2212 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Depending on how its electrochemical properties affect
pulp chemistry, it can make its separation from other min-
erals very challenging (Moslemi &Gharabaghi, 2017).
PYRITE ENRICHMENT BY FROTH
FLOTATION PROCESS
Pyrite co-exists with other sulfide minerals as a gangue min-
eral, which is usually depressed during the froth flotation
process using various surfactants such as lime or cyanide at
the cleaning stage (Nakhaei and Iranajad, 2015). The tail-
ings from both rougher and cleaner stages contain signifi-
cant pyrite content. Pyrite in these tailings can be floated
to enrich the contained critical minerals, however, surface
activation will be needed to enhance its floatability.(Miller
et al., 2006 Ranchev &Nishkov, 2018).
The floatability of pyrite depends on several factors,
including the ore origin, mineralogy, chemical composi-
tion, surface texture, pH, surfactant addition, and the elec-
trochemical complexes that form when exposed to water
and oxygen and milling processes (Altun, 2010 Bulut
et al., 2004 Jefferson et al., 2023 Jiang et al., 2023).
Elements that are present in the crystal lattice of pyrite such
as Bi, Se, Sb, As, Co, Ni, Au, Ag, Cu, and Pb alter pyrites’
magnetic and semiconductive properties thereby affecting
surface characteristics of pyrite and its interaction with the
surrounding environment including flotation surfactants
(Jefferson et al., 2023 Altun, 2010). Additionally, ore min-
eralogy and water chemistry seem to have a notable impact
on pyrite’s flotation behavior in the flotation process (Bulut
et al., 2004 Bulut &Yenial, 2016).
Based on previous research, natural pyrite shows differ-
ent textures due to the different ore formation conditions.
The coarse-grained textures (250μm) are subhedral, and
euhedral and exhibit low impurity levels coupled with low
to very little association with other surrounding sulfides
(Forbes et al., 2024 Jefferson et al., 2023). This type of
pyrite shows little galvanic interaction with other sulfides
and has low hydrophobicity therefore, it is easy to depress
under normal flotation conditions (Jefferson et al., 2023).
Another type of pyrite is the fine-grained texture phase (4μm
grain-size 40μm) which can easily oxidize and therefore
could promote the galvanic interactions between pyrite and
other metal sulfides in the flotation process and impact the
overall process outcomes. Moreover, there are other derived
and framboidal textured pyrite crystallographic phases
with altered morphologies and high impurity contents that
impact pyrite’s surface oxidation potential electrochemical
behavior (Jefferson et al., 2023).
Galvanic interactions between pyrite and chalcopyrite,
for example, involve loss of electrons by chalcopyrite, and
in the process of doing so, it loses Cu and Fe via oxida-
tion. These dissolve into solution as Cu and Fe ions. The
electrons from chalcopyrite are then transferred onto the
pyrite surface where the dissolved Cu ions get electrostati-
cally attracted to the negatively charged surface of pyrite
which gets absorbed and finally reduced to Cu+ (Castellón
et al., 2022 Moslemi &Gharabaghi, 2017 Qing You et al.,
2007). The process is shown in the schematic in Figure 1.
Furthermore, galvanic couplings are due to interactions
between two or more sulfides bearing different rest poten-
tials. The one with a highest rest potential acts as a cathode
while the one with a lowest rest potential acts as anode form-
ing a galvanic cell (Fuerstenau et al., 2009 Guo-huaDj et
al., 2004). Pyrite, being a sulfide mineral with the highest
rest potential of all the sulfides, acts as a cathode during gal-
vanic interaction with other sulfide minerals (Altun, 2010
Dos Santos et al., 2016, 2017). In such an electrochemical
active system, iron oxidation species, products of cathodic
processes may depress both pyrite and anodic-valuable sul-
fide minerals such as chalcopyrite (Altun, 2010 Liao et al.,
2020). However, anodic oxidation products of these sulfide
minerals would activate pyrite and reduce selectivity (Liao
Chalcopyrite
(Anode)
Pyrite
(Cathode)
/
()
Figure 1. A model showing galvanic interaction between pyrite and chalcopyrite. Source:
(Wu et al., 2020)
Depending on how its electrochemical properties affect
pulp chemistry, it can make its separation from other min-
erals very challenging (Moslemi &Gharabaghi, 2017).
