606 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
11.7 mg/L Si, and 13 mg/L Al, which are also considered
in this study as gangues. The advantage of AMD1 is a rela-
tively low (1.5 mg/L) concentration of Fe, which typically
complicates the recovery of valuable elements from AMD.
The second water sample (AMD2) is less acidic (its
pH is 6.3) but as hard as AMD1. Compared to AMD1,
AMD2 has much lower concentrations of valuable elements
(2.1 mg/L Zn, 1.6 mg/L Cu, 0.9 mg/L Co, and 0.5 mg/L
TREE) but a similarly high amount of Mn (29 mg/L).
Even though AMD2 has a higher amount of Fe, the Fe
concentration of 2.6 mg/L is still relatively low. An impor-
tant feature of AMD2 is the absence of Al.
The third sample (“Al-depleted AMD1”) was obtained
from AMD1 by removing 80% of Al by the chemical pre-
cipitation at pH 5.35 with NaOH, followed by filtering.
This treatment also dropped the concentrations of Cu and
REE but by only 10–20%, marginally affecting the rest
elements.
To delineate the effect of potential, AMD1 was treated
at –0.30 V, –0.50 V, and –0.75 V in one stage (directly). To
achieve higher selectivity, AMD1 was also treated in two
stages¾first at –0.30 V and then at –0.75 V. To delineate
the effect of Al, we compare the above results with those
obtained on Al-depleted AMD1 and AMD2 (which does
not have Al). Table 2 summarizes the results.
When –0.30 V is applied to a RVC electrode in AMD1,
pH briefly drops to pH 4.2 and then steadily increases
to 5.8 in 40 min (Figure 3a). During this time, the elec-
trode uptakes ca. 90% Cu and Al with an admixture of
50% U, while the co-uptake of other elements is negligible
(Figure 3a,b). Hence, given that Al (along with Fe) can be
easily separated by chemical precipitation [28], this elec-
trolysis regime is suitable for the selective recovery of Cu
from a U-free water.
The SEM/EDS analysis of the layer deposited in
AMD1 at –0.30 V shows that the Cu and Al phases are
segregated. Copper is deposited as micron-size rounded
particles that present agglomerates of nanoparticles, while
Al is co-deposited as a continuous layer (Figure 4). XRD
shows that the Cu phase consists of a mixture of Cu2O
and metallic Cu0, suggesting that Cu is electro-deposited
[25]. In contrast, the Al phase is amorphous, with no XRD
signature. This phase is deposited by SEP as Al3+ cannot be
electro-deposited in water.
The water treatment rate, WTR, in the test at –0.30 V
shown in Figure 3a is 9 L/(kg RVC×min), while the Cu
specific recovery rate, SRRCu/C0(Cu), is (8.0±0.2) × 10–3 L
Table 1. Elemental composition and pH of AMD samples
AMD1 Al-Depleted AMD1 AMD2
Concentration,
mg/L
Relative
Content*, %
Concentration,
mg/L
Relative
Content*, %
Concentration,
mg/L
Relative
Content*, %
Zn 7.1±0.4 1.18 6.78 1.15 2.1 0.35
Cu 32.2±0.8 5.35 25.7 4.36 1.6 0.27
Co 2.0±0.1 0.33 1.86 0.32 0.89 0.15
Ni 0.50±0.3 0.08 0.475 0.08 0.27 0.05
Mn 30.1±0.8 5.00 31.0 5.26 29 4.86
Y 0.21±0.02 0.03 0.196 0.03 0.02 0.00
La 0.88±0.07 0.15 0.913 0.15 0.19 0.03
Ce 1.8±0.3 0.30 1.62 0.27 0.23 0.04
Nd 0.41±0.04 0.07 0.437 0.07 0.04 0.01
Na 25 203
K 20.0±0.6 12
Mg 147±3 24.4 171 29.0 170 28.47
Ca 350±30 58.2 332 56.3 382 63.97
Fe 1.6±0.2 0.27 1.7 0.29 2.60 0.44
Al 14.6±0.8 2.43 3.32 0.56 0.004
Si 11.7±0.2 1.95 11.2 1.90 7.0 1.17
S 400±20 386
Sr 1.37±0.08 0.23 1.30 0.22 1.18 0.20
U 0.038±0.003 0.01 0.027 0 0 0
pH 4.7 5.35 6.33
*Calculated excluding Na, K, and S
11.7 mg/L Si, and 13 mg/L Al, which are also considered
in this study as gangues. The advantage of AMD1 is a rela-
tively low (1.5 mg/L) concentration of Fe, which typically
complicates the recovery of valuable elements from AMD.
