610 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
elements. In particular, 95% Cu is recovered at –0.30 V in
15 min (Figure 6a), while WTR and SRRCu/C0(Cu) increase
compared to that in the untreated AMD1 by a factor of
4 and 7, respectively (Table 2 and Figure 5). Within 50
min, 99% REE and 99% Zn are removed, while the co-
uptake of Co, Ni, and Si is only 20–25% (Figure 6a,b). The
improvements can be explained by the lower passivation of
the RVC electrode by Al as seen from the higher pH of the
solution: At –0.30 V, pH increases during 40 min from pH
5.35 to pH 8.0 (Figure 6a), while in the untreated water it
increases from pH 4.7 to pH 5.7 (Figure 3a). Hence, the
removal of Al from AMD allows Cu, Zn, and REE to be
separated as a group from the remaining ion matrix already
at –0.30 V.
Interestingly, in contrast to the deposit formed at
–0.30 V in the untreated AMD1 (Figure 4), where Cu
is segregated from Al, the deposit formed in Al-depleted
AMD1 at –0.30 V presents fluffy agglomerates in which
all immobilized elements including Cu and Al are homoge-
neously intermixed (Figure 7a,b). It follows that these ele-
ments are immobilized by the co-precipitation in SEP.
At –0.75 V, the uptake from Al-depleted AMD1 by
SEP becomes consistently faster than at –0.30 V (Figure 6c
and Figure 5). The uptake rates for Cu and Zn increase by
a factor of 3 and 7, reaching 0.16 L and 0.046 g(RVC)–1
min–1, respectively (Table 2). A similar uptake of the valu-
able elements as at –0.30 V after 50 min (95% Cu, 85%
Zn, 90–95% TREE, 20% Co, and 20% Ni) is achieved
at –0.75 V already in 3 min after the potential is applied.
Importantly, the co-uptake of the gangue elements (Ca, Mg,
Mn, and Si) remains below 5%. Hence, this SEP regime
holds potential for the on-line processing of Al- (and Fe-)
depleted AMD water.
The above conclusion is supported by the results
obtained in Al-free AMD2 at –0.30 V (Figure 8 and
Figure 5). As shown in Figure 8, 90–95% of Cu, TREE,
S Na Cl Ce
Zn Mg Mn Cu
La Al O Si
a b
c
Figure 7. SEM/EDS analysis of the deposit formed on RVC at –0.30 V in Al-depleted AMD1 (Table 1) in the test shown in
Figure 6a,b. The scale bar in the EDS images is 800 nm
elements. In particular, 95% Cu is recovered at –0.30 V in
15 min (Figure 6a), while WTR and SRRCu/C0(Cu) increase
compared to that in the untreated AMD1 by a factor of
4 and 7, respectively (Table 2 and Figure 5). Within 50
min, 99% REE and 99% Zn are removed, while the co-
uptake of Co, Ni, and Si is only 20–25% (Figure 6a,b). The
improvements can be explained by the lower passivation of
the RVC electrode by Al as seen from the higher pH of the
solution: At –0.30 V, pH increases during 40 min from pH
5.35 to pH 8.0 (Figure 6a), while in the untreated water it
increases from pH 4.7 to pH 5.7 (Figure 3a). Hence, the
removal of Al from AMD allows Cu, Zn, and REE to be
separated as a group from the remaining ion matrix already
at –0.30 V.
Interestingly, in contrast to the deposit formed at
–0.30 V in the untreated AMD1 (Figure 4), where Cu
is segregated from Al, the deposit formed in Al-depleted
AMD1 at –0.30 V presents fluffy agglomerates in which
all immobilized elements including Cu and Al are homoge-
neously intermixed (Figure 7a,b). It follows that these ele-
ments are immobilized by the co-precipitation in SEP.
At –0.75 V, the uptake from Al-depleted AMD1 by
SEP becomes consistently faster than at –0.30 V (Figure 6c
and Figure 5). The uptake rates for Cu and Zn increase by
a factor of 3 and 7, reaching 0.16 L and 0.046 g(RVC)–1
min–1, respectively (Table 2). A similar uptake of the valu-
able elements as at –0.30 V after 50 min (95% Cu, 85%
Zn, 90–95% TREE, 20% Co, and 20% Ni) is achieved
at –0.75 V already in 3 min after the potential is applied.
Importantly, the co-uptake of the gangue elements (Ca, Mg,
Mn, and Si) remains below 5%. Hence, this SEP regime
holds potential for the on-line processing of Al- (and Fe-)
depleted AMD water.
The above conclusion is supported by the results
obtained in Al-free AMD2 at –0.30 V (Figure 8 and
Figure 5). As shown in Figure 8, 90–95% of Cu, TREE,
S Na Cl Ce
Zn Mg Mn Cu
La Al O Si
a b
c
Figure 7. SEM/EDS analysis of the deposit formed on RVC at –0.30 V in Al-depleted AMD1 (Table 1) in the test shown in
Figure 6a,b. The scale bar in the EDS images is 800 nm