XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3115
Several evident differences between the behaviors
of AIBTC and IPETC were noticed. First, in the chemi-
sorption range, the passivation effect of AIBTC was more
significant than that of IPETC, as suggested by a broader
depressing potential window (passivation till +0.31 and
+0.25 V for AIBTC and IPETC, respectively). This stronger
passivation was further supported by a greater reduction in
the anodic current by AIBTC and a less significant impact
of IPETC concentration on passivation. The more signifi-
cant depressing effect of AIBTC on Cu oxidation suggests a
stronger chemisorption of AIBTC onto the Cu electrode or
a more robust bonding between them. Alternatively, greater
passivation might result from the longer hydrocarbon chain
length of AIBTC, and the lateral interactions amongst the
adsorbed AIBTC are also likely to be stronger.
Second, differences existed in the intensity of the
anodic peaks for the two ligands at 10–3 M, which prob-
ably can be assigned to the ligand-promoted Cu oxidation
due to the addition of AIBTC and IPETC. Compared to
IPETC, a slightly more intensive peak was displayed for
AIBTC, showing a larger gap from the curve when no
ligand was added. This enlarged peak on the AIBTC curve
might indicate a more robust chemical reaction between
AIBTC and Cu.
Third, an additional peak appeared on the 10–3 M
IPETC curve at a high potential range of over +0.60 V,
which remains unresolved. S-based ligands are oxidized at
elevated potentials, e.g., xanthate (Woods, 1971 Woods et
al., 1998). However, IPETC did not show oxidation on the
platinum electrode in the study by Basilio (1989). In con-
trast, no peak was observed within the same potential range
as that of AIBTC.
Cyclic Voltammetry
Cyclic voltammetry (CV) was carried out on IPETC
and AIBTC at various concentrations, using a sweep rate
of 50 mV/s under a stirring condition (Figure 10 and
Figure 11). The applied potential cycled between –0.60 V
and +0.60 V (vs. Ag/AgCl). The starting potential was set at
0 V. Potential was first increased to +0.60 V, then decreased
to –0.60 V, and eventually cycled back to 0 V.
At 0 ligand concentration, an anodic current showed
up at around –0.28 V, representing the beginning of Cu
oxidation to Cu2O and further to CuO, which showed con-
sistency with the results of Basilio (1989). As the applied
potential increased, the measured current continued to
grow, suggesting the continuous oxidation of the Cu. The
current breakage at 0 V indicated that within the measure-
ment duration of one cycle, the interactions between the Cu
electrode and O2 and the ligands had yet to be equilibrated.
After the introduction of ligands, net anodic currents and
moderate peaks were observed below about –0.20
V, suggesting the chemisorption of ligands occurred
under lower potentials where Cu oxidation was insignifi-
cant. When no ligand was introduced, on the returning
sweep, a distinct peak was observed at around –0.25 V, cor-
responding to the reduction of CuO to Cu2O, which is
consistent with the result of Basilio (1989). Another pos-
sible peak was anticipated to be below –0.60 V, attributed
to the reduction of Cu2O to metallic Cu0.
Figure 10. Cyclic voltammograms of IPETC at various
concentrations at 50 mV/s
Figure 11. Cyclic voltammograms of AIBTC at various
concentrations at 50 mV/s