XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3111
Gibbs adsorption isotherm (Equation 1) was used to
calculate surface excess, Γ (mmol/m2), and the minimum
surface area per molecule, Amin (Å2), was estimated from
(Equation 2) (Zhou &Rosen, 2003).
.303RT ln log RT C C
1
2
1
2
2c
2
2c C =-=-c d m n
A 10
min
23 =N C
∂γ /∂log(C) represents the highest slope in the plot of Γ vs.
log(C), which is –27.75 for AIBTC and –23.04 for IPETC.
T denotes the absolute temperature (K). R and N are the
universal gas constant (8.314 J/molK) and Avogadro’s
number, individually. The estimated minimum surface
area per molecule was 34.54 Å2 for AIBTC and 40.85 Å2
for IPETC. Results showed that AIBTC molecules had a
smaller minimum surface area than IPETC, indicating that
AIBTC can be more compactly packed at the air-water
interface than IPETC.
Electrochemistry Study
Many interactions between collectors, e.g., xanthate and
sulfide minerals, are acknowledged to take place through
an electrochemical mechanism (Rand &Woods, 1984).
Electrochemical methods, e.g., voltammetry, can extract
insights into interaction mechanisms occurring on sulfide
mineral surfaces.
Open Circuit Potential (OCP)
OCP values exhibited excellent reproducibility in borate
buffer without a ligand, measured as –0.038 V vs. Ag/AgCl.
At this potential, copper had already undergone oxidation
due to atmospheric oxygen (Figure 5, Celante &Freitas,
2009).
With increasing concentrations of both AIBTC and
IPETC, the OCP values decreased, and this decrease fol-
lowed an exponential pattern as a function of the logarithmic
concentration (Figure 6). This suggests that the addition of
ligands impacted the interface and interphase between the
copper electrode and the aqueous phase, causing a reduc-
tion in the potential of the Cu-solution interface. The nega-
tive shift in potential indicates the weak reducing property
of ligands. These results align with Lewis acid-base theory,
where ligands serve as electron donors, and the copper elec-
trode acts as the electron acceptor. Three common electron
donors coexist in AIBTC and IPETC, namely O, N, and S.
A study employing External Reflection Fourier Transform
Infrared Spectroscopy by Farinato et al. (1993) on 10–3 M
AIBTC and its analog N-propyl O-isobutyl thionocarba-
mate (NPIBTC) adsorbed onto copper demonstrated that
Figure 4. Surface tension of AIBTC and IPETC as a function of concentration

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Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3111
Gibbs adsorption isotherm (Equation 1) was used to
calculate surface excess, Γ (mmol/m2), and the minimum
surface area per molecule, Amin (Å2), was estimated from
(Equation 2) (Zhou &Rosen, 2003).
.303RT ln log RT C C
1
2
1
2
2c
2
2c C =-=-c d m n
A 10
min
23 =N C
∂γ /∂log(C) represents the highest slope in the plot of Γ vs.
log(C), which is –27.75 for AIBTC and –23.04 for IPETC.
T denotes the absolute temperature (K). R and N are the
universal gas constant (8.314 J/molK) and Avogadro’s
number, individually. The estimated minimum surface
area per molecule was 34.54 Å2 for AIBTC and 40.85 Å2
for IPETC. Results showed that AIBTC molecules had a
smaller minimum surface area than IPETC, indicating that
AIBTC can be more compactly packed at the air-water
interface than IPETC.
Electrochemistry Study
Many interactions between collectors, e.g., xanthate and
sulfide minerals, are acknowledged to take place through
an electrochemical mechanism (Rand &Woods, 1984).
Electrochemical methods, e.g., voltammetry, can extract
insights into interaction mechanisms occurring on sulfide
mineral surfaces.
Open Circuit Potential (OCP)
OCP values exhibited excellent reproducibility in borate
buffer without a ligand, measured as –0.038 V vs. Ag/AgCl.
At this potential, copper had already undergone oxidation
due to atmospheric oxygen (Figure 5, Celante &Freitas,
2009).
With increasing concentrations of both AIBTC and
IPETC, the OCP values decreased, and this decrease fol-
lowed an exponential pattern as a function of the logarithmic
concentration (Figure 6). This suggests that the addition of
ligands impacted the interface and interphase between the
copper electrode and the aqueous phase, causing a reduc-
tion in the potential of the Cu-solution interface. The nega-
tive shift in potential indicates the weak reducing property
of ligands. These results align with Lewis acid-base theory,
where ligands serve as electron donors, and the copper elec-
trode acts as the electron acceptor. Three common electron
donors coexist in AIBTC and IPETC, namely O, N, and S.
A study employing External Reflection Fourier Transform
Infrared Spectroscopy by Farinato et al. (1993) on 10–3 M
AIBTC and its analog N-propyl O-isobutyl thionocarba-
mate (NPIBTC) adsorbed onto copper demonstrated that
Figure 4. Surface tension of AIBTC and IPETC as a function of concentration

