoveries plateaued.
This plateauing behavior past 1.2× may be occurring due
to the mass transfer limitation posed by the sulfated layer.
The excess acid may then lead to the formation of undesir-
able (H3O)Fe(SO4)2, leading to wastage of acid. In con-
trast, Anawati et al. reported peak Sc recovery at 0.95 ml/g
solid [22]. It should be noted that the sample in the current
study also has over four times the Sc compared to the RM
used by Anawati et al., as well as twice the amount of Fe
[22]. These would require more acid for sulfation. The Sc
0
10
20
30
40
50
60
70
80
90
100
+35 mesh 2h -35 mesh 2h +35 mesh 6h -35 mesh 6h
Figure 6. Effect of particle size on Sc recovery
0
10
20
30
40
50
60
70
80
90
100
0.9 1.2 1.5 2
Acid/Red Mud Stoiciometric Ratio
Figure 7. Effect of acid dosage for baking on Sc recovery
Recovery
(%)
Sc
Recovery
(%)
significant difference in Sc recoveries between two hours
and six hours of baking, suggesting that the particle size
does not affect the Sc recovery from RM using TABWL. It
can be concluded that the RM agglomerates as large as 500
microns can be used without additional grinding energy.
Effect of Baking Parameters
Effect of Acid to RM Ratio
The TABWL tests were performed using 0.9 to 2 times the
stoichiometrically required amounts of H2SO4 (acid was
split in half for each baking stage). The range was selected
to evaluate the effect of the acid dosing on the Sc recov-
ery below and above the required stoichiometric ratio. The
samples were baked for two hours at 200°C and leached in
water at 75°C for two hours with an S/L of 1/20. Figure 7
shows that the sub-stoichiometric amount of acid was
insufficient to completely sulfate the major phases, limit-
ing Sc recovery to 70%. Increasing the acid dosage to 1.2
times the stoichiometric amount (1 ml/g) increased the
Sc recovery using TABWL to 78%. Beyond 1.2 times the
stoichiometric amount of acid, Sc recoveries plateaued.
This plateauing behavior past 1.2× may be occurring due
to the mass transfer limitation posed by the sulfated layer.
The excess acid may then lead to the formation of undesir-
able (H3O)Fe(SO4)2, leading to wastage of acid. In con-
trast, Anawati et al. reported peak Sc recovery at 0.95 ml/g
solid [22]. It should be noted that the sample in the current
study also has over four times the Sc compared to the RM
used by Anawati et al., as well as twice the amount of Fe
[22]. These would require more acid for sulfation. The Sc
0
10
20
30
40
50
60
70
80
90
100
+35 mesh 2h -35 mesh 2h +35 mesh 6h -35 mesh 6h
Figure 6. Effect of particle size on Sc recovery
0
10
20
30
40
50
60
70
80
90
100
0.9 1.2 1.5 2
Acid/Red Mud Stoiciometric Ratio
Figure 7. Effect of acid dosage for baking on Sc recovery
Recovery
(%)
Sc
Recovery
(%)