XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1659
sample [22]. However, compared with the 400°C roasted
sample, the Sc recoveries are lower and do not reach similar
levels until 75°C leaching temperature. Work is currently
being done to explain this difference in leaching behavior.
Solid-to-Liquid Ratio
The effect of S/L ratios for recovering Sc from RM using
the TABWL process was analyzed for two conditions, 1/10
and 1/20. The conditions were chosen based on previous
studies which showed that 1/20 was more than sufficient
for Sc recovery while 1/10 was the optimal ratio [22, 23].
S/L of 1/5 was attempted but found difficult to stir and fil-
ter, and the tests were abandoned. The samples were baked
at 200°C for two hours using a 1.2× stoichiometric amount
of acid and leached in water at 75°C using S/L of 1/20 for
two hours. Figure 11 shows the effect of S/L on Sc recovery.
It was observed that the Sc recovery is not affected by the
S/L tested. Sc2(SO4)3 does not reach its solubility limit at
an S/L of 1/10 [46]. The optimal S/L here is marginally
lower than that observed by Anawati et al. [22]. This dif-
ference may be affected by the difference in composition of
the samples in the two studies. The sample in the current
study has over four times the Sc compared to the RM used
by Anawati et al., as well as twice the amount of Fe [22].
This may lead to the formation of more soluble species,
which would require more water to become completely
soluble. Thus, the optimal S/L for leaching RM using the
TABWL process is 1/10.
Leaching Time
The effect of leaching Time on Sc recovery using TABWL
was tested over half an hour, one hour, and two hours.
The conditions were based on the study by Anawati et al.,
where half an hour was the optimal leaching time at 200°C
while 2 hours was taken as the extreme case for maximizing
recovery at higher temperatures. RM was baked at 200°C
for two hours using a 1.2× stoichiometric amount of acid.
The baked sample was leached in water at 75°C at an S/L
of 1/20. Figure 12 shows the effect of leaching time on Sc
recovery. It was observed that a majority of Sc (i.e., 70%)
can be recovered within the first half hour of leaching. This
may be because of the fast-leaching kinetics of Sc2(SO4)3 in
water. Further leaching till one hour recovers a total of 78%
Sc. Sc recovery past one hour of leaching time does not
change. These leaching times are slower than the obser-
vations by Anawati et al. [22]. The sample in the current
study has over four times the Sc compared to the RM used
by Anawati et al. as well as twice the amount of Fe, which
would mean more soluble species forming, requiring longer
0
10
20
30
40
50
60
70
80
90
100
25 50 75 95
Temperature (°C)
Sc
Figure 10. Effect of leaching temperature on Sc recovery
0
10
20
30
40
50
60
70
80
90
100
1/10 1/20
S/L
Sc
Figure 11. Effect of solid-to-liquid ratio on Sc recovery
0
10
20
30
40
50
60
70
80
90
100
0.5 1 2
Time (h)
Figure 12. Effect of leaching time on Sc recovery
Recovery
(%)
Recovery
(%)
Sc
Recovery
(%)
sample [22]. However, compared with the 400°C roasted
sample, the Sc recoveries are lower and do not reach similar
levels until 75°C leaching temperature. Work is currently
being done to explain this difference in leaching behavior.
Solid-to-Liquid Ratio
The effect of S/L ratios for recovering Sc from RM using
the TABWL process was analyzed for two conditions, 1/10
and 1/20. The conditions were chosen based on previous
studies which showed that 1/20 was more than sufficient
for Sc recovery while 1/10 was the optimal ratio [22, 23].
S/L of 1/5 was attempted but found difficult to stir and fil-
ter, and the tests were abandoned. The samples were baked
at 200°C for two hours using a 1.2× stoichiometric amount
of acid and leached in water at 75°C using S/L of 1/20 for
two hours. Figure 11 shows the effect of S/L on Sc recovery.
It was observed that the Sc recovery is not affected by the
S/L tested. Sc2(SO4)3 does not reach its solubility limit at
an S/L of 1/10 [46]. The optimal S/L here is marginally
lower than that observed by Anawati et al. [22]. This dif-
ference may be affected by the difference in composition of
the samples in the two studies. The sample in the current
study has over four times the Sc compared to the RM used
by Anawati et al., as well as twice the amount of Fe [22].
This may lead to the formation of more soluble species,
which would require more water to become completely
soluble. Thus, the optimal S/L for leaching RM using the
TABWL process is 1/10.
Leaching Time
The effect of leaching Time on Sc recovery using TABWL
was tested over half an hour, one hour, and two hours.
The conditions were based on the study by Anawati et al.,
where half an hour was the optimal leaching time at 200°C
while 2 hours was taken as the extreme case for maximizing
recovery at higher temperatures. RM was baked at 200°C
for two hours using a 1.2× stoichiometric amount of acid.
The baked sample was leached in water at 75°C at an S/L
of 1/20. Figure 12 shows the effect of leaching time on Sc
recovery. It was observed that a majority of Sc (i.e., 70%)
can be recovered within the first half hour of leaching. This
may be because of the fast-leaching kinetics of Sc2(SO4)3 in
water. Further leaching till one hour recovers a total of 78%
Sc. Sc recovery past one hour of leaching time does not
change. These leaching times are slower than the obser-
vations by Anawati et al. [22]. The sample in the current
study has over four times the Sc compared to the RM used
by Anawati et al. as well as twice the amount of Fe, which
would mean more soluble species forming, requiring longer
0
10
20
30
40
50
60
70
80
90
100
25 50 75 95
Temperature (°C)
Sc
Figure 10. Effect of leaching temperature on Sc recovery
0
10
20
30
40
50
60
70
80
90
100
1/10 1/20
S/L
Sc
Figure 11. Effect of solid-to-liquid ratio on Sc recovery
0
10
20
30
40
50
60
70
80
90
100
0.5 1 2
Time (h)
Figure 12. Effect of leaching time on Sc recovery
Recovery
(%)
Recovery
(%)
Sc
Recovery
(%)