XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1707
45 ml of a 494 ppm PGMs leach solution was added to
5 ml of the Purolite SAR in a glass bottle with a screw top at
25, 45 and 65 °C temperature (Goc et al. 2021 Kononova
et al., 2010). The pH values under study were 1.0, 1.5,
and 2.0, as precipitation occurred from pH 2.5 and above,
a condition, which could prevent the metal from loading
onto the resin. The glass bottles were then placed in a shak-
ing incubator at 150 rpm for 24 hours (Shen et al., 2010).
The solution was then filtered, and a sample collected for
analysis by ICP-MS for PGMs and ICP-OES for Al, Fe,
and Mg. The PGMs extraction by IX was calculated as a
percentage of PGMs on the resin to that initially present in
the chloride leach solution as per equation 10.
E% C
C C
100
i
i f #=
-
(10)
Where Ci and Cf are the concentration of metals before and
after extraction in the aqueous phase, respectively.
Effect of Contact Time on PGMs Extraction by Ion
Exchange
A volume of 90 ml at pH 2 was added to 10 ml of Purolite
SAR in a conical flask (Goc et al., 2021). The reaction was
run at 25 °C and the incubator speed was set at 150 rpm
(Shen et al., 2010). Samples were collected after 15, 45, 90,
115, and 1440 minutes for PGMs, Al, Mg and Fe analysis.
Calculation of CPE and IX Concentration Factors
The concentration factor, CF, of each process was calculated
by dividing the total PGMs concentration in the surfactant
phase by the initial total PGMs concentration in the leach
before CPE, as per equation 11 (Chagnes 2020).
C C
Csurf
F
i
=(11)
Where Csurf and Ci are the total PGMs concentration in
the surfactant phase and the total PGMs concentration in
the aqueous phase respectively. All testwork was conducted
in duplicates.
RESULTS AND DISCUSSION
Cloud Point Extraction Results
Effect of pH on Extraction and Selectivity in the
Presence of 10% Tin (II) Chloride Di-hydrate
The investigation into the pH impact on PGMs CPE was
conducted with a 10% (m/v) concentration of the reducing
and activating agent, tin (II) chloride di-hydrate, follow-
ing the CPE procedure. The results, depicted in Figure 1,
illustrate the effect of pH (1.00 to 5.75) on the extraction
of Pt, Pd, Rh, Al, Fe, and Mg. The influence of pH on
PGMs extraction is significant, affecting the PGMs species
and potential ligands.
At pH 1.00, extractions were 47% Pt, 50% Pd, and
0% for Rh, Al, Fe, and Mg, compared to higher values at
pH 4.00 (99% Pt, 99% Pd, 99% Rh, 11% Al, 45% Fe,
and 45% Mg) and pH 5.75 (87% Pt, 93% Pd, 86% Rh,
22% Al, 21% Fe, and 14% Mg). The low extractions at
pH 1.00 are attributed to the protonation of the N and
exocyclic S donor atoms on the complexing agent, 2-MBT,
which could have resulted in fewer bonding sites available
on the complexing agent (Ghaedi et al., 2009). Another
reason for the low PGMs extractions at pH 1.00 could also
be due to the lower hydrophobicity of the formed PGMs
complexes (Han et al., 2017). The PGMs extraction at pH
4.00 and 5.75 were 99% and this could be due to the high
availability of bonding sites on 2-MBT as the number of
free hydrogen ions to protonate 2-MBT was low. Another
reason for the high PGMs extraction could also be due
to the increased hydrophobicity of the PGMs complexes
formed at pH 4.00 and 5.75 (Han et al., 2017). Under
strong acidic conditions (pH 1.00), only Pt and Pd could
form complexes with 2-MBT due to their stronger affinity
compared to other elements (Galvão et al., 2016).
As pH increased above 1.00, extraction of Rh and
impurities also rose, which is unfavourable for the selectiv-
ity of the CPE process. Therefore, pH 1.00 was chosen for
further study due to its selectivity of Pt and Pd extraction
over Rh, Al, Fe, and Mg. However, the lack of Rh extrac-
tion prompted additional investigation into its recovery,
which involved a higher concentration of the reducing and
activating agent, tin (II) chloride-dihydrate, discussed in
the next section.
