XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2163
thiol collectors and presents an initial compilation of the
redox and pH domains that would fundamentally promote
hydrophobicity for these minerals. Open access theses and
published research articles were used for the compilation
of data. Unlike base metal sulfides the information in the
literature is limited as PGMs are a more niche commod-
ity however this paper also highlights the potential for the
PGM industry to utilize the redox potential alongside other
flotation parameters as a control philosophy to optimize
flotation of PGMs.
PLATINUM GROUP MINERALS AND
FLOTATION
Classification of PGMs
Platinum group minerals vary in chemical speciation
from sulfides to tellurides to alloys. Their abundances vary
according to geochemical mechanisms resulting in vari-
able amounts within different ore bodies. Two major ore
bodies contributing towards the production of PGEs are
the Bushveld complex and the Great Dyke complex of
Zimbabwe. A relative distribution of PGMs in the Great
Dyke obtained from Vermaak et al., (2004) is shown in
Figure 2(a). This particular ore body is shown to contain
majority Pt,Pd,Bi, Te minerals mainly merenskyite, mon-
cheite and kotulskite. Figure 2(b) provides an illustration
of relative abundances of PGMs in the Bushveld Complex
after O’Connor, (2013).
The Bushveld Complex has three major ore bodies vary-
ing in their distribution of the PGE species present. The
Platreef is closest in mineralogy to the Great Dyke complex
whilst the Merensky and UG-2 reefs are more similar to the
North American ore bodies in a high abundance of PGE
sulfides (Xiao and Laplante, 2004).
Flotation of PGMs
Although PGM grain sizes can range from sub 10 µm in
size to appreciable grain sizes 38 µm, it has been estab-
lished that poor floatability of PGMs is not always related
to poor liberation of these minerals. Small, liberated par-
ticles are known to be slow floating whilst coarser, liberated
particles are expected to be faster floating in any flotation
system (Corin et al., 2021). It is therefore expected that
with sufficient degree of hydrophobicity PGMs should
float. One of the earlier pieces of work to suggest that the
speciation of PGMs plays a significant role in the floatabil-
ity of such minerals is that of Penberthy et al. (2000) who
demonstrated that sulfide PGMs tend to float very well
whilst there is a decreasing hierarchy in terms of floatability
of non-sulfide PGMs according to the following sulfides
tellurides arsenides alloys. That study was conducted
on UG-2 ore which according to Figure 2(b) contains a
significant proportion of PGE existing as sulfides. A more
recent study by Carelse et al., (2022) focused on the specia-
tion and floatability of the Platreef ore that has virtually
no suphides but significant proportions of tellurides and
arsenides (Figure 2b). Through an analysis of liberated PGE
species recovered to the concentrates via froth flotation at
conditions of collector dosage that would create competi-
tion for hydrophobicity, they noted an order of floatability
according to the following PtS PdBiTe PtPdS PtBiTe
PtAs. These findings on a different ore corroborate the
observations of Penberthy et al. (2000) in that a hierarchy
of hydrophobicity of the different species was demonstrated
Figure 2. Relative percentage distribution of PGMs in the a) Great Dyke, data extracted from Vermaak (2004) and b) Bushveld
Complex, data extracted from O’Connor, (2013)
thiol collectors and presents an initial compilation of the
redox and pH domains that would fundamentally promote
hydrophobicity for these minerals. Open access theses and
published research articles were used for the compilation
of data. Unlike base metal sulfides the information in the
literature is limited as PGMs are a more niche commod-
ity however this paper also highlights the potential for the
PGM industry to utilize the redox potential alongside other
flotation parameters as a control philosophy to optimize
flotation of PGMs.
PLATINUM GROUP MINERALS AND
FLOTATION
Classification of PGMs
Platinum group minerals vary in chemical speciation
from sulfides to tellurides to alloys. Their abundances vary
according to geochemical mechanisms resulting in vari-
able amounts within different ore bodies. Two major ore
bodies contributing towards the production of PGEs are
the Bushveld complex and the Great Dyke complex of
Zimbabwe. A relative distribution of PGMs in the Great
Dyke obtained from Vermaak et al., (2004) is shown in
Figure 2(a). This particular ore body is shown to contain
majority Pt,Pd,Bi, Te minerals mainly merenskyite, mon-
cheite and kotulskite. Figure 2(b) provides an illustration
of relative abundances of PGMs in the Bushveld Complex
after O’Connor, (2013).
The Bushveld Complex has three major ore bodies vary-
ing in their distribution of the PGE species present. The
Platreef is closest in mineralogy to the Great Dyke complex
whilst the Merensky and UG-2 reefs are more similar to the
North American ore bodies in a high abundance of PGE
sulfides (Xiao and Laplante, 2004).
Flotation of PGMs
Although PGM grain sizes can range from sub 10 µm in
size to appreciable grain sizes 38 µm, it has been estab-
lished that poor floatability of PGMs is not always related
to poor liberation of these minerals. Small, liberated par-
ticles are known to be slow floating whilst coarser, liberated
particles are expected to be faster floating in any flotation
system (Corin et al., 2021). It is therefore expected that
with sufficient degree of hydrophobicity PGMs should
float. One of the earlier pieces of work to suggest that the
speciation of PGMs plays a significant role in the floatabil-
ity of such minerals is that of Penberthy et al. (2000) who
demonstrated that sulfide PGMs tend to float very well
whilst there is a decreasing hierarchy in terms of floatability
of non-sulfide PGMs according to the following sulfides
tellurides arsenides alloys. That study was conducted
on UG-2 ore which according to Figure 2(b) contains a
significant proportion of PGE existing as sulfides. A more
recent study by Carelse et al., (2022) focused on the specia-
tion and floatability of the Platreef ore that has virtually
no suphides but significant proportions of tellurides and
arsenides (Figure 2b). Through an analysis of liberated PGE
species recovered to the concentrates via froth flotation at
conditions of collector dosage that would create competi-
tion for hydrophobicity, they noted an order of floatability
according to the following PtS PdBiTe PtPdS PtBiTe
PtAs. These findings on a different ore corroborate the
observations of Penberthy et al. (2000) in that a hierarchy
of hydrophobicity of the different species was demonstrated
Figure 2. Relative percentage distribution of PGMs in the a) Great Dyke, data extracted from Vermaak (2004) and b) Bushveld
Complex, data extracted from O’Connor, (2013)