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3112 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
the ligands bonded to the copper surface through the sulfur
atom, rather than nitrogen, oxygen, or the allylic group in
AIBTC.
Moreover, the higher the ligand concentration, the
lower the OCP value, suggesting an increased reducing
environment and possibly a stronger coordination between
copper and sulfur. A comparison of the impact of AIBTC
and IPETC on OCP indicates only a minimal difference
across varying concentrations ranging from 10–6 to 10–3
M. The ratios of the difference in OCP between the two
ligands at each concentration to the OCP values for each
ligand are presented in Table 1. The rate of OCP decrease
versus the increasing concentration of two ligands exhib-
ited only a few minor variations.
Figure 5. Pourbaix diagram for copper in aqueous solutions
(Celante &Freitas, 2009)
Figure 6. Open Circuit Potential vs. Concentration for AIBTC and IPETC
Table 1. Open Circuit Potential vs. Concentration for AIBTC and IPETC
Concentration,
M
OCP, V ΔOCP,
V
ΔOCP/OCP, %
AIBTC IPETC AIBTC IPETC
0 –0.038 –0.038 0 0 0
1E–06 –0.040 –0.043 0.003 7.50 6.98
1E–05 –0.048 –0.045 –0.003 6.25 6.67
1E–04 –0.068 –0.068 0 0 0
1E–03 –0.123 –0.116 –0.007 5.69 6.03

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Extracted Text (may have errors)

3112 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
the ligands bonded to the copper surface through the sulfur
atom, rather than nitrogen, oxygen, or the allylic group in
AIBTC.
Moreover, the higher the ligand concentration, the
lower the OCP value, suggesting an increased reducing
environment and possibly a stronger coordination between
copper and sulfur. A comparison of the impact of AIBTC
and IPETC on OCP indicates only a minimal difference
across varying concentrations ranging from 10–6 to 10–3
M. The ratios of the difference in OCP between the two
ligands at each concentration to the OCP values for each
ligand are presented in Table 1. The rate of OCP decrease
versus the increasing concentration of two ligands exhib-
ited only a few minor variations.
Figure 5. Pourbaix diagram for copper in aqueous solutions
(Celante &Freitas, 2009)
Figure 6. Open Circuit Potential vs. Concentration for AIBTC and IPETC
Table 1. Open Circuit Potential vs. Concentration for AIBTC and IPETC
Concentration,
M
OCP, V ΔOCP,
V
ΔOCP/OCP, %
AIBTC IPETC AIBTC IPETC
0 –0.038 –0.038 0 0 0
1E–06 –0.040 –0.043 0.003 7.50 6.98
1E–05 –0.048 –0.045 –0.003 6.25 6.67
1E–04 –0.068 –0.068 0 0 0
1E–03 –0.123 –0.116 –0.007 5.69 6.03

3110 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
value was taken as the final result. The measured solubility
of AIBTC in water was 3.63×10–3 M and 2.98×10–3 M
in borate buffer. The solubility determined for IPETC was
2.24×10–2 M and 1.93×10–2 M in water and borate buffer,
respectively. The results for IPETC were close to the value
measured in 0.01 M KCl at a pH of 7.7 by Fairthorne et
al. (1996).
The solubility of AIBTC was found to be lower than
that of IPETC in both borate and water solutions, the rea-
sons for which may include the longer hydrocarbon chain
length of AIBTC (two carbons more than IPETC) and the
existence of the ally group. Furthermore, when the ionic
strength increased, both ligands’ solubilities decreased,
reducing by roughly 18% for AIBTC and 8% for IPETC.
The reduced solubility might suggest that AIBTC and
IPETC molecules can be ionized at elevated pH. Further
investigation on their pKa will be conducted.
The surface tension of aqueous solutions versus the
ligand concentration is depicted in Figure 4. The drop in
surface tension was more significant with the concentra-
tion of AIBTC, suggesting a more surface-active nature of
AIBTC. Interestingly, within the range of their maximal
concentration in water, the surface tension did not reach a
steady state, where surface tension would marginally change
with increasing concentration, thereby indicating micelle
formation. Micelle formation was not detected with either
AIBTC or IPETC over the concentration range study. This
differs from dithiocarbonates (aka, xanthates) and other
collectors (Han et al., 2018). This is probably due to the
limited solubility of the thionocarbamates.
Figure 3. (a)-(d). Ligand concentration vs. UV/VIS Absorbance for AIBTC-borate, AIBTC-water, IPETC-borate, and IPETC-
water

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Extracted Text (may have errors)

3110 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
value was taken as the final result. The measured solubility
of AIBTC in water was 3.63×10–3 M and 2.98×10–3 M
in borate buffer. The solubility determined for IPETC was
2.24×10–2 M and 1.93×10–2 M in water and borate buffer,
respectively. The results for IPETC were close to the value
measured in 0.01 M KCl at a pH of 7.7 by Fairthorne et
al. (1996).
The solubility of AIBTC was found to be lower than
that of IPETC in both borate and water solutions, the rea-
sons for which may include the longer hydrocarbon chain
length of AIBTC (two carbons more than IPETC) and the
existence of the ally group. Furthermore, when the ionic
strength increased, both ligands’ solubilities decreased,
reducing by roughly 18% for AIBTC and 8% for IPETC.
The reduced solubility might suggest that AIBTC and
IPETC molecules can be ionized at elevated pH. Further
investigation on their pKa will be conducted.
The surface tension of aqueous solutions versus the
ligand concentration is depicted in Figure 4. The drop in
surface tension was more significant with the concentra-
tion of AIBTC, suggesting a more surface-active nature of
AIBTC. Interestingly, within the range of their maximal
concentration in water, the surface tension did not reach a
steady state, where surface tension would marginally change
with increasing concentration, thereby indicating micelle
formation. Micelle formation was not detected with either
AIBTC or IPETC over the concentration range study. This
differs from dithiocarbonates (aka, xanthates) and other
collectors (Han et al., 2018). This is probably due to the
limited solubility of the thionocarbamates.
Figure 3. (a)-(d). Ligand concentration vs. UV/VIS Absorbance for AIBTC-borate, AIBTC-water, IPETC-borate, and IPETC-
water