1658 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
recovery (ppm) per g RM per ml H2SO4 for Anawati et
al. comes out to be 32.736 ppm/g RM/ml H2SO4, while
for this study, it is 130 ppm/g RM/ ml H2SO4 [22]. Thus,
1.2× the stoichiometric H2SO4 yielded peak Sc recovery
from the RM using TABWL. Further work is ongoing to
quantify the performance of this study vs. contemporary
studies.
Effect of Baking Temperature
The effect of baking temperature between 50°C and 400°C
(below and above 270°C at which the vaporization of
H2SO4 is noticeable) on the recovery of Sc was analyzed.
The samples were baked for two hours using a 1.2× stoichio-
metric amount of acid and leached for two hours in water
at 75°C with an S/L of 1/20. Figure 8 shows a recovery plot
as a function of baking temperature. The plot shows that
the Sc recovery plateaued at 200°C. While studying the
recovery of REEs from iron-rich fluorapatite concentrate,
Soltani et al. found that H2SO4 decomposes past 200°C
[45]. By 270°C, up to 25% of the H2SO4 is vaporized.
However, since the Sc recoveries plateaued at 200°C, the
kinetics of sulfation may be faster than the decomposition
rate of the acid, thereby negating the effect of acid decom-
position. It should, however, be noted that the Fe recovery
keeps increasing with an increase in baking temperature till
400°C. This may be because the kinetics of Fe sulfation are
increasing at higher temperatures. Thus, peak Sc recovery
using TABWL is at 200°C a baking temperature.
Effect of Baking Time
The effect of baking time on Sc recovery was tested for half
an hour, one hour, and two hours. This was based on the
results from previous studies on acid baking [22, 23]. The
samples were baked at 200°C using a 1.2× stoichiometric
amount of acid and leached for two hours at 75°C in water
with an S/L of 1/20. It was observed that the baking time
over one hour had an insignificant effect on the recovery
of Sc, as seen in Figure 9. Sc recovery plateaued at 78%.
These results corroborate the findings of Borra et al.[23].
However, Borra et al. used a higher baking temperature and
found that baking times as low as 30 min provided similar
Sc recoveries [23]. That may have been due to the much
faster kinetics of sulfation at 675°C vs 200°C. While Soltani
et al. did not provide the recovery data for Sc, the recov-
eries of Y, Ce, La, and Nd were only marginally affected
by baking time, with the improvement in recoveries being
less than 5% when incrementing the baking time from one
hour to two hours [45]. However, no triplicate analysis was
performed in that study to evaluate the significance of the
results. The optimal baking duration at 200°C is one hour.
Effect Of Leaching Parameters
Leaching Temperature
The effect of leaching temperature was tested at 25°C, 50°C,
75°C, and 95°C. Figure 10 shows the recovery of Sc using
TABWL vs. leaching temperature. The conditions were
chosen to explore the influence of temperature between
room temperature and near the boiling point of water. The
samples were baked at 200°C for two hours using a 1.2×
stoichiometric amount of acid and leached for two hours in
water at an S/L of 1/20. Maximum Sc recovery of 78% was
observed at 75°C while recoveries plateaued when elevating
to higher temperatures. Sc recovery (60%) was also lower
at room temperature than at 75°C. Compared to the results
obtained by Anawati et al., the Sc recovery using TABWL at
25°C was marginally higher than that of the 200°C roasted
0
10
20
30
40
50
60
70
80
90
100
50 100 150 200 250 300 400
Temp. (°C)
Sc
Fe
Figure 8. Effect of baking temperature on Sc recovery
0
10
20
30
40
50
60
70
80
90
100
0.5 1 2
Time (h)
Sc
Figure 9. Effect of baking time on Sc recovery
Recovery
(%)Recovery
(%)
recovery (ppm) per g RM per ml H2SO4 for Anawati et
al. comes out to be 32.736 ppm/g RM/ml H2SO4, while
for this study, it is 130 ppm/g RM/ ml H2SO4 [22]. Thus,
1.2× the stoichiometric H2SO4 yielded peak Sc recovery
from the RM using TABWL. Further work is ongoing to
quantify the performance of this study vs. contemporary
studies.
Effect of Baking Temperature
The effect of baking temperature between 50°C and 400°C
(below and above 270°C at which the vaporization of
H2SO4 is noticeable) on the recovery of Sc was analyzed.
The samples were baked for two hours using a 1.2× stoichio-
metric amount of acid and leached for two hours in water
at 75°C with an S/L of 1/20. Figure 8 shows a recovery plot
as a function of baking temperature. The plot shows that
the Sc recovery plateaued at 200°C. While studying the
recovery of REEs from iron-rich fluorapatite concentrate,
Soltani et al. found that H2SO4 decomposes past 200°C
[45]. By 270°C, up to 25% of the H2SO4 is vaporized.
However, since the Sc recoveries plateaued at 200°C, the
kinetics of sulfation may be faster than the decomposition
rate of the acid, thereby negating the effect of acid decom-
position. It should, however, be noted that the Fe recovery
keeps increasing with an increase in baking temperature till
400°C. This may be because the kinetics of Fe sulfation are
increasing at higher temperatures. Thus, peak Sc recovery
using TABWL is at 200°C a baking temperature.
Effect of Baking Time
The effect of baking time on Sc recovery was tested for half
an hour, one hour, and two hours. This was based on the
results from previous studies on acid baking [22, 23]. The
samples were baked at 200°C using a 1.2× stoichiometric
amount of acid and leached for two hours at 75°C in water
with an S/L of 1/20. It was observed that the baking time
over one hour had an insignificant effect on the recovery
of Sc, as seen in Figure 9. Sc recovery plateaued at 78%.
These results corroborate the findings of Borra et al.[23].
However, Borra et al. used a higher baking temperature and
found that baking times as low as 30 min provided similar
Sc recoveries [23]. That may have been due to the much
faster kinetics of sulfation at 675°C vs 200°C. While Soltani
et al. did not provide the recovery data for Sc, the recov-
eries of Y, Ce, La, and Nd were only marginally affected
by baking time, with the improvement in recoveries being
less than 5% when incrementing the baking time from one
hour to two hours [45]. However, no triplicate analysis was
performed in that study to evaluate the significance of the
results. The optimal baking duration at 200°C is one hour.
Effect Of Leaching Parameters
Leaching Temperature
The effect of leaching temperature was tested at 25°C, 50°C,
75°C, and 95°C. Figure 10 shows the recovery of Sc using
TABWL vs. leaching temperature. The conditions were
chosen to explore the influence of temperature between
room temperature and near the boiling point of water. The
samples were baked at 200°C for two hours using a 1.2×
stoichiometric amount of acid and leached for two hours in
water at an S/L of 1/20. Maximum Sc recovery of 78% was
observed at 75°C while recoveries plateaued when elevating
to higher temperatures. Sc recovery (60%) was also lower
at room temperature than at 75°C. Compared to the results
obtained by Anawati et al., the Sc recovery using TABWL at
25°C was marginally higher than that of the 200°C roasted
0
10
20
30
40
50
60
70
80
90
100
50 100 150 200 250 300 400
Temp. (°C)
Sc
Fe
Figure 8. Effect of baking temperature on Sc recovery
0
10
20
30
40
50
60
70
80
90
100
0.5 1 2
Time (h)
Sc
Figure 9. Effect of baking time on Sc recovery
Recovery
(%)Recovery
(%)