XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2375
Reaction (4) (Mu et al., 2017). Ferric oxide/hydroxide
resulted from oxidizing the pyrite surface. Peak A2 resulted
from the reverse of Reaction (4).
Cu S 2H O 2CuO S 4H 4e
2 2
0 "+++++-(2)
CuS H O CuO S 2H 2e
2
0 "+++++-(3)
Fe^OHh3 e Fe^OH OH
2 "++--h (4)
Figure 4 shows that the addition of Cu(II) ions did
not react with the surface of oxidized pyrite to form a new
Cu(I)S phase which could activate pyrite flotation. Without
forming Cu(I)S, Cu(II) ions would form hydrophilic cop-
per hydroxide on pyrite surface, depressing pyrite flotation.
This explains the reduced total sulfur recovery from flota-
tion of the oxidized ore when copper (II) ions were added
during grinding without subsequent sulfidization as shown
in Figure 3.
Formation of Cu(I)S on Pyrite Surfaces with
Sulfidization
Figure 5 shows the cyclic voltammograms of oxidized pyrite
in the presence of Cu(II) and Cu(I) with sulfidization at
–300 mV. Again, the CV scan in this work was initialized
in a positive direction from the OCP of pyrite to ensure the
initial oxidation of possibly formed Cu(I)S. Peak A1 which
indicates the formation of Cu(I)S appeared on both cyclic
voltammograms of oxidized pyrite in the presence of Cu(II)
and Cu(I) with sulfidization. The intensity of Peak A1 was
much higher when Cu(I) was added with sulfidization.
However, the coupled cathodic peak C1 was not noticeable
during the cathodic scan, indicating that the formation of
Cu(I)S on the surface of oxidized pyrite in both cases was
not that strong as observed on the surface of fresh pyrite
shown in Figure 4. A new couple of peaks, A3 and C3,
appeared on the cyclic voltammogram in both cases. As
found previously, Peak A3 indicates the formation of a new
metal sulfide phase during sulfidization, which was oxidized
during the anodic scan, while Peak C3 involved the reduc-
tion of sulfur and iron-related species during the cathodic
scan (Huai and Peng, 2020). Huai and Peng (2020) found
that the new iron sulfide phase cannot be sustained during
flotation when pulp potential is elevated through aeration.
Figure 5 reveals that Cu(I)S did occur on the surface
of oxidized pyrite during sulfidization when Cu(II) ions
were present. This is consistent with the flotation results
showing increased total sulfur recovery with sulfidization
after Cu(II) ions were added during grinding as shown
in Figure 3. The addition of Cu(I) ions during grinding
further increased total sulfur recovery with sulfidization as
shown in Figure 3. This is because the formation of more
Cu(I)S was promoted by replacing Cu(II) ions with Cu(I)
ions. Regardless the formation of Cu(I)S, Cu(I)S was still
not strong enough to induce complete flotation of oxidized
pyrite from the ore even with the addition of Cu(I) ions
with sulfidization. Given that Cu(I)S could form on the
surface of oxidized pyrite with sulfidization, and requires a
lower pulp potential for collector adsorption compared to
pyrite as discussed previously, this new sulfidization process
Figure 4. Cyclic voltammograms of fresh pyrite and oxidized pyrite in the presence of Cu(II) ions
Reaction (4) (Mu et al., 2017). Ferric oxide/hydroxide
resulted from oxidizing the pyrite surface. Peak A2 resulted
from the reverse of Reaction (4).
Cu S 2H O 2CuO S 4H 4e
2 2
0 "+++++-(2)
CuS H O CuO S 2H 2e
2
0 "+++++-(3)
Fe^OHh3 e Fe^OH OH
2 "++--h (4)
Figure 4 shows that the addition of Cu(II) ions did
not react with the surface of oxidized pyrite to form a new
Cu(I)S phase which could activate pyrite flotation. Without
forming Cu(I)S, Cu(II) ions would form hydrophilic cop-
per hydroxide on pyrite surface, depressing pyrite flotation.
This explains the reduced total sulfur recovery from flota-
tion of the oxidized ore when copper (II) ions were added
during grinding without subsequent sulfidization as shown
in Figure 3.
Formation of Cu(I)S on Pyrite Surfaces with
Sulfidization
Figure 5 shows the cyclic voltammograms of oxidized pyrite
in the presence of Cu(II) and Cu(I) with sulfidization at
–300 mV. Again, the CV scan in this work was initialized
in a positive direction from the OCP of pyrite to ensure the
initial oxidation of possibly formed Cu(I)S. Peak A1 which
indicates the formation of Cu(I)S appeared on both cyclic
voltammograms of oxidized pyrite in the presence of Cu(II)
and Cu(I) with sulfidization. The intensity of Peak A1 was
much higher when Cu(I) was added with sulfidization.
However, the coupled cathodic peak C1 was not noticeable
during the cathodic scan, indicating that the formation of
Cu(I)S on the surface of oxidized pyrite in both cases was
not that strong as observed on the surface of fresh pyrite
shown in Figure 4. A new couple of peaks, A3 and C3,
appeared on the cyclic voltammogram in both cases. As
found previously, Peak A3 indicates the formation of a new
metal sulfide phase during sulfidization, which was oxidized
during the anodic scan, while Peak C3 involved the reduc-
tion of sulfur and iron-related species during the cathodic
scan (Huai and Peng, 2020). Huai and Peng (2020) found
that the new iron sulfide phase cannot be sustained during
flotation when pulp potential is elevated through aeration.
Figure 5 reveals that Cu(I)S did occur on the surface
of oxidized pyrite during sulfidization when Cu(II) ions
were present. This is consistent with the flotation results
showing increased total sulfur recovery with sulfidization
after Cu(II) ions were added during grinding as shown
in Figure 3. The addition of Cu(I) ions during grinding
further increased total sulfur recovery with sulfidization as
shown in Figure 3. This is because the formation of more
Cu(I)S was promoted by replacing Cu(II) ions with Cu(I)
ions. Regardless the formation of Cu(I)S, Cu(I)S was still
not strong enough to induce complete flotation of oxidized
pyrite from the ore even with the addition of Cu(I) ions
with sulfidization. Given that Cu(I)S could form on the
surface of oxidized pyrite with sulfidization, and requires a
lower pulp potential for collector adsorption compared to
pyrite as discussed previously, this new sulfidization process
Figure 4. Cyclic voltammograms of fresh pyrite and oxidized pyrite in the presence of Cu(II) ions