3114 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
be explained by an AIBTC-promoted Cu oxidation, with
the potential falling within the range of Cu(I) oxidation
to Cu(II). The oxidation reaction became most appar-
ent at the highest tested concentration of 10–3 M, given
a peak around +0.35 V vs. Ag/AgCl. The passivation and
activation effects of AIBTC became more pronounced as
its concentration increased from 10–6 M to 10–4 M. This
trend suggests that higher concentrations facilitated the
adsorption rate, thus resulting in stronger passivation. Also,
the increasing concentrations might enhance the chemical
reaction kinetics and the formation of the bulk complex,
therefore leading to stronger activation. Seryakova et al.
(1975) found Cu in a complex with IPETC was Cu(I). This
finding was supported by a study by Leppinen et al. (1988),
which indicated that IPETC could be bonded to Cu(I)
through the sulfur atom. Further increasing concentration
didn’t strengthen the passivation effect, probably because
the chemisorption rate reached a plateau.
At 10 mV/s, current-potential curves lie closer to each
other than those at 50 mV/s because a lower scan rate gave
the electrodes a relatively sufficient residence time at each
potential point to react (Figure 8 (b)). In this specific case,
the degree of the oxidation of the Cu electrode was ampli-
fied by the extended reaction time. Contrasting this with
the higher sweep rate implies that the chemisorption of
AIBTC onto the Cu electrode was faster than the oxidation
of the Cu, suggested by the more significant passivation of
AIBTC when provided limited interaction time. A compa-
rable oxidation peak was observed for 10–3 M AIBTC at
10 mV/s. However, the peak intensity significantly shrank
compared to 50 mV/s, and the peak shifted towards a
lower potential. Unlike 50 mV/s, after the oxidation peak
at 10 mV/s, the curves at all concentrations converged,
indicating that the interaction between the Cu and AIBTC
was mitigated by the extended residence time and that Cu
oxidation was the predominant reaction.
A comparison was made between the voltammograms
at 50 mV/s of the two ligands under stirring (Figure 8 (a)
and Figure 9). Similarities were observed: first, the passiv-
ation effect after adding the ligands around OCP, which was
believed to be the consequence of the adsorption of AIBTC
or IPETC. The potential range for the chemisorption to
happen was in alignment with that for the adsorption of
IPETC on a Cu electrode in the study of Basilio (1989).
Second, activation appeared at a higher potential range.
An anodic peak following the chemisorption range was
observed for both AIBTC and IPETC, which is hypoth-
esized to imply the activated Cu oxidation by ligands.
Figure 8. Linear sweep voltammograms of AIBTC at (a) 50 and (b) 10 mV/s
Figure 9. Linear sweep voltammograms of IPETC at various
concentrations at 50 mV/s
be explained by an AIBTC-promoted Cu oxidation, with
the potential falling within the range of Cu(I) oxidation
to Cu(II). The oxidation reaction became most appar-
ent at the highest tested concentration of 10–3 M, given
a peak around +0.35 V vs. Ag/AgCl. The passivation and
activation effects of AIBTC became more pronounced as
its concentration increased from 10–6 M to 10–4 M. This
trend suggests that higher concentrations facilitated the
adsorption rate, thus resulting in stronger passivation. Also,
the increasing concentrations might enhance the chemical
reaction kinetics and the formation of the bulk complex,
therefore leading to stronger activation. Seryakova et al.
(1975) found Cu in a complex with IPETC was Cu(I). This
finding was supported by a study by Leppinen et al. (1988),
which indicated that IPETC could be bonded to Cu(I)
through the sulfur atom. Further increasing concentration
didn’t strengthen the passivation effect, probably because
the chemisorption rate reached a plateau.
At 10 mV/s, current-potential curves lie closer to each
other than those at 50 mV/s because a lower scan rate gave
the electrodes a relatively sufficient residence time at each
potential point to react (Figure 8 (b)). In this specific case,
the degree of the oxidation of the Cu electrode was ampli-
fied by the extended reaction time. Contrasting this with
the higher sweep rate implies that the chemisorption of
AIBTC onto the Cu electrode was faster than the oxidation
of the Cu, suggested by the more significant passivation of
AIBTC when provided limited interaction time. A compa-
rable oxidation peak was observed for 10–3 M AIBTC at
10 mV/s. However, the peak intensity significantly shrank
compared to 50 mV/s, and the peak shifted towards a
lower potential. Unlike 50 mV/s, after the oxidation peak
at 10 mV/s, the curves at all concentrations converged,
indicating that the interaction between the Cu and AIBTC
was mitigated by the extended residence time and that Cu
oxidation was the predominant reaction.
A comparison was made between the voltammograms
at 50 mV/s of the two ligands under stirring (Figure 8 (a)
and Figure 9). Similarities were observed: first, the passiv-
ation effect after adding the ligands around OCP, which was
believed to be the consequence of the adsorption of AIBTC
or IPETC. The potential range for the chemisorption to
happen was in alignment with that for the adsorption of
IPETC on a Cu electrode in the study of Basilio (1989).
Second, activation appeared at a higher potential range.
An anodic peak following the chemisorption range was
observed for both AIBTC and IPETC, which is hypoth-
esized to imply the activated Cu oxidation by ligands.
Figure 8. Linear sweep voltammograms of AIBTC at (a) 50 and (b) 10 mV/s
Figure 9. Linear sweep voltammograms of IPETC at various
concentrations at 50 mV/s