XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2373
Flotation with Sulfidization in the Absence of
Copper Ions
To improve flotation of the oxidized ore, the ore was sul-
fidized at a potential of –200 and –300 mV prior to flota-
tion. The flotation results are shown in Figure 2. A lower
sulfidization potential than –300 mV was also tested, but
it was challenging to raise and achieve the potential needed
for flotation to occur despite aeration, therefore this result
lacked practical significance and was not considered fur-
ther. This phenomenon also occurred in collecting the first
concentrate in the flotation after sulfidization at –300 mV,
corresponding to a low recovery of sulfide and total sulfur as
shown in Figure 2. However, with continuous aeration, the
potential increased afterwards and flotation became normal
in this case. Figure 2 (left) shows a final sulfide recovery
of 88.7% and 99.7% achieved after sulfidization at –200
and –300 mV, respectively, which was an increase from
79.4% achieved without sulfidization as shown in Figure 1
(left). Figure 2 (right) shows a final total sulfur recovery of
52.1% and 55.4% achieved after sulfidization at –200 and
–300 mV, respectively, which was an increase from 45.7%
achieved without sulfidization as shown in Figure 1 (left).
As can be seen, about 10 to 20% increase in sulfide recovery
and 7 to 10% increase in total sulfur recovery were brought
about by sulfidization. These increases demonstrate the
impact of the sulfidization on the oxidized pyrite surfaces
and a resulting improvement of surface hydrophobicity
during flotation. The lower increase in total sulfur recov-
ery indicates possible incomplete sulfidization on oxidized
pyrite surfaces. It was expected that complete sulfidization
would lead to a similar differential improvement in sulfide
sulfur and total sulfur recoveries as observed in flotation of
the fresh ore in Figure 1 (left).
It is likely that “superficial sulfidization” happened
here. As discussed previously, a new metal sulfide phase
can only be formed on the surface of oxidized pyrite after
sulfidization at a potential at and below –300 mV (SHE)
(Huai and Peng, 2020). In the study by Cao et al. (2018),
hydrophobic elemental sulfur and polysulfide were found
on the pyrite surface after being treated at 480 g/t Na2S
and contributed to improved pyrite flotation. 480 g/t Na2S
is comparable to the amount of Na2S used in the study,
500 g/t, to control the potential at –300 mV (SHE). Cao
et al. (2018) also conducted flotation by combining sulfidi-
zation at 480 g/t Na2S with the addition of PAX to float
oxidized pyrite, which is a case similar to this study. The
authors observed a synergy between sulfidization and the
application of PAX and proposed that the application of
PAX electrochemically reduced iron oxidation products on
the surface of oxidized pyrite, enhancing the formation of
hydrophobic elemental sulfur and polysulfide in the pres-
ence of Na2S. Apparently, this mechanism occurred in this
study as well.
Flotation with Sulfidization in the Presence of
Copper Ions
In order to further improve flotation of oxidized pyrite, or
total sulfur containing sulfide sulfur and the sulfur from
sulfide oxidation products, 200 g/t Cu(II) or Cu (I) was
added during grinding so that copper ions were present
during sulfidization. The dosage of copper ions reported
here was based on trial and error. To identify possible syn-
ergy between the addition of copper ions and sulfidization,
Figure 2. Flotation performance of the oxidized pyritic gold ore after sulfidization at –200 or –300 mV: sulfide sulfur grades
and recoveries (left) total sulfur grades and recoveries (right)
Flotation with Sulfidization in the Absence of
Copper Ions
To improve flotation of the oxidized ore, the ore was sul-
fidized at a potential of –200 and –300 mV prior to flota-
tion. The flotation results are shown in Figure 2. A lower
sulfidization potential than –300 mV was also tested, but
it was challenging to raise and achieve the potential needed
for flotation to occur despite aeration, therefore this result
lacked practical significance and was not considered fur-
ther. This phenomenon also occurred in collecting the first
concentrate in the flotation after sulfidization at –300 mV,
corresponding to a low recovery of sulfide and total sulfur as
shown in Figure 2. However, with continuous aeration, the
potential increased afterwards and flotation became normal
in this case. Figure 2 (left) shows a final sulfide recovery
of 88.7% and 99.7% achieved after sulfidization at –200
and –300 mV, respectively, which was an increase from
79.4% achieved without sulfidization as shown in Figure 1
(left). Figure 2 (right) shows a final total sulfur recovery of
52.1% and 55.4% achieved after sulfidization at –200 and
–300 mV, respectively, which was an increase from 45.7%
achieved without sulfidization as shown in Figure 1 (left).
As can be seen, about 10 to 20% increase in sulfide recovery
and 7 to 10% increase in total sulfur recovery were brought
about by sulfidization. These increases demonstrate the
impact of the sulfidization on the oxidized pyrite surfaces
and a resulting improvement of surface hydrophobicity
during flotation. The lower increase in total sulfur recov-
ery indicates possible incomplete sulfidization on oxidized
pyrite surfaces. It was expected that complete sulfidization
would lead to a similar differential improvement in sulfide
sulfur and total sulfur recoveries as observed in flotation of
the fresh ore in Figure 1 (left).
It is likely that “superficial sulfidization” happened
here. As discussed previously, a new metal sulfide phase
can only be formed on the surface of oxidized pyrite after
sulfidization at a potential at and below –300 mV (SHE)
(Huai and Peng, 2020). In the study by Cao et al. (2018),
hydrophobic elemental sulfur and polysulfide were found
on the pyrite surface after being treated at 480 g/t Na2S
and contributed to improved pyrite flotation. 480 g/t Na2S
is comparable to the amount of Na2S used in the study,
500 g/t, to control the potential at –300 mV (SHE). Cao
et al. (2018) also conducted flotation by combining sulfidi-
zation at 480 g/t Na2S with the addition of PAX to float
oxidized pyrite, which is a case similar to this study. The
authors observed a synergy between sulfidization and the
application of PAX and proposed that the application of
PAX electrochemically reduced iron oxidation products on
the surface of oxidized pyrite, enhancing the formation of
hydrophobic elemental sulfur and polysulfide in the pres-
ence of Na2S. Apparently, this mechanism occurred in this
study as well.
Flotation with Sulfidization in the Presence of
Copper Ions
In order to further improve flotation of oxidized pyrite, or
total sulfur containing sulfide sulfur and the sulfur from
sulfide oxidation products, 200 g/t Cu(II) or Cu (I) was
added during grinding so that copper ions were present
during sulfidization. The dosage of copper ions reported
here was based on trial and error. To identify possible syn-
ergy between the addition of copper ions and sulfidization,
Figure 2. Flotation performance of the oxidized pyritic gold ore after sulfidization at –200 or –300 mV: sulfide sulfur grades
and recoveries (left) total sulfur grades and recoveries (right)