XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2215
for flotation and causing pyrite depression (Nakhaei et al.
2023). Consequently, it is advisable to employ CuSO4 for
pyrite flotation solely at weak alkaline pH levels. In sum-
mary, the recovery of pyrite exhibits a slight increase in the
alkaline range in the presence of CuSO4 compared to its
absence, while acting as a depressant within the acidic pH
range (Nakhaei et al., 2023).
Nakhaei et al., (2023) examined the impact of CuSO4
dosage on sulfur (pyrite) removal from magnetic concen-
trate at pH=7.5. As shown in Figure 2, there is a signifi-
cant increase in sulfur recovery from 77% to 83.5% as the
CuSO4 dosage rises to 75 g/t. However, further addition
of copper ions did not enhance flotation, as an excess of
copper ions in the slurry resulted in the formation of an
insoluble complex. Moreover, excessive copper sulfate can
inhibit froth formation (Nakhaei and Irannajad, 2017).
Additionally, Hicyilmaz et al., (2004) investigates the
impact of redox potential and pH on the pyrite surface’s
contact angle measurements or wetting behavior. As shown
in Figure 3, the maximum contact angle in the absence of
Cu2+ measures 25° at pH 4.67 and at a pulp potential of
+400 mV. After adding Cu2+, pyrite gets activated, and the
maximum contact angle measures 49° at pH 4.67 and at the
redox potential of +400 mV. Figures 4 and 5 demonstrate
the mechanisms and reactions that occur during changes in
both pulp potential and pH and their impact on contact
angle of the pyrite surface. This investigation shows that
slight acid pH and oxidizing environment improve the con-
tact angle because hydrophobic sulfur forms on the pyrite
surface rendering it more hydrophobic. Furthermore, upon
activation with Cu2+ and under slight acid and oxidizing
conditions, CuS (covellite-like) and more element sulfur
are formed as additional hydrophobic species which further
improve the hydrophobicity of pyrite, and consequently its
contact angle.
Table 1. Zeta potential of pyrite particles after exposure to xanthate and copper sulphate in
different pH (Nakhaei et al. 2023)
pH/ Zeta Potential
-ζ (mV) ζ (mV) ζ (mV)
Pyrite Pyrite+Butyl Xanthate Pyrite+Copper Sulfate
3 +6.0 +13.0 +11.0
5 -7.5 -12.5 +6.0
7 -11.0 -20.0 +4.8
9 -27.0 -30.0 -6.0
11 -35.0 -30.2 -8.0
Figure 2. The effect of CuSO
4 dosage on sulfur recovery at pH=7.5 Source: (Nakhaei et
al., 2023)
for flotation and causing pyrite depression (Nakhaei et al.
2023). Consequently, it is advisable to employ CuSO4 for
pyrite flotation solely at weak alkaline pH levels. In sum-
mary, the recovery of pyrite exhibits a slight increase in the
alkaline range in the presence of CuSO4 compared to its
absence, while acting as a depressant within the acidic pH
range (Nakhaei et al., 2023).
Nakhaei et al., (2023) examined the impact of CuSO4
dosage on sulfur (pyrite) removal from magnetic concen-
trate at pH=7.5. As shown in Figure 2, there is a signifi-
cant increase in sulfur recovery from 77% to 83.5% as the
CuSO4 dosage rises to 75 g/t. However, further addition
of copper ions did not enhance flotation, as an excess of
copper ions in the slurry resulted in the formation of an
insoluble complex. Moreover, excessive copper sulfate can
inhibit froth formation (Nakhaei and Irannajad, 2017).
Additionally, Hicyilmaz et al., (2004) investigates the
impact of redox potential and pH on the pyrite surface’s
contact angle measurements or wetting behavior. As shown
in Figure 3, the maximum contact angle in the absence of
Cu2+ measures 25° at pH 4.67 and at a pulp potential of
+400 mV. After adding Cu2+, pyrite gets activated, and the
maximum contact angle measures 49° at pH 4.67 and at the
redox potential of +400 mV. Figures 4 and 5 demonstrate
the mechanisms and reactions that occur during changes in
both pulp potential and pH and their impact on contact
angle of the pyrite surface. This investigation shows that
slight acid pH and oxidizing environment improve the con-
tact angle because hydrophobic sulfur forms on the pyrite
surface rendering it more hydrophobic. Furthermore, upon
activation with Cu2+ and under slight acid and oxidizing
conditions, CuS (covellite-like) and more element sulfur
are formed as additional hydrophobic species which further
improve the hydrophobicity of pyrite, and consequently its
contact angle.
Table 1. Zeta potential of pyrite particles after exposure to xanthate and copper sulphate in
different pH (Nakhaei et al. 2023)
pH/ Zeta Potential
-ζ (mV) ζ (mV) ζ (mV)
Pyrite Pyrite+Butyl Xanthate Pyrite+Copper Sulfate
3 +6.0 +13.0 +11.0
5 -7.5 -12.5 +6.0
7 -11.0 -20.0 +4.8
9 -27.0 -30.0 -6.0
11 -35.0 -30.2 -8.0
Figure 2. The effect of CuSO
4 dosage on sulfur recovery at pH=7.5 Source: (Nakhaei et
al., 2023)