PYRITE ENRICHMENT BY FROTH
FLOTATION PROCESS
Pyrite co-exists with other sulfide minerals as a gangue min-
eral, which is usually depressed during the froth flotation
process using various surfactants such as lime or cyanide at
the cleaning stage (Nakhaei and Iranajad, 2015). The tail-
ings from both rougher and cleaner stages contain signifi-
cant pyrite content. Pyrite in these tailings can be floated
to enrich the contained critical minerals, however, surface
activation will be needed to enhance its floatability.(Miller
et al., 2006 Ranchev &Nishkov, 2018).
The floatability of pyrite depends on several factors,
including the ore origin, mineralogy, chemical composi-
tion, surface texture, pH, surfactant addition, and the elec-
trochemical complexes that form when exposed to water
and oxygen and milling processes (Altun, 2010 Bulut
et al., 2004 Jefferson et al., 2023 Jiang et al., 2023).
Elements that are present in the crystal lattice of pyrite such
as Bi, Se, Sb, As, Co, Ni, Au, Ag, Cu, and Pb alter pyrites’
magnetic and semiconductive properties thereby affecting
surface characteristics of pyrite and its interaction with the
surrounding environment including flotation surfactants
(Jefferson et al., 2023 Altun, 2010). Additionally, ore min-
eralogy and water chemistry seem to have a notable impact
on pyrite’s flotation behavior in the flotation process (Bulut
et al., 2004 Bulut &Yenial, 2016).
Based on previous research, natural pyrite shows differ-
ent textures due to the different ore formation conditions.
The coarse-grained textures (250μm) are subhedral, and
euhedral and exhibit low impurity levels coupled with low
to very little association with other surrounding sulfides
(Forbes et al., 2024 Jefferson et al., 2023). This type of
pyrite shows little galvanic interaction with other sulfides
and has low hydrophobicity therefore, it is easy to depress
under normal flotation conditions (Jefferson et al., 2023).
Another type of pyrite is the fine-grained texture phase (4μm
grain-size 40μm) which can easily oxidize and therefore
could promote the galvanic interactions between pyrite and
other metal sulfides in the flotation process and impact the
overall process outcomes. Moreover, there are other derived
and framboidal textured pyrite crystallographic phases
with altered morphologies and high impurity contents that
impact pyrite’s surface oxidation potential electrochemical
behavior (Jefferson et al., 2023).
Galvanic interactions between pyrite and chalcopyrite,
for example, involve loss of electrons by chalcopyrite, and
in the process of doing so, it loses Cu and Fe via oxida-
tion. These dissolve into solution as Cu and Fe ions. The
electrons from chalcopyrite are then transferred onto the
pyrite surface where the dissolved Cu ions get electrostati-
cally attracted to the negatively charged surface of pyrite
which gets absorbed and finally reduced to Cu+ (Castellón
et al., 2022 Moslemi &Gharabaghi, 2017 Qing You et al.,
2007). The process is shown in the schematic in Figure 1.
Furthermore, galvanic couplings are due to interactions
between two or more sulfides bearing different rest poten-
tials. The one with a highest rest potential acts as a cathode
while the one with a lowest rest potential acts as anode form-
ing a galvanic cell (Fuerstenau et al., 2009 Guo-huaDj et
al., 2004). Pyrite, being a sulfide mineral with the highest
rest potential of all the sulfides, acts as a cathode during gal-
vanic interaction with other sulfide minerals (Altun, 2010
Dos Santos et al., 2016, 2017). In such an electrochemical
active system, iron oxidation species, products of cathodic
processes may depress both pyrite and anodic-valuable sul-
fide minerals such as chalcopyrite (Altun, 2010 Liao et al.,
2020). However, anodic oxidation products of these sulfide
minerals would activate pyrite and reduce selectivity (Liao
Chalcopyrite
(Anode)
Pyrite
(Cathode)
/
()
Figure 1. A model showing galvanic interaction between pyrite and chalcopyrite. Source:
(Wu et al., 2020)