XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2171
chain length and found a linear relationship between the
heat of formation of the lead xanthate and the number of
carbon atoms in the xanthate alkyl chain as indicated by the
following relationship.
..218N H 62 29 7 0 =--
where ∆H0 is the heat of formation and N is the number of
carbon atoms in the alkyl chain.
This is remarkably similar to the linear relationship
found between xanthates of increasing chain length and
pyrite in a recent study by McFadzean et al. (2023) with
only small differences in the values of the slope (–7.21 kJ/
mol vs –8.17 kJ/mol) and intercept (–62.3 kJ/mol vs –35
kJ/mol). The intercept corresponds to the heat of interac-
tion of the reactive head group with the salt or mineral
and it is, therefore, logical that this differs between the two
studies since in the McFadzean study the interaction was
with the Fe2+ in pyrite, whereas in the Robledo-Cabrera
study it was with Pb2+. The very similar slope is driven by a
positive inductive effect of the increasing number of carbon
atoms in the xanthate alkyl chain and would be expected
to be similar. The slope of the computationally modelled
interaction in the McFadzean et al. (2023) study was even
more similar to the Robledo Cabrera study, at –7.02 kJ/
mol. This is likely due to the more ideal nature of the
lead salt-xanthate system than the pyrite mineral-xanthate
system.
Figure 1 shows an example of an ITC investigation of
a trithiocarbonate (TTC) collector with a platinum (II)
chloride salt. Each peak represents the introduction of
0.622 µmol TTC into the ampoule containing 0.01 mmol
of PtCl42–. The calorimetry software applies a ligand bind-
ing model to fit the various thermodynamic parameters
shown in Table 1 to the data. In the present example, the
model of best fit was that in which the number of moles of
collector were allowed to vary as a function of the number
of moles of platinum (Equation 1). Figure 2 shows the fit
of the model to the experimental data points.
Pt nC PtC K
n
2- )+(1)
where
Pt =platinum
C =collector
n =number of moles
-50
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500 600 700
Time (min)
Figure 1. Heat flow versus time for the titration of PnBTTC into PtCl4
Table 1. Thermodynamic parameters for a number of collectors as well as the microflotation
recoveries using synthetic PtAs2 mineral
Compound K ∆H (kJ/mol) ∆G (kJ/mol) Binding
Microflotation
recovery (%)
PnBTTC 3.8E+06 –157.1 –37.55 2 73.4
PnBX 1.9E+05 –179 –30.18 1.5 57.3
nBTU 1.8E+03 –24.3 –18.63 1 21.4
TT59 2.8E+01 –600 –8.264 1 11.8
Heat
flow
(uW)
chain length and found a linear relationship between the
heat of formation of the lead xanthate and the number of
carbon atoms in the xanthate alkyl chain as indicated by the
following relationship.
..218N H 62 29 7 0 =--
where ∆H0 is the heat of formation and N is the number of
carbon atoms in the alkyl chain.
This is remarkably similar to the linear relationship
found between xanthates of increasing chain length and
pyrite in a recent study by McFadzean et al. (2023) with
only small differences in the values of the slope (–7.21 kJ/
mol vs –8.17 kJ/mol) and intercept (–62.3 kJ/mol vs –35
kJ/mol). The intercept corresponds to the heat of interac-
tion of the reactive head group with the salt or mineral
and it is, therefore, logical that this differs between the two
studies since in the McFadzean study the interaction was
with the Fe2+ in pyrite, whereas in the Robledo-Cabrera
study it was with Pb2+. The very similar slope is driven by a
positive inductive effect of the increasing number of carbon
atoms in the xanthate alkyl chain and would be expected
to be similar. The slope of the computationally modelled
interaction in the McFadzean et al. (2023) study was even
more similar to the Robledo Cabrera study, at –7.02 kJ/
mol. This is likely due to the more ideal nature of the
lead salt-xanthate system than the pyrite mineral-xanthate
system.
Figure 1 shows an example of an ITC investigation of
a trithiocarbonate (TTC) collector with a platinum (II)
chloride salt. Each peak represents the introduction of
0.622 µmol TTC into the ampoule containing 0.01 mmol
of PtCl42–. The calorimetry software applies a ligand bind-
ing model to fit the various thermodynamic parameters
shown in Table 1 to the data. In the present example, the
model of best fit was that in which the number of moles of
collector were allowed to vary as a function of the number
of moles of platinum (Equation 1). Figure 2 shows the fit
of the model to the experimental data points.
Pt nC PtC K
n
2- )+(1)
where
Pt =platinum
C =collector
n =number of moles
-50
0
50
100
150
200
250
300
350
400
450
500
0 100 200 300 400 500 600 700
Time (min)
Figure 1. Heat flow versus time for the titration of PnBTTC into PtCl4
Table 1. Thermodynamic parameters for a number of collectors as well as the microflotation
recoveries using synthetic PtAs2 mineral
Compound K ∆H (kJ/mol) ∆G (kJ/mol) Binding
Microflotation
recovery (%)
PnBTTC 3.8E+06 –157.1 –37.55 2 73.4
PnBX 1.9E+05 –179 –30.18 1.5 57.3
nBTU 1.8E+03 –24.3 –18.63 1 21.4
TT59 2.8E+01 –600 –8.264 1 11.8
Heat
flow
(uW)