2166 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
same mineral at conditions that corresponded to a poten-
tial of 0.2 V and obtained recoveries as high as 99% using
micro-flotation. The data clearly suggests lower hydropho-
bicity at lower potentials with increased hydrophobicity
at more anodic potentials that will not only facilitate the
formation of the more hydrophobic dixanthogen but also
leverage the potentially increased surface coverage by two
different but hydrophobic species.
Pt-Pd-As
As previously indicated the arsenides of the PGE are
extremely difficult to float and both fundamental and
applied testwork have indicated this. Contributing a sig-
nificant proportion of some of the PGE’s in ore bodies such
as the Platreef and the Great Dyke they have been a topic of
investigation to unlock the reason behind their poor flota-
tion characteristics. Hydrophobicity domains for PtAs2 and
PdAs2 are shown in Figure 6. Figure 6 indicates that the
window of hydrophobicity for PdAs2 is very limited under
the standard pH conditions of PGM flotation. Shackleton
(2007) through Tof-SIMS showed that between 0.1 V and
0.2 V a mixture of metal thiolate and dixanthogen can be
found on the surface of this mineral. Using ethyl xanthate
as a basis the oxidation potential of dixanthogen occurs
above 0.15 V. For PtAs2 however Vermaak et al., (2007)
conducted electrochemical tests coupled with contact angle
measurements that indicated that above 0.25 V which is
the region of dixanthogen formation the contact angle
was 33° and above a potential of 0.30 V the contact angle
increased to 63°. Shackleton et al., (2007) showed that
at lower potentials evidence of the xanthate on synthetic
PtAs2 existed and speculated it to be in the form of the
metal thiolate species although the potential region does
extend towards the dixanthogen region. Wali et al., (2023)
recently conducted a study on sperrylite (PtAs2) and con-
firmed the mineral to be very poor floating with and with-
out the presence of collector species. Adsorption tests using
microcalorimetry indicated poor adsorption of potassium
amyl xanthate (PAX) compared to that of the collector on
base metal sulphides. It was speculated that poor dosage of
collector (1 monolayer) was responsible for poor flotation
response of the mineral by micro-flotation. Carelse et al.,
(2023) and Wali et al., (2023) suggest that whilst collec-
tor does adsorb on the mineral surface the extent is limited
and these are conditions that would correspond to the rest
potential. Figure 6 suggests that improved hydrophobicity
Figure 5. Eh and pH domains of hydrophobicity for PdBiTe
compiled from (Shackleton, 2007 Vermaak et al., 2004)
Figure 6. Eh and pH domains of hydrophobicity for PdAs
2 and PtAs
2 compiled from (Shackleton et al., 2007a Vermaak et al.,
2004)
same mineral at conditions that corresponded to a poten-
tial of 0.2 V and obtained recoveries as high as 99% using
micro-flotation. The data clearly suggests lower hydropho-
bicity at lower potentials with increased hydrophobicity
at more anodic potentials that will not only facilitate the
formation of the more hydrophobic dixanthogen but also
leverage the potentially increased surface coverage by two
different but hydrophobic species.
Pt-Pd-As
As previously indicated the arsenides of the PGE are
extremely difficult to float and both fundamental and
applied testwork have indicated this. Contributing a sig-
nificant proportion of some of the PGE’s in ore bodies such
as the Platreef and the Great Dyke they have been a topic of
investigation to unlock the reason behind their poor flota-
tion characteristics. Hydrophobicity domains for PtAs2 and
PdAs2 are shown in Figure 6. Figure 6 indicates that the
window of hydrophobicity for PdAs2 is very limited under
the standard pH conditions of PGM flotation. Shackleton
(2007) through Tof-SIMS showed that between 0.1 V and
0.2 V a mixture of metal thiolate and dixanthogen can be
found on the surface of this mineral. Using ethyl xanthate
as a basis the oxidation potential of dixanthogen occurs
above 0.15 V. For PtAs2 however Vermaak et al., (2007)
conducted electrochemical tests coupled with contact angle
measurements that indicated that above 0.25 V which is
the region of dixanthogen formation the contact angle
was 33° and above a potential of 0.30 V the contact angle
increased to 63°. Shackleton et al., (2007) showed that
at lower potentials evidence of the xanthate on synthetic
PtAs2 existed and speculated it to be in the form of the
metal thiolate species although the potential region does
extend towards the dixanthogen region. Wali et al., (2023)
recently conducted a study on sperrylite (PtAs2) and con-
firmed the mineral to be very poor floating with and with-
out the presence of collector species. Adsorption tests using
microcalorimetry indicated poor adsorption of potassium
amyl xanthate (PAX) compared to that of the collector on
base metal sulphides. It was speculated that poor dosage of
collector (1 monolayer) was responsible for poor flotation
response of the mineral by micro-flotation. Carelse et al.,
(2023) and Wali et al., (2023) suggest that whilst collec-
tor does adsorb on the mineral surface the extent is limited
and these are conditions that would correspond to the rest
potential. Figure 6 suggests that improved hydrophobicity
Figure 5. Eh and pH domains of hydrophobicity for PdBiTe
compiled from (Shackleton, 2007 Vermaak et al., 2004)
Figure 6. Eh and pH domains of hydrophobicity for PdAs
2 and PtAs
2 compiled from (Shackleton et al., 2007a Vermaak et al.,
2004)