XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1709
Ion exchange results
PGMs extraction by ion exchange
The extraction of Pt (IV), Pd (II) and Rh (III) were investi-
gated as shown in Table 2.
Table 2 shows that in the tested conditions, Pt and Pd
extraction were high while Rh extraction was low from pH
1.00–2.00 and at 25–65 °C. The contrast in the Pd, Pt, and
Rh extraction can be explained by the leach species present
and the IX mechanism of extraction. According to literature,
Pd is present as [PdCl4]2– in chloride concentrations equal
to or greater than 1.5 M, in the studied pH region, while
Pt and Rh are present as [PtCl5(H2O)]–, [PtCl4(H2O)2],
[RhCl5(H2O)]2–, [RhCl4(H2O)2]–, [RhCl3(OH)
(H2O)2]–, [RhCl3(H2O)3], and [RhCl2(H2O)4]+ respec-
tively (Bernardis, Grant, and Sherrington 2005 Aleksenko,
Gumenyuk, and Mushtakova 2002 Shelimov et al., 2000).
The SAR extracts ions through a mechanism which replaces
the Cl– counter ions with metal complex anions. As Pd and
Pt species are mostly anionic they are extracted much more
than Rh which forms various anionic, neutral, and cationic
species. Table 2 also shows the extraction of Fe possibly as
a ferric tetrachloride anion while Al and Mg form cations
and were not extracted as the resin only exchanges its anion
with other anions. The possible extraction reaction for Fe is
shown in equation 12 (Maranon et al., 1999).
R N Cl
R N Cl
3 3
3 3 4 "
-+
-+
+-
+--
^CH
^CH
^resinh ^aqh
^aqh
h
h 6FeCl
6FeCl4@-
@^resinh
(12)
Effect of Contact Time
The effect of contact time on PGMs extraction by IX is
presented in Figure 4.
Figure 4 illustrates that after 15 minutes of incubation,
significant extraction occurred only for Pd (II) at 76%,
whereas Pt (IV) and Rh (III) extractions were at 4% and
0%, respectively. A study conducted by Peng et al. (2009)
on the adsorption of precious metals (Ag (I), Au (II), Pt
(IV), and Pd (II)) by a strong base resin reported similar
findings. In their study, Pd extraction was 90% after 5 min-
utes, while 90% Pt extraction required 30 minutes incuba-
tion time. The difference in the extraction times with the
study by Peng et al. (2009) could be due to the increased
competition for bonding sites from other ions in the cur-
rent study
Several factors could contribute to the slow kinetics
of Pt (IV) and Rh (III) extraction in the current study. Pt
(IV) and Rh (III) exist as various aqua chloro complexes
Figure 3. (a) Effect of incubation time on PGMs extraction at 10% (b) and at 20% Tin (II)
(a) (b)
Table 2. Effect of pH and temperature on PGMs extraction
pH Temp, °C
Extraction %
Pt Pd Rh Al Fe Mg
1.00 25 99.8 98.2 21.5 0.0 26.7 0.0
1.50 25 99.8 98.1 20.2 0.0 22.9 0.0
2.00 25 99.8 98.0 36.5 0.0 44.0 0.0
2.00 45 99.6 97.9 24.0 0.0 44.3 0.0
2.00 65 99.6 98.0 36.0 0.0 76.0 0.0
Ion exchange results
PGMs extraction by ion exchange
The extraction of Pt (IV), Pd (II) and Rh (III) were investi-
gated as shown in Table 2.
Table 2 shows that in the tested conditions, Pt and Pd
extraction were high while Rh extraction was low from pH
1.00–2.00 and at 25–65 °C. The contrast in the Pd, Pt, and
Rh extraction can be explained by the leach species present
and the IX mechanism of extraction. According to literature,
Pd is present as [PdCl4]2– in chloride concentrations equal
to or greater than 1.5 M, in the studied pH region, while
Pt and Rh are present as [PtCl5(H2O)]–, [PtCl4(H2O)2],
[RhCl5(H2O)]2–, [RhCl4(H2O)2]–, [RhCl3(OH)
(H2O)2]–, [RhCl3(H2O)3], and [RhCl2(H2O)4]+ respec-
tively (Bernardis, Grant, and Sherrington 2005 Aleksenko,
Gumenyuk, and Mushtakova 2002 Shelimov et al., 2000).
The SAR extracts ions through a mechanism which replaces
the Cl– counter ions with metal complex anions. As Pd and
Pt species are mostly anionic they are extracted much more
than Rh which forms various anionic, neutral, and cationic
species. Table 2 also shows the extraction of Fe possibly as
a ferric tetrachloride anion while Al and Mg form cations
and were not extracted as the resin only exchanges its anion
with other anions. The possible extraction reaction for Fe is
shown in equation 12 (Maranon et al., 1999).
R N Cl
R N Cl
3 3
3 3 4 "
-+
-+
+-
+--
^CH
^CH
^resinh ^aqh
^aqh
h
h 6FeCl
6FeCl4@-
@^resinh
(12)
Effect of Contact Time
The effect of contact time on PGMs extraction by IX is
presented in Figure 4.
Figure 4 illustrates that after 15 minutes of incubation,
significant extraction occurred only for Pd (II) at 76%,
whereas Pt (IV) and Rh (III) extractions were at 4% and
0%, respectively. A study conducted by Peng et al. (2009)
on the adsorption of precious metals (Ag (I), Au (II), Pt
(IV), and Pd (II)) by a strong base resin reported similar
findings. In their study, Pd extraction was 90% after 5 min-
utes, while 90% Pt extraction required 30 minutes incuba-
tion time. The difference in the extraction times with the
study by Peng et al. (2009) could be due to the increased
competition for bonding sites from other ions in the cur-
rent study
Several factors could contribute to the slow kinetics
of Pt (IV) and Rh (III) extraction in the current study. Pt
(IV) and Rh (III) exist as various aqua chloro complexes
Figure 3. (a) Effect of incubation time on PGMs extraction at 10% (b) and at 20% Tin (II)
(a) (b)
Table 2. Effect of pH and temperature on PGMs extraction
pH Temp, °C
Extraction %
Pt Pd Rh Al Fe Mg
1.00 25 99.8 98.2 21.5 0.0 26.7 0.0
1.50 25 99.8 98.1 20.2 0.0 22.9 0.0
2.00 25 99.8 98.0 36.5 0.0 44.0 0.0
2.00 45 99.6 97.9 24.0 0.0 44.3 0.0
2.00 65 99.6 98.0 36.0 0.0 76.0 0.0