1240 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
It is seen that the maximum dissolution was achieved
within the first hour at room temperature. The recov-
ery percentage was fairly constant at 25°, 45°, and 65°C
throughout the 24 hours. At 85°C, maximum recovery was
achieved in the hour, but these values were still lower than
25° and 45°C. The curve plateaued till 6 hours, after which
there was a significant drop in the recovery values because
of the depletion of free oxalate. The drop in recovery is
plausible because of the solubility limit, and the dissolved
elements tend to precipitate out of the solution.
In the case of REE dissolution, the trend was similar
to Fe and P dissolution. REE dissolution did not behave
the same way with direct ores. This is because the REEs are
hosted in sulphate and phosphate compounds in the ACL
tailings, whereas they are a phosphate mineral in the direct
ores. The reactivity of ore and the leach tails in the oxalic
acid system differed greatly, as shown in Figure 4.
During oxalic acid leaching of the ore, phosphorus dis-
solution increased throughout the period. Most of the P
dissolution happened within the first hour, after which the
curve plateaus. The slower dissolution is probably because
of the lower solubility of REE phosphate complexes with
increasing temperature (Liu &Byrne, 1997 Wang et al.,
2010). The generation of phosphoric acid is also a plau-
sible reason for the lower P dissolution at higher tempera-
tures, as the effectiveness of phosphoric acid in dissolving
phosphate compounds is limited by the common ion effect
between phosphate minerals and phosphate anion in phos-
phoric acid (Soltani et al., 2019 Stone et al., 2016 Wu et
al., 2018).
0
10
20
30
40
50
60
70
80
90
100
0 3 6 9 12 15 18 21 24
Time (h)
0
10
20
30
40
50
60
70
80
90
100
0 3 6 9 12 15 18 21 24
Time (h)
0
10
20
30
40
50
60
70
80
90
100
0 3 6 9 12 15 18 21 24
Time (h)
Figure 3. Elemental behaviour of ACL tailings under varying temperature (0.57 mol/L oxalic acid, S/L ratio =1:10, 250 rpm)
FeDisolton(
)PDisolton(
)
T-EEDisolton(
)
It is seen that the maximum dissolution was achieved
within the first hour at room temperature. The recov-
ery percentage was fairly constant at 25°, 45°, and 65°C
throughout the 24 hours. At 85°C, maximum recovery was
achieved in the hour, but these values were still lower than
25° and 45°C. The curve plateaued till 6 hours, after which
there was a significant drop in the recovery values because
of the depletion of free oxalate. The drop in recovery is
plausible because of the solubility limit, and the dissolved
elements tend to precipitate out of the solution.
In the case of REE dissolution, the trend was similar
to Fe and P dissolution. REE dissolution did not behave
the same way with direct ores. This is because the REEs are
hosted in sulphate and phosphate compounds in the ACL
tailings, whereas they are a phosphate mineral in the direct
ores. The reactivity of ore and the leach tails in the oxalic
acid system differed greatly, as shown in Figure 4.
During oxalic acid leaching of the ore, phosphorus dis-
solution increased throughout the period. Most of the P
dissolution happened within the first hour, after which the
curve plateaus. The slower dissolution is probably because
of the lower solubility of REE phosphate complexes with
increasing temperature (Liu &Byrne, 1997 Wang et al.,
2010). The generation of phosphoric acid is also a plau-
sible reason for the lower P dissolution at higher tempera-
tures, as the effectiveness of phosphoric acid in dissolving
phosphate compounds is limited by the common ion effect
between phosphate minerals and phosphate anion in phos-
phoric acid (Soltani et al., 2019 Stone et al., 2016 Wu et
al., 2018).
0
10
20
30
40
50
60
70
80
90
100
0 3 6 9 12 15 18 21 24
Time (h)
0
10
20
30
40
50
60
70
80
90
100
0 3 6 9 12 15 18 21 24
Time (h)
0
10
20
30
40
50
60
70
80
90
100
0 3 6 9 12 15 18 21 24
Time (h)
Figure 3. Elemental behaviour of ACL tailings under varying temperature (0.57 mol/L oxalic acid, S/L ratio =1:10, 250 rpm)
FeDisolton(
)PDisolton(
)
T-EEDisolton(
)