Figure 1. Effect of pH on PGMs extraction at 10% m/v tin
(II) chloride di-hydrate
45 ml of a 494 ppm PGMs leach solution was added to
5 ml of the Purolite SAR in a glass bottle with a screw top at
25, 45 and 65 °C temperature (Goc et al. 2021 Kononova
et al., 2010). The pH values under study were 1.0, 1.5,
and 2.0, as precipitation occurred from pH 2.5 and above,
a condition, which could prevent the metal from loading
onto the resin. The glass bottles were then placed in a shak-
ing incubator at 150 rpm for 24 hours (Shen et al., 2010).
The solution was then filtered, and a sample collected for
analysis by ICP-MS for PGMs and ICP-OES for Al, Fe,
and Mg. The PGMs extraction by IX was calculated as a
percentage of PGMs on the resin to that initially present in
the chloride leach solution as per equation 10.
E% C
C C
100
i
i f #=
-
(10)
Where Ci and Cf are the concentration of metals before and
after extraction in the aqueous phase, respectively.
Effect of Contact Time on PGMs Extraction by Ion
Exchange
A volume of 90 ml at pH 2 was added to 10 ml of Purolite
SAR in a conical flask (Goc et al., 2021). The reaction was
run at 25 °C and the incubator speed was set at 150 rpm
(Shen et al., 2010). Samples were collected after 15, 45, 90,
115, and 1440 minutes for PGMs, Al, Mg and Fe analysis.
Calculation of CPE and IX Concentration Factors
The concentration factor, CF, of each process was calculated
by dividing the total PGMs concentration in the surfactant
phase by the initial total PGMs concentration in the leach
before CPE, as per equation 11 (Chagnes 2020).
C C
Csurf
F
i
=(11)
Where Csurf and Ci are the total PGMs concentration in
the surfactant phase and the total PGMs concentration in
the aqueous phase respectively. All testwork was conducted
in duplicates.
RESULTS AND DISCUSSION
Cloud Point Extraction Results
Effect of pH on Extraction and Selectivity in the
Presence of 10% Tin (II) Chloride Di-hydrate
The investigation into the pH impact on PGMs CPE was
conducted with a 10% (m/v) concentration of the reducing
and activating agent, tin (II) chloride di-hydrate, follow-
ing the CPE procedure. The results, depicted in Figure 1,
illustrate the effect of pH (1.00 to 5.75) on the extraction
of Pt, Pd, Rh, Al, Fe, and Mg. The influence of pH on
PGMs extraction is significant, affecting the PGMs species
and potential ligands.
At pH 1.00, extractions were 47% Pt, 50% Pd, and
0% for Rh, Al, Fe, and Mg, compared to higher values at
pH 4.00 (99% Pt, 99% Pd, 99% Rh, 11% Al, 45% Fe,
and 45% Mg) and pH 5.75 (87% Pt, 93% Pd, 86% Rh,
22% Al, 21% Fe, and 14% Mg). The low extractions at
pH 1.00 are attributed to the protonation of the N and
exocyclic S donor atoms on the complexing agent, 2-MBT,
which could have resulted in fewer bonding sites available
on the complexing agent (Ghaedi et al., 2009). Another
reason for the low PGMs extractions at pH 1.00 could also
be due to the lower hydrophobicity of the formed PGMs
complexes (Han et al., 2017). The PGMs extraction at pH
4.00 and 5.75 were 99% and this could be due to the high
availability of bonding sites on 2-MBT as the number of
free hydrogen ions to protonate 2-MBT was low. Another
reason for the high PGMs extraction could also be due
to the increased hydrophobicity of the PGMs complexes
formed at pH 4.00 and 5.75 (Han et al., 2017). Under
strong acidic conditions (pH 1.00), only Pt and Pd could
form complexes with 2-MBT due to their stronger affinity
compared to other elements (Galvão et al., 2016).
As pH increased above 1.00, extraction of Rh and
impurities also rose, which is unfavourable for the selectiv-
ity of the CPE process. Therefore, pH 1.00 was chosen for
further study due to its selectivity of Pt and Pd extraction
over Rh, Al, Fe, and Mg. However, the lack of Rh extrac-
tion prompted additional investigation into its recovery,
which involved a higher concentration of the reducing and
activating agent, tin (II) chloride-dihydrate, discussed in
the next section.
Figure 1. Effect of pH on PGMs extraction at 10% m/v tin
(II) chloride di-hydrate