XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2205
flotation at 500 g/t and selectively depressed pyrite when
added in the flotation cell.
Figure 1 (b) displays the changes in Cu grade upon
adding PMS in the mill or the flotation cell. As can be
found, when 500 g/t PMS was added in the mill, although
the Cu recovery improved by 8.7%, the Cu grade decreased
from 8.0 to 7.2% due to the increased pyrite flotation as
indicated in Figure 1 (a). On the other hand, when 500 g/t
PMS was added in the flotation cell, Cu grade increased
significantly from 8.0 to 10.4%, indicating a high quality
of Cu concentrate.
Based on the flotation results, it is clear that PMS dem-
onstrated a potential to selectively depress high-concentra-
tion pyrite in Cu flotation when added in the flotation cell,
whereas the PMS addition in the mill promoted pyrite flo-
tation. Furthermore, chalcopyrite flotation was improved
in the presence of PMS regardless of the addition point. To
understand the underpinning mechanism, electrochemi-
cal studies on pyrite and chalcopyrite electrodes were con-
ducted and reported in the following sections.
Electrochemical Studies
Oxidation of Cu-Activated Pyrite by PMS
Pyrite flotation in an alkaline medium relies on copper
activation (Aghazadeh et al., 2015 Peng et al., 2012).
Therefore, CV measurements were performed on a pyrite
electrode to investigate the effect of PMS on the oxidation
behavior of Cu-activated pyrite. In these measurements, Fe
ions were introduced to catalyze PMS to produce radicals.
The results are shown in Figure 2.
Figure 2 shows two anodic peaks (A1 and A2) and one
cathodic peak (C1) on pyrite in the absence of any reagents.
According to Guo et al. (2015), peak A1 (near –100 mV)
represents the initial pyrite oxidation to produce ferric
hydroxide (Fe(OH)3) and elemental sulfur (S0):
3 2S 3 3e FeS H O Fe^OHh3 H
2 2
0 +=++++-(1)
Peak A2 at an oxidizing potential of above 0.6 V was
reported to be non-reversible and aggressive oxidation of
pyrite that produces more hydrophilic species, in this case,
Fe(OH)3 and sulfate ions (SO4 2– )(Guo et al., 2015 Mu
and Peng, 2019):
11H2O
2 19 15e
FeS2
Fe^OHh3 SO H
4
2-
"+
++++-(2)
On the other hand, C1 was reported to be the reduction
of Fe(OH)3 to ferrous hydroxide (Fe(OH)2) as shown by
Reaction (3) (Hicyilmaz et al., 2004 Mu and Peng, 2019):
e Fe^OHh3 Fe^OH OH
2 )++--h (3)
When pyrite was conditioned with 0.5 mM Cu ions, it can
be seen from Figure 2 that a new peak (A3) was formed,
which is correlated to the Cu-S species formed on the
pyrite surface via the copper activation process (Mu and
Peng, 2021). At the same time, the presence of Cu ions
slightly enhanced the reaction at peak A2 due to cupric
(Cu2+) ions being oxidants. Correspondingly, peak C1
was also enhanced. When 0.5 mM PMS was added after
copper activation, the CV curve of pyrite remained simi-
lar, except that peak A3 disappeared, implying that PMS
Figure 2. CV curves of pyrite in the absence and presence of Cu ions, Fe ions and their
combinations with PMS obtained in Borax solution at pH 9
flotation at 500 g/t and selectively depressed pyrite when
added in the flotation cell.
Figure 1 (b) displays the changes in Cu grade upon
adding PMS in the mill or the flotation cell. As can be
found, when 500 g/t PMS was added in the mill, although
the Cu recovery improved by 8.7%, the Cu grade decreased
from 8.0 to 7.2% due to the increased pyrite flotation as
indicated in Figure 1 (a). On the other hand, when 500 g/t
PMS was added in the flotation cell, Cu grade increased
significantly from 8.0 to 10.4%, indicating a high quality
of Cu concentrate.
Based on the flotation results, it is clear that PMS dem-
onstrated a potential to selectively depress high-concentra-
tion pyrite in Cu flotation when added in the flotation cell,
whereas the PMS addition in the mill promoted pyrite flo-
tation. Furthermore, chalcopyrite flotation was improved
in the presence of PMS regardless of the addition point. To
understand the underpinning mechanism, electrochemi-
cal studies on pyrite and chalcopyrite electrodes were con-
ducted and reported in the following sections.
Electrochemical Studies
Oxidation of Cu-Activated Pyrite by PMS
Pyrite flotation in an alkaline medium relies on copper
activation (Aghazadeh et al., 2015 Peng et al., 2012).
Therefore, CV measurements were performed on a pyrite
electrode to investigate the effect of PMS on the oxidation
behavior of Cu-activated pyrite. In these measurements, Fe
ions were introduced to catalyze PMS to produce radicals.
The results are shown in Figure 2.
Figure 2 shows two anodic peaks (A1 and A2) and one
cathodic peak (C1) on pyrite in the absence of any reagents.
According to Guo et al. (2015), peak A1 (near –100 mV)
represents the initial pyrite oxidation to produce ferric
hydroxide (Fe(OH)3) and elemental sulfur (S0):
3 2S 3 3e FeS H O Fe^OHh3 H
2 2
0 +=++++-(1)
Peak A2 at an oxidizing potential of above 0.6 V was
reported to be non-reversible and aggressive oxidation of
pyrite that produces more hydrophilic species, in this case,
Fe(OH)3 and sulfate ions (SO4 2– )(Guo et al., 2015 Mu
and Peng, 2019):
11H2O
2 19 15e
FeS2
Fe^OHh3 SO H
4
2-
"+
++++-(2)
On the other hand, C1 was reported to be the reduction
of Fe(OH)3 to ferrous hydroxide (Fe(OH)2) as shown by
Reaction (3) (Hicyilmaz et al., 2004 Mu and Peng, 2019):
e Fe^OHh3 Fe^OH OH
2 )++--h (3)
When pyrite was conditioned with 0.5 mM Cu ions, it can
be seen from Figure 2 that a new peak (A3) was formed,
which is correlated to the Cu-S species formed on the
pyrite surface via the copper activation process (Mu and
Peng, 2021). At the same time, the presence of Cu ions
slightly enhanced the reaction at peak A2 due to cupric
(Cu2+) ions being oxidants. Correspondingly, peak C1
was also enhanced. When 0.5 mM PMS was added after
copper activation, the CV curve of pyrite remained simi-
lar, except that peak A3 disappeared, implying that PMS
Figure 2. CV curves of pyrite in the absence and presence of Cu ions, Fe ions and their
combinations with PMS obtained in Borax solution at pH 9