The second water sample (AMD2) is less acidic (its
pH is 6.3) but as hard as AMD1. Compared to AMD1,
AMD2 has much lower concentrations of valuable elements
(2.1 mg/L Zn, 1.6 mg/L Cu, 0.9 mg/L Co, and 0.5 mg/L
TREE) but a similarly high amount of Mn (29 mg/L).
Even though AMD2 has a higher amount of Fe, the Fe
concentration of 2.6 mg/L is still relatively low. An impor-
tant feature of AMD2 is the absence of Al.
The third sample (“Al-depleted AMD1”) was obtained
from AMD1 by removing 80% of Al by the chemical pre-
cipitation at pH 5.35 with NaOH, followed by filtering.
This treatment also dropped the concentrations of Cu and
REE but by only 10–20%, marginally affecting the rest
elements.
To delineate the effect of potential, AMD1 was treated
at –0.30 V, –0.50 V, and –0.75 V in one stage (directly). To
achieve higher selectivity, AMD1 was also treated in two
stages¾first at –0.30 V and then at –0.75 V. To delineate
the effect of Al, we compare the above results with those
obtained on Al-depleted AMD1 and AMD2 (which does
not have Al). Table 2 summarizes the results.
When –0.30 V is applied to a RVC electrode in AMD1,
pH briefly drops to pH 4.2 and then steadily increases
to 5.8 in 40 min (Figure 3a). During this time, the elec-
trode uptakes ca. 90% Cu and Al with an admixture of
50% U, while the co-uptake of other elements is negligible
(Figure 3a,b). Hence, given that Al (along with Fe) can be
easily separated by chemical precipitation [28], this elec-
trolysis regime is suitable for the selective recovery of Cu
from a U-free water.
The SEM/EDS analysis of the layer deposited in
AMD1 at –0.30 V shows that the Cu and Al phases are
segregated. Copper is deposited as micron-size rounded
particles that present agglomerates of nanoparticles, while
Al is co-deposited as a continuous layer (Figure 4). XRD
shows that the Cu phase consists of a mixture of Cu2O
and metallic Cu0, suggesting that Cu is electro-deposited
[25]. In contrast, the Al phase is amorphous, with no XRD
signature. This phase is deposited by SEP as Al3+ cannot be
electro-deposited in water.
The water treatment rate, WTR, in the test at –0.30 V
shown in Figure 3a is 9 L/(kg RVC×min), while the Cu
specific recovery rate, SRRCu/C0(Cu), is (8.0±0.2) × 10–3 L
Table 1. Elemental composition and pH of AMD samples
AMD1 Al-Depleted AMD1 AMD2
Concentration,
mg/L
Relative
Content*, %
Concentration,
mg/L
Relative
Content*, %
Concentration,
mg/L
Relative
Content*, %
Zn 7.1±0.4 1.18 6.78 1.15 2.1 0.35
Cu 32.2±0.8 5.35 25.7 4.36 1.6 0.27
Co 2.0±0.1 0.33 1.86 0.32 0.89 0.15
Ni 0.50±0.3 0.08 0.475 0.08 0.27 0.05
Mn 30.1±0.8 5.00 31.0 5.26 29 4.86
Y 0.21±0.02 0.03 0.196 0.03 0.02 0.00
La 0.88±0.07 0.15 0.913 0.15 0.19 0.03
Ce 1.8±0.3 0.30 1.62 0.27 0.23 0.04
Nd 0.41±0.04 0.07 0.437 0.07 0.04 0.01
Na 25 203
K 20.0±0.6 12
Mg 147±3 24.4 171 29.0 170 28.47
Ca 350±30 58.2 332 56.3 382 63.97
Fe 1.6±0.2 0.27 1.7 0.29 2.60 0.44
Al 14.6±0.8 2.43 3.32 0.56 0.004
Si 11.7±0.2 1.95 11.2 1.90 7.0 1.17
S 400±20 386
Sr 1.37±0.08 0.23 1.30 0.22 1.18 0.20
U 0.038±0.003 0.01 0.027 0 0 0
pH 4.7 5.35 6.33
*Calculated excluding Na, K, and S