XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 609
indicates that the electrode surface becomes passivated by
the precipitates faster at more negative potentials.
The increase in the uptake rates at more negative
potentials is explained by the more intensive production
of hydroxyl ions by the RVC electrode, which promotes
SEP [25]. The increase in the SEP rate with potential also
indicates that SEP at these potentials is controlled by the
precipitation rather than mass transport steps. In contrast,
the electro-deposition of Cu on RVC in synthetic solu-
tions at potential cathodic of –0.10 V is controlled by the
mass transport (diffusion) of Cu cations and hence does
not depend on potential [25]. Therefore, the increase in the
uptake rate for Cu at –0.50 V and –0.75 V vs. –0.30 V sug-
gests increasing contribution of SEP in the Cu uptake (see
below for more detail).
Notably, most of Fe, Mn, Ca, and Mg are rejected at
all three potentials (Figure 3). This result can be explained
by the stabilization of these cations in the bi-valent state as
ionic pairs with sulfate, which hampers their base precipita-
tion [25]. Thus, the regime at –0.75 V is suitable for the
fast direct continuous recovery of Cu, Al, REE, U, Co, and
Ni from AMD as a group, which can be implemented on an
AMD site or integrated online into a process circuit. These
elements can further be separated and purified one from
another offsite/offline.
To assess the detrimental role of Al on the uptake of
other metals, we compared the uptake in AMD1 with that
in Al-depleted AMD1 where the Al concentration is reduced
from 14.6 to 3.3 mg/L by chemical precipitation. The Al
depletion significantly improves the uptake of the valuable
0 2 4 6 8 10 12 14
0
20
40
60
80
100
Time (min)
Mg
Ca
Mn
Fe
Co
Ni
Cu
Zn
Sr
U
Al
Si
Y
La
Ce
Nd
2
3
4
5
6
7
8
9
pH
Von
a
b
0
20
40
60
80
100
Mg
Ca
Mn
Fe
Co
Ni
Cu
Zn
Sr
U
pH
0 10 20 30 40 50 60
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
Time (min)
0 10 20 30 40 50 60
0
20
40
60
80
100 Al
Si
Y
La
Ce
Nd
Time (min)
c
Al-depleted AMD1
Von
0.30 V 0.30 V
0.75 V
Figure 6. The recovery of elements from Al-depleted AMD1 at (a,b) –0.30 V in a 40-mL cell and (c) –0.75 V in a 20-mL cell by
a RVC electrode with size of 19×17×5 mm3 (0.114 g) .V
on shows the moment when potential is applied. (c) Copyright © 2023
Chernyshova, Suup, Kihlblom, Kota, Ponnurangam
Uptake(%)
pH
Uptake(%)
pH Uptake(%)
indicates that the electrode surface becomes passivated by
the precipitates faster at more negative potentials.
The increase in the uptake rates at more negative
potentials is explained by the more intensive production
of hydroxyl ions by the RVC electrode, which promotes
SEP [25]. The increase in the SEP rate with potential also
indicates that SEP at these potentials is controlled by the
precipitation rather than mass transport steps. In contrast,
the electro-deposition of Cu on RVC in synthetic solu-
tions at potential cathodic of –0.10 V is controlled by the
mass transport (diffusion) of Cu cations and hence does
not depend on potential [25]. Therefore, the increase in the
uptake rate for Cu at –0.50 V and –0.75 V vs. –0.30 V sug-
gests increasing contribution of SEP in the Cu uptake (see
below for more detail).
Notably, most of Fe, Mn, Ca, and Mg are rejected at
all three potentials (Figure 3). This result can be explained
by the stabilization of these cations in the bi-valent state as
ionic pairs with sulfate, which hampers their base precipita-
tion [25]. Thus, the regime at –0.75 V is suitable for the
fast direct continuous recovery of Cu, Al, REE, U, Co, and
Ni from AMD as a group, which can be implemented on an
AMD site or integrated online into a process circuit. These
elements can further be separated and purified one from
another offsite/offline.
To assess the detrimental role of Al on the uptake of
other metals, we compared the uptake in AMD1 with that
in Al-depleted AMD1 where the Al concentration is reduced
from 14.6 to 3.3 mg/L by chemical precipitation. The Al
depletion significantly improves the uptake of the valuable
0 2 4 6 8 10 12 14
0
20
40
60
80
100
Time (min)
Mg
Ca
Mn
Fe
Co
Ni
Cu
Zn
Sr
U
Al
Si
Y
La
Ce
Nd
2
3
4
5
6
7
8
9
pH
Von
a
b
0
20
40
60
80
100
Mg
Ca
Mn
Fe
Co
Ni
Cu
Zn
Sr
U
pH
0 10 20 30 40 50 60
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
Time (min)
0 10 20 30 40 50 60
0
20
40
60
80
100 Al
Si
Y
La
Ce
Nd
Time (min)
c
Al-depleted AMD1
Von
0.30 V 0.30 V
0.75 V
Figure 6. The recovery of elements from Al-depleted AMD1 at (a,b) –0.30 V in a 40-mL cell and (c) –0.75 V in a 20-mL cell by
a RVC electrode with size of 19×17×5 mm3 (0.114 g) .V
on shows the moment when potential is applied. (c) Copyright © 2023
Chernyshova, Suup, Kihlblom, Kota, Ponnurangam
Uptake(%)
pH
Uptake(%)
pH Uptake(%)