XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2207
From Figure 3, it can be found that the addition of
PMS slightly promoted reactions at peaks A1 and C1, mean-
ing an increased extent of reaction (7). On the other hand,
when Fe ions and PMS were added together, peaks A1 and
C1 became much stronger, indicating that chalcopyrite oxi-
dation by PMS was promoted by Fe ions. Therefore, the
radicals produced by PMS could also strongly oxidize chal-
copyrite. However, when pyrite was present, strong chal-
copyrite oxidation would not occur since the production
of radicals preferentially occurred on the pyrite surface, on
which Fe ions were drawn as discussed before. The flota-
tion results with PMS added in the flotation cell shown
in Figure 1 confirmed the selectively strong oxidation on
the pyrite surface. Instead, mild oxidation of chalcopyrite
occurring during grinding or flotation produced hydropho-
bic sulfur oxidation species, which are beneficial to chalco-
pyrite flotation, as reported by Fairthorne et al. (1997).
Figure 4 graphically shows the chalcopyrite-pyrite
(Cpy-Py) interaction in the flotation cell, and the selective
oxidation and depression of pyrite achieved by PMS.
As shown in Figure 4 (a), when chalcopyrite is con-
tacted with pyrite galvanically, chalcopyrite acts as an
anodic and pyrite acts as a cathode (Ekmekçi and Demirel,
1997 Lee et al., 2022). The oxygen reduction reaction
tended to occur on the cathodic surface in the flotation cell,
producing in-situ hydroxyl anions (OH–) which attracted
Fe cations to form Fe(OH)2,3 (Mu et al., 2020). On the
other hand, the oxidation of anodic chalcopyrite produced
CuS and S0 initially, and the Cu ions from Cu dissolution
repelled the Fe cations. Consequently, the Fe ions tended
to distribute on the cathodic pyrite surface. Cu ions also
mitigated to the pyrite surface to form CuS as an activating
species. As 500 g/t PMS was added into the flotation cell
(Figure 4 (b)), the pulp Eh increased from 123 to 309 mV,
and the more oxidizing Eh increased the initial oxidation of
chalcopyrite, leading to the formation of more hydrophobic
sulfur oxidation products that improved chalcopyrite flota-
tion. More importantly, the generation of radicals by PMS
was catalyzed locally on the pyrite surface by Fe(OH)2,3
species. These radicals strongly oxidized the pyrite surface,
Figure 4. Schematic diagram for (a) Cpy-Py interaction in the flotation cell and (b) the selective oxidation and depression of
pyrite after the addition of 500 g/t PMS
From Figure 3, it can be found that the addition of
PMS slightly promoted reactions at peaks A1 and C1, mean-
ing an increased extent of reaction (7). On the other hand,
when Fe ions and PMS were added together, peaks A1 and
C1 became much stronger, indicating that chalcopyrite oxi-
dation by PMS was promoted by Fe ions. Therefore, the
radicals produced by PMS could also strongly oxidize chal-
copyrite. However, when pyrite was present, strong chal-
copyrite oxidation would not occur since the production
of radicals preferentially occurred on the pyrite surface, on
which Fe ions were drawn as discussed before. The flota-
tion results with PMS added in the flotation cell shown
in Figure 1 confirmed the selectively strong oxidation on
the pyrite surface. Instead, mild oxidation of chalcopyrite
occurring during grinding or flotation produced hydropho-
bic sulfur oxidation species, which are beneficial to chalco-
pyrite flotation, as reported by Fairthorne et al. (1997).
Figure 4 graphically shows the chalcopyrite-pyrite
(Cpy-Py) interaction in the flotation cell, and the selective
oxidation and depression of pyrite achieved by PMS.
As shown in Figure 4 (a), when chalcopyrite is con-
tacted with pyrite galvanically, chalcopyrite acts as an
anodic and pyrite acts as a cathode (Ekmekçi and Demirel,
1997 Lee et al., 2022). The oxygen reduction reaction
tended to occur on the cathodic surface in the flotation cell,
producing in-situ hydroxyl anions (OH–) which attracted
Fe cations to form Fe(OH)2,3 (Mu et al., 2020). On the
other hand, the oxidation of anodic chalcopyrite produced
CuS and S0 initially, and the Cu ions from Cu dissolution
repelled the Fe cations. Consequently, the Fe ions tended
to distribute on the cathodic pyrite surface. Cu ions also
mitigated to the pyrite surface to form CuS as an activating
species. As 500 g/t PMS was added into the flotation cell
(Figure 4 (b)), the pulp Eh increased from 123 to 309 mV,
and the more oxidizing Eh increased the initial oxidation of
chalcopyrite, leading to the formation of more hydrophobic
sulfur oxidation products that improved chalcopyrite flota-
tion. More importantly, the generation of radicals by PMS
was catalyzed locally on the pyrite surface by Fe(OH)2,3
species. These radicals strongly oxidized the pyrite surface,
Figure 4. Schematic diagram for (a) Cpy-Py interaction in the flotation cell and (b) the selective oxidation and depression of
pyrite after the addition of 500 g/t PMS